Sacroiliac Joint, Pelvis, and Hip Joint

Introduction

Traumatic luxation of the sacroiliac joint results in displacement and laxity of the joint, variable pain, and is almost always seen with other major fractures of the pelvis and hind limbs, disabling both sides. Displacement of the ilial wing is usually cranial and dorsal, and it is not uncommon for the pelvis distal to the sacroiliac joint to be displaced medially to compromise the pelvic canal. Avoidance of severe and chronic pain, and compromise to the pelvic canal are the main indications for surgical repair of the sacroiliac joint. Fixation of the sacroiliac joint allows early weight bearing and reduction of pain, prevents complications from mal-alignment of the pelvis, and prevents potential compromise of other orthopedic repairs. The most commonly applied and effective fixation of the sacroiliac joint is deeply seated lag screws that compress and realign the joint (Figure 60-1A and B). Fixation promotes early weight bearing by reducing instability of the joint and its resultant pain.
 

General Considerations

There is little natural movement at the canine sacroiliac joint, but this joint does have typical anatomic structures including joint capsule, ligaments and a cartilage covered area described as the auricular surface.¹ The joint undergoes bony fusion in many dogs with age. Traumatic luxation of this joint is described with several other names including fracture-luxation and fractureseparation, all of which have identical meaning. However, sacral fracture indicates that fracture of the sacral bone is present, generally located at the site of the sacral wing. Sacral fractures are more likely to be associated with neurologic injury and have different and more complex surgical considerations. They will not be specifically discussed in this chapter.

Presentation and physical examination of a dog with sacroiliac luxation reveals the dog to be non-weight bearing on the affected side, and commonly unable to stand on either rear limb because of associated traumatic injury. The instability at the sacroiliac joint may be detected with careful digital pressure, however, local pain and swelling prevent effective palpation of this joint. Radiographic evaluation is essential to diagnose sacroiliac luxation and also fully characterizes displacement of the joint and the extent of associated pelvic or long bone injuries. The diagnosis of sacroiliac luxation is best observed on a ventrodorsal radiographic view and is seen in subtle cases as a step between the caudal sacral wing and the ilium. Those dogs with severe displacement have more instability at the joint with more severe pain. Neurologic injury with signs referable to injury of the lumbosacral trunk or to the innervation to the urinary bladder are observed infrequently, especially with severe displacement or bilateral injuries. Fortunately, neurologic injury associated with discrete sacroiliac luxation is most commonly (but not always) reversible within several weeks of the injury.

Surgical Indications

Surgical stabilization of the sacroiliac joint is selected for those cases with severe pain or displacement where lack of repair may compromise the pelvic canal, the alignment of the coxofemoral joint, or the stability of other orthopedic fixations of the pelvis or long bones. Displacement of sacroiliac luxation, especially the medial direction that could compromise the diameter of the pelvic canal, may progress in the first days post-trauma. If case selection for non-surgical care is based upon minimal displacement observed radiographically on the day of injury, additional radiographs should be taken 4 to 6 days later to ensure that the hemi-pelvis has not displaced medially to obstruct the pelvic canal.

Surgical Anatomy and Approaches

An approach to the sacroiliac joint through a dorsal incision allows access and direct visual identification of the anatomy of the sacral wing (Figure 60-2) for precise placement of lag screw fixtion for the routine sacroiliac injury.² A different approach is also described to the ventral aspect of the sacrum; however, it does not allow direct visualization of the sacral wing. The ventral surgical approach is useful in the uncommon circumstance when an ipsilateral ilial fracture must be repaired with a sacroiliac injury.³
 

The dorsal approach to the sacroiliac joint is completed with the dog in lateral recumbency, through an incision over the dorsal iliac spine that curves down along the cranial aspect of the ilial wing. After incisions through deep gluteal fascia and fat, the dorsal iliac spine is evident. A sharp incision is made in the dorsal periosteal attachment of the middle gluteal muscle and this muscle is elevated fully from the lateral aspect of the iliac wing. The sacrospinalis muscle is similarly elevated from the medial side of the ilium; however, this muscle and the dorsal sacroiliac ligament have often been disrupted by the trauma. Manipulation of the iliac wing with a bone forceps in a ventral direction and removal of fibrinous debris allows a direct view of the oblique surfaces of the sacral wing (Figure 60-3A). The curved cartilagecovered surface seen on the ventral aspect of the sacral wing is the auricular surface.⁴ The surgeon can also identify the dorsal and cranial aspects of the sacral wing by palpation through a layer of fascia. The locations of the spinal canal, the sacral nerve roots, and the sacral body can be deduced in relation to these two structures. The ideal location for the lag screw deeply seated into the sacral body is ventral to the spinal canal, caudal to the lumbosacral intervertebral disc, and cranial to the sacral nerve roots.
 

Lag Screw Fixation for Sacroiliac Luxation

One lag screw will be placed through a glide hole in the ilial wing and seated deeply, ventral to the spinal canal into the sacral body. The sacral body generally has space to allow for placement of only one screw, except perhaps in giant breed dogs. A shorter screw is placed through the ilial wing into the dorsocranial aspect of the sacral wing, stopping short of the spinal canal. The screw size selected will depend upon the size of the animal. A screw size of 2.0 to 2.7 mm is selected for cats and small dogs, 3.5 to 4.0 mm cortex or cancellous bone screws are employed in dogs up to approximately 20 kg, while 4.5 mm cortex or 6.5 mm cancellous bone screws can be used in larger dogs. The surgeon must be acutely aware of sacral anatomy to avoid placement of the sacral body screw into the intervertebral space or the spinal canal. Another common mistake is for the screw to exit the sacral body prematurely on its ventral surface resulting in a lag screw with insufficient strength of fixation.

To accomplish accurate screw placement, the surgeon must first identify the sacral wing and the auricular surface. The cranial edge of the sacral wing is established by projecting a line between the craniodorsal aspect of the sacral wing and the ventral aspect of the auricular surface.⁴ The screw hole for the sacral body screw is drilled just caudal to this line, approximately 40% from the ventral limit of the sacral wing, taking care to keep the drill hole perpendicular to the lateral surface of the dog. The site for this hole is often centered in the lesser curvature of the auricular surface (See Figure 60-2). If positioned properly, this hole is drilled beneath the spinal canal to a depth of at least 60% of the width of the sacrum (Fig. Figure 60-3B). To achieve this depth, the hole must be drilled in a perfect lateral to medial direction, with the dog perfectly positioned in lateral recumbency. The sacral wing surface is mildly sloped, so that the “safe corridor” drill hole angle, with respect to the sacral wing surface, has been characterized to be 97 + 4°.⁵ If the drill exits the sacrum ventrally, the depth must be measured and if insufficient, the angle of the drill must be corrected. When proper depth is achieved, the hole is measured and partially tapped. The glide hole is next drilled through the ilial wing. The site for this glide hole is identified by digital palpation of the roughened surface of the sacroiliac joint on the medial side of the ilial wing, caudal to a bony prominence at this site. The sacral body screw is then placed through the glide hole, and with reduction of the luxation using bone forceps on the ilial wing, the screw is directed by sight into the hole in the sacral body. The screw is tightened to compress the joint and the reduction achieved may be checked by palpation dorsally.

A second screw is placed immediately dorsal and cranial to the first screw, which will locate the screw into the dorsocranial aspect of the sacral wing. This second screw must be shorter to avoid penetration into the spinal canal (Figure 60-4). Closure includes simple interrupted sutures into the layers of the middle gluteal and sacrospinalis fascia, deep lumbar fascia and fat, subcutis, and skin.
 

Bilateral sacroiliac fracture-luxation is less common than unilateral injury, constituting approximately 23% of sacroiliac injuries.⁶ Surgical repair may be completed bilaterally by using the technique described. Although there will be limited space within the sacral body to receive one long screw from either side, screw placement is generally successful. Alternative surgical methods have been described for bilateral sacroiliac repair. One method involves placing the dog in ventral recumbency and approaching both sacroiliac joints simultaneously. A large aiming device is then used to drill a screw hole completely across the sacrum, through the sacral body and both ilial wings.⁷ One long screw is placed, compressing the sacroiliac joint on one side and providing a positional screw effect on the other. Another procedure uses a transilial pin, independent of the sacrum to stabilize the sacroiliac joints.⁸ This procedure provides less stable fixation, but may be used if lag screw fixation is for any reason unsuccessful.

Minimally Invasive Technique

A technique for closed reduction and percutaneous insertion of lag screw fixation for sacroiliac luxation has been described.⁹ Reduction of the hemipelvis is achieved by percutaneous intramedullary pin or bone forceps application to the ischium. Intraoperative fluoroscopic imaging of sacral anatomy is completed using c-arm and radiolucent table top technique. Reduction is achieved and a temporary pin is placed to maintain reduction of the joint. Lag screw fixation, with placement within the sacral body, is then applied using c-arm guidance through several stab incisions.⁹

Prognosis and Results

The clinical results in dogs undergoing sacroiliac repair are generally excellent. Weight bearing begins within several days, often depending upon the severity of associated fractures and other injuries. Slow improvement in lameness and musculoskeletal function can be expected over several months. Exercise restriction is maintained until healing of all fractures is evident clinically and radiographically. A retrospective study reported a rate of loosened sacroiliac fixation of 38%, with frequent shallow screw placement into the sacral body.⁶ This same study reported that those fixations with deep screw placement into the sacral body did not loosen. An in vitro biomechanical study of sacroiliac screw fixation reported that two screws placed for sacroiliac fixation were always stronger than one screw and that fixation strength was optimized by use of the largest screws possible.¹⁰

It is evident that precise and aggressive screw placement in sacroiliac repair improves with clinical experience and provides the best clinical result.

References

1. Miller ME: Ligaments and joints of the pelvic limb. In Evans HE, ed.: Miller’s Anatomy of the Dog, 3rd ed. Philadelphia: W.B. Saunders, 1993, p. 244.
2. Piermattei, DL, Johnson KA: Approach to the wing of the ilium and dorsal aspect of the sacrum. An Atlas of Surgical Approaches to the Bones of the Dog and Cat, 4th ed. Philadelphia: W.B. Saunders, 2004.
3. Piermattei, DL, Johnson KA: Approach to the ventral aspect of the sacrum. An Atlas of Surgical Approaches to the Bones of the Dog and Cat, 4th ed. Philadelphia: W.B. Saunders, 2004.
4. DeCamp CE, Braden TD: The surgical anatomy of the canine sacrum for lag screw fixation of the sacroiliac joint. Vet Surg; 14:131, 1985.
5. Shales CJ, Langley-Hobbs SJ: Canine sacroiliac luxation: anatomic study of dorsoventral articular surface angulation and safe corridor for placement of screws used for lag fixation. Vet Surg; 34(4):324-331, 2005.
6. DeCamp CE, Braden TD: Sacroiliac fracture-separation in the dog: A study of 92 cases. Vet Surg; 14:127, 1985.
7. Kaderly RE: Stabilization of bilateral sacroiliac fracture-luxations in small animals with a single transsacral screw. Vet Surg; 20(2):91-96, 1991.
8. Olmstead ML, Matis U: Fractures of the pelvis. In Brinker WO, Olmstead ML, Sumner-Smith G, Prieur WE, eds.: Manual of Internal Fixation in Small Animals, 2nd ed. Berlin: Springer-Verlag, 1998, pp. 148-154.
9. Tomlinson JL, et al: Closed reduction and lag screw fixation of sacroiliac luxations and fractures. Vet Surg; 28(3):188-193, 1999. 
10. Radasch RM, Merkley DF, et al: Static strength evaluation of sacroiliac fracture-separation repairs. Vet Surg; 19(2):155-161, 1990.

Introduction

Trans-ilial pin fixation is a useful technique for stabilizing fractures and luxations involving the sacrum. Trans-ilial pins can be used as primary fixation or in combination with other implants (sacro-iliac pin or lag screw fixation) to provide reliable stability with minimal additional morbidity. Implantation is technically simple and implant placement can be verified visually and palpably in surgery. The trans-ilial pin engages the thick dorsal iliac spine providing multiple points of fixation intended to maintain rigid pelvic alignment. Standard 5/64 to 1/8 inch Steinmann pins are sufficiently strong for most patients and suitably malleable for ease of application. The implants are solidly attached to the ilia through their own ilial penetration with additional stability provided by polymethylmethacrylate composite fixation to screws placed within the ilia. This fixation is intended to disperse force through multiple attachment sites in the thick dorsal iliac spine of the ilium. The composite repair provides a forgiving and adaptable construct which is less technique sensitive so that ideal apposition or implant position are not necessarily required for construct rigidity and clinical success. The technique is highly adaptable for odd injuries including severe sacral fractures, bilateral injuries and very small patients.

The sacrum has very unique anatomy due to its dual functional roles as a weight-bearing support and as a neurologic conduit. The sacroiliac joint is both a synovial joint and a fibrocartilaginous synchondrosis. Its distinctive anatomy results in a wide variety of injuries many of which do not necessitate surgical intervention. The majority of sacroiliac trauma requiring surgical stabilization occurs in patients with bilateral injuries. Frequently the contralateral injury is not sacral damage, but other orthopedic trauma such as a contralateral pelvic fracture. Therefore common indications for sacroiliac stabilization include providing weight-bearing function, reducing pain and protecting other orthopedic fixations. However, fixation must be provided while respecting the sacrum’s neurologic role. The unique structural architecture of the sacrum combines cancellous bone intertwined with nerve roots providing an extraordinary repair challenge. Due to the variety of sacral injuries that occur, the following chapter is subdivided into sections by injury type to provide coherent specific suggestions for different injuries.

Surgical Preparation

Surgical preparation for the majority of sacral injuries consists of placing the patient in ventral recumbency with the legs placed under the patient in a near normal sitting position with the stifles flexed under the body, but the tarsus extended for better stability. Towels, sand bags or positioning bags are placed to ensure symmetry and security of the patient. The patient is prepped from 10 cm cranial to the ilial wings caudally to the tail (which is commonly placed in a temporary wrap). The surgical preparation extends laterally and ventrally to below the greater trochanters of the femur. For patients requiring multiple orthopedic repairs, the sacral trauma is typically addressed first since the sacral repair is more position sensitive. The patient can then be repositioned as required for the additional repairs. Pelvic symmetry and implant position can be more easily assessed with the patient symmetrically positioned in ventral recumbency.

A key to facilitating exposure and pin placement is performing curvilinear incisions on each side of the ilia to facilitate exposure and pin placement. The incisions should start at the cranial ventral iliac spine extending vertically in a dorsal direction and curving caudally to follow the dorsal margin of the ilial shaft to a few centimeters cranial the acetabulum (Figure 60-5). This incisional technique provides good visibility of the sacral articular surface with minimal skin interference during implant placement. The dorsal medial skin edges of both incisions can be sutured to each other thus everting the skin to increase exposure. A more limited surgical approach can be used for single ilial pin placement (commonly performed on the contralateral side). Strong gluteal fascia overlies the iliac spine at the origin of the middle gluteal muscle. Sharply incising over the lateral aspect of the iliac spine and reflecting the middle gluteal muscle caudally provides good visibility and retains the integrity of the tissue for surgical closure. When trans-sacral implants are utilized, the incision is expanded and muscle elevation will include the origin of the deep gluteal muscle. Surgical closure includes reestablishing the gluteal fascia attachment which provides good mechanical strength, minimizes suture interference with functional muscle, and provides coverage of implants. The epaxial fascia and dorsal sacroiliac ligaments when disrupted are closed in a similar manner. The subcutaneous tissue and skin are closed in a traditional matter.
 

Cement Tips

The following surgical techniques utilize composite fixation in which a small quantity of polymethylmethacrylate (PMMA) bone cement is used to bond the metal implants forming a rigid brace that is firmly attached to the ilia. Care must be taken to ensure aseptic technique when using bone cement, since skin contamination could result in infection and colonization of the PMMA which is difficult to treat; for this reason prophylactic peri-operative antibiotics are commonly administered. A stockinette or towel can be sutured into the incisional edge to improve visibility and minimize skin exposure. Frequent lavage with sterile saline is encouraged. A 20 g packet of PMMA is sufficient for both sides. Setting of the PMMA following addition of the polymer powder to the liquid monomer takes approximately 8 to 15 minutes. The PMMA is typically mixed for 1 to 2 minutes prior to application and applied in a viscous liquid stage. Application of the cement with a syringe provides better control with less spillage. Screws are inserted into the lateral ilium with 3 to 4 mm of the screw head exposed above the bone surface to allow bonding to the PMMA. A flat instrument (such as a periosteal elevator) is used to form and mold the PMMA around the implants, but only a small quantity is required. A commercially available trans-ilial rod with nuts is also available which avoids the use of PMMA and the necessity for a contralateral surgical approach (IMEX Veterinary, Inc.).

Axial Sacral Fractures

The sacrum consists of an osseous spinal canal and multiple foramina which protect the cauda equina and associated ventral and dorsal spinal nerves (Figure 60-6). When the structural integrity of the sacrum is compromised, placing an implant such as a lag screw across the fracture risks inadvertent nerve root damage. Fixation across a sacral fracture may induce nerve trauma directly, by displacement or compression. Fortythree percent of patients undergoing sacral fracture fixation with traditional techniques had neurologic deficits following surgery that were not noted prior to surgery (Kuntz 1995). Transilial pin fixation relies on stabilization anchored at multiple points between contralateral ilia without necessitating placing implants through or compression across the sacrum.
 

Surgical Technique

Following surgical approach and alignment of the pelvis, two pins are placed transversely through both ilia dorsal to the sacrum (Figure 60-7). One pin is placed directly behind the lumbosacral diarthrodial joint resting on the dorsal surface of the sacrum and engaging both ilia at the caudal iliac spine. The second pin is placed transversely, cranially and parallel to the first pin engaging both ilia in the cranial dorsal iliac spine (approximately 2.5 cm cranial to the first pin in a 35 Kg dog). The fixation and pin penetration can be visualized to ensure adequate ilial bone pentration through the thick dorsal caudal iliac spine. The pin is typically driven with a power drill. A blunt instrument can be used to direct the penetration of the contralateral ilium which commonly requires ventral deflection of the pin for maximal bone engagement. Fracture alignment can be additionally adjusted during the placement of pins. Compression at the cranial pin location will displace the caudal pelvic alignment laterally correcting medial displacement which is common in these injuries. The pins are bent at a 90° angle against the lateral surface of the ilium and cut to a length so when rotated they will overlap (approximately 2 cm). Two screws are applied to the lateral surface of the ilia and polymethylmethacrylate is applied and molded to the pin and screw construct on each side. The ilium is subjected to torsional and fulcrum forces transferred through the acetabulum during weight-bearing. The two transilial pins are intended to provide a rigid brace with multiple points of fixation which counteract weight-bearing forces. Minimal pelvic displacement and good early weight-bearing were observed in dogs with sacral injuries, including comminuted sacral fractures, using this fixation. Anatomic reduction is not required for rigid fixation, thus intentional malalignment can be maintained when desired (i.e. prevention of further nerve root manipulation and possible entrapment).
 

Unilateral Abaxial Sacral Fractures and Sacroiliac Luxations

Abaxial sacral injuries occur lateral to the sacral foramina and include fractures of the wing of the sacrum and separation of the sacroiliac joint. Placement of implants through the sacral body or dorsal to the spinal canal through the ilia will provide mechanical support that is unlikely to cause additional neurologic injury. Traditional lag screw fixation through the ilium and into the sacral body with greater than 60% depth of penetration across the sacrum provides reasonable stability with 88% success achieved with ideal implant placement (DeCamp 1985) using open reduction or 100% success with fluoroscopic guidance in closed fixations (Tomlinson 1999). However, sacroiliac luxations often occur with fractures that obscure traditional landmarks making identification of the sacral body more challenging without the aid of fluoroscopy. In one study only 33% of lag screws were placed in the sacral body. Trans-ilial pin fixation can be used to reinforce stability of traditional lag screw repairs especially in polytrauma cases in which early increased stress across the repair is anticipated or in which lag screw fixation may be problematic. Single trans-ilial pin fixation has also been used as a less invasive alternative in juvenile patients with painful, less severe sacroiliac luxations.

Surgical Technique

In this technique, sacroiliac lag screw fixation is placed by traditional surgical technique into the sacral body and reinforced with a trans-ilial pin. The sacroiliac joint is exposed through a dorsal approach. The lateral surface of the sacrum is exposed by ventrolateral retraction of the ilial wing. Careful placement of a blunt Hohmann retractor under the ventral surface of the sacrum provides excellent retraction of the ilial wing and provides exposure of the lateral sacral surface. Care should be used to ensure the tip of the Hohmann remains lateral and does not penetrate medially. The landmarks of the lateral surface of the sacrum should be visible. These include the crescent shaped articular surface, a fibrocartilaginous dorsal articular surface, and a ventral edge of the sacrum (Figure 60-8). A line is visualized from the craniodorsal point of the sacral wing to the ventral point of the wing. The point of drill bit entry is just caudal to the line at 60% of the distance from dorsal to ventral (slightly caudoventral to the halfway point). Difficult placement of the transsacram screw hole can occur due to many reasons including loss of visible landmarks (most commonly due to fracturing of the craniodorsal landmark) and incorrect orientation of the transsacral screw hole (most commonly due to tilting of the sacral that arises during retraction or loss of proper patient position). The sacral wing notch and articular surface can be used as additional landmarks to confirm an ideal drill entry point. The orientation of the sacral drill hole can be aided within surgery by observing the lateral surface of the sacrum. A small Steinman pin (5/64 in.) can be used in place of a drill bit. The additional pin length, as compared to a drill bit, serves for better assessment of pin orientation with less interference with regional structures and additionally, trans-ilial pin penetration helps assure proper pin placement. Remember that the pin direction is not perpendicular to the surface of the lateral sacral surface since the lateral surface of the sacrum is tilted caudodorsal approximately 15 degrees. Aligning the pin perpendicular to the lateral surface of the sacrum typically causes the pin to breach the ventral surface of the sacrum or to enter the lumbosacral disk space. Pin placement should be perpendicular to the axis of the dog, but retraction can alter the orientation of the sacrum. Thus, some relaxation of the retraction can correct disorientation especially if hard retraction is being utilized.
 

Following placement of the screw pilot hole into the sacrum, a guide hole is placed through the ilial wing at the level of the sacroilial articulation on the medial aspect of the displaced ilium. The articular surface on the medial side of the ilium is palpable and can be used to assist guide-hole placement. Remember the ilium is also oriented obliquely so the guide hole should be tilted approximately 15 degrees from the saggital axis of the ilial wing and enters more ventrally than expected (approximately 1/3 the distance from the ventral border). The guide-hole diameter needs to be greater than the outside thread diameter of the screw to provide lag compression. A washer can be used in combination with the screw to ensure good compression across the sacroiliac joint especially in younger dogs with softer bone. Depth of screw purchase is estimated from pre-operative radiographs and a screw length is chosen that crosses greater than 60% of sacral width including the thickness of the ilium. The screw is placed through the guide hole in the ilium and lined up with the pilot hole in the sacrum. The sacroiliac joint is reduced as the screw is driven into the sacral body. Reduction most commonly requires caudal retraction and occasional rotation of the ilium. Symmetry and reduction can be ensured by palpation of the contralateral ilial wing prior to final tightening of the screw which will compress the sacroiliac joint.

Difficult reductions can also be aided by temporarily replacing the screw with a pin. The pin (with chuck) is placed through the ilial guide hole into the sacral pilot hole and used as a lever to reduce and align the sacroiliac joint. The pin provides a mechanical lever (no screw and driver interface) and the smooth pin surface allows it to slide without resistance. The sacroiliac joint is temporarily stabilized with an additional sacroiliac pin which is later removed after the original pin is again replaced with a screw or converted to a trans-sacral pin brace (see next section).

When additional stability is desired, a trans-ilial pin can be added intra-operatively. This requires a limited contralateral dorsal surgical approach to expose the dorsolateral aspect of the ilial wing. A Steinmann pin is driven transversely through both ilia, over the dorsal surface of the sacrum just behind the lumbosacral articulation. The pin location can be verified visually and by digital palpation to ensure that the ilia are well engaged and the pin contacts the dorsal surface of the sacrum. The ends of the Steinmann pins are bent over at the level of the ilial surface. One or two additional screws are placed through the lateral surface of the ilia adjacent to the pin and polymethylmethacrylate is applied incorporating the pins and neighboring screws (Figure 60-9).
 

Bilateral Sacral Iliac Luxations and Fractures

Repair of bilateral abaxial sacral injuries can be challenging due to anatomic limits in ideal bone purchase. Placing two lag screws into the sacral body with greater than 60% purchase can be problematic due to interference of the two converging screws in a very small target. Single screw techniques theoretically have some advantages, but become problematic due to technical difficulty and availability of proper implants in many practices (proper screw length and nut availability). Transsacral pin placement is relatively simple. It avoids the use of a bone tap, decreasing the opportunity for damage to the cauda equina. The pin orientation within the sacral body can be verified intra-operatively by comparing the exit points of the pin in the lateral surfaces of the sacrum. The pin is easily replaced if ideal orientation is not achieved. Reduction of the sacroiliac joint does not require alignment of drill holes which can be fickle with screw placement. Trans-sacral pin placement is done following reduction of the sacroiliac joint by simply advancing the pin through the ilium. Complete reduction can be achieved during bending of the pin using a chuck, but a trans-ilial pin is placed to provide additional stability. This fixation engages multiple cortices providing good quality bone purchase and stability, thus decreasing the chance of the implant fracturing out of the sacrum which can occur with screws. The trans-sacral pin is relatively uncomplicated to place and a viable alternative to placing bilateral lag screws in dogs with bilateral injuries, therefore simplifying the surgical technique and shortening operative time.

Surgical Technique

The lateral surfaces of the sacrum are exposed and visualized. The center of the sacral body is identified by visualizing a line from the craniodorsal point of the sacral wing to the ventral point of the wing (See Figure 60-8). The point of pin entry is just caudal to this line at 60% of the distance from dorsal to ventral (slightly caudoventral to the halfway point). The sacral wing notch or the crescent shaped articular cartilage can be used as additional landmarks which is especially helpful when landmarks are obscured due to trauma. The pin is advanced transversely across the sacrum and should exit at the same location on the opposite lateral surface of the sacrum (Figure 60-10). A “C” shaped drill guide is helpful in providing accurate drill orientation. Once proper trans-sacral pin placement is established, the pin is retracted on one side of the sacroiliac joint to allow unilateral sacroiliac reduction. Sacroiliac reduction is achieved and the trans-sacral pin is advanced through the ilium. The drill is replaced on the opposite end of the pin and the pin is retracted in the opposite direction to allow reduction of the contralateral sacroiliac joint. The pin is then advanced across this ilium just as before, but in the opposite direction.
 

Following trans-sacral pin placement, a trans-ilial pin is placed with the Steinmann pin driven transversely through both ilia, contacting the dorsal surface of the sacrum just caudal to the lumbosacral articulation (as previously described). The pin location can be verified visually and by digital palpation to ensure that the ilia are well engaged and the pin contacts the dorsal surface of the sacrum. The ends of the Steinmann pins are bent over at approximately 90 degrees and cut so that the pins can be rotated to overlap. One to two additional screws are placed into the lateral surface of the ilial wing adjacent to the overlapping pins. PMMA is applied to incorporate the pins and screws into a composite fixation.

Post-Operative Care

The trans-ilial pin provides a rigid fixation with low morbidity, so early weight-bearing is anticipated. Enforced restricted activity is recommended for six weeks. However, aggressive physical therapy has been performed for concurrent injuries in many patients. Pin migration, implant discomfort or infection has not been commonly associated with this technique and implant retrieval is seldom required.

Suggested Readings

Averill SM, Johnson AL, Schaeffer DJ. Risk factors associated with development of pelvic canal stenosis secondary to sacroiliac separation: 84 cases (1985-1995). J Am Vet Med Assoc 211:75, 1997.

DeCamp CE, Braden TD. Sacroiliac fracture-separation in the dog. A study of 92 cases. Vet Surg 14:127, 1985.

DeCamp CE, Braden TD. The surgical anatomy of the canine sacrum for lag screw fixation of the sacroiliac joint. Vet Surg 14:131, 1985.

Hulse DA, Shires P, Waldron D, Hedlund C. Sacroiliac luxations. Comp Contin Ed Pract Vet 7:493, 1985.

Jacobson A, Schrader SC. Peripheral nerve injury associated with fracture or fracture-dislocation of the pelvis in dogs and cats: 34 cases (1978-1982). J Am Vet Med Assoc 190:569, 1987.

Kuntz CA, Waldron D, Martin RA, Shires PK, Moon M, Shell L. Sacral fractures in dogs: a review of 32 cases. J Am Anim Hosp Assoc 31:142, 1995.

Pare B, Gendreau CL, Robbins MA. Open reduction of sacral fractures using transarticular implants at the articular facets of L7-S1: 8 consecutive canine patients (1995-1999). Vet Surg 30:476, 2001.

Tomlinson JL, Cook JL, Payne JT, Anderson CC, Johnson JC. Closed reduction and lag screw fixation of sacroiliac luxations and fractures. Vet Surg 28:188, 1999.

Ullman SL, Boudrieau RJ. Internal skeletal fixation using a Kirschner apparatus for stabilization of fracture/luxations of the lumbosacral joint in six dogs. A modification of the transilial pin technique. Vet Surg 22:11, 1993.
 

Introduction

It has been reported that 20 to 30% of all fractures in small animals are pelvic fractures and of these 18 to 46% are ilial in the canine.^1,2 In dogs, pelvic fractures are commonly the result of vehicular trauma, while in cats, falls from a great height are the most common cause. Due to the nature of these injuries, it is essential that other organ systems be assessed and treated appropriately before repair of the orthopedic injuries is initiated. Pelvic fractures have been associated with abdominal trauma, (urinary tract and abdominal organs), thoracic injury, and peripheral nervous system insult. In particular, cranial or craniomedial displacement of the iliac bone has been associated with damage to the L6 and L7 nerve roots and injury to the lumbosacral trunk.³

The lumbosacral trunk is composed of the ventral branches of the last two lumbar and first two sacral nerves and it runs caudally along the medial surface of the ilium. The ischiatic nerve begins when the second sacral nerve joins the lumbosacral trunk. Although the ischiatic nerve is located medial to the ilium it is less closely associated with bone and therefore less susceptible to direct injury (Figure 60-11). Ischiatic nerve injury is more often associated with acetabular fractures and secondary fibrosis associated with the healing of ischial fractures.³ Cutaneous, sensory, and voluntary motor deficits associated with the L6, L7, S1 and S2 nerve roots are the most common peripheral nerve deficits associated with pelvic fractures. However depression of the sciatic reflex (cranial tibial reflex) and decreased sensation of the lateral digit of the affected limb may also be present.
 

Classification of Ilial Fractures

Ilial fractures have been classified as either ilial body fractures with an interruption of the weight bearing arch or ilial wing fractures which are sustained cranial to the sacroiliac joint whereby the weight bearing arch is left intact.⁴ Ilial wing fractures have been further classified as either cranial avulsion fractures (where the most cranial part of the ilial wing is separated from the ilial body at the insertion site of the sartorius and tensor fascia latae muscles) or central ilial wing fractures (where the separation occurs in the region on the middle gluteal muscle insertion). Ilial fractures can be further described as simple or multifragmentary, unilateral or bilateral. Very often they are associated with other pelvic fractures.

For most ilial fractures, a lateral approach allows optimal visualization of all portions of the ilium (Figure 60-12).⁵ The patient is placed in lateral recumbency with the affected side up, and the limb is prepared for aseptic surgery. A skin incision is made starting cranially at the center of the iliac crest and continued caudally in a straight line to the greater trochanter. The subcutaneous fat and fascia are incised along the same line. The tensor fascia lata is reflected cranially to expose the middle gluteal muscle. Dissection is continued in a cranial direction between the tensor fascia lata and middle gluteal muscle to the wing of the ilium. Elevation and retraction of the middle and deep gluteal muscles exposes the wing and body of the ilium.

If exposure of the ventral ilium or sacroiliac joint is needed this can be accomplished by a ventral extension of the above approach.⁶ The iliacus muscle is incised along its origin at the ventromedial border of the ilium. The iliacus muscle is elevated subperiosteally allowing exposure of the ventral ilium and/or digital palpation of the sacroiliac joint and lumbosacral trunk. The lateral approach to the ilium can also be extended caudally and combined with either a craniolateral, dorsal approach, or a caudal approach to the coxofemoral joint, allowing access to the acetabulum and ischium when indicated.
 

Repair Options

Open reduction and internal fixation of ilial fractures is indicated when the weight bearing portion of the ilium is involved (ilial body fractures), when there is gross displacement of the fracture fragments, when the diameter of the pelvic canal is compromised, when the fracture impinges on the lumbosacral trunk, if there is gross pelvic instability( as is often the case with bilateral pelvic fractures) or when there are concurrent fractures of the ipsilateral acetabulum, ishium, and/or pubis. Precise reduction and rigid fixation will allow for early ambulation and healing. This in turn reduces complications associated with conservative management and prolonged recumbancy.

Plate fixation is the most common method of repair. Lag screw fixation has also been advocated and may also be useful to supplement plate fixation when needed. Pin/ wire fixation +/- polymethymethacrylate, external skeletal fixation, and miniplate fixation are also possible but have been associated with increased morbidity and complication rates.^2,7

Bone Plating

Stabilization of ilial fractures using a laterally placed bone plate is the most common repair technique used and the simplest to perform. The ilium is a wide, flat bone and lends itself readily to plating. The ilial fragments should be of sufficient length to allow at least two bone screws proximally and distally. Reduction can be accomplished by grasping the fragment ends with Verbrugge or speedlock forceps and bringing the ends into proper alignment; however, further manipulation is often needed. One technique that can be used when the hip joint is intact but the ischium is broken, is to grasp the greater trochanter with Lewin forceps and then manipulate the distal ilial fragment into reduction (Figure 60-13). Alternatively, if the hemipelvis is intact, Kern bone-holding forceps or an intramedullary pin can be placed in the tuber ischium to allow manipulation of the distal segment. Once the fracture has been reduced, bone holding forceps are applied, or an assistant maintains reduction while the plate is contoured and applied.
 

In some cases, the aforementioned reduction techniques are insufficient because of muscle contracture. In these patients the plate may be contoured, using the radiograph of the intact opposite side as a guide when possible, and is applied only to the distal fragment. The fragment ends are brought as close to reduction as possible. A Verbrugge clamp then is used to complete reduction, and the plate is secured to the proximal segment (Figure 60-14 A, B and C).⁸
 

During drilling, measuring with a depth gauge, and tapping of the screw holes, care must be taken not to injure medial structures such as the rectum and lumbosacral trunk. Optimally, at least one screw in the proximal segment should engage the wing or body of the sacrum. Although this maneuver results in greater holding power, care should be taken, just as in the repair of sacroiliac dislocation, to avoid penetrating the spinal canal in that area. Traversing the sacroiliac joint with a screw may lead to degenerative sacroiliitis, however to date there are no significant reports of this phenomenon in the dog.

If needed, rigidity of the repair can be increased by the addition of a mini or cuttable plate or intrafragmentary screws to the ventral (tension-side) of the ilium (Figure 60-15). Ventral fixation can be applied prior to the lateral plating to maintain reduction during plating.^2,7 Steinmann pins placed through the contoured plate screw-holes can also be used to maintain reduction. Pin size should not be greater that the diameter of the drill bit for the screws to be used. As plating proceeds the pins are removed and replaced with screws.
 

Fractures of the ilium with concurrent sacroiliac luxations are best treated with plate fixation. The ventral aspect of the ilium is exposed as described previously. Blunt dissection, preferably with the finger, is directed along the medial face of the ilium until the articular surface of the sacral body and ilium are palpated (Figure 60-16 A and B). Once the sacroiliac luxation has been reduced, a small Kirschner wire can be inserted through the ilium and into the sacral body to maintain reduction. The plate is applied as previously described for ilial fractures. If possible, one of the plate screws is placed thru the sacroiliac joint in a lag fashion to afford compression of the ilium to the sacrum. If the fracture precludes this, the sacroiliac luxation is reduced with a lag screw and the iliac fracture is reduced and plated separately.
 

Additional exposure via trochanteric osteotomy may be needed when repairing ilial fractures near the acetabulum or segmental ilial fractures with an acetabular component. Fixation of these fractures is achieved with a bone plate or a reconstruction plate contoured to match the dorsal aspect of the acetabulum (Figure 60-17).
 

Alternatives to Plating

When plating equipment is unavailable, some fractures of the ilium are amenable to lag screw fixation or pinning. Long oblique fractures of the ilial body can be effectively stabilized with two lag screws. The ventral aspect of the ilium is exposed as described previously and the iliacus muscle is retracted medially. Screws are inserted in a ventral to dorsal direction across the fracture line resulting in compression. When applied properly to the appropriate fracture, lag screw fixation may be mechanically equivalent to plate fixation.⁷

Although mechanically inferior, pinning can be successful in fractures involving the proximal or midbody area of the ilium in small dogs and cats. Fractures distal to the midbody of the ilium do not often permit sufficient length of the insertion of the pins to provide adequate stability.

Insertion of each pin is started in the proximal fragment near the cranial dorsomedial aspect of the wing of the ilium. The pin is driven down the shaft of the ilium and into the distal segment (Figure 60-18. A and B). A pin of identical length is used to check the distance traversed. The hip joint should also be palpated to determine whether the implant has entered the joint. If so, the pin is retracted until no palpable evidence of joint invasion is noted. At least two pins should be driven in a similar manner to improve rotational stability. Ilial pinning is technically difficult because the medullary cavity of the ilium is narrow, and the cortex is often penetrated during pin insertion.
 

Hemicerclage wiring also can be used in smaller dogs and cats to aid in stability in fractures of the ilial midbody.

Postoperative Care

Postoperative radiographs (ventrodorsal, lateral, and oblique hemipelvic) are indicated to evaluate the implants and reduction. Appropriate steps should be taken if errors in reduction have occurred. If adequate fixation is accomplished, no special aftercare is required. Appropriate bedding and nursing care, along with confinement for 4 to 8 weeks, are advised. Physical and radiographic assessment at 4 and 8 weeks post-operatively are recommended to evaluate implant stability and fracture healing. Surgical procedures can be staged approximately 1 to 2 days apart if the animal’s condition disallows simultaneous fixation of both sides.

References

1. Verstraete FJM, Lambrechts NE: Diagnosis of soft tissue injuries associated with pelvic fractures, Compend Contin Educ Pract Vet 14: 921, 1992.
2. Breshears LA, Fitch RB, Wallace LJ, et al: The radiographic evaluation of repaired canine ilial fractures. Vet Comp Orthop Traumatol 17: 64, 2004.
3. Jacobson A, Schrader, SC: Peripheral nerve injury associated with fracture or fracture-dislocation of the pelvis in dogs and cats: 34 cases (1978-1982) J Am Vet Med Assoc 190: 569, 1987.
4. Messmer M, Montavon PM: Pelvic fractures in the dog and cat: a classification system and review of 556 cases Vet Comp Orthop Traumatol 17: 167, 2004.
5. Hohn RB, Janes JM: Lateral approach to the canine ilium, J Am Anim Hosp Assoc 2: 111, 1966.
6. Montavoin PM, Bouchieau RJ, Hohn RB: Ventrolateral approach for the repair of sacroiliac fracture-dislocation in the dog and cat. J Am Vet Med Assoc 186: 1198. 1985.
7. Vangundy TE, Hulse DA, Nelson JK, et al: Mechanical evaluation of two canine iliac fracture fixation systems. Vet Surg 17: 321, 1988.
8. Brown SG, Biggart JF: Plate fixation of ilial shaft fractures in the dog. J Am Vet Med Assoc 167: 472, 1975.

Introduction

One of the principles of joint fracture repair is that the weight bearing articular surface must be reconstructed so that it is as anatomically correct as possible. This reduces the injured joint’s risk of developing osteoarthritis. The acetabulum is one half of the coxo-femoral joint and its cranial 2/3’s are generally considered its primary weight bearing area. Optimal surgical repair should restore normal joint mechanics and gliding motion.

Surgical treatment of acetabular fractures involves four steps: exposure of the fracture site, reduction of the fracture, fracture stabilization and closure. Several different approaches and surgical techniques have proven effective to successfully complete these steps.

Surgical Technique

Acetabular fractures are approached either by a trochanteric osteotomy or the caudal approach. In most cases the author prefers the caudal approach. The caudal approach provides exposure of the acetabulum equal to a trochanteric osteotomy, does not require creation of a femoral fracture and is more quickly closed than a trochanteric osteotomy.

With both approaches, the superficial gluteal muscle is first isolated, incised at its insertion and reflected dorsally. If the surgeon is performing an osteotomy of the greater trochanter, it is started at the level of the third trochanter and extended dorsally to the junction of the greater trochanter and the femoral neck. The middle and deep gluteal muscles are reflected dorsally with the greater trochanter. The caudal portion of the deep gluteal and the gemellus muscles are elevated with a periosteal elevator from their origin over the dorsal rim of the acetabulum. This exposes the fracture site. The sciatic nerve is identified and protected. Following repair of the fracture, the greater trochanter is reattached to the proximal femur with the tension band technique (Figure 60-19). The remaining layers are closed routinely.
 

In the caudal approach, after the superficial gluteal muscle is incised and retracted dorsally, the external and internal obturator muscles and gemelli muscle, are incised at their insertion in the trochanteric fossa, tagged and retracted caudo-dorsally. Elevation of these muscles exposes the caudal acetabulum. The muscles can be used to protect the sciatic nerve. The caudal portion of the deep gluteal and gemellus muscles are elevated exposing the dorsal aspect of the acetabular rim. The caudal ilium is exposed by inserting a Hohmann retractor under the middle and the deep gluteal muscles and hooking its tip just cranial to the acetabulum on the ventral border of the ilium. Pushing the retractor’s handle ventrally displaces the middle and deep gluteal muscles distally. Maintaining the hip in an extended and internally rotated position provides maximal exposure to the acetabular rim (Figure 60-20). After the fracture is stabilized with a fixation device, the external and internal obturator and gemelli muscles are sutured to fascial tissue over the lateral surface of the trochanter near their original insertion point. The remaining tissues are closed routinely.
 

The acetabulum must be anatomically reduced if a successful outcome is to be achieved. The caudal bone segment is often displaced cranially and medially. The fragment can be moved to a caudal position by one of two methods. An intramedullary pin is driven ventral to dorsal through the ischium just cranial to the ischial rim while the hip joint is flexed. The pin should penetrate the skin dorsal and ventral to the ischium. Pin chucks are attached to the exposed ends the pin and used as handles to pull the fracture segment caudally (Figure 60-21). Limited rotation of the segment is provided with this method. Another method for providing caudal traction uses a large Kern bone holding clamp. An incision wide enough to allow insertion of the end of the clamp is made parallel with the ischial rim. Because the fixation teeth of the Kern clamp provide 4 points of fixation, this instrument can be used for both caudal retraction and rotation of the segment (Figure 60-22). If the fracture segments are collapsed medially, the Lahey retractor is helpful in repositioning the fragments laterally. A Lahey retractor, which is blunt, strong, and bent 90° at its end, is passed along the medial wall of the free segment. The retractor’s tip is maintained on the bone’s surface as it is passed along the medial wall to avoid compromising the sciatic nerve. Pulling laterally moves the fracture segments laterally (Figure 60-23).
 

Acetabular fracture reduction is maintained by manually holding the fragments in place until the permanent stabilization procedure is completed. Reduction of an acetabular surface can be evaluated visually through an incision in the joint capsule or an existing capsular tear by applying ventral traction on the greater trochanter. This will pull the femoral head out of the acetabulum enough so the articular surface of the acetabulum can be observed.

Non-plating surgical techniques for repair of acetabular fractures have not proven to be as effective as bone plates. They also have not consistently provided the clinical results obtained with bone plates. Two different sizes of C-shaped acetabular plates, mini fragment plates and standard Dynamic Compression Plates^® [Synthes (USA), Paoli, Pennsylvania] have been used successfully to stabilize acetabular fractures. Some surgeons use reconstruction plates for acetabular fractures because they can be bent easily in several different planes.

Bone plates must be anatomically contoured to the dorsal rim of the acetabulum. The bone fragments will shift in position as the screws are tightened if the plate is not properly contoured. The C-shaped acetabular plates are easily contoured to the acetabulum’s dorsal surface. Mini plates are also easy to bend because they are thin. However, this makes them relatively weak and limits the size of animal in which they can be used. The acetabulum’s dorsal surface is used for plate placement because adequate bone is present there and this is the tension surface of the bone. In all acetabular fractures at least two screws should be located on either side of the fracture line, and they should be angled so that they do not penetrate the articular cartilage surface (Figure 60-24).
 

One of the most difficult fractures to stabilize is one that has a component of the medial wall of the acetabulum fractured out. If a large section of this wall is involved, the femoral head will displace medially into the pelvic canal. If the fracture segment containing the medial wall extends far enough cranially, a lag screw and/or intramedullary pin fixation of the ilial segment are used to stabilize the fragment. If the fragment can not be stabilized, a slight over-bending of the plate closing the diameter of the articular surface, makes it more difficult for the femoral head to displace medially. If the femoral head cannot be prevented from displacing medially, a salvage procedure, excision arthroplasty, should be considered. For severe acetabular fractures where reconstruction is not possible excision arthroplasty may also be performed. This procedure is done only as a last resort as it sacrifices joint function but is intended to save limb function.

The weight bearing surface of the acetabulum, its cranial 2/3’s, must be reconstructed if its integrity is to be maintained. Repair of fractures in the caudal 1/3 of the acetabulum is controversial. Although unrepaired fractures in this area will result in coxofemoral osteoarthritis, it has not been definitively proven that repairing fractures in this area will improve the patients’ recovery. Although osteoarthritis may be present, limb function may be unaffected. Due to their small size, fractures of the caudal 1/3 of the acetabulum can be difficult to adequately stabilize. With a caudal fracture the sciatic nerve is at greater risk of injury during surgery then when the fracture is located more cranially.

When both a fracture of the ilium and the acetabulum are present, the author prefers to repair the ilial shaft first. Repair of the ilium is often done with a stronger fixation system than is used on the acetabulum because usually more screws and a longer and stronger plate can be applied to the ilium. The reconstruction of the ilium does not have to be as anatomically exact as reconstruction of the acetabulum. When the acetabulum is repaired last it will be fixed to a solidly stabilized ilial segment. Also, its fixation will not be subjected to additional loads that would be generated during manipulation of the ilial fragments if the ilium were fixed last.

Suggested Readings

1. Boudrieau, RJ, Kleine, LJ: Nonsurgically managed caudal acetabular fractures in dogs: 15 cases (1979-1984). J Am Vet Med Assoc 193:701, 1988.
2. Hulse, DL: Acetabular Fractures. In Fossum T, ed.: Small Animal Surgery, 2nd ed. St. Louis: Mosby, 2002, p 971.
3. Olmstead ML. Surgical repair of acetabular fractures. In Bojrab, MJ,ed: Current Techniques in Small Animal Surgery, 4th ed. Baltimore: Williams & Wilkins, 1990, p 1036.
4. Olmstead, ML: Fractures of the Bones of the Hind Limb. In Olmstead, ML, ed: Small Animal Orthopedics. St. Louis: Mosby, 1995, p 219.
5. Piermattei DL., Johnson, KA: An Atlas of Surgical Approaches of the Bones of the Dog and Cat. (4th ed). Philadelphia: W.B. Saunders, 2004, p. 290.
6. Slocum B, Hohn RB: A surgical approach to the caudal aspect of the acetabulum and body of the ischium in the dog. J Am Vet Med Assoc 65:167, 1975.
7. Tomlinson, JL: Fractures of the Pelvis. In Slatter, D, ed. Textbook of Small Animal Surgery, 3rd ed. Philadelphia: W. B. Saunders, 2003, p 1989.

Introduction

Coxofemoral luxation is a common injury suffered by both dogs and cats after various forms of trauma to the pelvis. The hip joint is the most commonly luxated joint in dogs and cats. In most coxofemoral luxations the femoral head is displaced cranial and dorsal to the acetabulum. In about 10% of hip luxations, the femoral head is displaced either ventrally or caudodorsally

The severity of tissue damage associated with hip luxations varies. In all luxations, the round ligament and part of the joint capsule are torn. In more severe cases, part of the gluteal musculature also may be torn. Small avulsion fractures of the femoral head where the round ligament attaches are common. Erosion of the cartilage of the femoral head sometimes results from the femoral head’s rubbing on the ilium, especially in more chronic cases. On rare occasions, portions of the dorsal rim of the acetabulum are fractured off.

Diagnosis of a coxofemoral luxation usually is simple. Most animals have a history of trauma such as having been hit by a car. The animal does not bear weight on the leg and stands with the adducted and externally rotated with a craniodorsal luxation. On physical examination, a greater than normal distance can be palpated between the greater trochanter of the femur and the tuber ischiadicum. The “thumb test” also is useful in diagnosing a craniodorsal luxation. To perform this test, the animal is placed in lateral recumbency with the affected leg up. The examiner stands behind the animal and places the thumb of the hand closest to the spine in the depression between the greater trochanter of the femur and the tuber ischiadicum while the other hand is grasping the stifle joint. The leg is then externally rotated. In a normal animal, the greater trochanter of the femur should pinch or displace the thumb from the depression between the greater trochanter of the femur and the tuber ischiadicum during rotation, whereas in an animal with a dislocated hip, the thumb is not pinched or displaced. A third way to evaluate a patient for a luxated hip is to extend the animal’s legs out caudally while the animal is in either dorsal or lateral recumbency. With a craniodorsal luxation, the affected limb appears shorter than the normal leg; with a ventral luxation, the leg appears longer. Radiographs are needed to confirm the diagnosis, because animals with fractures of the femoral head or neck present with clinical signs similar to those of animals with luxations. The radiographs should be evaluated for direction of luxation, avulsion fractures of the femoral head, other pelvic fractures, and hip dysplasia.

Surgical Options

Closed reduction with application of a non weight bearing sling is the method of choice for most acute luxations. An Ehmer sling is applied after closed reduction as described in Chapter 63. Failure rates for coxofemoral luxations treated by closed reduction have been reported to be as high as 50 to 70%.^1,2

Open reduction is indicated for acute luxations that will not remain reduced closed, irreducible acute luxations, chronic luxations, luxations associated with avulsion fractures of the femoral head, and luxations associated with other fractures (ipsilateral pelvis, femur, or tibia). Animals with moderate-to-severe degenerative changes of the hip are not candidates for open or closed reduction. Other methods of treatment should be used with such animals.

Numerous methods for open reduction of coxofemoral luxations have been devised including DeVita pinning, Yarbough pinning, use of Knowles toggle pin, joint capsule imbrication with trochanteric transposition, acetabular rim extension, transacetabular pinning, and retention suturing with joint capsule imbrication. The goal of open reduction of a coxofemoral luxation is to reestablish normal function and conformation of the hip. Once healing is complete, the anatomic shape of the hip joint and fibrosis of the joint capsule hold the hip in place.

Surgical Techniques

The techniques for performing joint capsule imbrication with transposition of the greater trochanter, toggle pinning, transacetabular pinning and retention suturing are described in this section.

Open reduction of coxofemoral luxations can be performed by one of two surgical approaches to the joint. Transacetabular pinning, toggle pinning and single retention suturing are best performed through a craniolateral approach,³ except in patients with chronic luxations. Double retention suturing, and joint capsule imbrication with transposition of the greater trochanter are performed through a dorsal approach by osteotomy of the greater trochanter of the femur.³ With acute craniodorsal luxations, the femoral head is easily identified during the approach. If the luxation is chronic, the femoral head is surrounded by a fibrous pseudojoint capsule. With acute craniodorsal luxations, the acetabulum is caudoventral to the femoral head and may be difficult to find, especially in chronic luxations. The acetabulum may have joint capsule, blood, or fibrin clots, remnants of the round ligament, avulsed pieces of the femoral head, and fibrous tissue (chronic luxations) within the joint. The joint must be cleaned out before the femoral head can be reduced into the acetabulum. The joint capsule should be preserved for later suturing. The femoral head can be retracted caudal to the acetabulum with a Hohmann retractor by hooking the tip of the retractor on the caudal edge of the acetabulum and prying caudally against the proximal metaphysis of the femur. Care must be taken not to entrap the sciatic nerve under the retractor.

Joint Capsule Imbrication with Transposition of the Greater Trochanter

Joint capsule imbrication with transposition of the greater trochanter of the femur is a useful method for treating patients with acute luxations, chronic luxations, and luxations with concurrent lesions such as acetabular fractures that require an approach to the hip by osteotomy of the greater trochanter of the femur.

The animal is placed in lateral recumbency with the affected hip up and is prepared for aseptic surgery. The luxated joint is exposed through a dorsal approach by osteotomy of the greater trochanter of the femur.³

Great care must be taken during this approach to preserve the joint capsule for later suturing.
After the femoral head has been identified and the acetabulum cleared of debris, the luxation is reduced. If adequate joint capsule is present on both sides of the joint, a simple interrupted or horizontal mattress pattern of 3-0 or 2-0 polypropylene or PDS is used to appose the joint capsule (Figure 60-25A). Placement of sterile towels on the medial side of the leg is beneficial to hold the leg in abduction during the imbrication to relieve the pressure on the joint capsule. If insufficient joint capsule is present on the acetabular side of the joint, the joint capsule can still be attached by using screws or tissue anchors (IMEX™ Veterinary, Inc. 1001 McKesson Drive, Longview, Texas 75604) to secure the suture on the acetabular side (Figure 60-25B). Once the joint capsule repair is completed, the greater trochanter is replaced in a position caudal and distal to its normal position (See Figure 60-25B). By positioning the greater trochanter caudal and distal to its normal location, the gluteal muscles try to abduct and internally rotate the femur thus making it more difficult for the femoral head to luxate. The greater trochanter is attached using a tension band device.
 

Toggle Pinning

Toggle pinning is an old technique for open reduction of coxofemoral luxations that is still useful today. One of the benefits of using this technique to repair coxofemoral luxations is that the dog can be allowed to walk on the leg after surgery.⁴ Having a leg that can bear weight is very important for dogs with multiple leg injuries. Recent advancements in the equipment that is available for performing toggle pinning has simplified the technique and made it something that is realistic to do in small animal practices. Toggle pins, surgical buttons, an aiming device, and a suture passer that simplifies the procedure are commercially available (IMEX™ Veterinary, Inc.1001 McKesson Drive, Longview, Texas 75604). A cranial lateral approach to the hip is performed.³ Some surgeons prefer to approach the hip through an approach that osteotomizes the greater trochanter of the femur to provide greater exposure of the joint. In most cases, the cranial lateral approach to the hip provides adequate exposure to perform the surgery with less morbidity for the dog. Once the femoral head and acetabulum are exposed, blood clots and remnants of the round ligament are removed from the acetabulum. Any joint capsule that remains needs to be preserved for suturing. A hole is drilled through the acetabular fossa from lateral to medial with a drill bit or pin slightly larger than the diameter of the toggle pin (Figure 60-26). The toggle pin with suture is passed through the hole so that the toggle pin anchors on the medial wall of the acetabulum (Figure 60-27). Using the aiming device, a hole is drilled through the femur from an area just below the greater trochanter of the femur up the femoral neck and exits at the fovea capitus (the area where the round ligament normally attaches to the femoral head) (Figure 60-28). An alternative to using the aiming devise is to externally rotate the femur until the fovea capitus of the femoral head is visualized. The hole is then drilled from the fovea capitus down the femoral head and neck so that it exits slightly below the greater trochanter. Two types of suture material are used for this procedure. The first is fiber wire (IMEX™ Veterinary, Inc. 1001 McKesson Drive, Longview, Texas 75604) which has a small diameter but is very strong. The second type of suture is the same heavy leader line suture material many veterinarian use for cruciate repair. The suture is passed through the tunnel from the femoral head to the lateral side of the femur (Figure 60-29). A suture passer facilitates passing the suture if fiber wire type of suture is being used. Heavy nylon suture will slide through the hole without need for the suture passer. The easiest method of anchoring the suture on the lateral side of the femur is with a surgical button. The suture is passed through the two holes in the surgical button. The femoral head is reduced into the acetabulum and the suture tied over the button (Figure 60-30). If possible, the joint capsule is sutured into apposition. Closure of the surgical site is routine. The animal is allowed to bear weight on the leg in a controlled manner after surgery.
 

Transacetabular Pinning

Transacetabular pinning is a practical and successful procedure for repair of coxofemoral luxations. The best results are obtained when this procedure is used for acute luxations in nondysplastic patients, although I have used this procedure successfully for chronic luxations. The only equipment needed is standard operating instruments, Jacob’s pin chuck, and intramedullary pins.

The animal is placed in lateral recumbency on the operating table with the affected leg suspended from an intravenous pole. The leg is scrubbed and draped for aseptic surgery. For acute luxations, the hip is exposed through a craniolateral approach.³ For chronic luxations, a dorsal approach to the hip by osteotomy of the greater trochanter of the femur³ may be needed. Once the femoral head is exposed and the acetabulum is cleaned of debris, the luxation is reduced temporarily. The hip is reluxated, and the femur is rotated externally until the fovea capitis of the femoral head is visible (Figure 60-31A).

An intramedullary pin, with a diameter that is two-thirds to threefourths that of the fovea capitis, is selected. The pin is advanced from the fovea capitis, down the femoral neck, and out the cortex of the third trochanter of the femur (Figure 60-31B and C). The pin is adjusted until the tip is flush with fovea capitis (Figure 60-31D). After the luxation is reduced, the femur is placed parallel to the table top and at a 90° angle to the spine. The pin is driven across the acetabulum while firm downward pressure is applied to the greater trochanter of the femur. If inadequate pressure is applied to the greater trochanter, the femoral head will back part way out of the acetabulum. The pin is driven approximately 1cm into the pelvic canal for the average-size dog. An assistant can palpate the pin rectally to determine whether it has been driven the correct distance. Care must be taken not to puncture the colon. Once the pin has been driven the correct distance, the end of the pin is bent over and cut off (Figure 60-32A, B, and C). Bending the pin over prevents it from migrating further into the pelvic canal.
 

Postoperatively, the hip is radiographed to check for proper pin placement and reduction of the luxation. The leg is placed in a non-weight bearing sling (Ehmer or Robinson), and the animal is discharged with instructions for limited exercise until the pin is removed. The pin should be removed in 14 to 21 days; the animal’s activity is restricted for 3 weeks after pin removal.

Complications associated with transacetabular pinning include pin migration and breakage and reluxation of the hip. Pin migration and breakage generally result from failure of the owner to keep a sling on the animal. The owner should be instructed to return the animal immediately if the sling comes off.

Retention Suturing

Retention suturing can be a valuable technique by itself when the joint capsule is missing or traumatized to such an extent that it will not effectively hold sutures. Retention suturing can be combined with other methods of repair also. Two methods for retention suturing have been described. The single-suture method⁵ is started by drilling a hole dorsal to ventral at the attachment of the rectus femoris to the ventral aspect of the ilium (Figure 60-33A). An alternative method of anchoring the suture in the ilium is with a tissue anchor. A second hole is drilled cranial to caudal through the greater trochanter of the femur (after the trochanter is reattached) at about the level of attachment of the deep gluteal tendon (Figure 60-33B). Heavy nonabsorbable suture material (No. 5 Ethibond or nylon leader line [Ethicon, Inc., Somerville, NJ]) is threaded through the holes, and the suture is tightened (Figure 60-33C). The suture should not be tightened to the extent that flexion and extension of the hip are restricted or that the leg is internally rotated. Over tightening of the suture will result in poor leg function and suture breakage.
 

In the double-suture method, two sutures are passed from the greater trochanter to the dorsal rim of the acetabulum.⁶ Two holes are drilled in the dorsal acetabular rim at the 11 and 1 o’clock positions (Figure 60-34A) and a third hole is drilled cranially to caudally through the greater trochanter of the femur (Figure 60-34B). After screws or tissue anchors are inserted into the holes in the acetabular rim, two strands of heavy nonabsorbable suture material are passed through the femoral tunnel. One strand is passed around the cranial acetabular screw or through the hole in the tissue anchor and the other around the caudal screw or hole in the tissue anchor. The sutures are then tightened (Figure 60-34C). Spiked washers (Synthes, Paoli, PA) may be needed to hold the sutures in place if screws are used. The greater trochanter is reattached with two Kirschner wires and a tension band wire.

With either retention suture technique, the animal is placed in a non weight bearing sling for 2 to 3 weeks postoperatively with exercise restriction. Once the sling is removed, the animal is slowly returned to normal exercise over the next month.
 

References

1. Bone DL, Walker M. Cantwell RD. Traumatic coxofemoral luxation in the dog. Vet Surg l3:263, 1984.
2. Dobbelaar MJ. Dislocation of the hip in dogs. J small Anim Pract 4:101, 1963.
3. Pierrnattei DL, Greeley RG. An atlas of surgical approaches to the bones of the dog and cat. Philadelphia: WB Saunders, 1979.
4. Beckham HP, Smith MM, Kern DA. J Am Vet Med Assoc 208(1):81-84, 1996
5. Slocum B, Devine T. Dislocation of the canine hip: treatment of the normal and dysplastic hip. Am Anim Hosp Proc 372, 1987.
6. Allen SW, Chambers JN. Extracapsular suture stabilization of canine coxofemoral luxation. Compend Contin Educ Pract Vet 8:457, 1986.

Figures 60-35 through 6-39 are algorithms for treatment of hip disorders.
 

Clinical Observations

“Boxy” Hips

The observation of gait is important to distinguish between functional abnormalities such as ataxia, and conformational abnormalities. “Boxy” hips are a change in shape of the rump from smooth and rounded to that of a rounded square (Figure 60-40), caused by a luxated hip.
 

Observation Procedure

The patient is observed from behind during walking. The examiner notes the width between the animal’s feet in the transverse plane. The normal patient places the foot beneath the hip joint, which is 7 to 10 cm apart on a dog the size of a Labrador retriever. This is called base normal. On the same dog with boxy hips, the feet will be 2 to 5 cm apart, which is called base narrow. Some patients walk base narrow, convert to base wide (feet are 12 to 15 cm apart), and oscillate between the two (Figure 60-41).
 

The second characteristic to notice is the contour of the rump from behind. The rump of the normal dog is smooth and rounded, sloping ventrally from the caudal vertebrae, as the contour is traced laterally. The dog with “boxy” hips has minimal or no slope from the caudal vertebrae as the contour of the rump is traced laterally, and then it is round (with a smaller radius of curvature) as the contour curves around the greater trochanter to continue along the lateral thigh. Occasionally, the trochanter intermittently protrudes, causing the shape to change between the two contours (Figure 60-42).
 

The difference between normal and “boxy” hips is the difference between a normally reduced femoral head and a luxated femoral head. In the luxated hip, the femoral head has translated laterally and dorsally. This projects the greater trochanter laterally and dor-sally and gives the contour of the rump the “boxy” appearance of a rounded square. The luxated hip is supported by the joint capsule, rather than by the acetabulum. Abduction is limited because the adductor muscles, especially the pectineus, are excessively lengthened by the amount of displacement of the femoral head when abduction occurs. This abduction of the luxated femoral head creates extra forces on the already stretched and inflamed joint capsule, which causes the patient pain. The dog limits the amount of this abduction by walking base narrow (See Figure 60-41).

The reduced or normal position of the hip in the acetabulum is nonpainful. Because the increased slope of the acetabulum in the dysplastic hip allows the femoral head to drift into the luxated position, the patient has two means of reducing the femoral head into the acetabulum. The combined muscle forces of the hip abductors and rotators can create sufficient pull to reduce the femoral head, but this force must be sustained to maintain reduction. These muscles are not created with the purpose of maintaining the reduced hip. As these muscles fatigue, the hip again luxates.

The second means of creating hip reduction is to abduct the hip, a maneuver that redirects the axial muscle forces of the femur into the acetabulum. This requires minimal abductor forces to hold the hip in the reduced position, but the foot is not under the femoral head. The patient must walk base wide to maintain reduction of the luxated hip (See Figure 60-41). This base wide effect has been observed in several circumstances. Some dogs shift from a base narrow gait to a base wide gait and back, as the discomfort of luxation dictates a base wide configuration for comfort. Some dogs shift to base wide to go up stairs. Some dogs hesitate slightly before jumping into a car or the bed of a pickup truck, to go base wide and relocate the hip before jumping.

The presence of “boxy” hips indicates that the hips are luxated and are in a severe and rapid stage of degeneration. If the dog is young, these hips may be saved and made functional by a pelvic osteotomy. Most frequently, dogs are presented beyond this stage.

“Bunny Hopping” Gait

The observation of gait is important in the determination of functional abnormalities such as ataxia and conformational abnormalities. “Bunny hopping” gait is a running gait in which the patient runs with both feet in adduction, simultaneously.

Observation Procedure

The patient is observed from behind during running. The examiner notes the width between the feet in the transverse plane. The normal patient places the foot beneath the hip joint, which is 7 to 10 cm apart on a dog the size of a Labrador retriever. On the same dog with a “bunny hopping” gait, the feet are 2 to 5 cm apart, and use of the hind limbs is simultaneous (Figure 60-43).
 

The difference between the normal running and “bunny hopping” gait is that, in the normal gait, the feet are apart by approximately the width of the hip joints, and one hind foot is used slightly before the other. In the “bunny hopping” gait, the feet are placed close together and are used together, with the back performing the greater part of extension. The difference between the hips in the normal and “bunny hopping” gait is the difference between a normally reduced femoral head and a luxated femoral head. The luxated hip is supported by the joint capsule rather than by the acetabulum and is therefore limited in its abduction. When the femoral head is laterally displaced, the adductor muscles are excessively lengthened. Abduction of the luxated fem oral head creates large forces on the already inflamed joint capsule. This causes the patient pain and a base narrow gait. The patient seems to be incapable of reducing the femoral head into the acetabulum by either abductor and rotator muscle forces or abduction of the hip. By using both limbs together, the forces are greatly reduced in each hip.

The presence of a “bunny hopping” gait indicates that the hips are luxated and are in a severe and rapid stage of degeneration. These hips are usually beyond reconstruction by means of a pelvic osteotomy unless the patient is young and the severe luxation is a recent occurrence.

“Clunking” Hips

The observation of gait is important in the determination of functional abnormalities. “Clunking” hips are a result of the hip relocating from the luxated position to the reduced position during ambulation.

Observation Procedure

The client often brings the “clunking” of the hips to the attention of the orthopedist. The patient is observed during walking. The examiner’s hand can be placed on the animal’s rump to feel the hip being reduced during ambulation. One can also hear the “clunk” of reduction (Figure 60-44). A positive observation of “clunking” hips is to experience the feel of the “clunk” and to hear the “clunking” sound.
 

The presence of a “clunk” in a hip means that the hip begins in a luxated position, and the femoral head falls into an acetabulum of some depth. The combined muscle force of the hip abductors and rotators can create sufficient pull to reduce the femoral head, but this force must be sustained to maintain reduction. Because these muscles are not created with the purpose of maintaining hip reduction, they soon fatigue, and the hip again luxates. The reduced or normal position of the hip in the acetabulum is nonpainful, but the increased slope of the acetabulum in the dysplastic hip allows the femoral head to drift into the luxated position.

The presence of a “clunking” hip, whether by direct observation or by client observation, clearly indicates an orthopedic emergency in which the patient should be placed under absolute rest conditions until the hips can be evaluated and treated. If the hips are “clunking,” then usually enough acetabulum is left to reseat the femoral head. A pelvic osteotomy will be successful if the acetabulum has not filled with osteophytes and the dorsal acetabular rim (DAR) still has sufficient integrity and depth to maintain the femoral head in the acetabulum after pelvic osteotomy.

The DAR is under immediate trauma by the femoral head because the femoral head just proximal to the ligament of the femoral head is incongruent with the acetabulum and is concentrating forces on the DAR and the adjacent joint capsule. If the DAR breaks down, then the “clunk” will cease. The femoral head remains permanently in the luxated position in the dorsal joint capsule. Acetabular filling follows breakdown of the DAR because it is secondary to the inflammation generated by the breakdown process at the DAR. The hip will stop “clunking” if the hip is neglected because acetabular filling occurs. The window of opportunity to correct this patient’s acetabular hip dysplasia by pelvic osteotomy is lost if dorsal acetabular breakdown or acetabular filling occurs. Under these circumstances, the attending veterinarian has lost the chance to reconstruct the patient’s hip.

The presence of “clunking” hips indicates that the hips are luxated and are in a severe and rapid stage of degeneration. If the dog is young, these hips may be saved and made functional by a pelvic osteotomy; however, immediate action must be taken to identify the source of damage accurately and to correct the incongruity.

Stand Test

The stand test creates extension of the hip and lordosis of the spine (Figure 60-45). This test is a functional exercise that stresses the spine (especially the L7-S1 with cauda equina impingement) and hip in extension. Because the interaction to perform this test is between the owner and the patient, resistance to the test is minimal, and the results are reliable. If the owner is unable to handle the patient, or if the patient intimidates the owner, then the test should be bypassed to avoid injury.
 

Testing Procedure

Clear and specific instructions to the owner are the basis of this test:

1. “Allow your dog to stand on all four legs and face you.”
2. “Pick up your dog by the front legs as if you are going to dance with him or her. All the way up.”

The patient and owner are observed from the side. Some patients (but few) refuse to stand facing the owner because they have been disciplined for jumping up on the owner.

The normal dog stands in this position without discomfort and enjoys the attention. The dog does not attempt to get down. The dog extends to be closer to the owner. The dog’s back and hips are extended and flat as the dog stretches to reach the owner’s face.

The abnormal dog stands in this position with discomfort and does not enjoy the test. The dog attempts to get down. The dog does not extend to be closer to the owner and shifts body weight to the side to return to the ground. The dog’s back and hips are maintained in flexion, and the dog attempts to disengage from this activity. The dog may even mock bite at the owner’s hand as the owner holds the dog’s forelimbs.

The stand test stresses the hips and spine of the patient by forced extension. Dogs with abnormal hips respond differently, depending on the degree of inflammation and fibrosis. Young dogs with stretched joint capsules that have little inflammation give the response of a normal dog. The young dog with highly inflamed joints and joint capsules adamantly resists the test. Older dogs with capsular fibrosis of chronic hip dysplasia simply cannot flex at the hips and stand with their rump sticking out.

Dogs with an abnormal spine also vary in their response, depending on the degree of inflammation. The patient with a highly inflamed spine from a disease such as discospondylitis fights this test violently. Dogs with cauda equina syndrome resist to a lesser degree. Patients with mild spondylosis do not fight the test, but they prefer to stand with their rump sticking out.

Even though the stand test is not pathognomonic for a disease, it consistently regionalizes the problem to the back or hip. It is an easy test to perform to demonstrate a problem in these regions.

Physical Examination in an Awake Patient

Abduction External Rotation Test

The physical examination is the primary means of demonstrating that a patient’s lameness or soreness is coming from the hip, lower lumbar spine, or lumbosacral disc. The abduction external rotation test is not specific to hip dysplasia, but it suggests dorsal joint capsule inflammation. Because this test creates discomfort in the hip, the owner should be forewarned of the patient’s possible pain response. Only enough external rotation to elicit a response is necessary. This should be the last test performed on the caudal portion of the dog if patient cooperation is expected.

Testing Procedure

The orthopedist is caudal to the patient while an animal health technician restrains the patient’s head. The right and left hips are tested independently. The examiner’s right hand holds the patient’s right stifle. The stifle is used to flex and externally rotate the right hip. The hip is abducted, externally rotated, and extended simultaneously. A negative response from the patient is indifference. A positive response from the patient varies, depending on the dog’s personality, from guarding the hip against manipulation, to vocalization, to attempting to bite the operator.

The abduction external rotation test stresses the attachment of the joint capsule at the DAR, to stimulate a pain response in the inflamed hip. The hip inflammation is caused by repeated tearing of the joint capsule as the femoral head translates laterally and dor-sally. The final dorsal migration of the femoral head creates the capsular tearing. After the repeated tearing of the capsule dorsally, the capsule thickens and attempts to heal by fibrosis. The normal joint capsule at the DAR is thin and almost transparent, but it is stout cranially and caudally.

A positive response from the patient indicates that inflammation is present. This test does not quantify the amount of inflammation. The acute tearing of the young patient is usually painful, because it is complete and creates a tremendous stretching on the cranial and caudal capsule. The tearing of the older patient’s joint capsule is usually not so extensive. The joint capsule with a more chronic disorder supports the femoral head by hypertrophy and fibrosis. This test is also positive if the lower lumbar spine or lumbosacral disc is inflamed by causing a torsion of the affected inflamed disc.

Hip Extension Test

This physical examination is a primary means of demonstrating that lameness is emanating from the hip or back. This test is not specific to the hip because it tests the dog’s response not only to the inflamed and thickened joint capsule, but also to the contracted iliopsoas and lower back inflammation. Because the hip extension test creates discomfort, the owner should be forewarned of the possibility of aggressive or painful behavior.

Testing Procedure

The orthopedist is caudal to the patient while an animal health technician restrains the patient’s head. The right and left hips are tested independently. For testing a small dog’s right hip, the operator places his or her fingers around the cranial thigh and the thumb on the dorsal ischial table. The patient’s hip is extended by pulling the examiner’s fingers to the thumb. For large dogs, the fingers of the right hand are placed around the cranial right thigh at the stifle, and the left hand is placed over the dog’s rump. The operator extends the dog’s hip by pulling the femur caudally, while the left hand prevents the dog moving away from the doctor. The left hip is similarly tested. A negative response from the patient is indifference. A positive response from the patient varies, depending on the dog’s personality, from guarding the hip against manipulation, to vocalization, to attempting to bite the operator.

The hip extension test tightens the joint capsule around the neck of the femur. This stretches an inflamed joint capsule like wringing a mop. The hip inflammation is present because of repeated tearing of the joint capsule as the femoral head translates laterally and dorsally. After the repeated tearing of the capsule dorsally, the inflamed capsule thickens and attempts to heal by fibrosis. A positive response from the patient indicates that hip joint capsule inflammation is present. This test does not quantify how much inflammation is present, only that it is present. This test may show discomfort of the lower lumbar spine or lumbosacral disc inflammation by extending the lower back.

The stand test creates similar conditions of hip extension and lordosis (back extension), but in the stand test, the patient extends only as far as comfort allows. Interpretation of the hip extension test and the stand test is similar.

Hip Subluxation Test

This physical examination is a primary means of demonstrating that a patient’s lameness or soreness is coming from the hip. This test is specific to the dysplastic hip because it tests the dog’s response to the inflamed dorsal joint capsule. The owner should be forewarned that the patient may create its own discomfort by contracting the muscles that force the femoral head against the irritated joint capsule. This should be the last test performed on the caudal portion of the dog, if patient cooperation is expected.

Testing Procedure

The orthopedist is on the side of the hip to be tested, while an animal health technician restrains the patient’s head. The right and left hips are tested independently. For the right hip, the fingers of the examiner’s right hand are placed medial to the proximal femur from cranially, and the right thumb is placed on the right ilium. For large dogs, it may be helpful to prevent the hip from abducting by placing the left hand on the lateral stifle. The examiner pulls laterally on the femur and pushes medially on the ilium with the thumb at the same time. A negative response from the patient is indifference. A positive response from the patient varies from guarding the hip against further manipulation, to vocalization, to attempting to bite, depending on the dog’s personality. The left hip is similarly tested.

The hip subluxation test stresses the attachment of the joint capsule at the DAR. As the hip subluxates laterally by the examiner’s lateral pressure on the proximal femur, the patient contracts the thigh muscles to protect the hip against the anticipated pain. This muscular contraction causes the hip to translate dorsally into the inflamed dorsal joint capsule. This causes a positive pain response. The hip inflammation is present because of repeated stretching of the joint capsule as the femoral head translates laterally. The dorsal migration of the femoral head after lateral translation creates the capsular tearing and high inflammation in the diseased hip.

The normal joint capsule at the DAR is thin and almost transparent, but it is stout cranially and caudally. After repeated stretching and tearing of the capsule dorsally, the capsule thickens and attempts to heal by fibrosis. A positive response from the patient indicates that inflammation is present. This test does not quantitate the amount of inflammation. The acute stretching in the young patient is usually painful because it creates a tremendous stretching on the cranial and caudal capsules. The acute tearing of the dorsal joint capsule resulting from dorsal translation in the young patient is usually painful because it lacks capsular support of the more chronic cases. The per incident tearing of the older patient joint capsule is usually not so extensive, and the joint capsule with a more chronic disorder has the support of hypertrophy and fibrosis cranially and caudally.

The hip subluxation test is useful in distinguishing between hip and back pain because it is specific to the hip and independent of the lower lumbar spine or lumbosacral disc inflammation.

Iliopsoas Testing

This physical examination is a primary means of demonstrating that lameness is emanating from the iliopsoas muscle. This test is specific to the iliopsoas because it tests the dog’s response to the inflamed iliopsoas muscle. Because iliopsoas testing creates discomfort, the owner should be forewarned of the possibility of aggressive or painful behavior.

Testing Procedure

The orthopedist is lateral to the patient while an animal health technician restrains the patient’s head. The right and left hips are tested independently. For testing a dog’s right iliopsoas muscle, the operator places his or her fingers around the patient’s cranial thigh and applies digital pressure over the iliopsoas just caudal to the origin of the pectineus muscle. The iliopsoas muscle is further tested by extending the hip and digital palpation. In addition, the iliopsoas muscle is tested further by extending the hip plus digital palpation of the muscle with internal rotation of the hip. The left hip is similarly tested. A negative response from the patient is indifference. A positive response from the patient varies, depending on the dog’s personality, from guarding the hip against manipulation, to vocalization, to attempting to bite the operator.

The direct digital palpation of the iliopsoas muscle causes pain in the inflamed muscle. Extension of the hip causes pain by stretching the inflamed muscle. The internal rotation of the hip also lengthens the inflamed iliopsoas muscle. The pain experienced by the patient is in direct proportion to the amount of inflammation, digital pressure, and stretching of the muscle. This test does not quantify the degree of inflammation. The digital test and internal rotation test are specific to the iliopsoas muscle.

Physical Examination in an Anesthetized Patient

Angles of Reduction and Subluxation

The meaning of hip palpation has been incompletely understood because of imprecise definition and measurement. The Ortolani sign occurs during hip abduction and is created when the femoral head is reduced into the acetabulum from a luxated position with a “shift” or “clunk.” The angle of reduction is the measurement of the angle of abduction from the sagittal plane to the physical position at which hip reduction occurs.

The Barlow sign is a palpation event during which the femoral head is luxated from the acetabulum. The Barlow sign occurs during hip adduction and is created when the femoral head is luxated from the acetabulum into a position of joint capsular support with a “shift.” The angle of subluxation is the angle between the sagittal plane and the physical event of hip luxation at which the hip first begins to luxate. By definition, the angle of subluxation is measured as positive if the hip is lateral to the sagittal plane when subluxation occurs (Figure 60-46) and negative if the hip is medial to the sagittal plane when subluxation occurs.
 

Techniques of Measurement

The patient is anesthetized and is placed in dorsal recumbency.

Angle of Reduction

The stifle is brought to the starting position of vertical, without hip flexion or extension, by using a medially directed force of the operator’s hand on the lateral stifle. Axial femoral compression by the operator is not necessary in the immature patient, although it may clarify the angle at which reduction occurs in a patient with a chronic case. The hip is then abducted slowly by reducing the medially directed force at the stifle. When hip reduction occurs, abduction is stopped. Reduction of the hip is detected in three possible ways: a “clunk” is heard; a shift of the patient’s limb is seen or palpated; or the event can be recorded by cineradiography. In chronic hip dysplasia, a “fast spot” or rapid abduction is palpated, instead of a “clunk,” as the hip reduces under the influence of abduction.

The angle of reduction is measured by the Canine Electronic Goniometer (Slocum Enterprises, Eugene, OR), which was designed for this purpose. The probe is placed just caudal to the attachment of the pectineus on the iliopectineal eminence. The side of the goniometer is touched to the medial side of the stifle (Figure 60-47 and 60-48). The angle of reduction is read directly from the digital readout with accuracy to 0.1° (Figure 60-49).
 

Angle of Subluxation

To obtain the angle of subluxation, the stifle is slowly returned to vertical from the abducted position at which the angle of reduction was taken. The hip is adducted slowly by increasing the medially directed force at the stifle. When the hip begins to luxate (subluxate), adduction is stopped. Here again, axial femoral compression by the operator is not necessary, but it may clarify the angle at which subluxation occurs in patients with a chronic disorder.

Luxation of the hip is detected in three ways: a “shift” is palpated; a “shift” is seen; or the event can be recorded by cineradiography. In cases of chronic hip dysplasia, a “fast spot” or rapid abduction is palpated, instead of a “shift,” as the hip luxates under the influence of adduction. The angle of subluxation is measured by the Canine Electronic Goniometer. The probe is placed just caudal to the attachment of the pectineus on the iliopectineal eminence. The side of the goniometer is touched to the medial side of the stifle (Figure 60-50), and the measurements are recorded. The measurements of the angles of reduction and subluxation are repeated on the other hip.
 

Two angles are measured for each hip, the angle of reduction and the angle of subluxation. The format for recording this information is (angle of reduction/the angle of subluxation), that is, AR/AS = 29.9°/14.5°. The angle of reduction is always greater than the angle of subluxation.

The angle of reduction represents joint laxity, that is, the stretching of the joint capsule and its tearing from the DAR. The greater the angle of reduction, the greater is the stretching of the joint capsule dorsally. The stretching of the joint capsule dorsally determines where the DAR will contact the femoral head. The physical contact point between the rim and the femoral head determines the amount of abduction necessary before the axial force of the femur (the direction not the magnitude) is directed medial to that contact point. The femoral head falls into the acetabulum when that condition exists (Figure 60-51). For this reason, abduction is necessary to create hip reduction.
 

When the stretching of the joint capsule is small, the contact point is almost dorsal on the femoral head when the limb is in the sagittal plane. As the joint capsule stretches, the femoral head is allowed to translate laterally and then dorsally, and the point of contact between the DAR and the head moves further medially on the femoral head. The lateral and dorsal translation of the femoral head is limited by the ligament of the femoral head. This causes the contact point of the DAR and the femoral head to be just dorsal to the fovea capitis. This is the outer limit of capsular stretching without damage to the teres ligament. When the femoral head rests in this position, all the forces transmitted to the DAR from the femoral head have to do so through a reduced area of contact. This extreme force per unit area of contact between the femoral head and the DAR damages the cartilage of the femoral head just above the fovea capitis. This damage begins with fibrillation of the cartilage and ends with bone rubbing on bone and distortion of both the femoral head and acetabulum as end-stage events. The angle of reduction increases further only with stretching of the teres ligament or breakdown of the dorsal acetabulum. The angle of reduction decreases with capsular fibrosis and osteophyte production on the DAR that initiates capsular stabilization by resisting further dorsal translation.

The angle of subluxation represents the functional slope of the acetabulum beneath the dorsal rim. The actual slope of the DAR may be less than the angle of subluxation, if the ligament of the femoral head is redundant or the acetabulum is filling with osteophytes. For subluxation of the hip to occur, the femoral head and the acetabulum must interact, but not the joint capsule (Figure 60-52). The direction of the axial femoral force is into the acetabulum following the measurement of the angle of reduction. As the hip is adducted, the axial femoral force becomes normal to the DAR slope that was the last position of stability. Any further adduction of the hip directs the axial femoral force lateral to the perpendicular of the DAR surface, and so the femoral head translates laterally to rest in the joint capsule. In the normal hip, no significant joint capsule laxity exists to allow enough lateral translation of the femoral head for subluxation. All hips have some laxity, as clearly established by Penn-Hip. PennHip is a commercial registry which reads distraction and compression hip radiographs for hip laxity. The laxity is normalized to the femoral head and expressed as the Compression Index, C.I. (C.I. = displacement of the femoral head divided by the radius of the femoral head.) C.I. < 0.30 is normal for most breeds.
 

As some normal puppies undergo rapid growth between 4 and 6 months of age, the adductor muscle mass (and moment) overpowers the abductor muscles because of the temporary lack of adductor muscle length. As a consequence, the relative hip adduction directs the axial femoral force lateral to the DAR, and the femoral head is contained in its lateral translation by the joint capsule. The joint capsule is stretched, producing joint laxity. The result is an increased angle of reduction and distractive index of PennHip. In such patients, the angle of reduction is high because of the lax joint capsule, but the DAR angle is normal. The angle of subluxation may be 0° or negative because the DAR slope is normal. Such laxity is not hip dysplasia, because the conformation of the hip is normal and the stretched capsule is temporary, whereas hip laxity, caused by capsular stretching that accompanies acetabular hip dysplasia, is secondary to an increased slope of the DAR (the cause of stretching) and remain until the slope of the DAR is normalized by a pelvic osteotomy. This example of rapid growth syndrome in puppies with lax capsules that allow hip luxation confirms our clinical experience that hip joints can be lax without being pathologic. In addition, these puppies have become certified by OFA as normal when trauma to the hip is prevented by conservative management during 5 to 12 months of age. The angle of subluxation may even be a negative number in the nonpathologic hip or after a pelvic osteotomy.

In the pathologic hip, the angle of reduction is easily palpated in the young patient (6 months), but it may be difficult to palpate in the older patient (often by 2 years). The angle of reduction usually increases until the patient reaches the limit of stretching of the teres ligament and the joint capsule. Once the femoral head rests in the luxated position, the acetabulum fills with osteophytes, even though the femoral head may occasionally reduce. The joint capsule becomes fibrotic and thickened. As this dysplastic process progresses, the angle of reduction begins to decrease and finally becomes difficult to palpate.

In the pathologic hip, the angle of subluxation is greater than 0° and slowly increases, but it never decreases. This increasing angle is caused by the increased DAR slope because of acetabular filling and teres ligament redundancy. As the angle of reduction decreases and the angle of subluxation increases, one sees a single angle at which the femoral head shifts between capsular support and acetabular support. This is called the angle of translation (Figure 60-53).
 

Simply stated, a great difference between the angle of reduction and the angle of subluxation (i.e., 40/5) indicates a healthy hip with a stretched joint capsule, or a young dog’s hip in the early stages of hip dysplasia that can be readily repaired with good results and no arthritis. A moderate difference between the angle of reduction and the angle of subluxation (i.e., 30/15) indicates a hip in immediate need of a pelvic osteotomy, but the status of the articular cartilage and acetabular filling needs to be assessed. A small difference between the angle of reduction and the angle of subluxation (i.e., 25/22) indicates a hip that is filling with osteophytes and is no longer a candidate for a pelvic osteotomy. A small difference between the angle of reduction and the angle of subluxation in the near-0° range (i.e., 10/0) indicates a normal hip with some capsular stretching with no need for surgical intervention.

The angle of reduction and the angle of subluxation are critical parts of the hip evaluation and are excellent indicators of status of hip health, especially at 6 months of age. Hip palpation at the time of neutering is a perfect opportunity to assess the patient for future hip problems, because it gives the owners information about whether their pet is at risk for hip dysplasia.

Ortolani Sign

The Ortolani sign is a palpation finding which was originally used in human medicine as an indicator of hip dysplasia. This sign occurs when the luxated hip enters the acetabulum with a “clunk.”

Testing Procedure

The anesthetized patient is placed in dorsal recumbency. The palm of the operator’s left hand is lightly placed on the lateral side of the patient’s flexed right stifle. The left thumb is placed over the medial femoral condyle adjacent to the patella. The starting position is hip adduction without flexion or extension. In this position, the hip luxates from the acetabulum. The hip is slowly abducted.

If a “shift” or “clunk” in the hip is palpated, then the Ortolani sign is positive. If no “shift” or “clunk” in the hip is palpated, then the Ortolani sign is negative. The process is also repeated for the left hip by using the operator’s right hand on the patient’s left stifle.

The “shift” or “clunk” palpated in the hip is the reduction of the femoral head. Reduction of the femoral head into the acetabulum can only occur if the joint capsule has been stretched. A positive Ortolani sign means that the joint capsule is stretched. A negative Ortolani sign means either that the joint capsule is not stretched or that the hip is not reducible into the acetabulum. Chronic fibrosis of the joint capsule often makes the transition from luxation to reduction so subtle as to go undetected.

The Ortolani sign does not represent hip dysplasia, but it indicates joint capsule stretching, which often accompanies hip dysplasia. Joint laxity is not hip dysplasia, but it is one secondary manifestation of the hip dysplastic process. Joint laxity occurs when the joint capsule is stretched. Joint capsule stretching has many causes, the most common being hip dysplasia.

To reduce the hip, the femoral head must enter the acetabulum. The angle of abduction at which the head begins to enter the acetabulum during hip abduction is the angle of reduction. This angle is the angle at which the femoral head becomes stable and relocates because of the axial compressive force direction. The angle of reduction depends on the amount of stretching of the joint capsule.

Barlow Sign

The Barlow sign is a palpation finding originally used in human medicine as an indicator of hip dysplasia. This sign occurs when the reduced hip leaves the acetabulum.

Testing Procedure

The anesthetized patient is placed in dorsal recumbency. The palm of the operator’s left hand is placed lightly on the lateral side of the patient’s flexed right stifle. The left thumb is placed over the medial femoral condyle adjacent to the patella. The starting position is hip abduction without flexion or extension. This position reduces the hip into the acetabulum. The hip is slowly adducted.

If a “shift” of the femoral head is palpated, then the Barlow sign is positive. If no “shift” of the femoral head is palpated, then the Barlow sign is negative. The process is also repeated for the left hip by using the operator’s right hand on the patient’s left stifle.

The “shift” palpated with the Barlow sign is luxation of the femoral head. Luxation of the femoral head from the acetabulum can only occur if the joint capsule has been stretched. A positive Barlow sign means that the joint capsule is stretched. A negative Barlow sign means either the joint capsule is not stretched or the hip will not reduce into the acetabulum. If the hip has chronic disease with a thickened joint capsule, the shift may be so subtle that it is missed by the operator.

The Barlow sign does not represent hip dysplasia, but it indicates joint capsule stretching, which often accompanies hip dysplasia. Joint laxity is not hip dysplasia, but it is a secondary manifestation of the hip dysplastic process. Joint laxity occurs when the joint capsule is stretched. Joint capsule stretching has many causes, and the most common cause of joint laxity is hip dysplasia.

To luxate the hip, the femoral head must leave the acetabulum. The angle of adduction at which the head begins to leave the acetabulum during hip adduction is the angle of subluxation. This angle is the angle at which the femoral head becomes unstable because of the axial compressive force direction and luxates. The angle of subluxation depends on the functional slope of the DAR.

Bardens Palpation

Bardens recognized laxity in the hip joints of 8-week-old puppies and discovered that those puppies were dysplastic as adults. Later, Brown studied the laxity of hips in rottweiler puppies by the Bardens method and confirmed that laxity and hip dysplasia were associated. Recently, laxity testing has been addressed by radiography and statistical analysis and has been shown to be present in hip dysplasia.

Bardens Palpation

The anesthetized 6- to 8-week-old puppy is placed in right lateral recumbency for testing of the left (up) hip (Figure 60-54). The operator’s right hand is the measuring hand and the left hand is the testing hand. The thumb of the operator’s right hand is placed on the left lateral prominence of the patient’s tuber ischiadi-cum. The middle finger of the operator’s right hand is placed on the left wing of the ilium. The index finger of the operator’s left hand is placed on the left greater trochanter. The patient’s left femur is grasped just below the greater trochanter by the left hand of the operator. A medial to lateral force is exerted on the proximal femur by the left hand that translates the greater trochanter laterally. This translation is recorded and measured.
 

For testing of the right hip, the operator’s left hand is the measuring hand and the right hand is the testing hand. The experienced operator can distinguish among four groups of lateral hip translation: 1 to 2 mm; 3 to 4 mm; 5 to 6 mm; and greater than 6 mm:

Normal hip: 1 to 2 mm
Borderline hip: 3 to 4 mm
Dysplastic hip: 5 to 6 mm
Severely dysplastic hip: more than 6 mm

Although the Bardens palpation has never been well accepted as a definitive index of hip dysplasia, it is useful as a general indicator of hip dysplasia. The Bardens palpation has four main objectives. First, the method requires a skilled operator who can detect and measure the lateral laxity accurately. This makes the test difficult to generalize to all veterinarians. Second, the patient must be between 6 and 8 weeks of age to achieve uniformity in the population and the dysplastic process. Third, the scientific correlation of confirmation between the Bardens palpation and degree of hip dysplasia in the mature patient has not been clearly established. Fourth, hip laxity is not hip dysplasia but rather one measurable aspect of hip dysplasia and is dependent on joint capsule stretching. As we develop better means of measuring the lateral translation with accuracy and repeatability, this test may become the basis for future decisions about hip dysplasia.

Axial Compression Test of the Hip

The axial compression test is an intraoperative test for hip stability. Hip stability is achieved when the reduced hip remains in the acetabulum on axial compression of the femur in the sagittal plane.

Testing Procedure

To test the left hip, the patient is placed in right lateral recumbency. The examiner’s right hand is placed on the dorsal rump of the patient. The left hand gently grasps the stifle and applies axial compression of the femur in the sagittal plane to the reduced hip (Figure 60-55).
 

If a “shift” of the femoral head is palpated as the hip luxates from the acetabulum, then the axial compression test is positive and the hip is unstable. If no “shift” of the femoral head is palpated, then the axial compression test is negative and the hip is stable. When the test is applied to the right hip, the operator’s right hand is on the patient’s stifle, and the left hand is on the rump.

The palpated “shift” is luxation of the femoral head. Luxation of the femoral head from the acetabulum can only occur if the slope of the DAR is too great to contain the head, if acetabular filling is present, or if the femoral head has a redundant ligament. No “shift” means that the DAR is able to contain the femoral head. Surgically, it means the axial rotation of the acetabular segment by pelvic osteotomy is sufficient. A hip joint is either stable or unstable to axial compression in the sagittal plane. If a hip is stable in the sagittal plane, additional rotation of the acetabular segment by pelvic osteotomy will only limit abduction of the hip and cause hip degeneration.

Suggested Readings

Bardens JW. Palpation for the detection of joint laxity. In: Proceedings of the Canine Hip Dysplasia Symposium and Workshop. St. Louis: Orthopedic Foundation for Animals, 1972:105-109.

Bardens JW, Hardwick H. New observations in the diagnosis and cause of hip dysplasia. Vet Med Small Anim Clin 1968:63:238.

Belkoff SM, Padgett G, Soutas-Little RW. Development of a device to measure canine coxofemoral joint laxity. VCOT 1989;1:31-36.

Slocum B, AVORE. Pelvic osteotomy: the results of 285 pelvic osteotomies (abstract). Vet Surg 1986; 15:134.

Slocum B, Devine T. Pelvic osteotomy in the dog as treatment for hip dysplasia. Semin Vet Med Surg 1987;2:107.

Slocum B, Devine T. Femoral neck lengthening for hip dysplasia in the dog. Vet Surg 1989; 18:81.

Slocum B, Devine T. Pelvic osteotomy. In: Whittock W, ed. Canine orthopedics. 2nd ed. Philadelphia: Lea & Febiger, 1990:471.

Slocum B, Devine T. Pelvic osteotomy for axial rotation of the acetabular segment. Vet Clin North Am 1992,22:645.

Slocum B, Slocum TD. Slope of the dorsal acetabular rim for hip evaluation in the dog. In: 17th annual conference of the Veterinary Orthopedic Society. Jackson Hole, WY: Veterinary Orthopedic Society, 1990:12.

Smith G, Biery D, Gregor T. New concepts of coxofemoral joint stability and the development of a clinical stress-radiographic method for quantitiating hip joint laxity in the dog. J Am Vet Med Assoc 1990;196:59-70.

Wright PJ, Masson TA. The usefulness of palpation of joint laxity in puppies as a predictor of hip dysplasia in a guide dog breeding programme. J Small Anim Pract 1977; 18:513.
 

Evaluation of the canine hip for hip dysplasia involves gathering information on the history and attitude of the dog from the owner, performing a series of hip function assessment tests on the awake and anesthetized dog, and obtaining a three-dimensional view of the hip joint by radiographs. Examination of the dog for hip dysplasia is an important service to predict the physical ability of the young dog (6 months of age and older) to meet the owners’ expectations for function and to provide the appropriate treatment for a dysplas-tic dog. Although hip dysplasia is defined by many authors as a congenital, bilateral, degenerative joint disease, or as hip laxity, limitations of these definitions are recognized clinically as we expand our knowledge of the disease and separate acetabular hip dysplasia from femoral hip dysplasia. The most important aspect of any definition is to acknowledge that hip dysplasia is a dynamic process, and any view of the disease is a window at one point in its progression.

Most cases of dysplasia involve acetabular hip dysplasia, which is characterized by excessive slope of the dorsal rim of the acetabulum, and its secondary osteo-arthritic changes. Because the major forces of the hip run parallel to the long axis of the femur, the contact between the femoral head and the acetabulum should be perpendicular to the axial femoral forces for a stable hip joint. In the young puppy, the femoral head presses into the pliable acetabulum to form a deep socket. After 4 months, the formation of the acetabulum is becoming complete. If the acetabulum is shallow because of insufficient magnitude or direction of forces pushing the femoral head into the developing acetabulum, the joint capsule becomes stretched or, worse, the cartilaginous labrum becomes fractured. With insufficient dorsal support to the femoral head, muscular forces must be relied on to stabilize the joint by forcing the head into the acetabulum. As the muscles become fatigued, the joint capsule becomes stretched, and the dorsal rim becomes damaged. The femoral head resides in an incongruent subluxated position. As the restraints to subluxation, the joint capsule and teres ligament, stretch and tear, the vicious cycle of osteoarthritis becomes evident. When the hip cannot be maintained in the acetabulum, yet is within the joint capsule, the hip is considered luxated. When the acetabulum fills with osteophytes and the femoral head cannot be congruent with the acetabulum, the hip has irreducible luxating hip dysplasia. A dislocated hip occurs when the hip is outside the traumatically torn joint capsule. As the stages of acetabular dysplasia progress, the treatment and prognosis for the hip must also match the degenerative process. Physical and radiographic information must be combined to provide the best evaluation of the canine hip.

The hip is a three degree of freedom joint, which means that it allows rotation about three orthogonal axes but no translation along those axes. Normal movements are flexion-extension, internal rotation-external rotation, and adduction-abduction. The dog is examined at a walk, trot, and run. Leg alignment, stride length, and movement in the sagittal plane are all noted. With the dog standing, the hip is slowly flexed and extended. A thickened and inflamed joint capsule causes the patient discomfort, and extension is resisted. Similarly, dysplastic patients usually refuse to stand erect with the hip in an extended position. The leg is abducted and externally rotated. Any apprehension indicates irritation to the inflamed tissue between the femoral neck and the dorsal rim of the acetabulum. Inability to abduct the leg indicates a contracted pectineus muscle. With the patient under anesthesia, the hip is palpated to reveal the viability of the cartilage of the femoral head and the acetabulum. With the dog in dorsal recumbency, the angle of reduction (the angle from vertical when reduction occurs during abduction) is measured; this angle is an indicator of joint capsule laxity. The greater the angle of reduction, the greater is the stretching or tearing from the dorsal acetabular rim (DAR) that has occurred to the joint capsule. The angle of subluxation (the angle from vertical when the luxation occurs during adduction) is measured. This angle increases proportionally to the damage to the dorsal rim of the acetabulum and acetabular filling. The trochanteric compression test reveals the preferred position of the femoral head with respect to the acetabulum; normally, it is within the acetabulum. A normal dog shows no apprehension or pain during the physical examination and enjoys the attention. Under anesthesia, a dog with normal hips demonstrates no angle of reduction or subluxation and has a negative trochanteric compression test.

Clinically, our radiographic examination uses six radiographic views: ventrodorsal, lateral, DAR, frog, compressed ventrodorsal, and distracted ventrodorsal views. The ventrodorsal, lateral, and DAR views are orthogonal and therefore give a “threedimensional” study of the hip (Figure 60-56A and B). Because positioning is essential in evaluating these radiographs, the dog is anesthetized for this portion of the examination. In the normal hip, the ventrodorsal view shows the femoral head to be deeply seated under the acetabulum with at least 50% coverage by the dorsal rim. Congruence exists between the subchondral bone of femoral head and the cranial acetabulum. Any torsion of the femur or anteversion of the femoral head is readily recognized with this view. The ventrodorsal view is useful for determining pelvic torsion, which often mimics unilateral hip dysplasia and is usually associated with a transitional vertebra. In the sublux-ated hip, the femoral head is partially covered by the dorsal rim of the acetabulum. One sees incomplete congruence of the joint and cupping of the acetabulum. In the luxated hip, the femoral head resides outside the acetabulum, and there is no congruence of the hip joint. As the disease process worsens, one can see a thickening of the neck of the femur and, occasionally, dorsal acetabular osteophytes forming.
 

The frog view is useful to determine acetabular filling with osteophytes (Figure 60-57). The examiner must not lever the femoral head out of the acetabulum by abduction beyond 45°. The normal hip joint rests easily in the socket, whereas in the dysplastic hip, the femoral head is unable to seat fully in the acetabulum. This is indicative of filling of the acetabulum with osteophytes or a redundant teres ligament. As the dysplastic process progresses, the frog view demonstrates this condition.
 

The lateral radiograph of the pelvis and lower lumbar spine is useful for differentiating hip dysplasia from spondylitic bridging at L7-S1, which is often associated with the painful cauda equina syndrome. A normal hip shows congruence and concentricity of the femoral head within the acetabulum. In the dysplastic hip, the concentricity of the femoral head becomes less visible, and rather than a “white-black-white” description of normal congruence, a “white-gray-gray” description is common. Dorsal acetabular osteophytes are often seen as a white line over the femoral head.

Perhaps the most informative radiographic view is the DAR view. The dog is placed in a sternal recumbency with the hind legs pulled cranially to rest along the side of the thorax. A circumferential belt holds the stifles against the torso. Four-inch elevation of the hocks provides hamstring tension that causes enough rotation on most dogs to allow the x-ray beam to pass through the longitudinal axis of the pelvis. This view enables us to see the weightbearing portion of the acetabulum in cross section. In normal dogs, the DAR view shows the dorsal rim of the acetabulum to be sharply pointed. The femoral head is well seated and is covered by the acetabulum. When measured, the DAR angle is 7.5° or less, from a line perpendicular to the long axis of the pelvis. Normal hips have a combined left and right DAR measurement of 15° or less. Congruence of the hip joint is apparent with this view. A dog with normal hips continues to have a normal DAR angle throughout its lifetime.

As the hip is damaged by dysplasia, sclerosis of the rim can be seen on the DAR radiograph. The shape of the rim progresses from slightly rounded to blunted and broken off. Concurrently, the slope of the rim becomes increased. The dorsal acetabular osteophytes, so difficult to visualize on the ventrodorsal radiograph, are obvious with the DAR view. The femoral head moves dorsally and laterally, and filling of the acetabulum occurs. As the process of dysplasia progresses, the osteoarthritic changes can be seen clearly with this view. Lack of congruity and loss of cartilage are easily noted. When measured on the DAR view, dogs with hip dysplasia have a combined DAR slope of 20° or more. The slope continues to increase as the dysplastic changes occur.

The importance of the DAR view is that it corresponds to hip palpation under anesthesia and provides the information necessary to determine the treatment of choice for the individual dog. As stress is placed on the DAR with the early stages of dysplasia, the rim shows slight rounding. On palpation, the hip makes a smooth transition from the subluxated position into the acetabulum, indicating integrity of articular cartilage of the head and acetabulum and minimal stretching of the joint capsule. As frequent intermittent subluxation occurs, palpation reveals smooth cartilage and a stretched joint capsule, noted by a “clunk” as the hip moves from subluxation to reduction. The acutely luxating femoral head causes a bevel to the rim, characteristic of a torn joint capsule and a worn labrum. With palpation, this correlates to a fine granular crepitus of articular cartilage fibrillation and abrupt dorsal translation of the femoral head. In chronic conditions, no distinct transition between reduction and subluxation is palpated because of acetabular filling and capsular fibrosis. The DAR radiograph measurement provides the amount of pelvic rotation for a triple pelvic osteotomy in patients that still have cartilage on the femoral head. This measurement is the amount of rotation necessary for support of the femoral head by the acetabulum. If the DAR measurement shows a 20° slope, then a 20° Canine Pelvic Osteotomy Plate (Slocum Enterprises, Eugene, OR) is necessary for corrective surgery. Postsurgically, a tomogram of the DAR allows visualization of the amount of rotation performed with pelvic osteotomy. Overrotation can be prevented as a result of this radiographic technique.

Femoral dysplasia on physical examination has the same characteristics as acetabular dysplasia; however, it is most easily differentiated radiographically, and with palpation under anesthesia. The ventrodorsal radiograph shows a shortened femoral neck and a lack of coverage and congruity in the hip joint. In the early stages of femoral dysplasia, the hip may have an angle of reduction of less than 10° and an angle of subluxation of less than 0° on palpation. The lateral radiograph shows femoral head anteversion. The DAR view may appear normal if damage to the rim has not yet occurred. As the hip degenerates because of lack of support from the acetabulum, the dorsal rim becomes blunted. As a result, we then observe radiographically the same characteristics as acetabular dysplasia. Correct diagnosis of early femoral dysplasia is critical to the success of surgical treatment. If medially directed muscle force is insufficient to hold the hip in the acetabulum, an excessive amount of pelvic rotation will correct the situation but will lead to femoral neck impingement and reduced abduction. Femoral neck lengthening is the surgical treatment of choice. As the disease process continues, both femoral neck lengthening and pelvic osteotomy are necessary to obtain return of normal function. When both operations are necessary, a much lower rotation of the pelvis is adequate for correct coverage of the femoral head with acetabular stability.

Radiographic views taken using compression (Figure 60-58) and distraction (Figure 60-59) provide information on hip laxity. Bardens¹ first proposed a wedge technique to demonstrate radiographic joint laxity in the early 1960s, along with palpation. Radiographic techniques were further defined by Belkoff and associates in 1989² , using a distraction device. Although this device allows passive laxity to be seen radiographi-cally, this has been used by Stoll³ as a measure of the amount of femoral neck lengthening necessary when the dorsal acetabular slope has been reduced to 0°. Because passive capsular laxity is present in both dysplastic and nondysplastic hips, it should be considered a secondary indicator of hip dysplasia (Figures 60-60 and 60-61). The distraction displacement index is an indicator of passive joint laxity. Smith and colleagues⁴ determined that a distraction index of 0.30 is the dividing line between normal hips and hips predisposed to hip dysplasia. Some dysplastic hips, however, have a distraction index less than 0.30, and some hips with a distraction index greater than 0.30 fail to show other dysplastic characteristics. The compression displacement index is an indicator of acetabular filling. In the clinical situation, laxity of the joint capsule is palpated and measured as the angle of reduction. The angle of subluxation is a measure of the functional slope of the dorsal acetabulum because it is the result of interaction between the acetabulum and the femoral head.
 

In summary, correct evaluation of the hip joint is essential to understand the progression of hip dysplasia and to recognize the choice points of intervention. Physical and radiographic examination of dogs 6 months of age and older can provide accurate assessment of the hips. The patient can be treated appropriately to provide for the enjoyment and functioning of the dog for the rest of its lifetime.

References

1. Bardens J. Joint laxity as hip dysplasia. In: Canine Hip Dysplasia Symposium. St. Louis: , 1972:71.
2. Belkoff SM, Padgett G, Soutas-Little RW. Development of a device to measure canine coxofemoral joint laxity. Vet Compar Orthop Traumatol 1989;1:31-36.
3. Stoll S. Femoral neck lengthening using distraction measurements. In: American College of Veterinary Surgeons Surgical Forum.: American College of Veterinary Surgeons, 1996.
4. Smith G, Biery D, Gregor T. New concepts of coxofemoral joint stability and the development of a clinical stress-radiographic method for quantitating hip joint laxity in the dog. J Am Vet Med Assoc 1990,196:59-70.

Suggested Readings

Corley EA. Hip dysplasia: a report from the Orthopedic Foundation for Animals. Semin Vet Med Surg 1987;2:141.

Henry J, Park R. Wedge technique for demonstration of coxofemoral joint laxity in the canine. In: Canine Hip Dysplasia Symposium. St. Louis: Arthur Freeman, 1972:117.

Laming F. Canine hip dysplasia and other orthopedic problems. Loveland, CO: Alpine Publications, 1981.

Morgan JP, Stephens M. Radiographic diagnosis and control of canine hip dysplasia. Davis, CA: Venture Press, 1985.

Pappas AM. Congenital hip dysplasia. In: Tronzo R, ed. Surgery of the hip joint. Philadelphia: Lea & Febiger, 1973.

Rendano V, Ryan G. Canine hip dysplasia evaluation: a positioning and labeling guide for radiographs to be submitted to the Orthopedic Foundation for Animals. Vet Radiol 1985:26:170.

Rettenmaier J, Constantinescu G. Canine hip dysplasia. Compend Contin Educ Pract Vet 1991;13:643.

Riser WH. The dog as model for the study of hip dysplasia. Vet Pathol 1975:12:229.

Riser WH, Shirer JF. Hip dysplasia: coxofemoral abnormalities in neonatal German shepherd dogs. J Small Anim Pract 1966:7:7.

Riser WH, Rhodes WH, Newton CD. Hip dysplasia. In: Newton CD, Nunamaker DM, eds. Textbook of small animal orthopedics. Philadelphia: JB Lippincott, 1985.

Sage FP. Campbell’s operative orthopedics 4th ed. St. Louis: CV Mosby, 1963:1708-1709.

Slocum B, AVORE. Pelvic osteotomy: the results of 285 pelvic osteotomies (abstract). Vet Surg 1986,15:134.

Slocum B, Devine TM. Dorsal acetabular rim radiographic view for evaluation of the canine hip. J Am Anim Hosp Assoc 1990:26:289-296.

Slocum B, Devine T. Pelvic osteotomy in the dog as treatment for hip dysplasia. Semin Vet Med Surg 1987:2:107.

Slocum B, Devine T. Femoral neck lengthening for hip dysplasia in the dog. Vet Surg 1989; 18:81.

Slocum B, Devine T. Pelvic osteotomy. In: Whittick W, ed. Canine orthopedics. 2nd ed. Philadelphia: Lea & Febiger, 1990:471.

Slocum B, Slocum TD. Slope of the dorsal acetabular rim for hip evaluation in the dog. In: 17th annual conference of the Veterinary Orthopedic Society. Salt Lake City, UT: Veterinary Orthopedic Society, 1990:12.

Slocum B, Slocum TD. Examination of the canine hip. Canine Pract 1991;15:5-10.

Slocum B, Slocum TD. Pelvic osteotomy for axial rotation of the acetabular segment in dogs with hip dysplasia. Vet Clin North Am Small Anim Pract 1992;22:645-682.

Snavely JG. The genetic aspects of hip dysplasia in dogs. J Am Vet Med Assoc 1959;135:201.

Wallace L. Canine hip dysplasia: past and present. Semin Vet Med Surg 1987;2:92.
 

Acetabular Hip Dysplasia

Acetabular hip dysplasia is the malorientation of the acetabulum in the presence of normal depth. A slope of the dorsal acetabular rim (DAR) greater than 10.0° is considered to be acetabular hip dysplasia. The slope is usually reported as the sum of both the right and left DAR slopes, so a combined slope greater than 20.0° would be dysplastic. (A combined slope of 15.0 to 20.0° is suspect, whereas a combined slope of 15.0° or less is considered normal.) The minimum depth of the normal hip is 50% coverage of the femoral head by the DAR under ideal circumstances.

Angle of Reduction

The angle of reduction is the angle between the sagittal plane and the longitudinal axis of the femur when a “clunk” or shift is palpated as the femoral head enters the acetabulum during abduction of the hip in the anesthetized patient.

Angle of Subluxation

The angle between the sagittal plane and the longitudinal axis of the femur when a “clunk” or shift is palpated as the femoral head leaves the acetabulum during adduction of the hip in the anesthetized patient.

Barden Palpation

Barden palpation is a test for lateral translation of the hip. The lateral translation is a sign of joint capsule stretching: 1 to 2 mm is normal; 3 to 4 mm is suspicious; 4 mm or more is considered dysplastic.

Barlow Sign

The Barlow sign is the “clunk” or shift palpated as the femoral head leaves the acetabulum during adduction of the hip.

Coxarthrosis

Coxarthrosis is a general term for hip degeneration from nondysplastic sources that include, but are not limited to, rapid growth syndrome, osteochondritis dissecans of the lateral femoral condyle and transitional vertebra at the seventh lumbar vertebra or first sacral vertebral segment, osteochondritis dissecans of the femoral head, neurologic or neuromuscular insufficiency, degenerative myelopathy, intervertebral disc disease, autoimmune arthritis of the hip, infection of the hip joint, and neoplasia of the hip. Secondary manifestations of coxarthrosis are joint capsule laxity, tearing of the joint capsule, increase of synovial fluid, acetabular osteophytes, femoral osteophytes, acetabular filling, destruction of the dorsal acetabular rim, teres ligament hypertrophy or degeneration, and articular cartilage fibrillation or eburnation.

Darthroplasty

A DARrthroplasty is a dorsal acetabular rim arthroplasty. The dorsal rim of the acetabulum is augmented by bone graft that supports the joint capsule in cases that have a luxated hip. In essence, a new acetabulum is created to support the luxated hip.

Dislocation

The femoral head is unsupported by and resting outside the torn joint capsule, the ligament of the femoral head is torn, and the femoral head is outside the acetabulum.

Distraction Index

The distraction index is a ratio of the linear distance between the center of the femoral head and the center of the acetabulum with the hip in distraction, to the radius of the femoral head. In most breeds, normal hips have a distraction index up to and including 0.30.

Dorsal Acetabular Rim (DAR)

The DAR rim is that portion of the lateral rim of the acetabulum of about 30° that is crossed by a line through the centers of motion of the hip and stifle in the normal standing patient as viewed in the sagittal plane (lateral radiograph). This portion of acetabular rim is subjected to trauma by the femoral head during the dysplastic process.

Femoral Anteversion

Femoral anteversion is the cranial position of the femoral head when compared with normal. The femoral neck often has a valgus conformation. However, the relationships of other components of the femur are normal. Femoral ante-version alone is considered one form of hip dysplasia. Femoral anteversion in the presence of osteochondritis dissecans (OCD) of the lateral femoral condyle is considered a growth disturbance secondary to the OCD.

Femoral Hip Dysplasia

Femoral hip dysplasia is malorientation of the femoral head with respect to the greater trochanter when the limb is in the sagittal plane.

Femoral Neck Length

Femoral neck length is the distance from the lateral aspect of the greater trochanter to the medial aspect of the femoral head. A short femoral neck is considered one form of hip dysplasia.

Femoral Torsion

Femoral torsion is malorientation of the proximal femur with respect to the distal femur. However, the relationships of the components of the ends of the femur are normal. Femoral torsion is considered one form of hip dysplasia.

Hip Dysplasia

Hip dysplasia is an inherited condition of the hip that leads to the degeneration of the joint. Several anatomic variations from normal provide the biomechanical prerequisites for predictable and progressive degeneration of the hip. Acetabular hip dysplasia is caused by malorientation or shallowness of the acetabulum. Femoral hip dysplasia is caused by a short femoral neck, anteversion of the femoral neck, or femoral torsion. Secondary manifestations of hip dysplasia are joint capsule laxity, tearing of the joint capsule, increase of synovial fluid, acetabular osteophytes, femoral osteophytes, acetabular filling, destruction of the dorsal acetabular rim, teres ligament hypertrophy or degeneration, and articular cartilage fibrillation or eburnation. These secondary changes are not hip dysplasia, but rather result from hip disorders. Nondysplastic conditions can cause the same secondary manifestations as hip dysplasia.

Juvenile Hip Malformation

Juvenile hip malformation is the hip deformity in which an extraordinarily shallow acetabulum is elongated and fails to match the femoral head. The pathogenesis of this condition is thought to be of neuromuscular origin because these patients usually have poor muscular tone, muscular weakness, and an uncoordinated movement. The condition is usually seen in young German shepherd dogs. Because of the pathogenesis, one could term the problem “neuromuscular hip dysplasia” or developmental coxarthrosis of neuromuscular origin.

Luxation

The femoral head is supported by and resting in the intact joint capsule and is incongruent with and not supported directly by the acetabulum.

Normal Hip

A normal hip has no appreciable laxity of the hip joint capsule, with a distraction index less than or equal to 0.30, and no angle of reduction is palpated. The hip has normal acetabular orientation (combined dorsal acetabular rim slope of up to 15°), normal acetabular depth (at least 50%), normal sacral conformation, normal femoral neck length, normal white-black-white articular line on the lateral radiograph, and no palpable angle of subluxation. The determination of normal hips can be made at 6 months of age.

Ortolani Sign

The Ortolani sign is the “clunk” or shift palpated as the femoral head enters the acetabulum during abduction of the hip.

Pelvic Osteotomy

A pelvic osteotomy is a surgical procedure in which a triple osteotomy of the pelvis (pubis, ischium, and ilium) frees the acetabular segment for rotation about an axis parallel to a line tangent to the dorsal acetabular rim (DAR). The amount of axial rotation brings the slope of the DAR to 0°. Excessive rotation of the pelvic osteotomy causes interference between the DAR and the femoral neck. If the acetabulum is filled with osteophytes, then the articular cartilage of the femoral head will erode, and congruity of the femoral head and acetabulum is improbable.

Pelvic Torsion

Pelvic torsion is a spiral deformity of the entire pelvis around its median axis. It can be identified in the ventrodorsal, lateral, and dorsal acetabular rim radiographs. Pelvic torsion is associated with transitional vertebrae of the first sacral segment and is considered a secondary manifestation of the vertebral abnormality. One hip is usually considered normal, whereas the other is “dysplastic.” Because the origin of the problem is the sacral deformity, one should term the problem “sacral hip dysplasia” or coxarthrosis of sacral origin.

Rapid Growth Syndrome

Rapid growth syndrome is laxity of the hip joint capsule in the presence of normal acetabular orientation (combined dorsal acetabular rim slope up to and including 15°), normal acetabular depth (at least 50%), normal sacral conformation, normal femoral neck length, normal white-black-white articular line on the lateral radiograph, and normal angle of subluxation (up to and including 0°). The distraction index is greater than normal (greater than 0.30), and the angle of reduction is present (none is normal). The pathogenesis of this condition is the maldirection of the axial femoral force during a rapid growth spurt at 4 to 6 months of age. This maldirection of the axial femoral force stretches the hip joint capsule, but it is otherwise harmless to the hip. Restricted nutrition reduces the excessively rapid rate of growth and should have a preventive influence on capsular laxity. If the patient applies excessive axial load to the hip in the luxated position, the joint capsule can tear, the dorsal acetabular rim (DAR) can fracture, or the DAR can deform over time. If caught at the joint capsule stretching stage, strict confinement and elimination of play for 4 to 6 weeks allow the stretched joint capsule to contract. Normal hips are obtained on OFA examination at 2 years of age. A femoral neck lengthening is curative if performed before increase of the DAR slope into the pathologic range. If the affected patient is allowed to damage the DAR, then traumatic coxarthrosis will result and secondary manifestations of trauma will later be misdiagnosed as hip dysplasia. Because the origin of the problem is the rapid growth of the distal femur (12 to 15 mm per week for 6 to 8 weeks), one should term the problem “rapid femoral growth hip dysplasia” or coxarthrosis of rapid growth of distal femur origin.

Slope of the Dorsal Acetabular Rim (DAR)

The slope of the DAR is defined as the angle formed by a line normal to the sagittal plane (horizontal line) and a line created by the intersection of the acetabular subchondral bone at the DAR, and a plane defined by the intersection of the horizontal line and line through the centers of motion of the hip and stifle in the normal standing patient as viewed in the sagittal plane. The slope of acetabular subchondral bone at the DAR is linear, based on a study of 25 normal pelves. Clinically, the slope of the DAR is the angle between the tangent to the reduced femoral head at its first point of contact with the acetabulum and the horizontal line as seen on the DAR radiographic view.

Subluxation

The femoral head is incongruent and supported directly by the acetabulum, and it is allowed some lateral translation, but it is prevented from dorsal translation by the intact joint capsule.

Total Hip Replacement

A total hip replacement is a salvage procedure in which the worn acetabulum is replaced by a high-molecular-weight polyethylene acetabular cup, and the worn femoral head is replaced by a molybdenum-chromium-stainless steel alloy femoral prosthesis. The components are maintained in position by polymethylmethacrylate. The replaced components are devoid of nerve endings and therefore are pain free. This surgical procedure is best used when the femoral head rubs bone on bone with the acetabulum.
 

In the biomechanical sense, the femoral neck length is defined as the distance between the lateral limit of the greater trochanter and the medial limit of the femoral head. Both the internal and external rotator muscles attach to the greater trochanter and exert equal moments about the femoral head. The moment is defined as force times distance. By lengthening the femoral neck, the moments become greater, yet internal and external moments are still equal. This creates a greater medially directed resultant force more capable of holding the hip in the acetabulum.

The primary indication for a femoral neck lengthening is a short femoral neck. Short femoral necks are common in some breeds such as the akita, chow, and Tibetan mastiff. These hips are frequently diagnosed as dysplastic (Figure 60-62). Short femoral necks can also occur secondary to trauma to the growing capital physis (Salter type IV), as well as secondary to the surgical manipulation and fixation of a fracture of the capital physis. In dogs less than 6 months of age, rigid internal fixation of a fractured capital physis is likely to result in degeneration of the hip from a shortened femoral neck. Similar patients have no arthritis if the femoral neck is lengthened. If a nondisplaced capital physeal fracture is left undiagnosed or unattended, the femoral neck often resorbs, and a short femoral neck results.
 

Surgical Technique

The lateral approach to the femur is used to gain access to the lateral, cranial, and medial aspects of the femur. The vastus lateralis is detached from its origin just distal to the greater trochanter and is elevated from the femur as far as the distal lateral circumflex femoral vessels. A small Hohmann retractor is placed beneath the deep gluteal muscle and over the web between the greater trochanter and the femoral head. Two Gelpi retractors are used to separate the biceps femoris and vastus lateralis muscles. External rotation of the hip exposes the proximal femur and the femoral diaphysis for osteotomy.

The greater trochanter is freed from the femoral head by an osteotomy cut in the sagittal plane for two-thirds the length of the femur (Figure 60-63). The cranial cortex of the femur is penetrated by an oscillating saw beginning just proximal to the distal lateral circumflex femoral vessels. The cranial cortical cut is carried prox-imally in the sagittal plane to the Hohmann retractor between the greater trochanter and the femoral head. The cranial cortex is used as a saw guide to direct the osteotomy of the caudal cortex. Because the osteotomy is medial to the external rotator muscle group, little danger exists of traumatizing the sciatic nerve, which lies lateral to these muscles. Considerable hemorrhage is sometimes encountered at the level of the nutrient foramen, but this soon stops with minimal blood loss. If the patient’s profile indicates the potential for hemophilia, coagulation potential and von Willebrand factor should be tested before the operation.
 

Lateralization of the greater trochanter is accomplished by placing a 40-mm cortical screw in only the lateral cortex of the femur at the level of the third trochanter, perpendicular to the sagittal plane. With the limb held in the sagittal plane, the proximal femur is manually moved laterally (Bardens test). The laxity of the Bardens test is decreased by advancement of the screw through the lateral cortex, but not into the medial cortex. Interference of the cancellous surface of the medial segment separates the medial from the lateral cortex, which tightens the rotators as the femoral neck is lengthened. When laxity by Bardens palpation becomes zero, the advancement of the screw is sufficient.

The appropriate Femoral Neck Lengthening Wedge (US Patent No. 4,759,351, Slocum Enterprises, Eugene, OR) is inserted just proximal to the screw to maintain the femoral neck length. A towel clamp or small fragment reduction forceps is used to grasp and manipulate the wedge. The wedge is held in place by predrilling a 2.7-mm (7/64-inch) hole through the lateral cortex, wedge, and medial cortex and then placing a 3.2-mm (1/8-inch) threaded pin into the hole such that the point completely penetrates the medial cortex. A wire passer is used to pass a heavy (1.25-mm or 18-gauge) wire around proximal femur. The wire should be proximal to the lesser trochanter. The point of the pin keeps it from migrating distally. After directly observing the sciatic nerve to ensure that it not entrapped, the wire is securely tightened. The screw is removed.

Another wedge is placed hallway down the osteotomy and is secured in a like manner. Care is taken to avoid driving the wedge distally because this splits the femur. The cerclage wire is proximal to the pin on the lateral cortex and is distal to the pin on the medial cortex, to prevent the pin from migrating. A third pin and cerclage wire are placed at the distal end of the osteotomy (Figure 60-64). No bone graft is necessary because healing takes approximately 5 weeks.
 

Closure is direct. The vastus lateralis can be reattached with horizontal mattress sutures. Holes can be-drilled in the greater trochanter if greater purchase is necessary. The vastus lateralis is usually attached to the tendon of the deep gluteal muscle cranially.

Procedure for Capital Physeal Fracture

Femoral neck lengthening is indicated for a capital physeal fracture when growth potential has been lost, when chronic capital physeal nonunion has occurred because of the trauma of delayed treatment, or when the young patient has only one opportunity for surgical correction permitted by the owner. In the last circumstance, failure of the capital physis to grow after smooth pin fixation leads to a short femoral neck and degeneration of the hip without opportunity to compensate for this lack of growth surgically. The femoral neck length deficiency may be anticipated, and compensation by fusing the capital physis and adding the anticipated femoral neck deficit may be undertaken at the initial surgical procedure.

A lateral approach to the proximal half of the femur is achieved by unwrapping the origin of the vastus lateralis muscle from the femur as previously described, while leaving the femoral insertion of the deep gluteal intact. A 7.5-cm (3-inch) osteotomy of the greater trochanter in the craniocaudal direction from the web between the greater trochanter and the femoral head to the lateral cortex is made (Figure 60-65). The internal hip rotators (superficial, middle, and deep gluteal muscles) and the external hip rotators (gemelli, internal and external obturator, and quadratus femoris muscles) remain attached to the greater trochanter. The distal end of the trochanteric section is reflected dorsally to expose the hip joint capsule (Figure 60-66).

Subperiosteal elevation of the vastus lateralis from the cranial femoral neck to the joint capsule exposes the femoral side of the capital physis or the capital epiphysis if it is displaced cranially. The joint capsule is minimally opened cranially, to observe the articular surface of the femoral head. The capital epiphysis is anatomically reduced, if possible. If anatomic reduction is not possible because of trauma, then the capital epiphysis is positioned over the femoral neck to be functional for weightbearing. A lag screw is placed up the femoral neck or remnant of the femoral neck from the surface of the osteotomy to secure the relationship between the head and the neck. The screw head is countersunk only enough to avoid protrusion into the osteotomy kerf; overtightening the screw causes the end of the screw to protrude from the surface of the femoral head (See Figure 60-66). The cranial joint capsule is closed by cranial capsulorrhaphy.
 

Femoral neck lengthening is performed to establish the adult femoral neck length (Figure 60-67). This length is determined by measuring the neck length in the parent of the same sex (if the patient resembles that parent) or by measuring neck length in another dog of the same breed and body type. A Femoral Neck Lengthening Wedge of the appropriate thickness is placed at the level of the third trochanter. A lag screw is placed in the distal end of the trochanteric segment. The glide hole should be large enough to accommodate lateralization of the greater trochanter. The lag screw is tightened while taking care not to split the cortex of the trochanteric fragment. The Femoral Neck Lengthening Wedge can be fixed by a screw through the lateral cortex, wedge and medial cortex, but a pin and cerclage wire, as previously described, are more secure. Closure is similar to that described for classic femoral neck lengthening.
 

Modified Technique

A lateral approach to the proximal half of the femur is achieved by unwrapping the origin of the vastus lateralis muscle from the femur as previously described while leaving the femoral insertion of the deep gluteal intact. An osteotomy of the femur is made in the sagittal plane from the depression in the web between the greater trochanter and the femoral head to a point 6.5-cm (2.5-inch) distal. A small biradial or cylindric saw blade is used to complete the osteotomy between the kerf generated and the lateral cortex. The internal hip rotators (superficial, middle, and deep gluteal muscles) and the external hip rotators (gemelli, internal, and external obturator, and quadratus femoris muscles) remain attached to the greater trochanteric segment (Figure 60-68).
 

A 3.5-mm hole is drilled through the distal end of the trochanteric segment and also through the medial cortex. The depth of the hole is measured with a depth gauge, and a screw 2 to 4 mm longer is selected. The lateral cortex is overdrilled using a 4.5-mm drill bit and is countersunk. The medial cortex is tapped with a 3.5-mm tap. A 3.5-mm cortical lag screw is placed through the lateral cortex and loosely engaged in the medial cortex. A second hole is drilled through the lateral cortex at the level of the third trochanter, is countersunk, and is tapped. The depth of the hole is measured to the medial cortex. The screw selected is equal to the depth of the hole plus the displacement of the femoral head obtained by comparing the compression and distraction radiographic views. When the screw is placed in the second hole, the greater trochanter is lateralized the appropriate amount. Third and fourth screws are placed proximal and distal to the second screw, engaging both the lateral and medial cortices (Figure 60-69). The first screw is then firmly tightened. Closure is routine.
 

A more stable configuration is the application of an appropriately sized wedge placed at the second screw hole. The wedge size is determined from the displacement of the femoral head obtained by comparing the compression and distraction radiographic views. This configuration prevents the femoral neck lengthening from relying on the threads of the screws alone.

Although the primary indication for femoral neck lengthening is hip dysplasia, this technique can also be used with a pelvic osteotomy in patients with an excessively stretched joint capsule. The excessive slope of the dorsal acetabular rim is corrected before the femoral neck lengthening. A dorsal acetabular rim slope greater than 7.5° is addressed by a pelvic osteotomy because that surgical procedure deals with the axial compressive forces of the femur; the femoral neck lengthening technique increases the medial directed forces created by the rotators. Bone graft has not been necessary for augmenting bone healing, because bone marrow elements promote extraordinarily rapid bone healing, usually within 5 to 6 weeks.

The postoperative instructions are strict for femoral neck lengthening surgery. The patient must be kept under direct control of the owner while in the house, on good footing, with no playing, and with no other dogs or other excitable activities. The patient is allowed outside only to perform bodily functions on a leash with a bellyband. The patient is kept in a traveling kennel when the owner is not present, to prevent the patient from injuring itself. Tranquilizers may be necessary to maintain this confinement until the femoral neck lengthening is healed.

Femoral neck anteversion can also be corrected using the femoral neck lengthening procedure. In addition to lateralizing the greater trochanter, the lateral cortex is moved cranially to detorse the femur and to provide the appropriate relationship between the greater trochanter and the femoral head. The Femoral Neck Lengthening Wedge and internal fixation are applied with routine closure.

The femoral neck lengthening technique is powerful when used according to the proper indications. Overlengthening the femoral neck can cause the femoral head to move ventral to the acetabulum, particularly if performed concurrently with a pelvic osteotomy technique. The advantage of the femoral neck lengthening technique is that it provides an increase in the medially resultant force holding the hip in the acetabulum. This reestablishes stable hip biomechanics without the necessity for overrotating the acetabular segment in patients with excessive joint capsule laxity. In addition, this procedure is gentle on the patient, the owner, and the surgeon.

Acknowledgments

Kenneth Sinibaldi, DVM, Steven Stoll, DVM, and Gary Brown, DVM, have made contributions to the modification of the femoral neck lengthening technique.

Suggested Readings

Slocum B, Devine T. Pelvic osteotomy in the dog as treatment for hip dysplasia. Semin Vet Med Surg 1987,2:107.

Slocum B, Devine T. Femoral neck lengthening for hip dysplasia in the dog. Vet Surg 1989; 18:81.

Slocum B, Devine T. Pelvic osteotomy. In: Whittick W, ed. Canine orthopedics. 2nd ed. Philadelphia: Lea & Febiger, 1990:471.

Slocum B, Slocum TD. Pelvic osteotomy for axial rotation of the acetabular segment. Vet Clin North Am 1992;22:645.

Slocum B, Slocum TD. Femoral neck lengthening: the cutting edge. 1988. Stoll S. Femoral neck lengthening. San Francisco, CA: American College of Veterinary Surgeons, 1996.
 

The first principle in treating acetabular hip dysplasia is to neutralize any luxating force created by a slope of the dorsal acetabular rim (DAR) or adduction of the femur. This requires an axial rotation of the acetabular segment by pelvic osteotomy. The second principle is the establishment of a greater trochanteric muscle force moment for creating dynamic stability of the femoral head by femoral neck lengthening, when the femoral neck is short or the joint capsule is excessively lax. The third principle is to reduce the redundancy of the joint capsule by capsulorrhaphy, which adds static stability to the hip when the femoral neck is normal and excessive laxity of the joint capsule is greater than 6 mm. This discussion addresses the first principle, the surgical technique of pelvic osteotomy.

Pelvic osteotomy is a triple osteotomy of the pelvis that frees the acetabular segment for axial rotation to reduce the DAR angle to 0° (Figure 60-70). The primary indication for pelvic osteotomy is excessive slope to the DAR. By far the most common circumstance for this condition is acetabular hip dysplasia, which is an excessive slope of the DAR by definition. Occasionally, pelvic torsion, secondary to a transitional vertebra of the sacrum, causes a unilateral excessive slope of the DAR that is also treated by pelvic osteotomy. Dislocation of a dysplastic hip is an immediate indication for pelvic osteotomy, as long as the articular surfaces can be replaced with congruity. Reduction of a dislocated dysplastic hip fails unless pelvic osteotomy is performed. Reduction of a dislocated hip without treating the underlying hip dysplasia is unacceptable. A short femoral neck as in an akita, chow, or Tibetan mastiff, or secondary to premature closure of the capital femoral physis, requires femoral neck lengthening if found primarily, but damage to the DAR by the head of the femur with the shortened neck reduces the coverage of the DAR and requires a pelvic osteotomy to stabilize the hip.
 

The degree of correction for rotation of the pelvic osteotomy is determined by looking at the abnormalities in specific structures. Joint capsule laxity can be calibrated by the angle of reduction, stress radiography, and the Bardens palpation. Damage to the articular cartilage can be assessed by palpation, with the patient under anesthesia, to distinguish joint capsule distraction from tearing. The characteristics of the articular cartilage can also be distinguished by hip palpation as normal, fibrillated, or eburnated. The DAR radiographic view and linear tomography create a visual representation of articular cartilage thickness and damage to the weightbearing portion of the acetabulum. Acetabular depth can be evaluated radiographi-cally using the frog view at 45° of abduction, the compression view in the ventrodorsal position, and the DAR view. Acetabular depth can also be assessed by the angle of subluxation and the combined interpretation of actual DAR slope and ligament of femoral head redundancy.

The slope of the DAR is measured directly from the D AR radiograph. The subchondral surface of the dorsal acetabulum is linear unless distorted by acetabular filling or chronic luxation of the femoral head. The angle of subluxation provides a good assessment of the functional slope of the DAR.

Surgical Procedures

The acetabular segment of the pelvis is freed for axial rotation by osteotomies of the pubis, ischium, and ilium and is fixed with just enough rotation by a Canine Pelvic Osteotomy Plate (Slocum Enterprises, Eugene, OR) to stabilize the femoral head in the acetabulum (Figure 60-71). The patient is anesthetized, the limb is prepared for surgery with the dog in lateral recumbency, and the limb is hung by a foot wrap. The entire hindquarter is draped free to allow for access to the pubis, tuber ischiadicum, and ilium.
 

Pubic Osteotomy

The skin is incised over the proximal one-fourth of the pectineus muscle and inguinal crease. The gracilis and adductor muscles are elevated from the ventral pubis. The prepubic tendon and pectineus are elevated from the cranial pubis (Figure 60-72). The obturator nerve is retracted caudomedially. An osteotomy is made in the sagittal plane at both the medial and lateral limits of the pubis. The entire pubis along the cranial margin of the obturator foramen is removed and is saved for an ilial osteotomy bone graft. The gracilis muscle is closed to the prepubic tendon to prevent an inguinal hernia. Subdermal sutures are used to preclude difficult suture removal.
 

Ischial Osteotomy

A sagittal incision is made over the midtuber ischiadicum and is carried to bone of the dorsal ischial plateau. The internal obturator muscle is elevated from the dorsal table of the tuber ischiadicum. The sacrotuberous ligament is elevated from the lateral prominence of the tuber ischiadicum medially to laterally. An osteotomy of the tuber ischiadicum at the lateral limit of the obturator foramen (Figure 60-73) is performed in the sagittal plane. A 20-gauge fixation wire is preplaced through two holes on either side of the osteotomy site. Closure is delayed until after the ilial osteotomy and plate application is completed. Once the ilial osteotomy is plated, then the ischial wire is tightened. The perineal fascia is closed using a cruciate suture pattern. The skin of the ischial incision is closed with a simple interrupted pattern.
 

Ilial Osteotomy

A skin incision is made from the midcranial wing of the ilium to the base of the cranial aspect of the greater trochanter (Figure 60-74). The gluteal fascia is incised parallel to the skin incision. The separation between the middle gluteal muscle and the tensor fasciae latae is made. En masse, the deep and middle gluteal muscles are elevated from the body and wing of the ilium cranially, but they are left intact dorsally on the tuber sacrale (Figure 60-75). The cranial circumflex iliac artery is cauterized, but the cranial gluteal nerve to the tensor fasciae latae is preserved. A Langenbeck periosteal elevator is placed dorsal to the body of the ilium in the greater ischiatic notch and is moved cranially until contact is made between both the ilium and the sacrum. A relaxing incision in the tensor fasciae latae tendon provides the extra exposure to the greater ischiatic notch. A guide pin is placed dorsal to the lateral prominence of the tuber ischiadicum, beneath the internal obturator muscle. The pin is pushed cranially to the junction between the ventral and middle third of the cranial margin of the wing of the ilium (Figure 60-76). The ilial osteotomy is made perpendicular to the axis of the guide pin, just cranial to the Langenbeck elevator. The free acetabular segment is moved cranially into the operative field.
 

The caudal half of the Canine Pelvic Osteotomy Plate is applied to the body of the ilium (Figure 60-77) 3 mm dorsal to the ventral margin of the ilium using a spheric drill guide and 4.0-mm fixation screws. A 1.25-mm hemicerclage wire is placed through the wire hole in the caudal half of the plate, encircling the ilial body ventrally. The spike of ilial bone dorsal to the plate is removed.
 

The ilial osteotomy is reduced, and a 4.0-mm screw is placed in the ventral compression hole of the cranial portion of the Canine Pelvic Osteotomy Plate using a 1.0-mm compressive drill guide. The hip is tested for stability by axial compression of the femur in the sagittal plane (Figure 60-78). If the hip is unstable (the femoral head luxates), then the next larger angle of plate needs to be used. The screw holes of all Canine Pelvic Osteotomy Plates are in the same relative position. When applying the remaining two screws, care should be taken to place the screws perpendicular to the plate.
 

On small patients, these screws may have to be directed caudally to drill into the body of the sacrum. A bone graft of the pubis, fragmented to 3 mm or less, is placed caudal to the wing portion of the ilium between the sacrum and the acetabular segment. Closure of ilial approach is routine.

The objective of the pelvic osteotomy technique is to provide acetabular support and stability for the femoral head by increasing the acetabular coverage. Reducing the acetabular slope to 0° is optimal. The preoperative examination of the patient determines the angle for the Canine Pelvic Osteotomy Plate to be used. Although the angle of subluxation is theoretically the ideal angle for pelvic osteotomy, it is usually insufficient to provide hip stability unless the DAR is undamaged. The angle of reduction, which indicates joint capsule stretching, is the absolute maximum angle for pelvic osteotomy and is excessive, especially if a great difference exists between the angles of reduction and subluxation. The slope of the rim as determined from the DAR radiograph is an accurate reference for the amount of axial rotation for the acetabular segment.

If joint capsule laxity is excessive, femoral neck lengthening or capsulorrhaphy should be used to achieve hip stability while maintaining an optimum range of motion rather than overrotation of the acetabular segment. Overrotation causes impingement of the femoral neck, the advancement of degenerative joint disease, and pain.

Several aspects of the pelvic osteotomy need to be observed to ensure consistently good results from the procedure. Most important, only enough axial rotation of the acetabular segment to provide hip stability should be performed. The slope of the DAR should be brought to 0° and not beyond, for the benefit of the function of the patient. When the ilial osteotomy is placed as described, the ilial osteotomy overlies the sacrum about 3 mm cranial to its caudal margin. This prevents the saw from penetrating the ilium, to damage the pelvic plexus and cause dysuria, as may occur when the osteotomy is made caudal to the sacrum. Using the guide pin properly orients the osteotomy and prevents excessive angulation of the caudal portion of the acetabular segment, as occurs when the osteotomy is made perpendicular to the long axis of the ilium, rather than the long axis of the pelvis. Rotation of the acetabular segment and internal fixation are much more difficult when the cut is incorrect. A Hohmann retractor should not be used dorsal to the body of the ilium. The sciatic nerve, which lies medial to the body of the ilium, is easily crushed between the tip of the retractor and the bone during retraction. The well-intentioned assistant often replaces a displaced Hohmann retractor into a position of danger.

If the SI nerve root is encountered when drilling the dorsal holes in the cranial portion of the plate, then the screw applied to that hole should be short enough to avoid contact with the nerve or the hole should be redirected to avoid the nerve root.

The Canine Pelvic Osteotomy Plate has two characteristics which makes it superior to twisted linear plates. The width of this plate and the placement of screws more efficiently resist the torsional moments of the acetabular segment than the linear plates, which tend to pry the screws from the bone (Figure 60-79).
 

The sacrotuberous ligament release prevents elevation of the caudal acetabular segment during axial rotation that would otherwise malalign the ilial osteotomy and place static tension on the sacrotuberous ligament, leading to a gradual release of tension in the elongating ligament and subsequent loss of compression at the ilial osteotomy as the sacrotuberous ligament lengthens (Figure 60-80). The loss of compression by yielding of the sacrotuberous ligament causes cyclic forces on the screws with premature loss of fixation. This same effect is noted when the angle of the osteotomy is not perpendicular to the axis of the pelvis. The greater the angle of the osteotomy from the perpendicular to the guide pin, the greater is the ventralization of the tuber ischiadicum (Figure 60-81). With the release of the sacrotuberous ligament at surgery, the fixation relies on compression of the bone that statically loads the screws only in one direction and prevents cycling.
 

The results of pelvic osteotomy are predictably good if meticulous attention is paid to case selection, surgical technique, and aftercare. The technique provides for the return of normal function and activity for dogs with hip dysplasia and prevents the progression of degenerative osteoarthritis. The ideal candidate for this procedure has minimal filling of the acetabulum, an intact DAR, and an increased slope of the DAR of 10 to 20° on the dysplastic hip. The amount of joint capsule laxity (angle of reduction or distraction index) is smaller after healing of the pelvic osteotomy because the joint capsule tightens when the capsule-stretching forces created by the increased slope of the DAR are treated by the pelvic osteotomy. The most advanced stage of acetabular hip dysplasia that has a good functional result for the patient depends on the amount of acetabular filling and trauma to the DAR.

Suggested Readings

Slocum B. AVORE. Pelvic osteotomy: the results ol 285 pelvic osteotomies (abstract). Vet Surg 1986;15:134.

Slocum B, Devine T. Pelvic osteotomy in the dog as treatment for hip dysplasia. Semin Vet Med Surg 1987,2:107.

Slocum B, Devine T. Femoral neck lengthening for hip dysplasia in the dog. Vet Surg 1989; 18:81.

Slocum B, Devine T. Dorsal acetabular rim radiographic view for evaluation of the canine hip. J Am Anim Hosp Assoc 1990,26:289.

Slocum B, Devine T. Pelvic osteotomy. In: Whittock W, ed. Canine orthopedics. 2nd ed. Philadelphia: Lea & Febiger, 1990:471.

Slocum B, Slocum TD. Slope of the dorsal acetabular rim for hip evaluation in the dog. In: 17th annual conference of Veterinary Orthopedic Society. Jackson Hole, WY: Veterinary Orthopedic Society, 1990:12.
 

Introduction

Early stage canine hip dysplasia is manifested by coxofemoral joint laxity, lameness, pain and characteristic radiographic changes.¹ The first radiographic change is femoral head subluxation (Figure 60-82).² Subluxation results from the following causes, singly or in combination: increased femoral neck inclination angle; increased femoral neck anteversion; or loose supporting structures (muscles, joint capsule, ligaments).³ Subluxation decreases the contact area between the acetabulum and femoral head. Because the contact area is decreased in dysplastic dogs, the load per area of articular cartilage is increased. This continued biomechanical overloading of the joint surface results in cartilage necrosis, which leads to progressive worsening of the radiographic and clinical signs of Canine Hip Dysplasia (CHD).⁴
 

The first report⁵ of successful use of the intertrochanteric osteotomy treatment of coxofemoral osteoarthritis in human beings appeared over 60 years ago, although the procedure itself was first described by Kirmission in 1894.⁶ The purpose of the intertrochanteric osteotomy is to reestablish or improve the contact area of the acetabular and femoral head surfaces and thus improved the biomechanical function of the hip joint.^7,8 This is accomplished using the intertrochanteric osteotomy by changing the femur’s position relative to the acetabulum in three planes. The first plane, the inclination of the femoral neck, is changed from a valgus to a varus position.⁹ The second plane, the anteversion of the femoral neck, is rotated toward normoversion.^10,11 The third plane is medialization of the femoral head, neck and trochanteric region in relation to the shaft of the femur (See Figures 60-82 and 60-83).
 

Indications for Intertrochanteric Osteotomy

Intertrochanteric osteotomy is indicated when both the radiographic and clinical signs of early stage CHD are present. The typical clinical signs are stiffness on rising, rising using the front legs only, bunny hopping, pain, and lameness. Any or all of these signs may be present. The radiographic signs of early stage CHD are subluxation of the head of the femur from the acetabulum, with minimal or no deformity of the acetabulum or femoral head, and minimal or no arthritis of the joint (See Figure 60-82). In the early manifestation of this disease, the most common radiographic sign is subluxation of the hip. Subluxation of the coxofemoral joint also may be present in dogs without CHD.¹² Therefore, subluxation of the coxofemoral joint alone is not diagnostic of early stage CHD. Subluxation of the femoral head with the appropriate clinical signs is necessary for the initial diagnosis of early-stage CHD. If the subluxation advances to luxation, or if the deformity to the femoral head or acetabulum (shallowness) is significant, or if there is moderate to severe arthritis, this procedure is not indicated. In those situations, a total hip replacement would be indicated.

Greater than 95% of dogs that have CHD are affected bilaterally. The radiographic pathology is not generally symmetric; that is, one side usually is worse than the other, but most of the time both sides have some pathology (See Figure 60-82). The indications for surgical intervention on the first side, as mentioned previously, are radiographic subluxation of the coxofemoral joint and clinical signs of CHD. The indication for surgery for the second side (4 to 6 weeks later) are radiographic subluxation with or without the clinical signs. Surgery on the second side generally is prophylactic, whereas the first side is therapeutic. Because of the dog’s ability to shift weight, if the surgery is performed on the second side only after clinical signs are noticed, there are too many secondary changes to the acetabulum and femur, and an intertrochanteric osteotomy is no longer indicated. Subluxation of the second hip must be seen at least once (either on the initial examination radiograph, the postoperative radiograph of the first hip, or the 4 to 6 week postoperative follow-up radiograph). Greater than 95% of the time, subluxation can be seen at one or all of these times on the second hip, and the second surgery is indicated (Figures 60-84 and 60-85). If all three of these radiographic examinations are negative for subluxation, the surgery is not recommended on the second side.
 

Preoperative Planning

The first step in the preoperative planning for an intertrochanteric osteotomy is determination of the angle of inclination of the femoral neck. This is the angle between the axis of the femoral shaft and the axis of the femoral neck. Properly positioned ventrodorsal hip (pelvis and femurs) radiographs are absolutely essential in establishing these axes. The femurs must not be rotated; therefore, the patellas must be centered on the intercondylar sulci and the outline of the intertrochanteric fossa must be well-visualized. The pelvis must not be rotated; therefore, the obturator foramen must be equal in size on both sides of the pelvis (See Figure 60-82).

A transparent paper is placed over the ventrodorsal (V-D) radiograph, and the femur is traced. The axis of the shaft of the femur s established by drawing two lines perpendicular to the long axis from the medial to the lateral cortices (Figure 60-86). One is drawn at the junction of the proximal and middle third of the shaft (line A), and the second is drawn at the junction of the middle and distal third of the shaft (line B). These two lines are then bisected (points A and B), and these points are connected by a straight line extended to the top of the femur (See Figure 60-86). This is the axis of the femur.

To determine the axis of the femoral neck, a line is drawn perpendicular to the femoral axis line, connecting the most distal point of the intertrochanteric fossa to the medial cortex of the femoral neck (line C). The bisect of this line is point D (See Figure 60-86).
 

The center of rotation of the femoral head (point E) is determined, using the concentric circles of a standard goniometer (Roentgen Ischiometer MEM, Protek AG, Berne, Switzerland), which has a number of concentric rings with a known central point. By matching the identically sized ring with the femoral head, the center of the head is easily determined (Figure 60-87).¹³ Points E and D are connected, and this line is continued until it crosses line AB. The obtuse angle formed by these two lines is the angle of inclination (a of I) of the femoral neck (See Figure 60-86).
 

The average angle of inclination of the femoral head in the dog is 149 degrees with a range of 141 to 157 degrees. The desired angle of inclination resulting from an intertrochanteric osteotomy is 135 degrees. The degree of overcorrection is thought to decrease stress on the joint cartilage by increasing the loaded surface area of both the femoral head and acetabulum. The difference between 135 degrees and the measured angle in the dog with early stage CHD is the size of the wedge removed in the intertrochanteric osteotomy. The typical wedge removed is approximately 25 degrees. On severe cases of valgus inclination of the femoral neck, a 35 degree wedge is removed.

On a second transparent paper overlying the V-D radiograph of the hip, a line perpendicular to the line of axis of the femoral shaft is drawn connecting the lateral cortex (point F) and the point of the lesser trochanteric (point G). This represents the first osteotomy site (Figure 60-88). Using a goniometer or a protractor to measure the degrees of the wedge to be removed, a mark (point H) is made on the medial cortex of the femoral neck, above the lesser trochanter. Points F and H are connected. This line is the second osteotomy (See Figure 60-88). The triangular wedge of bone, HFG, is removed.
 

Care must be taken that the line F-H, the second osteotomy, does not enter the ventral medial aspect of the femoral head. In dogs with a short area between the femoral head and the lesser trochanter, the calculated edge may be too large to remove without taking part of the ventral femoral head. In those cases, the second osteotomy is directed to the junction of the femoral neck and femoral head.

The transparency paper is cut in half from point F to point G. Then, the wedge (point F to Point H) is cut out of the paper. The paper femur is reduced, and the plate (Double Hook Plate, Synthes, Paoli, PA) is contoured to the lateral aspect of the paper femur. The center of the solid portion of the plate, between the first and second proximal holes (Figure 60-89), should be aligned over point F. Additional bending of the plate may be necessary during surgery.
 

The second step in the preoperative planning for an intertrochanteric osteotomy is measuring the anteversion. The anteversion of the femoral neck and head can be measured from an axial radiograph of the femur. With the dog on its back on the radiographic table, the long axis of the femur is positioned at a right angle to the table and the x-ray beam is aimed down the shaft of the femur from the stifle to the coxofemoral joint (Figure 60-90). Femoral head and neck anteversion is defined as the angle formed by the plane containing the axis of the shaft and the plane containing the axis of the femoral neck.¹³ In other words, with the medial condyle being medial, the lateral condyle being lateral, and the patella being anterior, the shaft of the femur is in anatomic position. With the femur in anatomic position, the direction the femoral neck takes as it leaves the shaft of the femur is either normoverted (straight medial), anteverted (anterior towards the ilium), or retroverted (posterior towards the ischium). An excellent radiographic sign of anteversion is the outline of the lesser trochanter. With the femur in a normal anteversion (10 to 20 degrees), only the tip of the lesser trochanter will be seen on the standard ventrodorsal (V-D) radiograph of the pelvis and femurs. With increased anteversion, more or the entire lesser trochanter will be seen on the standard (V-D) radiograph (See Figure 60-82).
 

To measure the angle of anteversion, a piece of transparent paper is placed over the axial radiograph of the femur (Figures 60-91 and 60-92). A straight line is drawn from the most posterior point of the medial condyle (point M) to the most posterior point of the lateral (point L) condyle (Figure 60-93). Next, a straight line is drawn from the point where the femoral head meets the femoral neck dorsally (point J) to the ventral femoral head-neck junction (point I). Also, a straight line is drawn between the points where the femoral neck meets the femoral shaft dorsally (point K) and ventrally (point N). A line is drawn connecting the bisect of these two lines. This line is the axis of the femoral neck. This axis line is extended to the condylar line (Figure 60-93). The angle between the two lines is the angle of anteversion of the femoral neck.
 

Preoperative Planning - Shortcut

The above radiographic measuring and preoperative planning should be carried out on each surgeon’s first half a dozen cases, or until the surgeon has a really good feel for the three dimensional geometry of the coxofemoral joint. During those first surgeries you will notice that the size of the wedge you surgically remove is almost always the same even though your measurements were different. The reason for this is twofold. One, there is 5 to 10% error in everyone’s measuring, i.e., if you come back a day later and remeasured your angles, you would vary 5 to 10%. The second reason is there is a 2 to 5 degree variation in the surgery itself, even with the instrumentation available. This all adds up to a 2 to 10 degree variation between what you measured and what you accomplished surgically.

Therefore, the philosophy that can be practiced (after you have a firm three dimensional mental vision of the geometry of the coxofemoral joint) is to improve the relationship of the femoral head to the acetabulum, you should not think you are returning the angles of the femoral neck to normal. Mainly because most people do not agree what normal is, it varies with different breeds, your measurements are not exact and your surgery is not exact (within 1 or 2 degrees).

Therefore with the philosophy of improving the subluxated coxofemoral joint, you can skip the measuring and proceed directly to removing a wedge from the intertrochanteric region that has a base 1/4” (6 mm). The base of the wedge is H-G (See Figure 60-88). This is accomplished by making a mark on the lateral surface of the femur directly opposite the lesser trochanter. This mark and the point of the lesser trochanter is the line of your first osteotomy (point F on Figure 60-88). After the first osteotomy, the proximal part of the femur is steadied with a bone clamp on the greater trochanter and the muscles elevated off the medial femoral neck with a periosteal elevator. The second osteotomy is started at the same point the first osteotomy was started and directed so the wedge of bone has a base of 1/4 inch (6 mm). You can stop as often as necessary and check to see that your saw blade is directed correctly. Please realize that this generalization or shortcut is only possible because most of the dogs are large breed young dogs, very similar in size. If you decide to do this procedure on a medium size dog or a giant breed dog, you can adjust the base of your wedge +/- 1 or 2 mm.

After removing the wedge of bone, the proximal metaphysis of the femur is reduced to the diaphysis of the femur. This reduction (making sure you have bone on bone and no gap) will improve the angle of inclination 15 to 25 degrees.

The other two planes of correction (antiversion and medialization) of the proximal femur are accomplished as directed in the surgical procedure, and without the need of presurgical measurements.

In conclusion, this shortcut was presented not to save time or because of laziness. It was presented to inspire in each surgeon the surgical goal of improving the biomechanical potential of the coxofemoral joint, not returning the joint to normal (or so-called normal) angles.

Surgical Procedure

The dog is prepared for aseptic surgery of the intended rear leg from the dorsal midline to the hock and placed in lateral recumbency. The proximal half of the femur is exposed by routine incision of the skin, subcutaneous tissues, and fascia lata. The biceps femoris muscle is retracted posteriorly. The superficial gluteal muscle is elevated from its insertion and retracted dorsally.

The posterior half of the origin of the vastus lateralis muscle (on the lateral aspect of the femur) is incised and retracted cranially (Figure 60-94). The lesser trochanter is palpated with the forefinger on the posterior-medial aspect of the femur, and a mark is made in the bone with a bone saw on the lateral aspect of the femur exactly opposite the lesser trochanter (See Figure 60-94). The special drill guide (No. 380.01, Synthes, Paoli, PA) is laid on the lateral aspect of the femur so that the line on the drill guide is exactly above the mark scored on the bone (Figure 60-95). Using the leveling screw, the long axis of the drill guide is set parallel to the shaft of the femur (Figure 60-95). If the long axis of the drill guide is not parallel, there will be the possibility that the first osteotomy may not be perpendicular to the long axis of the femur. The proximal-caudal hole is drilled with a 3.2 mm drill bit (Drill bit with stop, No. 380.03, Synthes, Paoli, PA) into the greater trochanter to the stop on the drill bit. The 3.2-mm locking pin from the drill guide is placed through the guide into the hole in the greater trochanter. The most distal hole of the three proximal holes in the guide is drilled with a 2.0 mm drill bit into the greater trochanter. The 2.0 mm locking pin is placed through the drill guide into the bone. The remaining hole (proximal-cranial) is now drilled in the greater trochanter with the 3.2 mm drill bit down to the stop. Using this specially designed drill guide ensures that holes in the greater trochanter are exactly placed to accept the hooks on the plate (See Figure 60-89). Next, a 2mm hole is drilled through the center of the distal hole in the tail of the drill guide through one cortex only (Figure 60-95). This hole will be used later for anteversion correction.
 

The first osteotomy is now performed, cutting the femur from the mark scored on the lateral aspect of the shaft to the point of the lesser trochanter. There is a saw guide (No. 380.07, Synthes, Paoli, PA) available that hooks into the two 3.2 mm holes in the greater trochanter (Figure 60-96). After the hooks of the saw guide are in place, the blade of the saw guide is adjusted and directed so it is lined up on the score in the bone on the lateral aspect of the femur and the tip of the lesser trochanter on the medial side of the femur. After the first osteotomy is performed, the goniometer (No. 380.05, Synthes, Paoli, PA) is placed in the osteotomy and the femur reduced with two bone clamps. The goniometer is held stable by the pressure of the reduced femur. The blade of the saw guide is now changed to the degree as calculated from the radiograph during the planning stage or to give you a 1/4 inch (6 mm) base to your wedge (Figure 60-97). The saw guide blade is tightened. Using the saw guide, the second osteotomy is made and the wedge of bone removed (Figure 60-98). The femur is now reduced taking extreme care that there is 100% bone contact at the osteotomy site. To have the varus correction of the angle of inclination of the femoral neck, there must be bone-to-bone contact with no gap where the wedge was removed. While maintaining this reduction at the osteotomy site, an aluminum template is laid on the lateral aspect of the femur and contoured to match the femur. The template slides into the saw guide allowing coordinated bending of the proximal plate and the three predrilled holes in the proximal femur. The final bending of the plate is performed to match the template. The hooks are then inserted into the greater trochanter.
 

The femur is now reduced again, making sure there is no gap at the osteotomy site. The hole just distal to the two hooks in the proximal segment is now redrilled with a 2.5 mm drill bit. This hole is tapped with a 3.5 mm cortical tap. The plate is loosened approximately 4 mm and two washers (No. 219.99, Synthes, Paoli, PA) are placed between the hook plate and the bone, in line with the hole in the plate and bone (Figure 60-99). The screw is then placed and tightened. The washers placed under the plate will medialize the proximal femur 3 mm compared to the shaft of the femur, and this pushes the head of the femur deeper into the acetabulum. If the placement of these washers interferes with reduction at the osteotomy site, the screw and the plate should be removed. The plate is recontoured as needed to conform to the perfectly reduced femur. The plate is then reapplied. This step is repeated as necessary until the reduction at the osteotomy site is perfect, with no gap between the proximal and distal femur.
 

With the femur reduced at the osteotomy site, the shaft of the femur is rotated outwardly so that the stifle rotates outward until the 2 mm hole that was drilled in the distal lateral cortex is just visible at the caudal edge of the plate. This degree of rotation will cause a 15 degree reduction in anteversion of the femoral head toward normoversion (Figures 60-100 and 60-101). The hole just distal to the osteotomy site is now drilled with a 2.5 mm drill bit through a compression (loaded) drill guide, tapped, and a 3.5 mm cortical bone screw is placed. After each screw placement, the reduction must be checked at the osteotomy site and at the rotation guide hole. The remainder of the holes in the plate are now filled with 3.5 mm screws placed in a neutral position.

The vastus lateralis muscle is pulled over the plate and sutured to its incised origin. The superficial gluteal muscle is pulled over the greater trochanter and proximal plate and sutured to the lateral fascia of the vastus lateralis muscle. The biceps femoris muscle is sutured to the fascial lata. The subcutaneous tissue and skin are sutured closed.
 

Postoperative Care

After surgery, a wound bandage is applied and left in place until suture removal 12 to 14 days later. If the dog removes the bandage, it usually is not replaced. Candidates for an intertrochanteric osteotomy are usually young, healthy animals with no preoperative traumatized tissue; therefore, prophylactic antibiotics are not needed. The dogs are allowed to use the leg immediately. When the procedure is properly performed, there is little concern about fixation loosening before clinical union. Dogs usually are dismissed from the hospital 1 or 2 days after surgery to be confined to the house or kennel and walked restrained by a leash. Running and jumping are not permitted for 4 weeks, and no yard freedom is allowed.

The second side is reconstructed 4 to 6 weeks later, if necessary. Postoperative care for the second side is the same as the first. Owners are requested to give a progress report 6 weeks later. The plates are not removed unless a problem, such as loose screw(s), cause clinical signs of pain or lameness.

Results

There have been two retrospective studies on this procedure.^11,14 The first study¹¹ was performed on 210 dogs that underwent intertrochanteric osteotomies. Clinical evaluation from 1 to 7 years after surgery on 183 of the dogs revealed an 89.6% excellent or good return to motor activity. The results relating to motor activity at a minimum of 1 year were rated as follows: excellent, walking and running normally without pain for long distances; good, was defined as walking or running normally without pain but with a slight limp appearing after exercise. Postoperative physical examinations on 90 dogs from 6 months to 1 year after surgery demonstrated an increase in circumferential thigh muscle mass over the operated leg in the dogs that showed good to excellent results.¹¹

Dogs operated on before the appearance of radiographic signs of degenerative joint disease had better results than those operated on after degenerative joint disease was established.

Only 12.1% of the dogs with severe osteoarthritis had excellent results, whereas a 51.4% of the dogs without preoperative osteoarthritis changes and 45.8% of those rated as having moderate osteoarthritis were considered to have excellent results.

The second study involved a clinical evaluation after 7 years of using this surgery on dogs with early stage CHD.¹⁴ The retrospective study was performed on 37 dogs that had 43 hips reconstructed. The clinical evaluation consisted of a questionnaire, and/or an orthopedic examination; and/or a report from the owner(s) via telephone. At least one form of evaluation was conducted for 42 of 43 hips (98%). Before surgery, on 11 of 37 hips (30%) had been evaluated as functionally good or excellent. In this study, excellent function was defined as normal function. Good function was defined as normal weight bearing with joint stiffness after strenuous exercise or long rest. On the basis of the owner’s telephone report, 19 of 28 hips (68%) were functionally good or excellent at postoperative month 11 (on average). On the basis of the questionnaire data, 17 of 24 hips (70%) were functionally good or excellent at postoperative year 1. On the basis of the orthopedic examination findings, 27 of 33 hips (84%) were functionally good or excellent at postoperative month 15 (on average). Of 36 owners, 33 (91.6%) reported they would have the procedure performed again if the circumstances were the same.

Results of statistical analysis indicated that the procedure was helpful for up to 3 years after surgery.¹⁴ This observation was true regardless of who examined the dog after surgery, surgeon or owner. Because there were not enough data after postoperative year 3, no statement could be made concerning whether the benefit of surgery would still be detected after that point.

After performing the intertrochanteric osteotomy for the treatment of early-stage hip dysplasia for twenty-five years, we have found a 92% success rate for the surgery, if performed on dogs without moderate or severe degenerative joint disease, i.e., with no or only mild degenerative joint disease and subluxation. The remaining 8% of the dogs have advanced their osteoarthritis from mild to severe, and have been treated with a total hip replacement or with pain medication if the owner did not wish the replacement.

Discussion

Because the potential for remodeling is greatest early in life, corrective orthopedic procedures such as the three-plane intertrochanteric osteotomy ideally should be performed while the bones and joints have the greatest remodeling potential.^1,14,15,16 Therefore, as soon as clinical signs of CHD and subluxation of the coxofemoral joint are detected, surgery should be recommended.

In early stage CHD, the femoral head is movable in and out of the acetabulum; therefore, subluxation may not always be demonstrable on each radiographic exam. This may be due in part to the inward rotation that the holder puts on the limbs; this will torque the joint capsule and may move the head into the acetabulum. Others feel this same torque is developed by overextending the hind limbs to obtain the standard V-D view of the pelvis. It also may be influenced by muscle tension; therefore, some have recommended all radiographic exams of the canine pelvis be performed under anesthesia or at least heavy tranquilization.

Because there is a direct correlation between increasing age and severity of osteoarthrosis¹¹ and because there is an inverse relationship between severity of osteoarthrosis and improvement after surgery, intertrochanteric osteotomy is best performed in young dogs prior to the development of osteoarthrosis. Once degenerative changes occur, the prognosis for return to normal function diminishes.

In early stage CHD, relief of pain owing to the three-plane intertrochanteric osteotomy may be explained by biomechanical principles involving 1) improved congruity of the head and acetabulum with wider surfaces of contact, 2) a medial shifting of the line of weight bearing, and 3) relief of pressure by release of muscle contracture.¹⁷

The results of the two studies are remarkably similar. In the first study, 89.6% of the dogs were evaluated as excellent or good in return to motor activity. In the second study, 91.6% of the owners indicated they were pleased with the results and would have the procedure performed again if the circumstances were the same.

The intertrochanteric osteotomy is a conservative procedure because the option of a conversion to a total hip replacement in unsuccessful situations remains.¹⁷ In fact, when this procedure was adopted 25 years ago, it was performed with the goal eliminating pain and improving function in young dogs until they were old enough for total hip replacement. Of the first 240 hips in which an intertrochanteric osteotomy was performed, 9 have subsequently required a total hip replacement to relieve the pain of osteoarthritis secondary to CHD.

Intertrochanteric osteotomy provides relief of pain in humans for an average 5 to 6 years.¹⁸ Although each dog varied as to duration of benefit, most remained comfortable and had normal function for their entire lives.

In conclusion, the goal of the three-plane intertrochanteric osteotomy is to decrease stress in the coxofemoral joint, thereby relieving pain associated with early stage CHD. Although radiographically detectable degenerative changes within the coxofemoral joint continue, the degenerative changes proceed at a slower pace than if the surgery was not performed and the clinical signs of hip pain do not manifest for the greater majority of the dogs having this procedure (Figure 60-102).
 

References

1. Brinker WO: Corrective osteotomy procedures for treatment of canine hip dysplasia. Vet Clin North Am 1:467, 1971.
2. Archibold J, Ballatyne JH: A practical prosthesis for the canine and feline femoral head. North Am Vet 34:496, 1953.
3. Prieur WD: Coxarthrosis in the dog. Part 1: Normal and abnormal biomechanics of the hip joint. Vet Surg 9:145, 1980.
4. Pauwels F: Uber eine Kausale Behandlung der coxa valgu luxans. Z Orthop 79:305-315, 1950.
5. Hey Groves EW: Surgical treatment of osteoarthritis of the hip. Br Med J 1:3, 1933.
6. Kirmission E: De l’osteotomie sous trochanterienne applique a certains cas de luxation congenitale de la hauche: Rev Orthop 5:137, 1984.
7. Knodt H: Pressure-reducing effects of hip osteotomies. Clin Orthop 77:105, 1971.
8. Prieur WD: Intertrochanteric osteotomy in the dog: theoretical consideration and operative technique. J Small Anim Pract 28:3, 1987.
9. Prieur WD, Scartazzini R: Die Grundlagen und Ergebrisse der intertrochanteren variationsosteotome bei huftdysplasia. Kleintur-Prax 25:393, 1980.
10. Dueland DJ: Femoral torsion and its possible relationship to canine hip dysplasia. Vet Surg 9:48, 1980.
11. Walker T, Prieur WD: Intertrochanteric femoral osteotomy: Semin Vet Med Surg (Small Animal) 2:117, 1987.
12. Belkoff SM, Padgett G, Soutas-Little RW: Development of a device to measure canine coxofemoral laxity. Vet Comp Orthop Trauma 1:31-36, 1989.
13. Montavon PM, Hohn RB, Olmstead ML, et al: Inclination and anteversion angles of the femoral head and neck in the dog. Vet Surg 14:277, 1985.
14. Braden TD, Prieur WD, Kaneene JB: Clinical evaluation of intertrochanteric osteotomy for treatment of dogs with early-stage hip dysplasia: 37 cases (1980-1987). J Am Vet Med Assoc 196:337, 1990.
15. Salter RB: Innominate osteotomy in the treatment of a congenital dislocation and subluxation of the hip. J Bone Joint Surg (Br) 43:518, 1961.
16. Salter RB: Role of innominate osteotomy in the treatment of congenital dislocation and subluxation of the hip in the older child. J Bone Joint Surg (Am) 48:1413, 1966.
17. Goldie MD, Dumbleton JH: Intertrochanteric osteotomy of the femur. Clinical Biomechanics: A case history approach. New York, Churchill Livingstone, 1981, p 72.
18. Reigstad A, Gronmark T: Osteoarthritis of the hip treated by intertrochanteric osteotomy. J Bone Joint Surg (Am) 66: 1, 1984.

Introduction

In hip dysplasia, laxity and incongruity of the hip joint lead to progressive degenerative changes, inflammatory responses, and pain. The consequences of these responses are gait abnormality, lameness, and limb weakness.

Treatment for hip dysplasia has historically included four options: 1) long-term medications, 2) femoral head and neck excision arthroplasty (FHE), 3) triple pelvic osteotomy (TPO), and 4) total hip replacement (THR). Each of these approaches has its benefits and drawbacks. The ultimate objective is to return the patient to the most comfortable and functional status possible. FHE will often leave the patient with gait abnormalities and limb weakness (especially larger patients weighing over 25 pounds). Results with TPO are best when done in young patients with minimal degenerative changes, reasonably good joint congruity, and minimal to no acetabular filling. Cases with more advanced degenerative changes, acetabular filling, and laxity usually continue to show progressive degenerative changes. Consequently, we choose to perform TPO’s on patients with the restricted criteria of minimal degenerative changes and incongruity of the hip joints, no appreciable acetabular filling, and the presenting complaint is essentially pain and lameness with joint laxity. THR is not recommended in young patients less than a year old. It is primarily recommended as a salvage procedure for hips with extensive loss of cartilage. Consequently, a “gap” in surgical treatment options has developed between the candidate for TPO and the candidate for THR.

A fifth option is DARthroplasty.¹ This procedure was designed to create additional dorsal bone support of the femoral head and prevent the pain associated with joint capsule tears from the dorsal acetabular rim by creating a bony extension of the dorsal acetabular rim (DAR) of the acetabulum. The new DAR shelf should dramatically reduce dorsal subluxation and often significantly reduces the tendency for lateral translation. The additional dorsal bone support should provide the patient more joint stability and thus allow the patient to gain more strength in the limb.

The Surgical Procedure

The DARthroplasty technique is a two-part process which involves harvesting cortical and cancellous bone graft from the wing of the ilium and applying that bone graft to the dorsal acetabulum. One, two, or even three corticocancellous strips can be used, which are tied together and then anchored to the dorsal hip joint capsule with strong absorbable sutures that are passed through drill holes in the bone strips, and the strips are placed next to or overlapping the original dorsal acetabular rim. Holes are drilled into the original DAR and the new shelf is overlaid with cancellous bone graft.

The dog is placed in lateral recumbency to prepare for surgery. The hair is shaved over the affected hip dorsally to the midline of the spine, to 5 cm cranial to the wing of the ilium, ventrally 10cm distal to the greater trochanter, and caudally to the level of the tuber ischium. Appropriate sterile surgical preparation and draping of the surgical site is done. A 5 cm incision is made half way between the tuber sacrale and the tuber coxae from the cranial limit of the ilium toward the greater trochanter. A standard gluteal muscle roll-up approach is used. A Gelpi retractor is placed just under the gluteal fascia.

A Langenbach elevator is used to elevate the middle and deep gluteal muscles by placing it on the wing of the ilium at the sartorius muscle and sliding along the ilium toward the greater trochanter. Elevate only to the level of the deep gluteal nerve. Three to five corticocancellous bone strips are harvested from the lateral aspect of the wing of the ilium using a bone gouge to obtain appropriate sized graft curls. Cut parallel to the long axis of the ilium with the bone gouge, being careful not to perforate the medial cortex of the ilium. Note the order of the corticocancellous strips for easy assembly later. Cancellous bone graft is then harvested with a curette from the same site. Closure of this incision is routine.

A dorsal approach is made to the acetabular rim, either via a second incision or an extension of the first one. The skin incision is made parallel to the cranial margin of the biceps femoris muscle, from the level of the third trochanter to the level of the sacrotuberous ligament. The fascia along the cranial margin of the biceps femoris is incised and the biceps femoris is retracted caudally. The sacrotuberous ligament is isolated from the sciatic nerve and caudal gluteal vessels. In cases where two or three strips are used, the sacrotuberous ligament may need to be transected to minimize the risk of sciatic nerve impingement. The superficial and middle gluteal muscles are retracted cranially. The joint capsule can be palpated between the deep gluteal muscle and the cranial margin of the gemellis muscles. A small vessel can usually be identified at this landmark between these muscles. Handheld retractors are used to gently retract the gemellis caudally and the deep gluteal muscle cranially and these muscles are freed from the joint capsule cranially, caudally and dorsally to the bone of the acetabulum with a periosteal elevator. Always be aware of the sciatic nerve and be very careful not to be too aggressive in retracting the gemellis. Pushing the femoral head distally, withdraw any excessive joint fluid. We also inject bupivacaine into the joint to provide postoperative pain relief.

A protected 1/8 inch (3.2 mm) Steinman pin or a drill bit is used to drill 6-10 holes in the lateral cortex around the acetabulum (Figure 60-103), being careful to avoid perforation of the acetabulum. The dorsal apex of the femoral head is palpated through the joint capsule. The leg can be manipulated to help identify the point of maximal subluxation of the femoral head. The number of corticocancellous strips anchored to the joint capsule depends upon how many are needed to cover the joint capsule from the high point of femoral head luxation to the edge of or to slightly overlap the acetabular rim. If 2 or 3 strips are needed, they are sutured together with absorbable sutures at the ends and in the middle to create an appropriate bone “cap” over the femoral head. The corticocancellous bone strips are contoured to create an appropriate bone cap using Kelly forceps to put a curve in the strips. The corticocancellous bone cap is laid over the joint capsule, cortical side to the joint capsule and cancellous side toward the dorsal rim drill holes, placed beneath the external rotators and the deep gluteal muscles, then anchored to the joint capsule with 1 or 2 heavy absorbable sutures, passed through the joint capsule from medial to lateral, then through drill holes in the middle of the most lateral bone strip and tied snugly in place. Place a strip of graft on its edge dorsally to prevent medial migration of graft. Cancellous bone graft is placed over the drill holes and between the strips. The cancellous bone graft should be in contact with the drill holes so blood supply and the conditions for healing directly between the graft and acetabulum are established. Any additional corticocancellous strips are packed over the new graft to provide a cortical shell.
 

The deep gluteal muscle is pulled over the new graft and sutured to the internal obturator tendon and muscle. This helps stabilize the graft and minimizes its tendency for movement and/or migration. The superficial gluteal muscle is reattached to its incised fascia, the biceps femoris muscle is reapposed to the gluteal fascia, and the remainder of the closure is routine. Post-operatively, 3 radiographic views are taken: hip-extended, lateral, and DAR views.

Results

We have been performing this procedure for several years. Our criteria for performing a DARthroplasty are simple. As long as there is joint cartilage present in cases of hip dysplasia, then a DARthroplasty can be done (Figures 60-104 and 60-105). If joint cartilage is completely worn away and the joint palpates with notable crepitus, then that hip is not a candidate for DARthroplasty. We have performed DARthroplasties on cases where one hip had a TPO done and the other hip was a DARthroplasty. Thigh circumference is usually slightly greater on the TPO side, which would be anticipated since TPO requires a hip with no acetabular filling, whereas the indications for DARthroplasty include both acetabular filling and distortion of the DAR. What was surprising was that, in most cases, the DARthroplasty hip was deemed as strong and as functional as the TPO hip by the owners, even though the DARthroplasty was performed on the “poorer” hip. We have also performed DARthroplasties on hips that were markedly arthritic, but had intact cartilage, that also did very well clinically.
 

Weight bearing is surprisingly rapid after surgery and most patients are sent home with their owners the day after surgery. Exercise and activity are restricted to leash walking for the first month after surgery, and then allowed to increase once the graft is radiographically fused to the pelvis (usually 8 to 16 weeks after surgery). Pain free, normal activity can be noted as early as 2 weeks after surgery and the hip joint palpates stable, with no evidence of subluxation noted. All patients experience a decrease in abduction due to the extended DAR. By 4 months post-operatively, most patients are running, jumping, and playing normally, without pain. Radiographs 2 to 4 months after surgery may show that the femoral head has migrated medially, back into the acetabulum.

Long-term follow-ups have also been rewarding. We have found that patients continue to be active, athletic, and pain free and a very high percentage do not require any anti-inflammatory medications. As the shelf arthroplasty matures, it provides a stable bony support for the femoral head and the joint capsule becomes an extension of the joint cartilage weightbearing surface. The joint capsule loses its collagenous appearance, which is presumed to undergo metaplasia to a fibrocartilage. Because pain free activity results, limb strength and muscle mass increase. As noted, abduction remains minimally to moderately limited, but all other ranges of motion usually remain at or near normal.

Complications with the procedure primarily involve temporary sciatic dysfunction. The sciatic nerve may be injured during retraction or drilling and may, in cases requiring very large grafts, become trapped between the bone graft and the sacrotuberous ligament. This can be prevented by severing the sacrotuberous ligament at the time of surgery. These complications should be minimized as the surgeon and assistants gain experience. Infections are almost nonexistent. Although the criteria are very broad for performing DARthroplasties, one limitation, besides lack of cartilage, may be patients with completely luxated hips.

Conclusion

DARthroplasty has been a very effective procedure that fills the gap between the cases with narrow indication criteria for TPO and the end-stage salvage criteria for total hip replacement. DARthroplasty was originally developed by Dr. Barclay Slocum with the idea that additional bone could be produced that would enhance future THR. Although previous DARthroplasty does not preclude THR, none of our patients that have undergone DARthroplasty have developed signs that would even suggest considering total hip replacement. As stated before, we have been pleasantly surprised at how small a percentage of cases that have undergone DARthroplasty even require anti-inflammatory medications to remain comfortable.

Suggested Readings

Slocum, B. & Slocum, T.D. “DARthroplasty”. In: Bojrab, M.J., ed. Current Techniques in Small Animal Surgery, 4th Ed. Baltimore: Williams & Wilkins 1998: 1168-1170.
 

Surgical Description: Total Hip Arthroplasty

Total hip arthroplasty is also known as total hip replacement. It is the most effective way to provide a canine patient with a mechanically sound, pain free, ball and socket hip joint, once osteoarthritis is present. Both cemented and cementless prosthesis have been successfully used to treat non-infectious, non-neoplastic disabling conditions of the canine coxo-femoral joint. The cementless hip is commercially available. Most dogs can be successfully treated with either a cemented or a cementless total hip arthroplasty. However, some small boned dogs can have a cemented prosthesis implanted but not a cementless one. Also large boned dogs with a straight or “stove pipe” femur are not good candidates for implantation of a cementless stem, as the risk of subsidence is high. In the event of a failure of a cementless prosthesis, a cemented prosthesis is often used to successfully preserve the total hip arthroplasty. The cementless hip prosthesis is also less forgiving during implantation than the cemented prosthesis. For these reasons, a surgeon should be very comfortable with the technique for cemented hip arthroplasty before learning the technique for implanting a cementless prosthesis. Thus, this chapter will concentrate primarily on cemented techniques.

The most commonly implanted prosthesis is a cemented modular prosthesis made by BioMedtrix Inc. (Boonton, NJ), which also manufacture cementless implants that use the same head as the cemented prosthesis. This allows the surgeon to implant a cemented component in one portion of the hip (either the acetabulum or the femur) and a cementless component in the hip’s other portion. This creates a hybrid total hip arthroplasty.

Dogs with clinical signs related to hip dysplasia or other disabling hip conditions are candidates for surgery once their physis have closed at 9 to 10 months of age and they have a skeletal size that will accommodate the available prosthesis, which generally starts at 14 kg. They are candidates if they are not responsive to medical management or if medical management is no longer relieving clinical signs. When the dog’s function is used as an indicator of the need for total hip arthroplasty and not just radiographic evaluation, 80% of dogs will only need one total hip arthroplasty.

Special care must be taken to insure that the surgery is done under strict aseptic conditions. The dog’s hind limb is clipped the day prior to surgery. The skin is evaluated for bacterial dermatitis, which, if present, will delay the procedure until the condition is resolved. If the skin is dirty, the dog is bathed. Intravenous antibiotics are administered immediately prior to surgery. Draping of the patient with sterile paper and self-adhering plastic drapes provides a barrier at the surgical site that is impermeable to bacteria. Special instrumentation has been developed to facilitate the implantation of the modular prosthesis (BioMedtrix Inc., Boonton, NJ). Radiographic templates are used prior to surgery to estimate the size of acetabular cup and femoral stem that will be implanted.

The coxo-femoral joint is exposed via a cranial lateral approach. The skin incision starts dorsal and caudal to the greater trochanter and curves along the front edge of the femur. The tensor fascia lata is reflected cranially. Retracting the middle and superficial muscles dorsally with an Army-Navy retractor exposes the deep gluteal muscle. The deep gluteal muscle is incised at its origin and split into 2 segments. The joint capsule is incised along with the vastus medialis and lateralis muscles (Figure 60-106).
 

At various points in the surgical procedure the femur will be rotated in position. All references in the following text to the lateral, medial, cranial or caudal surface of the femur refer to that surface when the femur is in normal position. To properly perform the femoral osteotomy, the femur is externally rotated so the patella is oriented 90% lateral to its normal position. The medial edge of the greater trochanter is identified. The femoral osteotomy originates at this point. A template of the femoral prosthesis is aligned parallel to the long axis of the femur and the axis of the femoral neck (Figure 60-107). The template acts as a guide for performing the osteotomy. The diseased femoral head is removed. Instrumentation developed specifically for the modular prosthesis allows power reaming of the femur and acetabulum. Although the reaming can be done by hand it is easier and more accurately done with power.
 

The acetabular bed is prepared first using the acetabular reamer (Figure 60-108). No flush is used during the acetabular reaming so that the cancellous bone shavings can be collected and saved for possible use later. The shavings can be packed into areas of deficit in the acetabulum or along fissures in the femoral neck, should either of these be present. The acetabulum is reamed until the medial cortical wall is exposed. Remnants of ligament of the head of the femur may need to be removed to fully expose the medial wall. Three or more holes are drilled around the rim of the acetabulum using a drill bit from the modular system and the tissue guard, which protects soft tissues (Figure 60-109). The holes are connected with a curette. This undercut provides anchor sites for the bone cement or polymethyl methacrylate (PMMA).
 

The femoral shaft is rotated laterally 90%. A wide tipped Hohmann retractor is used to elevate its proximal end lateral to the tissues that lie dorsal to it. The femoral shaft is first drilled with a drill bit that matches the size of the femoral stem that has been selected for insertion (Figure 60-110). It may be necessary to start drilling with the bit oriented perpendicular to the osteotomy line. As soon as the proximal cancellous bone is penetrated the drill bit should be reoriented so it is parallel with the long axis of the femur. The fluted reamer, that is the same number as the drill bit used, widens the hole in the femoral shaft (Figure 60-111). The final preparation of the femoral shaft is done by hand with a finishing file and sometimes a broach (Figure 60-112). It is important to ream the femoral shaft along the medial edge of the trochanter to insure complete access to the femoral canal. In some cases the wall of the trochanteric fossa must be removed with a rongeur after the drill bit has created an opening to insure that the femoral canal is adequately opened. Reaming along the endosteal surface of the femoral neck accommodates for the curved portion of the femoral prosthesis. A trial prosthesis the same size as the one to be implanted is inserted to ensure the prosthesis will fit properly and that there will be an adequate cement mantel around the prosthesis. The trial prosthesis should move freely in all directions after it is inserted. This motion indicates that there is adequate room for cement around the stem.
 

Thoroughly cleaning the acetabular bed and the femoral shaft is necessary before the cement is injected. The PMMA should be mixed according to the manufacture’s specifications. Only PMMA with a liquid phase of 3 to 7 minutes can be injected. PMMA is injected through a catheter tip syringe into the acetabular bed first. Specific landmarks and the acetabular cup positioner are used to achieve proper position of the acetabular cup (Figure 60-113). All excess PMMA is removed. A second batch of PMMA is mixed for the femoral shaft injection. The shaft is cleared of blood and debris and PMMA is injected into the femoral canal using a 60 cc catheter tip syringe. The cobalt chrome femoral stem is aligned with the long axis of the femur and inserted down the shaft until the prosthesis collar rest is flush with the osteotomy line. The stem is held solidly in place with the stem impactor. Excess PMMA is removed while the cement in the femoral canal hardens.
 

A trial plastic head is placed on the femoral stem so that neck length can be assessed (Figure 60-114). The prosthesis with the trial head is reduced and the tightness of fit tested. Once the proper neck length has been determined the cobalt chrome head is placed on the stem and tapped securely into position. The head is reduced into the acetabular cup. Cultures are taken and the joint capsule is tightly closed. The surgical site is closed in layers.
 

Lateral and ventro-dorsal pelvic radiographs are taken immediately post operatively so the position of the acetabular and femoral components and the fill of the PMMA can be assessed. Antibiotic therapy is continued until the culture results are known. If the results are negative, which is almost always the case, antibiotics are discontinued. On the rare occasion when results are positive, antibiotics based on sensitivity patterns should be continued for at least 4 weeks. The dogs are maintained on limited activity for 2 months following the surgery. No activity more strenuous than a walk is allowed and the dog s to be outside only on a leash. After that period the dog can gradually return to normal activity.

Discussion

The modular system has improved the technique of total hip arthroplasty in the dog over the previously used fixed head prosthesis. It gives the surgeon state of the art instrumentation, a wider choice of neck lengths and increased implant sizes. Thus it is possible for the veterinary surgeon to offer better care for the dog with disabling hip conditions. Smaller dogs can be treated because a wider range of prosthesis sizes is available. The size of the femoral canal and acetabulum are limiting factors in prosthesis implantation. The modular system allows the proper size of prosthesis to be chosen for each dog’s femoral canal and acetabular cup. The clinical results achieved with the modular system are better than those of the fixed head system. Experience obtained with the fixed head system has shortened the learning curve for the modular system.

Dogs with THAs have achieved normal or near normal hind limb function 95% or more of the time. Pain free function, a full range hip motion, increased exercise tolerance, increased muscle mass and an improved quality of life are standard findings. Working dogs returned to field or police work and pets were exercised more without pain. It has been found that 80% of the dogs will not need the other un-operated hip replaced. They get enough relief from 1 THR that operating on the other side is not necessary. Often on reevaluation it was found that neither hip was painful when both had been hurt before surgery. The thigh circumference of the side with the THR is routinely 1 to 4 cm larger than the un-operated side. Because the prosthesis provides the normal ball and socket arrangement of the hip joint, the femur maintains its normal position relative to the pelvis and the hind limb is able to generate maximal propulsion forces during locomotion. This is not the case if the ball and socket joint configuration is not present.

Total hip arthroplasty in the dog is a very effective way of treating disabling conditions of the dog’s hip joint. To be proficient at this procedure a surgeon must be well trained in the technique and do it routinely. Not every veterinarian should be doing THAs. However, every veterinarian should know enough about the procedure to be able to discuss it as a treatment option when indicated.

Total hip arthroplasty is well known by the general public as a treatment for people with hip problems. Because of this more owners are demanding it for their pets and more referral centers are offering it as part of their service. The future of THAs in veterinary medicine is bright and will continue to be so as long as the latest information and technical developments are incorporated into the total hip arthroplasty protocol.

Suggested Readings

DeYoung, DJ, DeYoung BA, Aberman Ha, et al: Implantation of an uncemented total hip prosthesis: Technique and initial results of 100 arthroplasties. Vet Surg 21: 168, 1992.

Hoefle, WD: a surgical procedure for prosthetic total hip replacement in the dog. J Am Animal Hosp Assoc 10:269, 1974.

Leighton, RL: The Richard’s II canine hip prosthesis. J Am Anim Hosp Assoc 15:73, 1979.

Lewis RG, Jones JP: A clinical study of canine total hip replacement. Vet Surg 9:20, 1980.

Olmstead, ML, Hohn RB: Ergbisse mt der hufltoltal-prostheses bei 103 klinischen fallen an der Ohio State University. Klin Prox 25; 407, 1980.

Olmstead, ML, Hohn, RB, Turner, TM: A five year study of 221 total hip replacements in the dog. J Am Vet Med Assoc 183:191, 1983.

Olmstead, ML: Total hip replacement. Vet Clin N Am 17:943, 1987.

Olmstead, ML: The canine cemented modular total hip prosthesis: surgical technique and preliminary clinical results. J Am Anim Hosp Assoc 31:109, 1995.

Parker, RB, Bloomberg, MS, Bitetto, W et al: Canine total hip replacement: a clinical review of 20 cases. J Am Anim Hosp Assoc 20:97, 1984.

Paul HA, Bargar WL: A modified Technique for canine total hip replacement. J Am Anim Hosp Assoc 23:13, 1987.
 

Introduction

Numerous pathologic conditions exist that interfere with the normal function of the canine coxofemoral joint. Regardless of the inciting cause, dogs with coxofemoral joint pathology usually experience pain during motion of the joint. Surgery of the coxofemoral joint is usually performed to improve comfort and function.

Femoral head and neck excision is one of the most common surgeries performed on the coxofemoral joint. A more common name for the procedure is femoral head ostectomy (FHO). However, the term FHO is misleading because it is necessary to remove both the femoral head and neck to consistently achieve satisfactory results.

Removal of the femoral head and neck allows formation of a pseudoarthrosis (false joint) between the femur and the acetabulum. This procedure is considered a salvage operation to improve the quality of life in patients with severe coxofemoral joint disease. Pain is relieved and function is improved by eliminating the articulation of the femur and the acetabulum.

Indications

Femoral head and neck excision is suitable for most conditions that compromise the integrity of the coxofemoral joint. Common indications in dogs and cats include aseptic necrosis of the femoral head (Legg- Perthes disease), severe fractures of the coxofemoral joint, chronic or recurrent coxofemoral luxations, coxofemoral joint instability, or severe osteoarthritis. Femoral head and neck excision is most commonly used as a lower cost alternative to total hip replacement, or in animals that are too small for hip replacement. There is a tendency for some veterinarians to overuse femoral head and neck excision for conditions that can be managed by primary repair.

Results of femoral head and neck excision depend on a number of factors, including body size, body condition, animal temperament, surgical technique and postoperative physical therapy. There is a general consensus that success varies with the size of the patient. Cats and small breed dogs can, in general, be expected to do well. With adequate postoperative care, satisfactory results can be consistently achieved in non-overweight dogs up to 50 kg or more. However, dogs over 25 kg will usually perform better with primary repair or total hip replacement if appropriate or affordable to the owners. Results in giant breed dogs are, at best, inconsistent, and a femoral head and neck excision should only be considered as a last resort in these breeds.

Surgical Technique

Several approaches to the coxofemoral joint have been described. The currently accepted standard technique for femoral head and neck excision is the craniolateral approach. Some surgeons prefer the ventral approach because it is more cosmetic and allows for bilateral excision without repositioning the patient. However, the exposure with the ventral approach is more limited and should only be used in small patients.

Craniolateral Approach

The patient is positioned in lateral recumbency. A straight or slightly curved incision is centered at the level of the greater trochanter along the cranial border of the femur. The incision should extend distally approximately one-fourth to one-third of the length of the femur and proximally two-thirds the distance to the dorsal midline. After dissecting through the subcutaneous tissue, the incision is continued through both layers of the fascia lata along the cranial border of the biceps femoris muscle, extending proximally along the cranial border of the superficial gluteal muscle. The incision through this layer should include the insertion of the tensor fascia lata muscle in the deep layer of the fascia lata. The fascia lata and tensor fascia lata muscle are retracted cranially and the biceps femoris and superficial gluteal muscles are retracted caudally to expose the underlying vastus lateralis, middle gluteal and deep gluteal muscles. The middle gluteal muscle is then retracted caudodorsally to expose the insertion of the deep gluteal muscle on the greater trochanter (Fig. 62-115). To improve exposure of the hip joint, a partial tenotomy of the ventral two-thirds of the deep gluteal insertion can be performed prior to dorsal retraction to expose the underlying joint capsule of the coxofemoral joint.
 

A transverse incision is made in the joint capsule to expose the femoral head. A second longitudinal incision should be made through the joint capsule, along the femoral neck through the origin of the vastus lateralis muscle for adequate exposure of the femoral neck. The femoral head should be luxated prior to the osteotomy. It is necessary to cut the ligament of the head of the femur if it is still intact. The femur should then be externally rotated ninety degrees so the cranial aspect of the femoral head and neck are facing up. The osteotomy to excise the femoral neck can be made with an oscillating saw or an osteotome. An oscillating saw will provide the smoothest and most accurate cut. An osteotome also works well as long as it is sharp. Use of a dull osteotome can result in a subtrochanteric fracture of the femur. A proper osteotomy should remove all of the femoral head and neck without damaging the greater or lesser trochanter. With the femur held in ninety degrees of external rotation, the oscillating saw or osteotome should be placed on the upward facing cranial surface of the femoral neck at an angle demonstrated in Fig. 62-116. The cut should be directed caudally and medially. If the cut is directed perpendicular to the surgery table, a portion of the caudal femoral neck will remain because of anteversion of the femoral neck. The cut should extend from the base of the greater trochanter across the neck, in a line that will completely remove the neck without removing the lesser trochanter. The osteotomy must be smooth, without bony projections or irregularities. If present, they may be removed with a bone rasp or rongeurs. Incomplete removal of the femoral neck may result in increased contact between the femur and acetabulum, resulting in long-term discomfort.
 

After completing the osteotomy, the femoral head is grasped and any remaining attachments of the joint capsule are divided to allow removal of the femoral head and neck. Closure is achieved by placing one or two mattress sutures in the deep gluteal tendon. The incised edge of the vastus lateralis muscle is sutured to the cranioventral edge of the deep gluteal muscle. The fascia lata and tensor fascia lata muscle are sutured to the cranial edge of the biceps muscle. The remainder of the closure is routine.

Ventral Approach

This approach provides a much more limited exposure than the previously described craniolateral approach. The patient is placed in dorsal recumbency with the hind legs abducted. The skin incision is made over the pectineus muscle, which is easily palpable. The underlying fascia is divided and the pectineus muscle is isolated, taking care to avoid the femoral artery, vein, and saphenous nerve cranial to the muscle belly. The pectineus muscle is transected at its origin on the pubis. The pectineus is then reflected distally. The iliopsoas muscle is retracted cranially and the adductor muscle is retracted caudally to expose the ventral joint capsule. Care must be taken to avoid the deep femoral artery and vein, as well as the obturator nerve, which lie ventral and medial to the joint. The joint capsule is then incised to reveal the ventral femoral head and neck. The osteotome or oscillating saw is then positioned on the ventral-most aspect of the femoral neck and directed to the trochanteric fossa to the allow complete removal of the femoral head and neck as described previously. The pectineus muscle can be re-attached to its origin or the prepubic tendon with mattress sutures. The remainder of the closure is routine.

Muscle Transposition

Early postoperative lameness following femoral had and neck excision is thought to be at least partly due to bone on bone contact between the femur and the pelvis. This contact may be more pronounced in larger dogs because their greater body mass tends to drive the bones together. Pain in the early postoperative period can significantly slow the return to function and result in a more restrictive pseudoarthrosis. Techniques that interpose a muscular pad between the osteotomy site and the acetabulum have been developed in an effort to decrease early postoperative pain and lameness. These flaps can be used at the surgeon’s discretion.

There are two commonly used muscle pad techniques; the deep gluteal flap and the biceps sling. Biceps slings provide more coverage of the femoral osteotomy site then deep gluteal flaps. The biceps sling can be either a full or partial thickness flap. In a controlled experimental setting, the use of full thickness bicep slings was associated with high postoperative morbidity. This morbidity was not seen in a similar study using partial thickness slings.

Both deep gluteal flaps and biceps slings are performed through the previously described craniolateral approach. To create a deep gluteal flap, a tenotomy of the ventral two-thirds of the deep gluteal tendon is performed at its insertion on the greater trochanter. The muscle is then incised longitudinally from the tenotomy to its origin on the ilium. This creates a muscular flap that can be rotated distally (Fig. 62-117). After the femoral head and neck excison is performed, the femur is rotated externally to expose the insertion of the iliopsoas muscle on the lesser trochanter. The distal end of the deep gluteal flap is then sutured to the insertion of the iliopsoas muscle (Fig. 62-118). When the femur is returned to its normal position, the deep gluteal flap is drawn across the osteotomy site to form a pad between the osteotomy site and the acetabular rim (Fig. 62-119).
 

To create a biceps sling, the previously described skin and fascial incision for the craniolateral approach must be extended to the stifle. Creation of a partial thickness sling is recommended to avoid excessive postoperative morbidity. The muscle flap is created from the craniolateral portion of the biceps femoris muscle. The free end of the flap should be widest at the base (approximately 1.5 times the width of the osteotomy site) and should taper distally (Fig. 62-120). The sling is elevated by sharp dissection with the cut angled to produce a flap 0.5 to 1 cm thick, depending on the size of the patient. A wide fenestration is made in the caudal aspect of the coxofemoral joint capsule to allow easy passage of the sling through the joint in a caudal to cranial direction. Use of a suture snare to pull the muscle flap through the joint, minimizes muscular trauma (Fig. 62-121). The sling is then positioned to cover the osteotomy site and the distal portion of the sling is sutured to the vastus lateralis muscle (Fig. 62-122). To prevent movement of the sling across the osteotomy site, the sling can also be sutured to the deep gluteal muscle dorsally and the iliopsoas muscle ventrally. The fascia lata is then sutured to the remaining biceps muscle.
 

Postoperative Management

An early return to function is necessary for the development of a functional pseudoarthrosis. Motion of the coxofemoral joint in the early postoperative period will aid in the formation of a fibrous joint with a good range of motion. If postoperative motion is restricted, the pseudoarthrosis that forms will have a limited range of motion and the long-term function will be less desirable.

Appropriate doses of analgesics for at least one to two weeks (longer if necessary) are essential to encourage early use. The owners should perform passive range of motion exercises at least two to three times a day. Exercise should be encouraged in the form of walking or swimming. Swimming is one of the best forms of postoperative physical therapy, and owners should be encouraged to pursue this option if it is available.

Proper surgical technique and proper postoperative physical therapy can produce consistent satisfactory results in non-overweight dogs of most breeds. Results may still be inconsistent in overweight dogs and giant breeds.

Suggested Readings

Lippincott CL: Excision arthroplasty of the femoral head and neck. Vet Clin North Am [Small Anim Pract] 17:857, 1987.

Berzon JL, Howard PE, Covell SJ, et al.: A retrospective study of the efficacy of femoral head and neck excisions in 94 dogs and cats. Vet Surg 9:88, 1980.

Tarvin G, Lippincott CL: Excision arthroplasty for treatment of canine hip dysplasia using the biceps femoris muscle sling: An evaluation of 92 cases. Semin Vet Med Surg [Small Anim] 2:158, 1987.

Mann FA, Tanger CH, Wagner-Mann C, et al.: A comparison of standard femoral head and neck excision and femoral head and neck excision using a biceps femoris muscle flap in the dog. Vet Surg 16:223, 1987.

Lippincott CL: Improvement of excision arthroplasty of the femoral head and neck utilizing a biceps femoris muscle sling. J Am Anim Hosp Assoc 17:668, 1981.

Lippincott CL: Excision arthroplasty of the femoral head and neck utilizing a biceps femoris muscle sling. Part two: The caudal pass. J Am Anim Hosp Assoc 20:377, 1984

Gendreau C, Cawley AJ: Excision of the femoral head and neck: the long-term results of 35 operations. J Am Anim Hosp Assoc 13:605, 1977.

Lewis DD, Bellah JR, McGavin MD, Gaskin JM: Postoperative examination of the biceps femoris muscle sling used in excision of the femoral head and neck in dogs. Vet Surg 17:269, 1988.

Prostredny, JM, Toombs, JP, Van Sickle, DC: Effect of two muscle techniques on early morbidity after femoral head and neck excision in dogs. Vet Surg 20:298, 1991.

Bjorling DE, Chambers JN: The biceps femoris flap and femoral head and neck excision in dogs. Compend Contin Educ Pract Vet 8:359, 1986

Piermattei DL, Johnson KA: An Atlas of Surgical Approaches to the Bones and Joints of the Dog and Cat. 4th ed. Philadelphia: Saunders 2004, 290.

Hosgood G, Toombs JP: The suture snare technique for passage of tissue strips or flaps. J Am Anim Hosp Assoc 26:322, 1990.

Millis DL. Levine D, Taylor RA: Canine Rehabilitation and Physical Therapy 1st ed. Saint Louis: Saunders 2004.