Tibia and Tarsus

Introduction

Tibial fractures commonly occur in dogs and cats. Specifically, tibial fractures range from 9 to 18% of fractures occurring in dogs.¹ Proximal and distal fractures in immature animals are generally physeal fractures, most often Salter-Harris Type I or II. In mature dogs, proximal metaphyseal fractures may be single or comminuted and may cause loss of integrity of the tibial plateau. Distal tibial fractures in mature dogs often involve malleolar fractures, and are generally associated with road trauma. (See next section on malleolar fractures). Tibial diaphyseal fractures encompass the following: greenstick or incomplete fractures in immature animals; transverse, short oblique, long oblique and spiral reducible fractures; and comminuted fractures which may be reducible (one butterfly fragment) or nonreducible (multiple fragments). The tibia may be treated with cast, intramedullary pins and orthopedic wire, interlocking nail, external fixator, or bone plate and screw fixation. The surgeon should consider the mechanical, biological and clinical environment of the fracture and the patient before choosing the appropriate implant system for treating diaphyseal fractures.²

Preoperative Assessment and Management of Animals with Tibial Fractures

Animals that have received an external blow severe enough to cause a tibial fracture often have concurrent external or internal organ system injury. Cardiovascular, pulmonary, urinary, and neurologic systems should be examined thoroughly to detect any abnormalities prior to anesthesia and surgical repair of the fracture. A minimum database should include a complete blood count, chemistry profile, urinalysis and radiographs of the affected tibia. It is often useful to take radiographs of the conta-lateral tibia for comparison and to serve as a template for plate contouring. Because 33 to 42% of fracture patients have some degree of pulmonary injury, preoperative evaluation should include thoracic radiographs.³ Fractures of the tibia are best managed preoperatively with a modified Robert Jones bandage to reduce or prevent soft tissue swelling which interferes with landmark identification. Prophylactic antibiotics should be administered in contaminated cases (open injuries), cases with severe trauma (significant soft tissue bruising and swelling or multiple bone fractures), and cases requiring lengthy operative times (2 hours or longer). Prophylactic antibiotics are also effective in closed tibial fractures and should be administered intravenously at the time of anesthetic induction, repeated every 2 to 4 hours, and discontinued at completion of surgery.³

General Issues with Tibial Fracture Management

Issues unique to the tibia include the presence of minimal soft tissue coverage on the medial surface of the bone. The paucity of soft tissues increases the possibility of open fractures and potentially decreases the extra-osseous blood supply, both of which can delay bone healing. Minimal soft tissue coverage of bone plates results in tissue irritation and cold hypersensitivity which may require plate removal to resolve. However, the minimal muscle coverage on the medial side is an advantage for placing an external fixator while minimizing muscle trauma.

The tibia is an ideal bone for external fixator application because it is straight from the lateral perspective and allows the potential for all frame constructions including use of the circular and hybrid fixators. Conversely, the tibia can be a difficult bone for placing an intramedullary pin or nail because of the S shaped curve apparent from the cranial perspective and the presence of the joints directly above and below the bone. In order to prevent untoward stifle joint penetration with intramedullary implants, only antegrade implant pin placement is recommended. The S shape of the tibia also contributes to the requirement for accurate plate contouring to avoid angular deformity.

Clinically Relevant Anatomy of the Tibia

The tibia articulates with the femur proximally, the tarsus distally and the fibula both proximally and distally on the lateral side. The lateral collateral ligament of the stifle inserts on the fibular head. The medial collateral ligament of the stifle inserts on the caudal proximal portion of the medial surface of the tibia. The proximal epiphysis of the tibia is triangular in shape with the articular surface on the caudal half. The tibial tuberosity where the patella ligament inserts encompasses the cranial half of the proximal epiphysis. The tibial tuberosity continues distally forming the tibial crest on the cranial surface of the tibia. The proximal tibial metaphysis is flat medially with minimal soft tissue coverage and concave laterally where the extensor muscles are located. The tibial diaphysis is round in cross section and describes an S shaped curve when viewed from the cranial aspect. The tendons of the cranial tibial and long digital extensor muscles cross the cranial surface and the medial saphenous vein crosses the medial surface of the distal tibia. The medial malleolus of the distal tibia and lateral malleolus of the fibula extend distal to the articulating surfaces of the distal tibia and talus. The long and short parts of the medial and lateral collateral ligaments arise from the medial malleolus of the tibia and the lateral malleolus of the fibula respectively and are essential for hock stability.

Proximal Tibial Fractures

Physeal Fractures

Salter I and Salter II fractures of the proximal tibial physis occur in immature dogs and cats. Animals usually present with a nonweight bearing lameness of the affected limb subsequent to a traumatic episode. Palpation of the proximal tibia reveals soft tissue swelling, instability and crepitus. Radiographs are used to confirm the diagnosis of proximal physeal fracture. The epiphysis is generally displaced caudally to the metaphysis.

Physeal fractures which are minimally displaced may be stabilized with a cast applied to the leg with the stifle in extension. However, in many cases adequate fracture reduction cannot be obtained without surgical manipulation. Surgical treatment consists of open reduction and stabilization with two or three Kirschner wires. A medial approach through skin, subcutaneous tissue and crural fascia over the proximal diaphysis of the tibia may be used to expose the fracture.⁴ The fracture is reduced by extending the stifle and gently levering the epiphysis into position. Reduction is maintained with pointed reduction forceps while the fracture is stabilized with two or three Kirschner wires or small intramedullary pins (Figure 62-1). The implants may be bent to prevent migration and aid removal.⁵

Postoperatively, the patient should be confined to a small area with activity limited to leash walking. Follow up radiographs may be made at 3 and 6 weeks after treatment. Physeal fractures generally heal within three to four weeks. If a cast is used, it should be removed as early as possible. Physical therapy may be necessary to restore range of motion to the stifle. Premature closure of the physis usually occurs because of the trauma inflicted on the growing cells during the initial injury. Owners of very immature animals should be warned of the potential for growth deformities.
 

Avulsion of the Tibial Tuberosity

Avulsion of the tibial tuberosity also occurs in immature dogs and cats. The tibial tuberosity is the insertion point for the patella ligament and is subjected to avulsion forces when the quadriceps muscle is contracted. Animals usually present with considerable joint effusion, soft tissue swelling and lameness. Radiographs are made to confirm the diagnosis. In some cases, confusion may exist over the appearance of the physis. Radiographs should be made of the opposite limb to verify the presence of an avulsion versus irregular ossification of the tuberosity. Obtaining flexed and extended stifle views may be useful to confirm the mobility of the avulsed fragment.

Avulsions of the tibial tuberosity which are minimally displaced may be stabilized with a cast applied to the leg while the stifle is extended. Surgical treatment consists of open reduction and stabilization with two Kirschner wires and figure of eight orthopedic wire functioning as a tension band. A medial approach is used to expose the fracture.⁴ The avulsed tibial tuberosity is reduced by extending the stifle and securing the tuberosity to the tibia with a pointed reduction forceps. The tuberosity is secured with a tension band wire (Figure 62-2).⁵ Postoperative radiographs should be evaluated for fracture reduction and implant placement.

Postoperatively, the patient should be confined to a small area with activity limited to leash walking. Follow up radiographs may be made at 3 and 6 weeks after treatment. If a cast is used, it should be removed in 3 to 4 weeks. Physical therapy may be necessary to restore range of motion to the stifle. In very immature animals, the tension band wire should also be removed at 3 weeks to allow physeal growth. Premature closure of the tibial tuberosity physis in a very young animal may adversely affect stifle conformation. Additional implant removal may be required if soft tissue irritation occurs.
 

Proximal Metaphyseal Fractures

Proximal metaphyseal fractures in mature dogs are uncommon. These fractures may involve the articular surface, and may be either single or comminuted fractures. They are generally managed with a buttress plate application to shore up the tibial plateau.(Figure 62-3) The addition of a cancellous bone autograft may be necessary if there is bone loss.
 

Tibial Diaphyseal Fractures

Tibial diaphyseal fracture stabilization has been described using casts, intramedullary pins and orthopedic wire, interlocking nails, bone plates and screws, and linear and circular fixators. The keys to optimal fracture fixation include accurate decision making to guide reduction technique and implant choice, and preoperative fracture planning for the procedure.

Implant systems are chosen after an assessment has been made of the mechanical, biological and clinical environments of the fracture and the patient. The mechanical environment is influenced by the size and activity of the patient, the type and reducibility of the fracture, and the presence or absence of multiple limb injury or pre-existing disease. The mechanical environment dictates how much load the implant must support. The biological environment is influenced by the age and health of the animal, the location of the fracture, the energy involved in creating the fracture, and the presence and condition of the surrounding soft tissues. The biologic environment can also be disturbed with open anatomic reduction techniques. The biologic environment dictates the length of time the implant must function. The clinical environment includes the intended function of the animal, the attitude of the animal and the client’s ability to care for the animal. If the mechanical environment is poor, the implant system must be relatively strong. If the biological environment is poor, the implants must be able to function for a prolonged time period and should purchase the bone with an interlocking hold (bone screws and positive profile threaded pins). Some fixation systems, especially external fixation systems are inappropriate for certain animals and clients.²

After the appropriate implant system has been selected, preoperative fracture planning includes selecting a reduction technique and predetermining where implants will be placed. Epidural anaesthesia with a local anaesthetic agent and a narcotic, combined with general anaesthesia, provides analgesia and profound relaxation of the muscles of the rear limb and is a useful aid to tibial fracture reduction. Reducible fractures, single fractures and fractures with one or two large fragments are treated with open reduction, anatomical reconstruction and rigid stabilization to restore the bone column and promote load sharing between the bone and the implant, and enhance the mechanical environment. Transverse and short oblique fractures may be reduced by exposing the fracture and tenting the bone ends out of the incision then pressing the reduced fracture back into position. Alternatively, a limited approach may be made and a lever used to manipulate the bone back into position. Long oblique or spiral fractures may be reduced by exposing the fracture and distracting the bone segments to approximate the fracture surfaces while using pointed reduction forceps to manipulate the bone segments into reduction.⁶

Non-reducible fractures, or comminuted fractures with multiple small or large fragments where fragment reconstruction would not restore the bone column should be treated with closed indirect reduction or “open but do not disturb the fragments” indirect reduction techniques to preserve the biological environment.⁷ The tibia is particularly suitable for the indirect reduction techniques essential to the success of “biologic” treatment of non-reducible fractures. Distraction of the major bone segments may be achieved with the hanging limb technique or by using an intramedullary pin to push the distal segment away from the proximal segment. As the bone ends are distracted the tension on the surrounding soft tissues guides the fragments into alignment.⁶

In addition to choosing the reduction technique, it is helpful for preoperative planning for the surgeon to draw the fracture lines on an outline of the intact tibia. The implants should then be drawn onto the tibia in the order and location in which the surgeon intends to place them. The fracture plan may be taken into the operating room to serve as a guide.^8,9

Diaphyseal tibial fractures which are treated with open reduction will often benefit from the addition of a cancellous bone autograft, or cancellous bone allograft with demineralized bone matrix. Cancellous bone autograft may be harvested from the ipsilateral proximal humerus which is accessible when the animal is positioned for surgery. The donor site must be prepared for aseptic surgery prior to moving the animal into the operating room. The graft is usually harvested after the fracture has been stabilized. Alternatively, cancellous bone allograft with demineralized bone matrix is available commercially and eliminates the the need for preparing a donor site.

Treatment of Tibial Diaphyseal Fractures with a Cast

Full cylinder casts which incorporate the hock and the stifle are a very effective fixation for stable fractures in young dogs or cats when the fracture shares the load of weight bearing with the cast and will heal quickly. Greenstick or incomplete fractures of the tibia fit these criteria. The cast should be applied with the limb positioned slightly in extension and with varus angulation to overcome the contraction of the extensor muscles lying on the lateral side of the tibia.¹⁰ Postoperatively the animal must be confined to a small area with very limited activity allowed. The client must be willing to protect the cast from adverse environments. Weekly rechecks will minimize cast related complications.

Operative Treatment of Tibial Diaphyseal Fractures

Treatment of Tibial Diaphyseal Fractures with Intramedullary Pins and Orthopedic Wire

An intramedullary (IM) pin may be combined with multiple cerclage wires to stabilize long oblique or spiral tibial fractures in immature animals (Figure 62-4). A medial approach is made to the fracture area. The IM pin is placed in an antegrade manner starting at a point on the edge of the tibial plateau midway between the tibial tuberosity and the medial tibial condyle. The pin is driven into the medullary canal to exit at the fracture. The fracture is reduced and secured with pointed reduction forceps. The cerclage wire is applied. The IM pin is then driven distally to insert in the distal metaphysis. Care must be taken to avoid penetrating the articular cartilage. Using a similar length pin as a guide pin can help the surgeon determine the location of the inserted pin. The exposed end of the pin is cut below the level of the skin.¹¹
 

Treatment of Tibial Diaphyseal Fractures with an Interlocking Nail

Interlocking nails can be used effectively to treat a wide variety of mid diaphyseal tibial fractures. Because the screws or bolts securely lock the nail to the respective bone segment, the interlocking nail not only provides resistance to bending, but also resists rotational and axial loading forces and can effectively bridge a nonreducible fracture. An open approach is used to reconstruct reducible fractures. An open but don’t touch approach is used when major segment alignment is the goal. The nail selected should correspond to the width of the medullary canal at the isthmus of the bone. The interlocking nail is inserted in a normograde manner starting at the cranio-medial aspect of the tibial plateau. A medial parapatellar approach is used to expose the point of insertion. Flexing the stifle 90 degrees facilitates nail insertion. The medullary canal is prepared for nail placement by inserting a series of progressively larger Steinmann pins or by using a hand reamer. The nail is inserted using the extension and the insertion tool. The insertion tool is removed and the drill-guide jig attached to the extension. Using the drill guide jig, the interlocking nail is secured in place with two screws each placed through the proximal and distal fracture segments and the nail¹² (Figure 62-5).
 

Treatment of Tibial Diaphyseal Fracture with External Fixators

External fixators may be applied to stabilize most tibial diaphyseal fractures. The stiffness of the fixator may be manipulated by adding fixation pins and using biplaner or bilateral frames to manage a wide variety of fractures in most dogs and cats. The hanging limb technique may be used for positioning the limb and to aid reduction of the fracture.⁶ The patient is placed in dorsal recumbency and the affected limb is suspended from the ceiling and draped out in the hanging position. The table can be lowered to allow the animal’s weight to fatigue the muscles and help align the joints. For single fracture lines the fragments may be levered into position through a limited surgical approach to the fracture. For closed reduction of comminuted fractures, proximal and distal fixation pins may be placed initially and then manipulated to align the joint surfaces. The reduction is maintained by securing the connecting bars.

A type Ia external fixator is applied to the cranial medial surface of the tibia. Positive profile or Duraface end threaded fixation pins are placed in the metaphysis of each segment and about 1 centimeter on either side of the fracture line. At least two and preferably three fixation pins are placed in each bone segment. The pins are secured to a connecting rod creating a unilateral, uniplanar frame (Figure 62-6). To apply a type Ib frame, an additional unilateral frame is placed on the cranial lateral surface of the tibia to create a unilateral, biplanar frame (Figure 62-7). Type Ib frames may be connected with articulating rods. A type II frame is applied to the tibia by inserting transfixation pins through the metaphyses and securing them to the connecting rods. Fixation pins are then placed about a centimeter on either side of the fracture. These pins can be unilateral, secured only to the medial connecting bar, or transfixation pins which are secured to both connecting bars. Additional pins are placed when there is adequate bone¹³ (Figure 62-8). This frame is a bilateral, uniplanar construct. Rarely, a type III frame is applied by adding a unilateral frame to the cranial surface of the tibia forming a bilateral, biplanar frame.

Treatment of Tibial Diaphyseal Fractures with Bone Plates and Screws

Bone plates and screws may be used to stabilize both single and comminuted tibial diaphyseal fractures. Single transverse or short oblique fractures should be anatomically reduced and stabilized using the bone plate as a compression plate (Figure 62-9). Long oblique fractures should be anatomically reduced and compressed with lag screws. The reconstructed bone is then protected with a bone plate used as a neutralization plate (Figure 62-10). A comminuted nonreducible fracture should be realigned and bridged with a bone plate functioning as a bridging plate (Figure 62-11A). The plate may be combined with an IM pin when stabilizing comminuted nonreducible fractures to reduce strain on the plate and extend fatigue life of the fixation (Figure 62-11B).^14,15
 

A cranial medial approach to the shaft of the tibia is used to expose the fracture site and the medial surface of the bone for plating.¹⁶ When treating comminuted nonreducible fractures, an open but don’t disturb the fragments technique should be used to expose the proximal and distal bone segments with minimal disturbance of the fracture hematoma and bone fragments.⁷ Cranial caudal radiographs of the contralateral intact tibia are useful to serve as a template for plate contouring. The tibia has an S shaped curve which must be reproduced when contouring the plate to avoid a valgus deformity of the limb postoperatively.

General Postoperative Treatment of Tibial Diaphyseal Fractures

Postoperative treatment starts with radiographs made of the tibia to document fracture reduction or appropriate limb alignment, and implant placement. Radiographs of comminuted fractures treated by realigning the limb should be evaluated closely to determine that the proximal and distal joint surfaces are parallel to each other and the joints are not rotated in relationship to each other. Mal-aligned limbs with varus or valgus deformity which are treated with external fixators may be corrected postoperatively by loosening the distal fixation clamps and realigning the limb. Mal-aligned limbs treated with plates cannot be corrected without a second surgical procedure. The surgeon must make the decision about severity of the mal-alignment and act appropriately.
 

General postoperative management instructions given to clients consist of recommending close confinement of the patient with activity limited to leash walking until there is radiographic evidence of bone bridging the fracture. Radiographic re-evaluations should be made at 6 week intervals.

Animals treated with internal fixation do not require special management of the limb. Animals treated with external fixators require extensive aftercare. Postoperatively, gauze sponges should be packed around the fixation pins and secured with a bandage, which also incorporates the paw, to limit postoperative swelling. External fixator management includes daily pin care and pin packing as needed. Additionally, the external fixator can be destabilized as dictated by the radiographic evidence of bone healing by removing one unilateral frame from a type Ib fixator: removing selected fixation pins from a type Ia or type II fixator; removing the lateral connecting rod of the type II fixator, or downsizing the connecting rods in a frame.

In immature animals, fracture bridging is generally observed by 6 weeks, with additional remodeling occurring in 12 weeks. Mature animals generally are healed in 12 to 18 weeks (depending on fracture configuration and signalment of the animal).

External fixators are removed when there is evidence of bone bridging the fracture site on both radiographic views. Intramedullary pins are generally removed after bone healing because of the morbidity associated with the pin end irritating the insertion site. Interlocking nails, orthopedic wire and lag screws are left in situ unless they are associated with a clinical problem. Plate removal may be necessary after the fracture heals if soft tissues irritation or cold sensitivity occurs.

Distal Physeal Fractures

The most common physeal fractures of the distal tibia are Salter Harris type I and II fractures. If the fracture is nondisplaced, treatment with cast application is generally sufficient. If the fracture is displaced, then a cranial approach to the distal tibia is made to allow anatomic reduction of the fracture.¹⁷ Crossed Kirschner wires or small intramedullary pins are driven from the medial malleolus across the physis, into the tibial metaphyses, seating in the lateral cortex; and from the medial aspect of the distal tibial metaphysis, across the fracture into the epiphysis avoiding the articular surface. Alternatively, the second wire may be driven from the fibular malleolus into the tibia (Figure 62-12).¹⁷

Postoperative radiographs must be evaluated for accuracy of reduction and implant placement. Generally, a lateral splint is applied for 2 to 3 weeks to support internal fixation. Postoperatively, the patient should be confined to a small area with activity limited to leash walking. Follow up radiographs may be made at 3 and 6 weeks after treatment. Physeal fractures generally heal rapidly, within 3 to 4 weeks. If a cast is used, it should be removed as early as possible. Physical therapy may be necessary to restore range of motion to the hock. Premature closure of the physis usually occurs because of the trauma inflicted on the growing cells during the initial injury. Owners of very immature animals should be warned of the potential for growth deformities. Implant removal may be required if soft tissue irritation occurs.
 

References

1. Johnson JA, Austin C, Breur GJ: Incidence of canine appendicular musculoskeletal disorders in 16 veterinary teaching hospitals from 1980 through 1989. Vet Comp Orthop Traumatol 7:56, 1994.
2. Johnson AL: Fundamentals of orthopedic surgery and fracture management, decision making in fracture management, in Fossum TW (ed) Small Animal Surgery, 4th edition St. Louis, Mosby 2013, p 1055.
3. Johnson AL: Fundamentals of orthopedic surgery and fracture management, perioperative patient management in Fossum TW (ed) Small Animal Surgery, 4th edition St. Louis, Mosby 2013, p 1044.
4. Johnson KA and Piermattei DL: Surgical Approaches to the Bones and Joints of the Dog and Cat, 4th edition, Philadelphia, WB Saunders Co, 2004, p 366.
5. Johnson AL, Dunning D. Atlas of Orthopedic Surgical Procedures in the Dog and Cat. St. Louis, Elsevier Saunders, 2005, p 196.
6. Johnson AL. Current concepts in fracture reduction. Vet Comp Orthop Traumatol 16:59, 2003.
7. Aron DN, Palmer RH, Johnson AL: Biologic strategies and a balanced concept for repair of highly comminuted long bone fractures, Compend Cont Educ Pract Vet 17:35, 1995.
8. Johnson AL, Johnson K, Houlton J, et al: AO-ASIF Small Animal Preoperative Planning Guide: Synthes (USA); 1999.
9. Johnson AL, Fracture planning website, University of Illinois http:// vetmed.illinois.edu/fractureplanning/ January 2014
10. Johnson AL: Fundamentals of orthopedic surgery and fracture management, perioperative patient management in Fossum TW (ed) Small Animal Surgery, 4th edition St. Louis, Mosby 2013, p 1201.
11. Johnson AL, Dunning D. Atlas of Orthopedic Surgical Procedures in the Dog and Cat. St. Louis, Elsevier Saunders, 2005, p 202.
12. Dueland RT, Johnson KA, Roe SC, et al: Interlocking nail treatment of diaphyseal long bone fractures in dogs, J Am Vet Med Assoc 214:59, 1999.
13. Johnson AL, Dunning D. Atlas of Orthopedic Surgical Procedures in the Dog and Cat. St. Louis, Elsevier Saunders, 2005, p 206.
14. Johnson AL, Dunning D. Atlas of Orthopedic Surgical Procedures in the Dog and Cat. St. Louis, Elsevier Saunders, 2005, p 204.
15. Schwarz G: Fractures of the tibia. In Johnson AL, Houlton JEF, Vaninni R.(editors) AO principles of fracture management in the dog and cat, New York, Thieme for AO Publishing, 2005, p 310 .
16. Johnson KA and Piermattei DL: Surgical Approaches to the Bones and Joints of the Dog and Cat, 4th edition, Philadelphia, WB Saunders Co, 2004, p 370.
17. Johnson AL, Dunning D. Atlas of Orthopedic Surgical Procedures in the Dog and Cat. St. Louis, Elsevier Saunders, 2005, p 198.
     

Fractures of the medial or lateral malleolus of the tibia result in instability of the tarsus because of disruption of the origin of the collateral ligament complex. Subluxation or dislocation may occur if instability is severe. Occasionally, both the medial and lateral malleoli are fractured concurrently. The fractures may be simple and closed, or they may involve loss of bone and soft tissue in cases of shear wounds. External coaptation is usually inadequate because accurate anatomic reduction and rigid stabilization are necessary to decrease the chance of developing degenerative joint disease. Most fractures are best repaired using open reduction and internal fixation. Bone screws and pins and tension bands are the most common implants used to stabilize these fractures (Figure 62-13).

Pin and tension band fixation provides good stability and anatomic reduction in most cases. An approach to the fractured malleolus is performed by incising skin and subcutaneous tissues directly over the fragment. A periosteal elevator is used to expose the distal aspect of the tibia or fibula and the fracture site. The fracture site is cleaned of hematoma and fibrinous debris, to allow better visualization of the articular surface and the edges of the fracture fragments. The fracture is reduced anatomically; this is extremely important because of the intra-articular nature of the fracture. Bone-reduction forceps can be used to provide temporary stability. Two pins are driven in normograde fashion sequentially through the fractured malleolar fragment perpendicularly across the fracture site into the main fragment, with care taken to avoid the articular surface of the tibiotarsal joint. In small fragments, a single pin may be used. The pin size varies, depending on the size of patient and the size of malleolar fragment. Most cats and small dogs can accommodate 0.035- or 0.045-inch Kirschner wires, whereas medium-size and large dogs may accommodate 0.062-inch Kirschner wires or 5/64-inch pins. The tension band wire used is 20 or 22 gauge in cats and small dogs and 16 or 18 gauge in medium and large breed dogs. A hole, large enough to pass the selected wire, is drilled from cranial to caudal in the main fragment approximately 1 cm proximal to the fracture line. A small loop is created in the wire to permit tightening of the wire on the opposite side of the knot formed by twisting the ends of the wire. The wire is passed through the hole and around the Kirschner wires in figure-of-eight fashion.
 

The wire is tightened by simultaneously twisting the loop and ends of the wire while applying moderate traction. This forms a knot on each side of the loop that allows greater and more even wire tension after tightening. The knots should be centered if possible. The wires are tightened onto the surface of the bone, they are cut leaving a minimum of three twists, and they are bent over if irritation of the soft tissues is likely.

Lag screw fixation of the medial malleolus provides excellent stability if the distal fragment is large enough to accommodate a screw. Lag screw fixation of the medial malleolus may be preferred to pin and tension band fixation, especially if the fracture involves a large articular segment. Lag screw fixation of the lateral malleolus usually requires its attachment to the tibia, rather than to the fibula, because of the thin distal fibial diaphysis. The screws should be placed in lag fashion, by either using partially threaded cancellous screws or overdrilling the near cortex when using cortical screws. The size of screw (1.5 to 4.5 mm) selected depends on the size of the fragment size and the patient. One or two screws can be placed; placement of two screws may help to prevent rotation of the fragment. The fracture can be reduced and temporarily stabilized with bonereduction forceps. The appropriate thread hole and gliding hole (if using a cortical screw) are drilled perpendicularly across the fracture line, with care taken to avoid the articular surface of the tibiotarsal joint. Alternatively, a hole can be pre-drilled in the small fragment to allow more precise centering. The fragment is reduced and temporarily stabilized. The far hole is drilled. After drilling, the hole is measured and tapped, and the screw is inserted and tightened.

External coaptation is recommended for 4 weeks after internal stabilization. A lateral fiberglass splint is inexpensive and easily applied. The splint is applied while placing the tarsus at a functional angle. The bandage is changed if it becomes soiled or wet. After 4 weeks, the splint is removed, and physical therapy is performed several times daily until range of motion is improved. Exercise should be limited to leash walks only for 2 months postoperatively or until radiographic healing is evident. Running and jumping should be prevented. Implant removal is not necessary unless the implant migrates or loosens.
 

Functional Anatomy¹

Many luxations, subluxations, and shear injuries directly involve the tarsocrural joint. The major ligaments providing stability on the medial side of the joint are the long medial ligaments and tibiotalar short component ligament (Figure 62-14A). The major ligaments providing stability on the lateral side of the joint are the long lateral ligament and the calcaneofibular short component ligament (Figure 62-14B). The components of the medial and lateral ligaments complement each other in maintaining the talus in the mortise provided by the tibia and fibula. Certain parts of the ligament complexes are tighter in extension (long lateral and long medial ligaments) or flexion (calcaneofibular and tibiotalar short component ligaments).

The tibiotalar and calcaneofibular short component ligaments of the medial and lateral sides, respectively, are especially important for maintaining stability when the hock is flexed and should be accorded primary attention with any reconstruction procedure. It is possible that these short ligaments are stressed when the hock is flexed and subjected to concussive forces encountered in jumping or running, thus, needing to be particularly strong to prevent excessive ligament deformation or failure. The joint capsule and malleoli also contribute to joint stability.

The gross anatomy of the medial and lateral collateral ligament complexes is similar (See Figure 62-14). The components cross at the tarsocrural joint space, providing the greatest amount of ligament and an advantageous spatial arrangement directly over the joint.

Mechanism and Diagnosis of Injury

Based on personal experience and published reports protective stenting (augmentation) or prosthetic replacement for severe ligamentous disruption of the tarsocrural joint is indicated.² The shear injury produces especially severe disruption and instability of the joint. With this injury, not only are the supporting ligaments lacking, but the support to the respective side of the joint mortise provided by the malleolus and joint capsule are missing. The closed dislocation of the tarsocrural joint also can result in severe ligamentous disruption and joint instability. Most closed injuries cannot be adequately repaired by primary suturing of the joint capsule and collateral ligaments owing to the severity of the tissue damage.

Tarsocrural luxation results from different combinations of injuries including fractures of both malleoli, fracture of one malleolus and damage to the contralateral ligament complex, fracture of the fibula and damage to the medial ligament complex. Uncommonly, damage to both the lateral and medial collateral ligament complexes can occur with no fractures. Tarsocrural subluxation usually results from complete rupture or avulsion of either the lateral or medial collateral ligament complex. In medial ruptures, the paw tilts abnormally toward the lateral direction with a lateral (valgus) applied force. In lateral ruptures, the tilt is in a medial direction with a medial (varus) applied force. Occasionally, there is primary damage to only the long or short components of the medial or lateral ligament complexes. Less joint laxity makes these subluxation injuries more difficult to diagnose. In these situations determine joint laxity by placing lateral and medial tilt forces on the hock at different joint angles. Laxity in extension but not flexion suggests major damage to the long medial ligament, or long lateral ligament; laxity in only flexion suggests that most damage is isolated to the tibiotalar or calcaneofibular short components. Make a dorsoplantar (stress) radiograph while applying lateral and medial tilt forces on the hock. Take the stress radiograph at the tarsocrural joint angle that produces the subluxation. For subtle subluxations, compare this radiograph with a similar radiograph of the contralateral (normal) hock. Routine dorsoplantar and lateral radiographic views are always needed to check for concomitant tarsal injuries. Stress radiographs are useful to confirm the diagnosis in less straightforward situations but are not always necessary.
 

Surgical Technique

The double-ligament method closely reproduces the components of the intact medial and lateral collateral ligament complexes, thus, allowing nearly normal joint stability to be maintained throughout a functional range of motion. The double-ligament method provides the surgeon consistent locations for application of the stenting or prosthetic sutures. Further, these locations closely mimic the origins and insertions for the medial and lateral tarsocrural collateral ligament complexes. It has been shown that the stability of both the medial and lateral tarsocrural joint is dependent upon the interaction of the components of the respective collateral ligament complexes. The double-ligament method closely reproduces components of the medial and lateral collateral ligament complexes. This similarity to normal ligament components allows nearly normal joint stability to be maintained throughout a functional range of motion when using the double-ligament method.¹ Similar to the components of the normal collateral ligaments, the stenting or prosthetic sutures becomes taut and lax upon flexion and extension Because of this, wire is not advocated as a useful material with the double-ligament method. Monofilament polybutesterⁱ (preferred) or braided polyesterⁱⁱ sutures are successful with the double-ligament method, seemingly due to the retention of elasticity upon cyclic loading.

Clinically, the double-ligament method gives results superior to conservative management with splints or nonanatomic single-ligament replacement methods. The prognosis is good for long-term function with most closed luxation and subluxation injuries, depending on timely repair (within five to seven days of injury) and absence of articular damage.

ⁱ Novafil^*, Syneture^TM, Norwalk, CT 06856
ⁱⁱ Tevdek^®, Polydek^®, Deknatel^TM, Fall River, MA 02720

Surgical Technique - Closed Injury

Clip the injured limb from the level of the proximal femur, extending distally to include the paw. Include the paw in the sterile field to allow direct manipulation. Place the patient in lateral recumbency, with the injured limb up for lateral replacement or down for medial replacement, and prepare the limb for aseptic surgery. Expose the injury through a curved skin incision centered over the medial or lateral malleolus. Begin from the distal one-fourth of the tibia and continue to the proximal metatarsal bones. Locate the medial or lateral collateral ligament complex along the same line by incising the subcutaneous tissue and deep fascia. Inspect the components of the ligament complexes for damage. To help assess the damage, stress the ligament components with a varus or valgus tilt in both flexion and extension. It is unlikely that there will be a totally isolated injury to only one component of the ligament complex. The ligaments can appear intact but may have lost considerable function owing to internal derangement of the collagen fibers. Usually, the ligament components are too badly damaged to allow primary suturing of the torn ends or reattachment to bone. Replace irreparable ligaments with prosthetic sutures and protect repaired ligaments with stenting sutures. Replace or protect the medial or lateral ligament complexes with figure-eight heavy sutures fastened to the bone directly, with bone anchors,^iii-vi or with bone screws. (It is preferred to secure the sutures to the bone directly or with bone anchors as bone screws are too bulky, which can irritate overlying tissue.) Drill bone tunnels in the malleolus in locations similar to the origins of the components of the ligament complex (Figure 62-15). Bone tunnels serve as anchors for the suture prostheses. Secure the suture prosthesis that mimics the lateral or medial short components to tags of the torn ligament at the insertion site. Use a locking loop suture pattern to grip the torn ligament. A bone anchor may be needed to fix the prosthesis to the insertion site (Figure 62-15). Secure the suture prosthesis that mimics the lateral or medial long components to a drill hole in the tubercle of the distal talus or distal calcaneus (Figure 62-15). A bone anchor may be used to fix the prosthesis (Figure 62-15). For each ligament stenting or replacement use one or two (for large patients) strands of #0-2 braided polyester or monofilament polybutester (preferred) sutures for prosthetic replacement or protection. Set the sutures in a figure-eight pattern. Do not use wire, absorbable sutures, or sutures with a high degree of plasticity. Do not use monofilament polypropylene for sutures as it tends to stretch permanently (high plasticity) and is better suited for primary repair of torn ligaments. Do not use monofilament nylon (fishing leeder) as it is very stiff and tends to function like wire. Tie the long and short suture prostheses. Tie the short prosthesis with the tarsocrural joint held in approximately 90° flexion for dogs and 70° for cats. Tie the long suture prosthesis with the joint in a functional standing angle of 135° for dogs (varies with breed) and 120° for cats. After the sutures are tied, tighten the bone anchors against the bone.
 

Expose and provide stenting or ligament replacement to the luxation injury through separate surgical incisions on the medial and lateral sides of the joint. Fix a malleolar fracture with a tension band technique and replace or protect the contralateral ligaments. To manage luxations due to fracture of the fibula and damage to the contralateral ligament complex replace or protect the medial ligaments and stabilize the fibula to the tibia with K-wires or bone screws.

ⁱⁱⁱ BoneBiter^TM Suture Anchor System, Innovative Animal Products, Rochester, MN 55901 
^iv FlexiTwist Suture Anchor, Innovative Animal Products, Rochester, MN 55901
^v Bone Anchor, SECUROS, Charlton, MA 01507
^vi Suture Anchor, IMEX^TM Veterinary Inc., Longview, TX 75604

Shear Injury

Shear injuries usually occur when an animal is trapped by a moving vehicle, resulting in shearing by the road surface of supporting ligaments, bone, joint capsule, and malleolus. The medial side of the joint is injured more commonly than the lateral side of the joint. Perform wound management and ligament replacement when the bone and cartilage damage is isolated primarily to the malleolus. Severe soft tissue damage makes stabilization difficult and prolongs healing. Although a successful ligament replacement gives better results than a tarsocrural joint arthrodesis, consider joint arthrodesis if there is extensive bone and cartilage damage.

Technique – Shear Injury

Before debridement and ligament replacement, cover the shear wound with a temporary sterile dressing and apply a temporary splint to prevent further damage to the unstable joint. Exteriorized material will contaminate deeper recesses if replacement into the wound is attempted before formal debridement. Therefore, do not push or “stuff” extruded soft tissue, bone, or cartilage back into the wound. Do not soak the wound. Perform debridement as soon as the animal is a stable candidate for surgery, ideally within 6 hours from the time of injury for moderate wounds, and within or less than 1 to 2 hours for severe wounds. Ligament replacement and wound closure can be delayed but do not delay wound debridement.

Anesthetize the animal and remove the temporary splint. Keeping the wound covered, clip the limb, and cleanse with an appropriate antiseptic. Remove the dressing and thoroughly irrigate the wound with copious amounts of a pre-warmed balanced electrolyte solution. After moving the animal to the operating area, perform a final surgical scrub and drape the limb. Debride the wound of all visible necrotic tissue and debris. Be careful to avoid damage to articular surfaces. During the debridement process, lavage continuously with copious amounts (1 L or more) of a balanced electrolyte solution such as lactated Ringer’s, using a moderate amount of pressure, through a 30 to 60 ml syringe and 18 or 19 gauge needle or catheter. Fluid pressure on the tissues should approximate 7 psi. Perform ligament replacement at this time or delay for repeat wound debridement or orthopedic referral. If delaying replacement cover the wound with an absorbent dressing to keep the wound moist and stabilize the joint with a rigid coaptation splint such as a fiberglass slab incorporated into a padded wrap. Change the dressing once a day or more frequently if there is fluid striking through the bandage. Repeat wound debridement if necrotic tissue is left in the wound after the first procedure. Continue this process of serial debridement until only viable tissue is present in the wound.

The prosthetic ligament replacement technique for the shear injury usually requires three bone anchors (preferred) or three bone screws and figure-eight heavy sutures. Bone anchors are required for the shear injury because some bone is usually sheared off, thus, making it difficult to create bone tunnels as with the closed injury. Place the anchors as close as possible to the origin and insertion of the components of the ligament complex (Figure 62-16). Position the origin anchor in the distal tibia for the medial ligament or the distal fibula and tibia for the lateral ligament. Direct this anchor slightly proximal to avoid penetrating joint cartilage and to obtain maximum bony purchase. Position the insertion anchor for the medial tibiotalar short ligament in the proximoplantar quadrant of the medial trochlear facies of the talus. Direct this anchor slightly distal to avoid the trochlear sulcus of the talus. Position the anchor corresponding to the insertion of the medial long ligament through the tubercle at the plantar base of the talus. Direct this anchor slightly proximodorsally. Position the anchor corresponding to the insertion of the calcaneofibular short ligament proximoplantar to the base of the lateral articular facies of the tuber calcis. Position the insertion anchor for the long ligament through the tubercle at the dorsal extent of the base of the calcaneus. Direct this anchor slightly proximoplantar. Using one or two (for large patients) strands of #0-5 polyester sutures or monofilament polybutester sutures as prosthetic replacements, place suture(s) from the origin anchor and the short insertion anchor, and separate suture(s) from the origin anchor to long insertion anchor. Set the sutures in a figure-eight pattern (See Figure 62-16). Tie taut the tibiotalar or calcaneofibular short suture prosthesis with the tarsocrural joint held in approximately 90° flexion for dogs and 70° for cats. Tie taut the medial long or lateral long suture prosthesis with the tarsocrural joint in a functional standing angle of 135° for dogs (varies for some breeds) and 120° for cats. Tighten the anchors against the bone. Never perform primary soft tissue closure over a shear injury. If possible, allow second intention healing; alternatively, perform delayed closure or apply a skin graft after all surfaces of the wound and prosthetic sutures are covered with healthy granulation tissue.
​​​​​​​

Postoperative Care

The postoperative rehabilitation is crucial to achieving a consistently high long-term result with these tarsocrural injuries. For both the closed and shear injuries the rehab is similar in that there are three phases: progressive decrease of inflammation and increase of tissue proliferation, gain of muscle strength, and reintroduction of normal activity. A vital point is that all during rehab and beyond, inflammation must not be exacerbated. Whenever activity exacerbates inflammation the rehab activity must be reduced until the inflammation is once again diminished and more healing and strength is attained.

To facilitate clearing the inflammation and promote rapid healing, the first phase of rehab depends on early and strong controlled weight-bearing to stimulate positive physiology of the limb. However, allowing too much tissue strain to occur will be detrimental by adding to the inflammation and risking implant breakdown and tissue damage. During this phase, strain is controlled through coaptation splints (mobilization aids). Immediately after surgery apply a below the knee firm coaptation splint that allows slight strain. This can be done several ways such as with a fiberglass slab or aluminum rod incorporated into a padded wrap. This type of splint will allow periodic bandage changes for the shear wound. Concurrently, perform progressive controlled walking and encourage the animal to bear strong weight. The weight-bearing is as strong as possible but controlled to limit the exacerbation of inflammation as indicated by subtle to gross worsening of weight-bearing. Avoid using a transarticular external skeletal fixator (ESF) during this phase of rehab as this rigid form of immobilization does not allow positive physiology to the limb and is very detrimental to the joint. However, if an ESF must be used it should only be maintained for two weeks or less. Remove the firm coaptation after two to six weeks (shorter time period for closed injury and rapid healing situations and longer for shear injury). Next, place the limb in a mobilization aid that allows progressive strain for three to eight weeks. This is accomplished by using a below the knee four to ten layer soft cast.^vii The amount of tissue strain produced (moderate to high) can be greatly altered by the number of layers in the soft cast.³ If the shear wound has not completely been covered by healthy epithelial tissue a “window” can be easily cut into the soft cast. During use of the supple soft cast mobilization aid, perform controlled low impact mobilization by allowing increasingly longer walks and by progressively unwrapping layers from the splint to increase tissue strain as healing advances and muscles gain strength. Once the soft cast is completely removed, initially back down the walking time but continue progressive controlled mobilization by, once again, slowly increasing the animal’s walking activity over a four to eight week period. Controlled muscle building techniques (underwater treadmill, exercise ball, etc) are valuable during this stage of rehabilitation. When a high level of muscle strength has been regained, slowly and progressively bring the animal back to normal activity. As all during rehab, if the animal shows signs of increased lameness or pain, progress more slowly with controlled mobilization in a manner that does not create lameness or discomfort.

^vii Scotchcast^TM Soft Cast Casting Tape, 3M^TM, St. Paul, MN 55144

Prognosis

The prognosis is good for long-term pain-free function if there is no damage to the articular surfaces other than the malleolus and if surgery is timely. Careful rehabilitation through progressive controlled mobilization is critical to success.

Suggested Readings

Aron DN: Luxation, subluxation, and shearing injuries of the tarsal joint. In Birchard SJ, Sherding RG, eds.: Saunders Manual of Small Animal Practice. 2nd ed. Philadelphia: W. B. Saunders, 2000, p 1168.

Piermattei DL, Flo GL: Brinker, Piermattei, and Flo’s Handbook of Small Animal Orthopedics and Fracture Repair. 3rd ed. Philadelphia: W.B. Saunders, 1997, p 610.

References

1. Aron DN, Purinton PT: Collateral ligaments of the tarsocrural joint. An anatomic and functional study. Vet Surg 14:173, 1985.
2. Aron DN: Prosthetic ligament replacement for severe tarsocrural joint instability. Am Anim Hosp Assoc 23:41, 1987.
3. Rytz U, Aron DN, Foutz L, Thompson SA: Mechanical evaluation of soft cast (scotchcast, 3m) and conventional rigid and semirigid coaptation methods. Vet Comp Orthop Traumatol 9:14, 1996.
    

Introduction

Fractures of the tarsus, in the authors’ experience, occur with greatest incidence in the racing greyhound population, but are also encountered in other working breeds, in pet dogs, and in the cat. Clinical presentation varies depending upon the particular bone or bones involved. Diagnosis and accurate characterization of tarsal fractures can be challenging because the radiographic appearance of the region is complex, with superimposition of the bones. Standard orthogonal studies often must be supplemented by oblique and stressed views. Computed tomography could be considered the modality of choice for detailed imaging of the tarsus1 (Figure 62-17), though financial considerations often preclude its’ use. Successful surgical repair of tarsal fractures demands a comprehensive knowledge and understanding of the normal regional anatomy (Figure 62-18).
 

Repair of the Talus

Fractures of the medial or lateral trochlear ridge are intra-articular and therefore anatomical reduction and rigid stabilization are imperative. A dorsomedial or dorsolateral approach may be used if the fracture is restricted to the dorsal part of the trochlea. More proximal fractures can be approached by osteotomy of the relevant malleolus. Accessing the talus by osteotomy of the medial malleolus should be avoided wherever possible however, as significant morbidity in the form of degenerative joint disease is associated with this approach. When a lateral malleolar osteotomy is performed, it is wise to pre-drill the screw holes that will be required for reconstruction of this articular surface. The fracture is reduced with small bone forceps or digital pressure, and fixation achieved through the use of Kirschner wires. Multiple 0.035 or 0.045-inch Kirschner wires driven perpendicular to the fracture line are the fixation method of choice. Alternatively, small (2.0 or 1.5 mm) lag screws can be used. All implants must be countersunk below the articular surface. A lateral malleolar osteotomy is repaired with positional screws as previously alluded to (Figure 62-19), or with a pin and tension band wire. Where osteotomy of the medial malleolus must be performed it is repaired using pin and tension band fixation. In one case where the condylar fragment was too large to simply remove, and too small for internal fixation, a transarticular external fixator was applied which achieved indirect repair and a good functional result (Figure 62-20).

Fractures of the neck of the talus are approached from the medial aspect. There is often a concurrent luxation of the distal segment at the talocentral articulation. Reduction may be facilitated by flexing the tarsus and simultaneously applying pressure to the lateral surface to open the medial aspect of the joint. A Vulsellum forceps can be used to temporarily stabilize the fragments. Talar neck fractures are repaired by Kirschner wire or lag screw fixation. If the fracture has sufficient obliquity, a screw or wire may be directed from the distomedial aspect of the distal fragment into the lateral trochlear ridge. In the case of more transverse fractures, the distal segment is stabilized by directing a lag or positional screw from its dorsomedial aspect in a plantarolateral direction into the body of the calcaneus.
 

Fractures of the head of the talus are accessed by a medial or dorsomedial approach. They may be extra or intra-articular. An extra-articular, transverse fracture of the head is stabilized with crossed Kirschner wires or a modified T-plate. Reduction is maintained by the use of forceps or digital pressure – holding the joint in extension may enhance stability. A wire is driven from the plantaromedial aspect of the distal fragment into the dorsolateral aspect of the talar trochlea. The second wire is driven from the plantaromedial aspect of the trochlea into the dorsolateral aspect of the distal fragment. In larger dogs, it is possible to repair this fracture by use of a modified (three hole) T-plate placed on the dorsal aspect of the head and neck. The racing greyhound with a severe (grade IV or V) fracture of the central tarsal bone may, on occasion, suffer a concurrent dorsal or medial slab fracture of the talar head. These are best repaired by the use of a single countersunk lag screw.

Any repair of the talus should be supported by a lateral splint for four to six weeks postoperatively. After removal of the splint, physical therapy should be encouraged to preserve range of motion. Exercise must be restricted to short leash walks for two months postoperatively. Provided there is radiographic evidence of healing, a gradual return to normal activity can then be permitted.

In the case of a severe, comminuted, articular fracture of the talus, a pantarsal arthrodesis should be considered over any attempt to reconstruct the fragments.

The talus is the most frequently fractured tarsal bone in the cat.² These fractures can be managed using techniques described for the dog, though internal fixation of the feline talus is a challenging prospect. Small avulsed fragments of the medial or lateral trochlear ridge may be removed to restore joint function, albeit with inevitable progression of degenerative joint disease. Larger fragments are repaired with countersunk Kirschner wires. Fractures of the neck (Figure 62-21) may be repaired with a lag screw or a solitary Kirschner wire (Figure 62-22) but these methods are technically demanding. A more conservative approach is worth considering, because excellent results have followed closed reduction of feline talar neck fractures and application of a transarticular fixator.³ Transarticular external fixation is a good means of protecting the repair of any feline tarsal injury as this species is often intolerant of bandages and splints. A tarsal injury particular to the cat is luxation of the talus with rupture of the short ligaments of the talocalcaneal and talocalcaneocentral joints (Figure 62-23). The luxation is often accompanied by a distal fibular fracture and avulsion of a fragment from the lateral trochlear ridge. The fibular component is repaired using positional screws (Figure 62-24) or an intramedullary pin and tension band wire. To help prevent reluxation the talus may be fixed by a positional screw to the calcaneus.
 

Repair of the Calcaneus

Fractures of the calcaneus have a multitude of configurations but all are accessed via a lateroplantar approach. The author prefers to position the patient in sternal recumbency as this negates some of the forces of the extensor mechanism, facilitating fragment reduction.

An avulsion of the medial or lateral insertion of the superficial digital flexor tendon from the tuber calcanei can be managed in two ways depending upon the size of the bone fragment. Small fragments are removed and the insertion of the tendon reconstructed. Larger fragments may be reattached using lag screws. Avulsion of the entire tuber calcanei is usually seen in skeletally immature animals and is repaired using Kirschner wires or a small Steinmann pin, driven from proximal to distal, seated in the base of the calcaneus. Pin fixation is combined with a figure-of-eight tension band wire. In immature animals the implants are removed once the fracture has healed. The pin and tension band method of fixation may be applied to many calcaneal fractures with minor variations in seating of the pin and placement of the wire. Taking a simple oblique midshaft fracture as an example, pin and wire fixation is carried out as follows. The calcaneus is a very dense bone and therefore a hole, slightly smaller than the pin to be used, is drilled from proximal to distal in the proximal fragment. A hole for the wire is drilled through the distoplantar aspect of the base from lateral to medial and a single-loop wire passed, with the loop on the lateral side. Vulsellum forceps are applied to the tuber calcanei and base of the calcaneus to reduce the fragments and the pin is now seated in the base. The wire is wrapped around the proximal end of the pin to form a figure eight and is tightened; the pin is bent over and cut with the proximal end orientated to point dorsally. Some surgeons use two pins, though this has no proven advantage (Figure 62-25). The implants will lie under the superficial digital flexor and may cause some irritation though the clinical significance of this is unknown. If the surgeon prefers to interfere with the superficial digital flexor as little as possible, the wire may be passed through a transosseous tunnel drilled proximally (from lateral to medial), and the pin countersunk (Figure 62-26).
 

In more distal fractures that approach the base, the pin should be seated in the fourth tarsal bone (T4). The wire may be passed through T4 in the region of the plantar process. The pin and figure-of-eight wire method is also applicable to comminuted fractures; this may be supplemented by the use of lag screws or cerclage wire to reconstruct the calcaneal shaft. In one case a tension band wire alone was successfully combined with lag screw reconstruction (Figure 62-27). Application of a neutralization or buttress plate to the lateral aspect of the calcaneus has been advocated in comminuted fractures, with or without a supplemental figure-of-eight wire. The authors would suggest that a pin and figure-of-eight wire can be applied to virtually all comminuted calcaneal fractures, with a decreased surgical time and inventory when compared with plate fixation. Fractures with a plantarodistal component benefit from the addition of a “reverse” pin and tension band, with the pin orientated from plantarodistal to dorsoproximal and the wire passed through the calcaneal shaft. Small plantarodistal chip fractures representing an avulsion of the origin of the middle plantar ligament may not be amenable to reconstruction. Such cases are best managed by arthrodesis of the calcaneoquartal joint space. This procedure again utilizes pin and tension band fixation with the pin seated in T4 and the tension band passing through the same bone in the region of the plantar process.

Lateral sagittal fractures of the base and shaft of the calcaneus are repaired using multiple lag screws placed from lateral to medial (Figure 62-28). Dorsomedial slab fractures involving the base and sustentaculum tali are a challenge to diagnose radiographically. Repair is similarly challenging: lag screws have been used in a few instances but often external coaptation must be resorted to.

Post-operatively, simple fractures of the tuber calcanei or shaft do not require external coaptation. Comminuted fractures should be supported by a lateral splint for around 6 weeks. Exercise must be restricted to short leash walks for two months postoperatively, followed by a gradual return to normal activity provided there is radiographic evidence of healing.
 

Repair of the Central Tarsal Bone

Stress fracture of the central tarsal bone (CTB) occurs in the racing greyhound.⁴ Five types of CTB fracture have been described in this breed based on radiographic and intra-operative appearance⁵ (Table 62-1). A fracture-luxation of the CTB occurs sporadically in all breeds;⁶ the fracture occurs at the plantar process which remains attached to the plantar ligaments. The rest of the bone is displaced dorsomedially.
 

Repair of type 4 CTB fractures in the greyhound proceeds as follows,⁷ and is illustrated in Figure 62-29. With the patient positioned in dorsal recumbency and the tarsus immobilized parallel to the table surface, the CTB is approached on its dorsomedial aspect. The 5 cm skin incision runs between the dorsal branches of the medial and lateral saphenous veins. The CTB is found, by blunt dissection, just distal to the oblique tendon of the tibialis cranialis muscle (Figure 62-29A). The tendon of the long digital extensor is retracted laterally, and those of the tibialis cranialis and extensor digitorum brevis retracted medially to expose the fracture fragments. The fracture is reduced through hyperextension and eversion of the hock, and reduction is maintained with Vulsellum and/or pointed reduction forceps (Figure 62-29B). The medial fragment is repaired first. A 4.0 mm partially threaded cancellous screw is driven mediolateral, from a point just proximal to the origin of the oblique intertarsal ligament that joins the CTB to the third tarsal bone (T3), and the threads are engaged in the body of T4 (Figure 62-29C). This screw is placed in lag fashion and countersunk. The dorsal slab component is then repaired. A 2.0 or 2.7 mm screw is driven perpendicular and just proximal to the mediolateral screw to seat in the plantar process of the CTB. The screw is lagged and countersunk (Figure 62-29D). Figure 62-30 illustrates optimal lag screw positioning in repair of type 4 fractures. Repair of fracture types I and II is achieved as described for repair of the dorsal component of a type 4 fracture (Figure 62-30). Type III fractures are best managed as if they were type IV because it is possible that a dorsal fragment exists, but is non-displaced, and therefore not visible radiographically. This recommendation has been borne out by experience.⁷ The poor prognosis for return to racing that accompanies the type V fracture means that many are treated by external coaptation alone, resulting in a permanent varus deformity though a basically functional limb. Repair may be attempted in a number of ways. If the dorsal and medial fragments are large enough, repair can proceed as for type IV fractures though the reconstruction will not be perfect. Alternatively, a buttress plate can be placed on the dorsal aspect of the tarsus from talar neck to T3 and the central tarsal space filled with bone graft. Central tarsal prosthesis or allograft could also be considered. As the level of experience increases and instrumentation improves, a number of type V CTB fractures have been successfully reconstructed by placing up to five lag screws in this bone. One such racing greyhound has returned to win. The most rational course of action for management of type V fractures will depend upon the proficiency of the surgeon, the patients’ ability on the track, and the owners’ expectations. Repair of the CTB fracture-luxation in non-greyhound breeds is accomplished by directing a lag screw mediolaterally to seat in T46. A threaded Kirschner wire has been used in place of a screw in small toy breeds.
 

In the author’s experience approximately two thirds of fractured CTB’s have associated secondary fractures, with fractures of the calcaneus, T4, and avulsion fracture of the lateral aspect of the base of the fifth metatarsal being the most common⁵ (See Figures 62-17, 62-27, 62-28, 62-29 62-33, and 62-35). It is important to actively look for secondary fractures when evaluating fractures of the CTB as they have implications for prognosis as well as for management.
 

Postoperatively, a lateral splint is applied and maintained for six to eight weeks while restricting activity to leash walks. Radiographic evidence of healing is assessed around one month post-operatively. A gradual increase in activity leads into training and finally racing. Overall, prognosis for return to function may be good. In one study, 71 (88%) of 81 greyhounds with a central tarsal fracture that was treated by internal fixation returned to racing.⁷

Repair of the Fourth Tarsal Bone

Fracture of this bone may be considered rare in the general pet population (Figure 62-32). However, around 40% of type IV and V CTB fractures in the racing greyhound are accompanied by a compression fracture of T4⁵. Repair of these fractures is almost always achieved indirectly through repair of the CTB which restores hock length and axial alignment. If required, a second mediolateral screw can be placed through the second and third tarsal bones and seated in T4 to provide additional stability (Figure 62-33).
 

Repair of the Third Tarsal Bone

Dorsal slab fracture of T3 occurs in the racing greyhound (Figure 62-34) though it would be considered uncommon compared with fracture of the CTB. Based on experience, these fractures should be managed by internal fixation where a return to racing is desired. The approach to T3 is a distal extension of the approach to the CTB. Location of T3 is simplified by first identifying the second tarsal bone (T2) and tarsometatarsal joint space. Reduction is achieved by application of Vulsellum forceps. A 2.0 or 2.7 mm cortical screw is driven in a dorsoplantar direction, perpendicular to the fracture line, and seated in the plantar process. The screw is lagged and countersunk. Post-operative management is the same as for CTB fractures.

Repair of the SecondTarsal Bone

Fractures of this bone can be considered extremely rare. When they do occur, repair is by lag screw fixation (Figure 62-35) illustrates a T2 fracture in conjunction with a number of other tarsal injuries in a racing greyhound, and 2.0 mm lag screw repair. Somewhat more common is subluxation of T2, which may accompany fracture of T3 (Figure 62-36) or tarsometatarsal subluxation. To repair a T2 subluxation, the bone is approached on its’ medial aspect and a positional or lag screw driven from medial to lateral, seating in T3 and T4.
 

Post-operative management will depend upon the nature of any concurrent tarsal injury but in general, external coaptation for six to eight weeks is appropriate.

Repair of the First Tarsal Bone

Transverse fracture of the first tarsal bone (T1) has recently been reported in conjunction with tarsometatarsal subluxation in a small breed dog.⁸ It is hypothesized that fracture of this bone represents an avulsion of the long component of the medial collateral ligament from its insertion on T1. Since then, another case with an almost identical injury has been recognized by the authors. Stress radiography was used to accurately characterize the injury (Figure 62-37). Both dogs were successfully treated by external coaptation of the affected limb, for six weeks, in a lateral splint. The T1 fractures went on to heal (Figure 62-38), stability was restored to the joint, and the dogs were sound two months after the initial injury. A greater number of T1 fractures need to be documented and managed before strong recommendations can be made regarding this injury.
 

References

1. Gielen I, De Rycke L, van Bree H, Simoens P: Computed tomography of the tarsal joint in clinically normal dogs. Am J Vet Res 62:1911, 2001.
2. Matis, U. Complex fractures of the tarsus – cats. In: Lecture abstracts: advanced techniques in small animal fracture management course. Arbeitsgemeinshaft für Osteosynthesefragen. Columbus, Ohio, 2007.
3. McCartney WT, Carmichael S. Talar neck fractures in five cats. J Small Anim Pract 41:204, 2000.
4. Muir P, Johnson KA, Ruaux-Mason CP. In vivo matrix microdamage in a naturally occurring canine fatigue fracture. Bone 25: 571, 1999.
5. Boudrieau RJ, Dee JF, Dee LG. Central tarsal bone fractures in the racing greyhound: a review of 114 cases. J Am Vet Med Assoc 184:1486, 1984.
6. Piermattei DL, Flo GL, DeCamp CE. Fracture-luxation of central tarsal bone. In: Piermattei, DL, Flo GL, DeCamp CE, eds. Brinker, Piermattei and Flo’s handbook of small animal orthopedics and fracture repair. 4th ed. St Louis: Elsevier Inc, 2006 p698.
7. Boudrieau RJ, Dee JF, Dee LG. Treatment of central tarsal bone fractures in the racing greyhound. J Am Vet Med Assoc 184:1492, 1984.
8. Marshall WG, Dee JF, Spencer CP. What is your diagnosis? Tarsometatarsal subluxation. J Am Vet Med Assoc. 2007 Dec 15;231(12):1809-10.

Suggested Readings

Beale B. Surgical treatment of talus fractures. In: Bojrab MJ, Ellison GW, Slocum B, eds. Current techniques in small animal surgery. 4th ed. Baltimore: Williams and Wilkins, 1998 p1264.

Dee JF, Dee LG, Eaton-Wells RD. Injuries of high performance dogs. In: Whittick WG, ed. Canine Orthopedics. 2nd ed. Philadelphia: Lea and Febiger, 1990 p519.

Dee JF. Tarsal injuries. In: Bloomberg MS, Dee JF, Taylor RA, eds. Canine Sports Medicine and Surgery. Philadelphia: WB Saunders Co, 1998 p120.

Evans HE: Millers’ anatomy of the dog. 3rd ed. Philadelphia: WB Saunders Co, 1993.

Piermattei DL, Johnson KA: An atlas of surgical approaches to the bones and joints of the dog and cat. 4th ed. Philadelphia: Elsevier, 2004.
 

Lesions associated with osteochondritis dissecans (OCD) of the hock occur on the medial or lateral trochlear ridge of the talus. The lesions may be characterized as small, cartilage flaps or large, osteochondral fragments. Early diagnosis and prompt surgical removal of these fragments are recommended, before the onset of significant degenerative joint disease (DJD). Several approaches have been described to gain access to the flaps. Severance of either collateral ligament allows subluxation of the joint and excellent visualization of the trochlear ridges; however, this approach should be avoided because of the probability of causing iatrogenic joint instability, predisposing the dog to greater DJD. Osteotomy of the medial or lateral malleolus also gives excellent surgical exposure; however, this approach can also be associated with increased morbidity. Medial malleolar osteotomy is technically demanding and requires iatrogenic formation of an articular fracture of the distal tibia. Precise reduction and rigid stabilization is necessary to prevent DJD. Lateral malleolar osteotomy is preferred, but precise reduction and rigid stabilization are necessary to prevent joint instability or nonunion of the osteotomy site. The preferred approaches are the dorsolateral and plantarolateral approaches to the lateral trochlear ridge and the dorsomedial and plantaromedial approaches to the medial trochlear ridge. Accurate radiographic assessment of the location of the OCD lesion is necessary to select the appropriate surgical approach. Most OCD lesions can be accessed through a single approach; however, a combination of the dorsal and plantar approaches is necessary to gain access to some large lesions or lesions located on the midportion of the trochlear ridges. A combined approach to the medial trochlear ridge allows access to all but approximately 5% of the ridge (the midportion). A combined approach to the lateral trochlear ridge allows access to the entire ridge. The advantage of using the combined approaches is the preservation of the collateral ligaments without the need for a technically demanding, time-consuming osteotomy. If these approaches fail to provide sufficient surgical exposure, a malleolar osteotomy can then be performed. Because of the low morbidity associated with these procedures, bilateral lesions can be operated on at the same time.

All four approaches are performed by making a curvilinear skin incision centered over the appropriate region of the trochlear ridge. Subcutaneous tissues are incised and are retracted. Certain anatomic structures should be avoided during each approach. The dorsolateral approach requires lateral retraction of the tendons of the extensor digitorum longus, tibialis cranialis, and extensor hallucis longus muscles, the dorsal branch of the lateral saphenous vein, and the superficial peroneal nerve (Figure 62-39). This approach also requires plantar retraction of the tendons of the peroneus longus, extensor digitorum lateralis, and peroneus brevis muscles. In the plantarolateral approach, the tendons of the peroneus brevis, extensor digitorum lateralis, and peroneus longus muscles must be avoided dorsally (Figure 62-40). The plantar branch of the lateral saphenous vein and branch of the caudal cutaneous sural nerve are retracted in a plantar direction, and the flexor hallucis longus tendon is retracted medially. The dorsomedial approach requires lateral retraction of the tibialis cranialis tendon, saphenous nerve, cranial tibial artery and vein, and dorsal branches of the saphenous artery and vein (Figure 62-41). In the plantaromedial approach, the tendon of the flexor digitorum longus muscle and the distal attachment of the tibialis caudalis tendon are retracted dorsally, and the flexor hallucis longus tendon, tibial nerve, and medial saphenous vein and artery are retracted laterally (Figure 62-42). The collateral ligament complex is preserved in all four approaches. The joint capsule is incised longitudinally, directly over the palpable trochlear ridge, and is retracted. Extension and flexion of the joint allow access to the trochlear ridge for removal of the OCD fragment. Removal is usually simple using a Freer elevator or similar instrument. If present, synovial attachments to the fragment are sharply incised. Reattachment of the fragment with Kirschner wires or lag screws is not recommended because of the typical remodeling of the fragment present at the time of surgery, the technical difficulty of the procedure, and the possibility of implant failure. Gentle curettage of the subchondral lesion can be performed to remove loose debris and undermined edges at the periphery of the lesion. Fibrocartilaginous repair tissue within the defect should be left undisturbed. Forage (drilling of several small holes into the subchondral bone) of the defect to encourage vascular ingrowth has been proposed, but its efficacy is unknown. The joint capsule and subcutaneous tissues are closed in two layers using synthetic absorbable suture. The skin is closed using synthetic nonabsorbable suture. A soft, padded bandage is recommended for 7 to 10 days. Exercise should be restricted to leash walks only for 6 weeks.
 

Introduction

When performing arthrodesis of the tibiotarsal joint, as in pancarpal arthrodesis, it is recommended to include the fusion of the intertarsal and tarsometatarsal joints. Fusion of the tibiotarsal joint alone creates added stress to these secondary joints. Tibiotarsal arthrodesis has a better prognosis then elbow or stifle arthrodesis for a successful return to function. Dogs and cats can tolerate the loss of motion in the hock and carpus better then a mid limb joint (elbow and stifle). However, arthrodesis is never simple because the surgeon is trying to overcome motion in areas where the body is constructed to maintain motion. Although the lever arm is shorter for the hock than for the stifle or elbow, the angle of the arthrodesis is more acute than for the carpus. A stiff, straight structure is hard to bend but once it is bent, and the more acute the angle, the easier it is to bend. The same is true for a plate-bone composite structure, thus the straighter or more oblique the angle of a joint being fused the more stable it is. Even the plate alone is weaker when bent at more acute angles. The normal standing angle of the hock is 130 to 150°, but if the arthrodesis angle is straighter it will be more stable and more likely to succeed. When the plate is placed on the cranial aspect of the joint, which is most commonly described, it is on the compression side which adds to the instability. Other positions for the plate have been described but are problematic for pantarsal arthrodesis. A plate is now available for placement on the medial aspect of the joint at a fixed angle of 135 degrees to overcome this weakness.

Indications

The tibiotarsal joint is subject to trauma and degenerative disease just as in any other joint. When these conditions lead to chronic pain and dysfunction, arthrodesis is indicated.

Any fracture or luxation where the articular surface cannot be reestablished or is permanently damaged, such as a gunshot or infected nonunion, arthrodesis is indicated. Shearing injuries to the medial aspect of the tibiotarsal joint with ligamentous and bone loss are frequently seen. This occurs when the leg is dragged on the ground. Most of these injuries heal by second intention and the scar tissue or screws (bone anchors) and stainless steel orthopedic wire are enough to provide stability. But, if the bone loss is excessive then arthrodesis is an alternative.

OCD of the talus is probably the most common reason for arthrodesis of the tibiotarsal joint. Even after the osteochondral fragment is removed any improvement tends to be temporary with degenerative joint disease progressing to chronic lameness. When conservative therapy is no longer effective, arthrodesis is indicated. Rheumatoid or polyarthritis also commonly affects the tibiotarsal joint and, as in the carpus, arthrodesis is beneficial for individual joints. But the disease tends to affect multiple joints. Septic arthritis or secondary degenerative arthritis can be severe enough to warrant arthrodesis.

A unique indication for a talocrural fusion is in sciatic nerve paralysis. A muscle transfer of the vastus lateralis to the long digital extensor tendon requires fusion of the tibiotarsal joint providing mechanical advantage to dorsiflex the paw when walking. The fusion helps position the paw and removes a point of motion along the path of the transferred tendon.

A failed repair of the calcanean (Achilles) tendon can be salvaged with a tarsocrural or pantarsal arthrodesis. The rupture of the plantar ligament however, can be repaired with fusion of the proximal intertarsal joint alone. This is a very common injury especially in collies and shetland sheep dogs, but all breeds can be affected. These dogs present with hyperextension of the hock with the tubercalcus more parallel to the tibia then normal. This varies from the complete luxation of the intertarsal joint where the talocentral joint is also unstable. With luxations of the individual joints, such as the intertarsal and tarsometatarsal joints, fusion of the involved joints alone is sufficient. The extent and location of the soft tissue injuries may differ and dictate the repair. This will be discussed later.

Procedure

In all cases the cartilage must be removed from the adjacent surfaces. The articular surfaces of the talocrural joint can be approached by cutting either of the collateral ligaments or by an osteotomy of the medial maleolus or fibula and incising the joint capsule. For the tibiotarsal joint either the cartilage itself can be removed with a power bur or a curette leaving the original saddle shape of the distal tibia and tallus intact. Alternatively, two flat surfaces can be developed with a saw or bur (Figure 62-43). In either case, autogenous cancellous bone should be packed between the surfaces to fill in the gaps. If a significant amount of bone is removed to create flat planes then this will act to effectively shorten the leg and to compensate for this the joint should be fused at a straighter angle which is also more stable. The angle of the cuts will determine the final angle of the arthrodesis. The normal standing angle in dogs is between 130 and 150°, but there are significant differences between individuals and breeds such that measurement of the normal standing angle of the contrlateral limb is the best method for determination of the desired angle. The normal standing angle of this joint in cats is usually 115 to 125°. The cartilage of the intertarsal and tarso-metatrsal joints is removed in a routine manner with a curette or bur.
 

In small dogs or cats the tibiotarsal joint can be fused with compression screws. One screw is generally placed from the sustentaculum tali into the medullary canal of the tibia, and another screw is placed from the tibia calcaneus into the tibia to hold the position of the joint and oppose flexion (Figure 62-44). Once the medulary canal is wider than the thread of the screw, then multiple screws must engage the cortex of the tibia, the talus and fibular tarsal bone. They can either be passed from proximal to distal or vise versa (Figure 62-45). Either orthopedic wire or another screw should go from the calcaneus to the tibia to resist flexion and protect the other screws from bending forces. A Kirschner wire can be used to hold the joint temporarily while the holes for the screws are drilled. The problem with this technique is that only the tibiotarsal joint is fused and although it can be successful (especially when muscle transfer is done for sciatic nerve paralysis) there are some dogs that will develop problems in the other tarsal joints. A study by Gorse and co-workers found better function with pantarsal arthrodesis than for talocrural arthrodesis alone. External coaptation with a splint or cast should be maintained until there are radiographic signs of healing with all screw fixations.
 

Preferred methods for stabilization of a pantarsal arthrodesis are bone plate fixation or external skeletal fixation (ESF). The most common placement of the plate is along the cranial aspect of the tibia, tarsus and metatarsal bones (Figure 62-46). This is, however, the compression side of the construct and not ideal. A straight plate can be placed caudolaterally, but a new tarsal arthrodesis plate (Jorgensan labs) is available with a built-in angle of 135° which can be placed medially (Figure 62-47). The 3.5mm plate has 2.7mm holes distally for the metatarsal bones and the 2.7mm plate has 2.0 mm holes distally. For medial placement of a plate, the medial maleolus may need to be shaved. Regardless of the aspect of plate placement, three to four screws should be applied to the tibia; one to three screws should be applied to the talus, calcaneus and central tarsal bones; and three screws should be applied to the metatarsal bone. In a cranial plating, one of the screws should be placed across the arthrodesis under compression, and either a screw or wire should immobilize the calcaneus to resist bending. Motion between the calcaneus and talus post arthrodesis can cause lameness. The plate should engage either the 3rd or the 4th metatarsal bone. A separate screw can be used to compress the arthrodesis and grab the calcaneus when the plate is applied medially. Even with plate fixation, some form of splinting should be considered until radiographic signs of healing are evident (usually 2 to 3 months). Since we are not worried about joint stiffness, as would be the case in fracture fixation, extra support is warranted, especially in large active dogs. The complications of soft tissue irritation has to be weighed against this added support. Therefor a ESF can be used for additional support instead of coaptation.

External fixation is also well adapted as primary repair for pantarsal arthrodesis, especially in shearing injuries or open, contaminated, comminuted fractures (Figure 62-48). A type II construct is needed for rigid fixation but a modified type II, using full pins only in the most proximal and distal position or positions, and using half pins in between is technically easier without sacrificing too much stability. Fixation pins with a positive thread profile or Duraface pins should be used. These should be applied using pre-drilling technique and slow speed power insertion. If the older Kirschner Ehmer or newer Securos clamps are used, the stainless steel connecting bars are contoured to the desired angle. A reinforcing bar applied from proximal to distal bilaterally will triangulate the construct and strengthen it. With the SK system, titanium or carbon fiber composite connecting rods are generally used and these cannot be contoured. Instead, modified SK connecting clamps can be used to create an adjustable articulation to create the desired angle between two connecting rods (Figure 62-49). The metatarsal bones form an arch and it is rarely possible to get a full-pin through all four. It is better to aim for the 2nd and 5th, or the 3rd and 4th metatarsal bones. Half-pins are a simpler way of securing the metatarsal bones. Compression should be placed across the arthrodesis site so ideally a full-pin should be placed in the talus and at least one of the pins in the tibia. Two to three pins should be placed in the tibia. The greater the number of fixation pins used, the less stress there will be on any individual pin and the less chance of pin loosening. As long as the frame is rigid and all the joints are spanned with compression across the arthrodesis site, the surgeon has some leeway in regard to pin placement sites. A third bar can be triangulated, spanning the cranial aspect of the frame for added strength. Ring fixators or hybrids also work well in this joint.
 

When an injury involves just the intertarsal or tarsometatarsal joints, only the affected joints need to be fused. When the plantar ligament ruptures causing hyperextension of the hock, the cartilage is removed between the fourth tarsal bone and the calcaneus, and a Steinmann pin is placed through the calcaneus, fourth tarsal bone and into the 3rd or 4th metatarsal bone. Cancellous bone is placed in the gap and a 20 or 18 gauge tension band wire is placed from a hole drilled in the calcaneus to a hole in the 4th tarsal or metatarsal bone (Figure 62-50). This bone is very dense and pre-drilling the hole for the pin facilitates pin placement. The proximal end of the pin is either countersunk or bent over but still can cause irritation. A laterally applied plate is a quick and very stable alternative. When there is a complete luxation of the proximal intertarsal joint, bone plate fixation is preferable (Figure 62-51).
 

With luxations or fracture-luxations of the intertarsal and tarso-metatarsal joints, stress radiographs are helpful to accurately define the injured structures. Often combinations of pins, wires and screws can be used to stabilize these injuries. If the inter-tarsal luxation involves only the dorsal ligaments, weight bearing stabilizes the injury and coaptation alone will often suffice. If the instability is in one plane only, then screws and figure eight wire will stabilize the injury, but if two planes are involved, as in tarsometatarsal fracture luxations, cross pins and wire will be necessary for stability. It is always best to remove the cartilage and graft these partial fusions, but if the luxations involve only capsular and ligamentous disruption, it may not be necessary to remove the cartilage especially in smaller patients. Coaptation during healing is also a good idea due to the large weight bearing stresses encountered post operatively. The pins and wire can be removed once healing has occurred, usually in 8 to 12 weeks.

Suggested Readings

Gorse MJ, Early TD, Aron DN: Tarsocrural arthrodesis: Long term functional results. J Am Anim Hosp Assoc 27:231, 1991.