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Humerus and Elbow Joint
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Repair of Fractures of the Humerus
Dennis A. Jackson
Editor’s Note – The reader is encouraged to review other sections of this text regarding more recent options for the repair of humeral fractures: Chapter 50 – Interlocking Nailing; Chapter 51 – SOP Locking Plates; Chapter 52 – Plate-Rod Fixation; and Chapter 53 – Hybrid External Skeletal Fixation.
Proximal Fractures
Greater Tubercle
Fractures involving the greater tubercle of the humerus are rare. In young animals, these fractures are stabilized with two Kirschner wires or small Steinmann pins. In mature animals, a tension band wire technique is recommended. In both cases, open reduction is required through a craniolateral approach to the proximal humerus. External coaptation is not required, but restricted weightbearing is recommended until bone healing is confirmed by radiographic evaluation.
Humeral Head
Most fractures of the humeral head are caused by gunshot injuries and are highly comminuted. Reconstruction of the articular surface must be exact and is paramount to the successful return of joint function. Exposure of the articular surface of the humeral head can be difficult. A craniolateral approach to the shoulder joint is combined with an osteotomy of the acromion process and tenotomy of the infraspinatus and teres minor muscles as required to obtain surgical exposure. A supraspinatous tenotomy may be necessary to provide adequate visualization of the joint.
The fracture is reduced, and large articular fragments are compressed with lag screw fixation. Small fragments are reduced and are stabilized with multiple Kirschner wires or Stille nails placed at divergent angles. All pins and screws should be countersunk below the articular cartilage. Small Kirschner wires may be used to immobilize articular fragments temporarily while lag screws are placed. The Kirschner wires can be removed once lag screw fixation is completed. Autogenous cancellous bone grafts are used to fill large bone defects. After placement of each implant, the joint should be palpated in all planes to evaluate range of motion and crepitus. If crepitus is detected, the fixation is adjusted before the placement of the remaining implants. The fracture is stabilized, and the joint is lavaged thoroughly before joint capsule closure. Osteotomy of the acromion process is repaired with a tension band wire. The tenotomies and remaining soft tissues are sutured routinely.
For patients with fractures with severe comminution of the articular surface, surgical arthrodesis should be considered as a salvage procedure. Arthrodesis is especially indicated in medium to large breed dogs with severe joint comminution. For small dogs and cats with irreparable joint damage, the humeral head may be excised, or a Velpeau bandage or spica splint may provide adequate coaptation for functional healing. The goal of external coaptation or excision of the humeral head is to produce a functional, pain-free joint or pseudoarthrosis. Failure to obtain functional use of the limb or persistent pain in these patients is an indication for arthrodesis of the joint.
Growth Plate Injuries
Growth plate injuries, which occur in young animals with an open epiphyseal plate, are usually secondary to direct trauma or avulsion injuries. Physeal or epiphyseal plate injuries are classified by the Salter system. This clarifies the site of injury and is useful when selecting treatment and for predicting outcome. A Salter I fracture extends across the epiphyseal plate parallel to the joint surface. A Salter II fracture extends through the epiphyseal plate and includes a small portion of the metaphysis. These fractures are the most common growth plate injuries of the proximal humerus, and both carry a good prognosis if they are repaired early and accurately.
Most Salter I and II fractures require open reduction and internal fixation. The exception is selected Salter I fractures of less than 24 hours’ duration in small dogs and cats. These fractures may be managed by closed reduction with the animal under general anesthesia. Manual traction of the distal limb is performed to fatigue the muscle contraction and to achieve reduction and alignment. The proximal physeal fragment is immobilized by grasping the acromion process of the scapula while the distal segment is gently reduced by abduction and adduction of the elbow. Care must be taken to avoid splitting the proximal physis at the thin junction between the humeral head and greater tubercle. Once reduction is achieved, closed normograde pinning using Kirschner wires or Steinmann pins is performed. The pins or wires are passed from the craniolateral aspect of the greater tubercle at a 20 to 30° angle to the long axis of the humeral shaft (Figure 56-1). Alignment and fixation are evaluated with anteroposterior and lateral postreduction radiographs.
Failure to obtain closed reduction or fracture duration of more than 24 to 36 hours is an indication for an open craniolateral approach to the proximal humerus. The fracture should be reduced carefully by gentle levering and distraction to ensure that soft tissues do not become interposed in the fracture site. A small Adson periosteal elevator or a Hohmann retractor facilitates levering and reduction of the fragment. Small Kirschner wires, Steinmann pins, or double Rush pins are the preferred methods for internal fixation. Tension band wires, screws, and bone plates are not used because they cross the epiphyseal plate, create compression, and may lead to premature physeal arrest and growth deformity. Double Rush pinning, with the pins placed craniomedially and craniolaterally through the greater tubercle, is the preferred method of repair. Prebending the pins and using a Rush awl to create guide holes facilitate their insertion. Rush pins of appropriate size are driven in normograde fashion at an angle of approximately 20° to the long axis of the bone. While placing the pins, the lateral pin is directed toward the caudomedial cortex and the medial pin is directed toward the caudolateral cortex of the shaft (Figure 56-2). The pins should cross distal to the fracture site and should seat firmly against the cortex to provide rigid three-point fixation. For small dogs and cats, Kirschner wires can be substituted for Rush pins by a similar technique. No additional fixation is required, and early restricted weightbearing is encouraged postoperatively.
Infrequently, Salter injuries of the physis may occur simultaneously with fractures of the greater tubercle and humeral head. In young, growing animals, the repair involves pin fixation of the greater tubercle and humeral head through a craniolateral approach to the shoulder joint combined with tenotomy of the infra-spinatous and teres minor muscles. Pin fixation technique is selected in these animals to avoid interfering with future growth potential of the physis (Figure 56-3).
In mature animals, these fractures are repaired using tension band wire fixation of the greater tubercle combined with lag screw and Kirschner wire stabilization of the humeral head (Figure 56-4). Surgical exposure is through a craniolateral approach, with tenotomy of the infraspinatus and teres minor muscles, as described for a young, growing animal.
General Comments on Treating Proximal Fractures
For surgery, the animal is positioned in lateral recumbency, and the site is aseptically prepared from the proximal scapula to the level of the elbow. The limb is positioned through the body drape to facilitate surgical manipulation of the fragments. When exposing the proximal humerus by osteomy of the acromion process, the surgeon should be careful to preserve the suprascapular nerve, which courses deep to the infraspinatus muscle. The nerve lies lateral to the joint and medial and deep to the acromion process. In cats, a small metacromion protuberance is encountered just proximal to the acromion process. Its presence has no clinical significance and does not alter the surgical approach. The acromion process frequently is not ossified in young animals, and tenotomy of the acromion deltoid, rather than osteotomy, is recommended for exposure. For most proximal fractures, external support is usually not required, and an early return to weight-bearing is encouraged after surgery. The exception is a questionable repair of a comminuted articular fracture. Unstable articular repairs should be immobilized with a Velpeau bandage or a spica splint for 2 to 4 weeks postoperatively. Active physical therapy of the shoulder joint combined with swimming is recommended to obtain the best functional results. For patient comfort, appropriate analgesics should be used in the postoperative period to control pain and to facilitate physical therapy sessions. Early limb use is encouraged by slow, controlled leash walking. Activity during the third through eighth postoperative week should be confined to house and leash. For cases of articular fractures, the client should be advised of the possibility for developing secondary degenerative joint disease and the potential need for anti-inflammatory therapy.
Healing time with epiphyseal injuries can be as short as 3 to 4 weeks. Articular fractures may take several weeks to obtain clinical union. Depending on the age of the animal and the type of fracture, follow-up radiographs are scheduled for 3 to 6 weeks postoperatively. Serial radiographs are obtained at 3 to 4 months postoperatively to evaluate bone healing further. Unless contraindicated, all implants should be removed once radiographic union is complete.
Shaft Fractures
Proximal Metaphysis
The proximal metaphysis of the humerus is broad and strong relative to the rest of the bone. Proximal fractures may be described as transverse, short or long oblique, spiral, segmental, or comminuted. Fractures of this area are rare and usually result from a gunshot injury, vehicle injury, or other direct force or from a pathologic condition. Most cases occur in medium to large breed dogs. When animals are presented with pathologic fractures, nutritional, metabolic, or neoplastic causes should be considered and managed appropriately.
Simple transverse metaphyseal fractures of short duration in immature dogs and cats can be managed by closed reduction and normograde intramedullary pinning. A single intramedullary pin of appropriate size is placed normograde from the greater tubercle and is passed toward the medial epicondyle and seated at that site. A smaller-diameter pin placed in similar fashion often exits through the medial epicondyle in close proximity to the ulnar nerve. Stack-pinning with two or more smaller pins may be used to increase resistance to rotational forces. Application of an external half- or full Kirschner splint in combination with intramedullary pinning may also be used to neutralize rotational forces.
Open reduction is required if the fracture is of long duration or if soft tissue swelling is significant. Fixation can be achieved with two Rush pins placed as described for repair of a proximal Salter epiphyseal fracture (See Figure 56-2). Alternatively, pins and tension band wire may be applied using appropriately sized Kirschner wires or Steinmann pins and orthopedic wire. With the tension band technique, pins are placed parallel and penetrate the midpoint of the greater tubercle. The wire is positioned in figure-of-eight fashion over the pins and is anchored in the distal fragment through a hole drilled in the bone (Figure 56-5).
Proximal Shaft
Proximal shaft fractures usually occur at or just distal to the deltoid tuberosity. Contraction of the deltoideus and latissimus dorsi muscles produces caudal displacement of the proximal fragment. Closed reduction with normograde intramedullary pinning or application of a Kirschner splint may be difficult because of fragment distraction and soft tissue swelling.
For oblique, segmental, and comminuted fractures of this area, open reduction is the preferred method of repair. A craniolateral approach to the proximal shaft with subperiosteal elevation of the deltoideus muscle is used to gain exposure. Several options are available for fixation, including single intramedullary pinning, stack-pins, Rush pinning, pin and tension band wire, hemicerclage wire, half- or full Kirschner splint, and bone plating.
Intramedullary pinning combined with half- or full Kirschner splinting usually provides good fixation for transverse fractures. Shear forces that occur with oblique fractures may be neutralized by the addition of full-cerclage or hemicerclage wire, Kirschner pins, or interfragmentary screws. Secure placement of cerclage wires is enhanced by creating grooves in the cortex or by placing transverse Kirschner pins to prevent the wires from migrating distal on the shaft and becoming loose. The use of single cerclage wires is avoided because it may create a fulcrum effect.
In large to giant breed dogs, or in animals with segmental and comminuted fractures of the proximal shaft, bone plating is the preferred method of repair. Evaluation of preoperative radiographs should ensure that sufficient bone is present to allow placement of two and preferably three bone screws on either side of the fracture site. Subperiosteal elevation of the insertion of the deltoid muscle is performed to provide exposure for reduction of the fracture, and the limb is held in external rotation to facilitate application of the bone plate. The bone plate is conformed to the cranial aspect of the proximal shaft and is applied to the bone.
Comminuted proximal fractures with loss of bone, as occurs with gunshot injuries, result in an unstable fracture and slow bone healing. These fractures are subjected to considerable rotational, compression, and bending forces and are susceptible to infection. Such fractures require rigid internal bone plate fixation combined with an autogenous cancellous bone graft. Alternatively, intramedullary pinning (single or stack) combined with autogenous cancellous bone grafting and Kirschner splint may be used. With open fractures of this type, Penrose drains should be placed at the surgical site. The Penrose drains are removed 3 to 5 days postoperatively.
Middle and Distal Shaft
Most humeral fractures involve the middle or distal diaphyseal regions of the bone. They present as transverse, oblique, spiral, comminuted, or multiple fractures. Overriding of bone fragments is common with midshaft to distal shaft fractures, and most cases require open reduction for repair. Select transverse midshaft fractures can be managed by closed reduction and intramedullary pinning.
Open intramedullary pinning is most applicable to transverse and short oblique shaft fractures in cats and small to medium breed dogs. This type of fixation can also be used for long oblique, spiral, comminuted, or multiple fractures in combination with cerclage wires, stack-pins, and Kirschner splints. Kirschner splints alone are most frequently used to stabilize open or closed, multiple, or comminuted shaft fractures. Bone plates are used most commonly for midshaft to distal shaft fractures in large and giant breed dogs.
Intramedullary Pin Fixation
Closed Reduction and Pinning
Closed reduction may be possible in small breed dogs and cats with recent transverse or short oblique midshaft to distal shaft fractures; closed reduction may be possible if the fracture site can be readily palpated. In medium to large breed dogs, closed reduction can be difficult because of the large muscle mass, soft tissue swelling, and fragment distraction. Open reduction is usually required for repair of shaft fractures in these breeds of dogs. When closed reduction is possible, an intramedullary pin is placed by inserting the pin in normograde fashion from the midpoint of the greater tubercle into the shaft. An intramedullary pin is selected that fills 70 to 75% of the medullary cavity at the fracture site. The size of the medullary cavity can be readily estimated and used to select the pin size based on the preoperative craniocaudal radiograph.
The pin is passed down the medullary cavity to a point just distal to the fracture site. The fracture is reduced by toggling the distal fragment onto the exposed pin. The pin is advanced to the distal fragment and is seated at a point just proximal to the supratrochlear foramen. Care is taken at this point to avoid penetrating the olecranon fossa (Figure 56-6). The joint should be palpated to ensure a full range of crepitus-free motion after pin placement. For closed intramedullary pinning of fractures at the junction of the middle and distal third of the shaft, a smaller pin is selected to allow for placement into the medial epicondyle. The pin should be of sufficient size to fill the medial epicondyle, based on the preoperative craniocaudal radiograph. The pin is inserted at the midpoint of the greater tubercle, is passed in normograde fashion down the medullary cavity, and is seated in the medial epicondyle. The pin is advanced until the tip is felt to penetrate the distal surface of the medial epicondyle. To ensure that the pin does not penetrate the medial olecranon fossa, the joint should be palpated repeatedly for crepitus and limited range of motion during pin placement. After insertion of an intramedullary pin for stabilizing either middle or distal diaphyseal fractures, persistent rotational instability can be controlled by closed application of a half-Kirschner splint.
Open Reduction and Pinning
Although closed reduction is possible, open reduction is preferred for repair of midshaft and distal shaft fractures in all breeds of dogs and cats. The animal is placed in dorsal recumbency to allow for a lateral or medial approach to the shaft. Although the medial approach avoids muscle mass, it does encounter extensive neurovascular structures; for this reason, most fractures are handled by a lateral approach. The lateral approach provides exposure of the proximal three-fourths of the humeral shaft. The superficial cephalic vein and radial nerve lying between the brachialis muscle and the lateral head of the triceps brachii muscle should be identified and preserved. Proximal exposure of the shaft, when necessary, can be obtained by subperiosteal elevation of the deltoideus muscle. Distal exposure can be gained by extending the incision to the lateral epi-condyle and by dissecting the brachialis muscle to allow cranial and caudal retraction of the muscle and radial nerve as a unit. Gelpi retractors placed at either end of the wound facilitate muscle retraction and surgical exposure.
Reduction of shaft fractures often requires considerable traction with bone-holding forceps or the use of a bone distractor in large breed dogs to correct overriding from muscle contraction. In small dogs and in cats, open reduction and fixation may be achieved with a single intramedullary Steinmann pin. A pin of appropriate size is passed in retrograde fashion from the fracture site to the greater tubercle, the fracture is reduced, and the pin is seated in the distal fragment. To ensure proper pin placement, the pin is directed to accentuate placement either in the distal medullary cavity just proximal to the supratrochlear foramen or in the medial epicondyle. For midshaft fractures repaired by intramedullary pinning, the pin is started against the caudal cortex of the proximal fragment and is directed toward the greater tubercle (See Figure 56-6). For distal shaft fractures in which pin placement is desired in the medial epicondyle, the pin is started against the caudomedial cortex of the proximal fragment and is directed toward the midpoint of the greater tubercle (Figure 56-7). If the fracture remains unstable after single intramedullary pinning, additional fixation by cerclage wire, stack-pins, or a half-Kirschner splint is added. The intramedullary pin can be included within a hemicerclage wire to gain additional stability by compressing the pin against the cortex of the bone. Fractures most applicable to full-cerclage wire technique include fissure fractures, long oblique fractures, and spiral fractures of the shaft. For cerclage techniques, monofilament wire of sufficient size and strength should be used. Twenty- to 22-gauge wire is usually sufficient for small dogs and cats. Eighteen-gauge wire should be used for medium to large breed dogs. When using cerclage, a minimum of two wires is recommended to avoid creating a fulcrum effect.
In large dogs with spacious medullary cavities, stack-pins provide more points of bone contact and improve rotational stability. Two pins or more of appropriate size are placed by directing the first pin in retrograde fashion into the proximal fragment and then seating it in the medial epicondyle. Alternatively, the second or subsequent pins are started at a point cranial and distal to the greater tubercle and are passed in a normograde direction down the medullary cavity to a point just proximal to the supratrochlear foramen. The second and subsequent pins can also be passed in a retrograde direction into the proximal fragment and then seated distally (Figure 56-8).
Half-Kirschner splints may be used with intramedullary pinning to provide rotational stability. A single intramedullary pin is seated in the medial epicondyle, allowing sufficient room between the pin and the cranial cortex of the shaft for placement of two Kirschner pins. Estimation of the combined Kirschner and intramedullary pin diameters can be obtained by studying the preoperative lateral radiograph. A Kirschner pin is placed in each fragment at 35 to 40° to the long axis of the bone and should penetrate both cortices. Both pins enter the bone through separate stab wounds away from the primary incision site. The pins are joined by a connecting bar and two single Kirschner clamps (Figure 56-7). The half-Kirschner splint is usually removed in 3 to 6 weeks after development of a bridging callus, as demonstrated by radiographic examination.
Full Kirschner Splint Fixation
A full Kirschner splint can be used as the sole means of fixation for shaft fractures in cats and in small to medium breed dogs (Figure 56-9). Kirschner splints, when used alone, are placed by closed reduction or by a limited approach to the fracture site to facilitate reduction and fixation. They cause minimal disruption of blood supply and allow for free joint movement and the nursing care of open wounds during the healing period. When deciding on pin placement for a full Kirschner splint, preoperative radiographs should be evaluated carefully for the presence and location of fissure fractures. The presence of fissures may necessitate altering pin placement or may contraindicate the application of a Kirschner splint.
When placing a full Kirschner splint, two pins are positioned craniolaterally in each major fragment. When possible, all pins are placed at 35 to 40° to the long axis of the bone and should penetrate both proximal and distal cortices. The proximal pin is placed just distal to the greater tubercle, and the distal pin is placed just proximal to the supratrochlear foramen or in transcondylar fashion using the epicondyles as landmarks. The two pins are joined with a connecting bar containing empty Kirschner clamps for placement of the two middle pins. The deltoid tuberosity is used as a landmark for placement of the second pin in the proximal fragment. The second pin in the distal fragment is placed just proximal to the epicondylar ridges. The surgeon must be careful to avoid striking the radial nerve when placing this pin. For Kirschner splinting, a limited lateral approach can be useful to facilitate fracture reduction. For both closed and open repairs, a half-Kirschner splint is initially positioned as described, and traction is applied to obtain axial alignment of the proximal and distal fragments. The two end Kirschner clamps are tightened to maintain reduction while the two middle pins are placed and seated in the bone through clamps previously positioned on the connecting bar. When inserting the two middle pins, medial support should be provided with the surgeon’s free hand to prevent medial collapse of the fragments and loss of reduction. When open reduction is performed through a limited surgical approach, lag screws or cerclage wires can be combined with the Kirschner splint as needed to provide additional fixation. Cortical defects should be packed with autogenous cancellous bone grafts harvested from the iliac crest, proximal tibia, or proximal humerus.
Bone Plate Fixation
Bone plates can be applied to most shaft fractures, but they are especially indicated in large and giant breed dogs and for multiple and comminuted fractures. A dynamic compression plate is recommended, with three screws placed on each side of the fracture. When plating the humeral shaft, the surgeon should use as broad a plate as possible. In cases with oblique, spiral, or multiple fractures, lag screws or cerclage wires can be combined with plate fixation as indicated to provide additional fixation.
Exposure is through a craniolateral approach to the proximal shaft, with subperiosteal elevation of the superficial pectoral and deltoideus muscles and caudal retraction of the brachialis and triceps brachii muscles. For midshaft fractures, the plate is conformed to the bone and is placed on the cranial surface of the shaft (Figure 56-10).
For distal shaft fractures, the plate is positioned laterally along the musculospiral groove, the lateral epi-condyle, and the lateral epicondylar crest (Figure 56-11). The plate is conformed to the surface of the distal musculospiral groove and lateral epicondyle and is positioned under the brachialis muscle. Exposure is obtained using a lateral approach to the shaft, and the incision is extended proximally and distally as required.
For distal-third shaft fractures with a comminuted medial cortex, the plate can be applied to the caudal medial surface of the medial shaft and epicondyle (Figure 56-12). Surgical exposure can be achieved using a medial approach to the distal shaft. Care must be taken to preserve the brachial and collateral ulnar vessels and the ulnar and median nerves. The nutrient artery located on the caudal surface of the bone should also be preserved. A transolecranon osteotomy can be performed if additional distal exposure is required.
General Comments for Managing Shaft Fractures
For repair of shaft fractures, the animal is positioned in lateral recumbency with the injured limb suspended and aseptically prepared from the midradius to the proximal scapula. Placing the affected limb outside the body drape facilitates fracture manipulation and reduction.
Midshaft fractures frequently occur where the radial nerve crosses the musculospiral groove medially to laterally. These patients often have considerable overriding of sharp bone fragments, especially with oblique or spiral fractures. Radial nerve function should be evaluated carefully in these animals because of the close proximity of the nerve to the fracture site. The radial nerve courses over the musculospiral groove of the distal humerus in association with the brachialis muscle. During the surgical procedure, the nerve should be identified, tagged, and assessed for damage. A large-diameter Penrose drain is passed around the brachialis muscle and radial nerve and is used to retract these structures cranially and caudally during the reduction process.
Autogenous cancellous bone grafts enhance healing of severely comminuted or multiple shaft fractures repaired with open reduction and internal fixation. Indications include middle-aged and older patients or patients with large bone defects at the fracture site. Cancellous bone is taken from surgically prepared sites at the greater tubercle, the tibial crest, or the wing of the ilium. Once the graft is harvested, it is immediately placed in the fracture site before closure of the soft tissues.
Severely comminuted shaft fractures with large bone defects may require full-cylinder cortical bone grafting. Suitably prepared cortical bone allografts can be used for this purpose. Bone grafts of this type are usually reserved for comminuted shaft fractures that cannot be repaired by conventional reconstructive techniques.
Postreduction radiographs are obtained to evaluate reduction and fixation. Appropriate analgesics are provided to ensure patient comfort. Most patients with shaft fractures benefit from a Robert Jones bandage applied to the limb for 3 to 5 days postoperatively to control swelling. Twice-daily hydrotherapy is recommended to clean pin sites when a Kirschner splint is used. For patients with these fractures, activity is restricted to house and leash for 6 to 8 weeks or until bone healing is demonstrated by radiograph examination.
Supracondylar and Condylar Fractures
Supracondylar Fractures
Most supracondylar fractures pass through the supratrochlear foramen. In young animals, an epiphyseal separation may occur in association with a supracondylar fracture. Metaphyseal fractures with no involvement of the supratrochlear foramen can also be seen. Closed reduction is not advisable with this type of fracture. Open reduction with internal fixation provides early joint motion and weightbearing and produces the best results. Surgical exposure is through a medial or lateral approach to the distal shaft, or, if necessary, the two approaches are combined to facilitate reduction. A transolecranon approach provides the best exposure for large breed dogs requiring double bone plating for multiple or comminuted supracondylar fractures.
Transverse Fractures
The preferred method for repair of transverse supracondylar fractures involving the foramen is open intramedullary pinning combined with cross-pinning of the lateral epicondyle (Figure 56-13). This technique provides rigid internal fixation for most transverse supracondylar fractures and is applicable to all sizes of dogs and cats. The fracture is reduced, and the proximal fragment is immobilized with bone-holding forceps. With the patient’s elbow flexed, a pin of sufficient size to fill the medial epicondyle is passed in normograde fashion from the medial epicondyle to the greater tubercle. The pin is advanced parallel to the caudomedial cortex of the medial epicondyle and penetrates the greater tubercle. During pin placement, reduction is maintained by counterforce applied through Kern boneholding forceps attached to the proximal fragment. Rotation of the distal fragment is controlled by bone-holding forceps placed over the fracture site of the lateral epicondyle. The fracture site is inspected repeatedly during pin placement to ensure that reduction is maintained. When the pin penetrates the greater tubercle, the bone chuck is removed, and the distal point of the pin is cut off. The bone chuck is reapplied to the proximal portion, the distal part of the pin is drawn into the medial epicondyle, and the proximal pin is cut off at the greater tubercle.
An alternate method advances the pin in a retrograde direction up the caudomedial cortex of the proximal fragment from the fractured site. The fracture is reduced and the pin is passed into the distal fragment and is seated in the medial epicondyle. With both methods, a Kirschner wire or a small Steinmann pin is passed from distal and caudal to the lateral epicondyle to penetrate the medial cortex of the humeral shaft. The pin in the lateral epicondyle should pass between the intramedullary pin and cranial cortex of the shaft (Figure 56-13C).
Double Rush pinning provides an alternative technique for repair of transverse supracondylar fractures. Rush pins of appropriate size are prebent to facilitate their insertion and are placed slightly distal and caudal to the medial and lateral epicondyles. During pin placement, reduction is maintained with bone-holding forceps. Guide holes are made with an intramedullary pin or a Rush awl to allow introduction of the pins at approximately 20 to 30° to the long axis of the bone. The pins should be placed so they cross above the fracture site and provide rigid three-point fixation (Figure 56-14). In small dogs and in cats, Kirschner wires or small Steinmann pins can be substituted for Rush pins and placed in similar fashion.
Oblique Fractures
Oblique supracondylar fractures in cats and small to medium breed dogs can be repaired with intramedullary pinning and hemicerclage wires. The intramedullary pin is directed from the fracture site in a retrograde fashion into the proximal fragment, the fracture is reduced, and the pin is seated in the medial epicondyle. Hemicerclage wire, preplaced through the bone and around the pin, is tightened to provide additional stability and rotational control. To control rotational forces unstable fractures may require addition of a half-Kirschner splint.
Multiple and Comminuted Fractures
Fixation of multiple and comminuted supracondylar fractures in cats and small to medium breed dogs can be achieved by intramedullary pinning of the medial epicondyle combined with cerclage wire and a full Kirschner splint (Figure 56-15). Surgical exposure for repair of these fractures requires a combined medial and lateral or transolecranon approach. Reduction and repair are first attempted through a combined lateral and medial approach. If surgical exposure is inadequate, a transolecranon osteotomy can be performed. A Steinmann pin is placed in the medial epicondyle in retrograde fashion, and the fracture site is reduced. The pin is advanced in normograde fashion into the proximal fragment and exits at the greater tubercle. For additional fixation, a fullKirschner splint is applied to the craniolateral aspect of the bone. The proximal Kirschner pin is inserted below the greater tubercle and passes between the intramedullary pin and the cranial cortex of the bone. The distal pin is placed in transcondylar fashion from the lateral epicondyle and angles toward the medial epicondyle. A connector bar containing two single Kirschner clamps for placement of the middle pins is connected between the proximal and distal pins. Traction is applied, and the fragments are placed in axial alignment and are immobilized temporarily by tightening the proximal and distal Kirschner clamps. The Kirschner splint can be adjusted as required to provide for surgical manipulation and reduction. The proximal and distal clamps are tightened once reduction is achieved. Cerclage wires or lag screws are used to stabilize any comminuted or multiple bone fragments. The cortex of the bone is grooved to accept the cerclage wire and to prevent it from becoming loose. At this point, the second Kirschner pin in the proximal fragment is seated in the shaft between the intramedullary pin and the cranial cortex. The second pin in the distal fragment is placed in transcondylar fashion from the lateral to the medial epicondyle. The result is two Kirschner pins placed in cross-pin fashion within the condylar bone. Care is taken to support the fracture site during placement of the two middle Kirschner pins to prevent medial collapse and loss of fracture reduction (Figure 56-16).
In large dogs, double bone plating is usually required to provide fixation for comminuted or multiple supracondylar fractures (Figure 56-17). A transolecranon approach creates the best exposure for application of the plates. To use the bone plating technique, the condylar fragment must be large enough to allow placement of at least two screws distal to the fracture site. The larger plate is positioned on the caudomedial surface of the medial epicondyle. The second, smaller plate is placed on the caudal surface of the lateral epicondyle and the lateral epicondylar crest. Consideration is given to placement of all screws in both plates before drilling the holes to allow interdigitation of the screws. Compression of large bone fragments by lag screws placed through the plates should be performed whenever possible. Inadvertent placement of screws into the joint or olecranon fossa must be avoided to ensure an unrestricted, crepitus-free range of motion and a functional joint.
Condylar Fractures
Fractures of the lateral condyle of the humerus occur more frequently than medial condyle fractures. Forces transmitted along the radius largely affect the lateral condyle, creating shear forces and predisposing it to fracture. Radiographs of lateral condyle fractures usually reveal a subluxated elbow joint with cranial and lateral rotation of the fragment secondary to contraction of the extensor muscles. Fracture of the medial condyle causes caudal and medial displacement of the fragment.
Closed reduction of lateral condyle fractures is possible if soft tissue swelling is minimal and if the fracture is not of more than 24 to 36 hours’ duration. Closed reduction requires considerable surgical expertise and is not generally recommended.
Lateral and medial condyle fractures are best managed by open reduction. A transolecranon approach provides the best exposure, although a medial or lateral approach may be adequate in selected cases. Subperiosteal elevation of the extensor carpi radialis muscle provides better visualization for reduction of lateral condyle fractures. Accurate anatomic reduction is paramount to a successful repair of the articular surface. Gentle curettage of the fracture site removes fibrin clots and interposed soft tissue that facilitates reduction. The fragment is reduced by digital manipulation and is stabilized temporarily with a condyle or bone clamp placed over the epicondyles. The clamp is positioned to allow access to an area slightly distal and cranial to the epicondyles for placement of a transcondylar screw. Reduction is evaluated by palpating the caudal surface of the lateral epicondyle, by assessing joint motion and by direct articular visualization. In cats and small breed dogs, a C-cIamp placed across the condyles maintains reduction and provides a guide for drilling the condylar hole. The hole is measured with a depth gauge and is tapped to receive a cortical bone screw. The fracture is separated, the condyle fragment is overdrilled to create a glide hole, and the fracture is reduced. A transcondylar cortical screw of appropriate length is inserted and is tightened to provide lag screw compression.
An alternate technique predrills the lateral or medial condyle fragment from the fracture site and uses the hole as a guide to drill the opposite condyle. With both techniques, a Kirschner wire is placed caudal to the screw head and is driven up the lateral or medial epicondyle to the opposite cortex to prevent rotation (Figure 56-18). The transolecranon approach is repaired and is stabilized using a tension band wire technique. The joint is palpated to ensure a crepitus-free and unrestricted range of motion before closure. Postreduction radiographs are taken to assess implant placement, fracture reduction, and alignment of the articular surface.
General Comments for Management of Supracondylar and Condylar Fractures
For repairs of this type, the animal is positioned on its back, and the affected limb is aseptically prepared from the scapula to the carpus. A lateral approach is made, and the skin and subcutaneous layer are undermined and reflected as required to expose both sides of the elbow joint and distal shaft. When approaching the supracondylar area in cats, special care should be taken to preserve the median nerve, which passes through the supratrochlear foramen, and the ulnar nerve, which is located under the medial head of the triceps brachii muscle. Comminuted or multiple supracondylar fractures may require autogenous cancellous bone grafting, as described for comminuted shaft fractures. When bone grafting is anticipated, one or more donor sites are prepared preoperatively. After reduction and fixation, the graft is harvested and is placed in the fracture site immediately before closure.
A Robert Jones bandage is placed on the limb for 2 to 3 days postoperatively to control soft tissue swelling. Early physical therapy and restricted weightbear-ing are encouraged for the first 6 to 8 weeks. Unless contraindicated, removal of implants is recommended when the bone has healed, as demonstrated by radiograph examination. Appropriate analgesics are administered postoperatively to provide for patient comfort.
Intercondylar Fractures
Supracondylar fractures of the humerus occurring simultaneously with a condyle fracture are referred to as T or Y fractures. They are usually seen in mature animals in which the epiphysis has fused. Closed reduction with external fixation is not advisable. These fractures involve articular surface, and open reduction with internal fixation should be recommended as early as possible.
A transolecranon approach provides good visualization and facilitates anatomic reduction of the articular surface. The fracture site is exposed and is curetted to remove fibrin clots and interposed soft tissue. Reduction is performed and evaluated by observing the articular surface of the condyles and the alignment of the humeral shaft with the epicondylar ridges. The multiple fracture is converted to a single supracondylar injury by first repairing the intercondylar fracture. The condyles are immobilized with a condyle clamp or bone forceps, and two small Kirschner wires are passed in a transcondylar fashion to provide temporary fixation. A guide hole for a drill bit is placed distal and cranial to the lateral epicondyle using a small intramedullary pin. The drill site is located on a line 45° cranial and distal to a line passing through the lateral epicondyle and shaft of the humerus (Figure 56-19). The drill is directed toward a similar point cranial and distal to the medial epicondyle. Placement of the screw should be in the center of the condyles and parallel to the joint surface. In small breed dogs and cats, a C-clamp can be used to immobilize the condyles and to provide a guide for screw placement. A depth gauge is used to determine the screw length, and the hole is threaded with a bone tap. The lateral fragment is overdrilled to create a glide hole, and a cortical screw is inserted to create lag screw compression. Care must be taken to avoid over-compressing the fracture when tightening the screw and collapsing the soft cancellous bone of the condyle.
An alternative method for drilling the condyle is to predrill the proximal hole from the fracture site to a point cranial and distal to the lateral epicondyle. The hole is carefully centered in the lateral condyle. The fracture is reduced and is immobilized with a condyle clamp or small Kirschner wire. The medial condyle is drilled using the hole in the lateral condyle as a guide. The depth of the hole is measured, and the entire length is threaded with a bone tap. The lateral condyle is overdrilled, and a cortical screw is selected and inserted to provide lag screw compression. The transcondylar Kirschner wires are removed, except when additional fixation may be desirable. In cats and extremely small dogs, threaded pins or Kirschner wires can be substituted for screws to provide fixation.
Before repairing the supracondylar fracture, the condyles are palpated to ensure a crepitus-free, unrestricted range of motion. The condyles are attached to the shaft using the intramedullary pinning technique described for supracondylar fractures. After reduction of the supracondylar fracture, a pin of sufficient size to fill the medial epicondyle is selected, based on assessment of the preoperative craniocaudal radiograph. The pin is passed parallel to the caudal cortex of the medial epicondyle and is advanced in normograde fashion to penetrate the greater tubercle. The distal pin is cut off, and the bone chuck is applied to the proximal pin. The distal pin is drawn into the medial epicondyle, and the proximal portion is cut off at the greater tubercle. During placement of the intramedullary pin, the supracondylar and condylar fracture sites are checked repeatedly to ensure that reduction is maintained.
An alternative method of intramedullary pin placement passes the pin in retrograde fashion through the medial epicondyle. The fracture is reduced, and the pin is passed in normograde fashion up the humeral shaft, penetrating the greater tubercle. The pin is cut off as described in the previous technique. A Kirschner wire or a small Steinmann pin of appropriate size is directed up the lateral epicondyle to provide rotational stability. This pin enters the epicondyle immediately caudal to the transcondylar screw head, passes between the intramedullary pin and the cranial cortex of the humeral shaft, and penetrates the medial cortex (See Figure 56-18B). The combination of transcondylar screw fixation with pinning of the supracondylar fracture is applicable to all sizes of dogs and cats and provides an excellent method of fixation for this type of fracture.
A third technique for repair of these fractures uses double Rush pinning or cross-pinning of the supracondylar fracture combined with transcondylar lag screw fixation of the condylar fracture. This technique is more challenging, and maintaining anatomic reduction between the condyles and the shaft during pin placement can be more difficult (Figure 56-19).
Comminuted T or Y condylar fractures are unstable and usually require double bone plating for repair. These challenging fractures require exact anatomic reduction to achieve the best functional results. A trans-olecranon approach provides good exposure for reducing and stabilizing the fracture. A transcondylar lag screw is used to stabilize the condyles, and two bone plates are applied. One plate is positioned over the medial epicondyle and humeral shaft, and the other is placed over the lateral epicondyle and lateral epicon-dylar crest. For each plate, two screws are placed in the condylar fragment, and three screws are positioned in the humeral shaft. An autogenous cancellous bone graft is harvested and is placed in the fracture site before closure. The transolecranon osteotomy is repaired with a tension band wire technique.
Postreduction radiographs are obtained to assess articular reduction and implant placement. Analgesics are administered to ensure patient comfort in the postoperative period. A Robert Jones bandage is applied to the limb for 3 to 5 days, followed by swimming physical therapy and range-of-motion exercises with controlled weightbearing for 6 to 8 weeks. The intramedullary pin should be removed when the bone has healed. The transcondylar screw, Kirschner wires, Steinmann pin, and bone plates are usually not removed unless they loosen or cause soft tissue irritation.
Suggested Readings
Brinker WO, Piermattei DL, Flo GL. Handbook of small animal orthopedics and fracture treatment. Philadelphia: WB Saunders, 1983.
Egger EL. Complications of external fixation: a problem-oriented approach. Vet Clin North Am 1991;21:705.
Evans HE, Christensen GC. Miller’s anatomy of the dog. 2nd ed. Philadelphia: WB Saunders, 1979.
Hulse D, Hyman B. Biomechanics of fracture fixation failure. Vet Clin North Am 1991;21:647.
Lipowitz AJ, Caywood DD, Newton CD, et al. Complications in small animal surgery: diagnosis, management, prevention. Baltimore: Williams & Wilkins, 1996.
Newton CD, Nunamaker DM. Textbook of small animal orthopaedics. Philadelphia: JB Lippincott, 1985.
Olmstead ML. Complications of fracture repaired with plates and screws. Vet Clin North Am 1991,-21:669.
Piermattei DL, Greely RG. An atlas of surgical approaches to the bones of the dog and cat. 2nd ed. Philadelphia: WB Saunders, 1979.
Treatment of Elbow Luxations
Robert A. Taylor
Elbow luxation refers to the disruption of the articular congruity of the three bones that constitute the elbow joint. Luxation can be traumatic or congenital, with the former more common. Most acute traumatic luxations can be reduced by closed methods; chronic luxations sometimes require open reduction. Surgical repair of congenital elbow luxation is directed at the underlying defect.
The elbow joint is a compound joint formed by the articulation of the humeral condyle, the radial head, and the semilunar notch of the ulna. It is classified as a hinge joint; that is, its major motion is confined to swinging in one plane. The humeral radial articulation allows for 90° supination of the distal extremity.1 The unique configuration of the articulation with the anconeal process located deep in the olecranon fossa, the prominent medial epicondyle of the humerus, and the ligaments of this joint creates a stable articulation. The medial and lateral collateral ligaments connect all three bones; in addition, the oblique ligament, olecranon ligament, and annular ligament further enhance the stability of the elbow.
Congenital Luxations
Congenital elbow luxation is most common in small breed dogs and is thought to have a hereditary basis.2 Agenesis or hypoplasia of the medial collateral ligament allows for rotation of the proximal radius and ulna with subsequent subluxation. The humeral trochlea and anconeal process usually are underdeveloped, and other secondary joint changes may exist in affected animals. This disorder has been reported to occur in combination with ectrodactyly.3
Closed and open methods of reduction of congenital elbow luxation have been reported.4 Limb salvage and function, rather than complete articular reconstruction, should be the main objectives of surgical correction. Closed reduction has been recommended for dogs under 4 months of age. In older animals with long-standing luxation, open reduction is necessary.
Surgical repair of congenital elbow luxation may involve capsulorrhaphy, reconstruction of the humeral trochlea, reconstruction of the semilunar notch, partial removal of the anconeal process, and capsular imbrication. One should be aware of possible iatrogenic injury to the physis associated with elbow development during surgical reduction. In some cases, owners may elect conservative treatment or euthanasia. Owners should be counseled with regard to the probable hereditary nature of this problem.2
Traumatic Luxations
In the absence of fractures, traumatic elbow luxation results in caudolateral or lateral displacement of the radius and ulna. The larger size of the medial condylar surface of the humerus compared with the lateral condyle partly explains the motion of luxation. In addition, the orientation of the oblique ligament and the olecranon ligament is such that lateral luxation is more likely than medial luxation.
Animals with acute traumatic elbow luxation present with a nonweightbearing lameness of the affected limb. The limb usually is flexed, abducted, and pro-nated. Pain is evident on manipulation, and crepitus and articular incongruity are present. The elbow usually is twice its normal width.
Radiographs taken in two planes are needed to confirm the diagnosis (Figure 56-20). The surgeon must rule out articular fractures before attempting closed reduction of a luxated elbow.
Closed Reduction
General anesthesia is required for closed reduction of elbow luxations. Because the animal has sustained a recent trauma, a careful physical examination and assessment of associated injury must be performed before anesthesia is induced.
The animal is positioned in lateral recumbency with the affected limb uppermost. In long-haired patients, clipping the hair may be helpful to aid in the manual reduction of the luxation. Radiographs should be examined to determine the location of the anconeal process. If the anconeal process is laterally luxated, the elbow is flexed and the forepaw is rotated internally to force the anconeal process into the olecranon fossa.
With digital pressure on the radial head, the elbow is held flexed and the radius is pushed onto the humeral capitulum; the leg is then extended and flexed several times to ensure joint congruity. With the elbow flexed 90°, the forepaw can be rotated medially and laterally to check for collateral ligament integrity. If marked postreduction instability is present, surgical repair of the ligaments is indicated.
A soft padded bandage is used to support the limb and to limit swelling. Because early mobilization of the joint surfaces is necessary, the duration of immobilization is limited to 5 to 7 days. During this time, passive range-of-motion exercise should be encouraged.
The trauma necessary to produce luxation in a joint as stable as the elbow invariably results in damage to the articular cartilage, joint capsule, and collateral ligamentous support. Given time, some degree of degenerative joint disease usually results, and owners should be made aware of this possibility.
Open Reduction
Open reduction rarely is required in patients with acute elbow luxations; however, those with chronic luxations with associated capsular adhesions and contractures may require open reduction. In general, a lateral approach to the elbow is satisfactory, although in long-standing cases, a transolecranon approach gives greater exposure.5 It is helpful to lever the radius and ulna6 into place with a smooth periosteal elevator. Caution is necessary to avoid undue articular cartilage damage. Once reduced, the joint is worked through a normal range of motion, and any fibrin tags and debris are removed. If the lateral collateral ligament has been ruptured, the surgeon must decide to select primary repair or use screw and suture augmentation of the ligament.
Postreduction support is similar both with surgically reduced elbow luxations and with manually reduced luxations. Early activity, range-of-motion exercise, and weightbearing are important for proper rehabilitation.
References
- Evans H, Christensen G. Miller’s anatomy of the dog. 2nd ed. Philadelphia: WB Saunders, 1979.
- Bingel SA, Rizer, WH. Congenital elbow luxation in the dog. J Small Anim Pract 1977;18:45.
- Montgomery M, Tomlinson J. Two cases of ectrodactyly and congenital elbow luxation in the dog. J Am Anim Hosp Assoc 1985;21:781.
- Nunamaker DW. Fracture and dislocation of the elbow. In: Small animal orthopedics. Philadelphia: JB Lippincott, 1985.
- Piermattei DL, Greeley RG. Atlas of surgical approaches to the bones of the dog and cat. Philadelphia: WB Saunders, 1979.
- Stayak JW. Elbow luxations. In: Bojrab MJ, ed. Current techniques in small animal surgery. Philadelphia: Lea & Febiger, 1975.
Surgical Treatment of Ununited Anconeal Process of the Elbow
Ursula Krotscheck
Anatomy
The elbow, or cubital, joint is the convergence of three separate bones: the humerus, radius, and ulna. These form a hinge (ginglymoid) joint composed of three smaller joints: the humeroulnar (trochlea and trochlear notch), humeroradial (capitulum and radial head), and proximal radioulnar joints. The olecranon fossa of the humeral condyle articulates with the anconeal process (AP) of the ulna during joint extension beyond 90 degrees and restricts elbow movement in the sagittal plane.8,38 The normal elbow joint has 3 distinct areas of contact: the craniolateral aspect of anconeus, the radius, and medial coronoid process (MCP). The latter two are continuous across the radioulnar articulation. There is no articular contact at the medial aspect of the anconeus as well as the central trochlear notch. Neither the size nor the location of the contact areas is affected by the amount of axial loading.
The soft tissue structures surrounding and supporting the elbow joint are important for examination purposes as well as for surgical and arthroscopic procedures. The joint capsule encloses all three bones into one space; its cranial and caudal pouches are important for arthroscopy and arthrocentesis.6 The lateral collateral ligament originates on the lateral epicondyle, splits into cranial and caudal crura, and inserts on the proximal radius and ulna, respectively. The medial collateral ligament originates on the medial humeral epicondyle, crosses the annular ligament, and also divides into cranial and caudal crura. The annular ligament of the radius encloses the cranial aspect of the radial head and inserts on medial and lateral extremities of radial incisure of ulna. Several important nerves surround the elbow joint. The ulnar and median nerves are on the medial aspect of the joint. The ulnar nerve is caudal and superficial, and can easily be palpated as it crosses the caudomedial aspect of the joint. The median nerve, on the other hand, is deeper and more cranial. It crosses the joint distal to the medial epicondyle, continues deep to the pronator teres muscle along the median artery, and may be seen during a medial arthrotomy. The radial nerve is on the cranial and lateral aspect of the elbow joint; a deep branch extends under the extensor carpi radialis muscle while two superficial branches course along the medial and lateral borders of the cephalic vein.
In small dogs the MCP and AP mature by 16 weeks of age, while in large dogs AP ossification is not completed before 14 weeks of age and MCP ossification is completed approximately 6 weeks later.1
Pathogenesis
Ununited anconeal process (UAP) is defined as the failure of the anconeal process to undergo normal bony fusion with the proximal ulnar metaphysis by 20 weeks of age.4 The anconeal process may exhibit partial or complete separation or it may be fused in an abnormal location.23 Several explanations for development of an ununited anconeal process have been proposed, including abnormal formation of the trochlear notch, osteochondrosis, and most recently, articular incongruency secondary to asynchronous growth of the radius and ulna.34,39 In chondrodystrophic breeds, a shortened ulna relative to the radius occurs due most likely to growth retardation or premature closure of the distal ulnar physis. The resultant short ulna causes the radius to push upward on the humeral condyle during its continued growth, thereby forcing the ventral margin of the anconeal process against the humeral trochlea. This upward force leads to separation or lack of fusion of the physis, resulting in an ununited anconeal process. This theory has been supported by clinical evidence: in 15 of 18 dogs examined, the anconeal process was proximally displaced the same distance as the radius relative to the ulna.34 Though spontaneous fusion of an UAP has been reported, it is considered rare.9,10,34 If an ununited anconeal process is left in situ, elbow osteoarthritis (OA) will progress leading to suboptimal limb function.41
Clinical Presentation
Ununited anconeal process occurs much less frequently than fragmented coronoid process (FCP) or osteochondritis (OC).19,27 It is most commonly seen in large to giant breed dogs as well as chondrodystrophic breeds such as the Basset hound and Dachshund.23,34 Of the large to giant breed dogs, German Shepherds are over-represented.33,39 Breeds with a secondary center of ossification of the anconeal process are likely predisposed to UAP,38 though asynchronous growth may play a secondary role (chondrodystrophic breeds). Males are affected approximately twice as commonly as females, and breeding of affected animals is not recommended.3,9,34,36,42
Radiographic Examination
Radiographs are indicated in any dog in which UAP or any other form of elbow dysplasia is a differential diagnosis for forelimb lameness. The diagnosis of a UAP can usually be made using a maximally flexed lateral radiograph of the elbow joint (Figure 56-21). The cranio-caudal view is indicated to document the degree of OA. Many patients will resist flexion of the elbow due to the discomfort associated with UAP and may require sedation to obtain diagnostic quality radiographs. Radiographs of both elbows are always indicated as this is considered a developmental disease. A definitive diagnosis of UAP can be made if a line of cleavage separating anconeal process from ulnar metaphysis is radiographically apparent. This line can be of differing widths and the anconeal process can be normal or abnormal in position, size, shape and radiographic density. The degree of osteoarthritis apparent radiographically depends on the chronicity of disease (Figure 56-22).
Treatment Options and Indications for Surgery
Surgical intervention is recommended for treatment of UAP.38 If an ununited anconeal process is treated conservatively (left in situ), elbow OA will progress and likely cause less than optimal limb function.41 Medical therapy includes weight management, controlled exercise, and appropriate medications (non-steroidal anti-inflammatories, osteoarthritis modifying supplements).38 Conservative management is less successful than surgery and results in rapid progression of osteoarthritis.4 The goal of treatment of an ununited anconeal process is the complete restitution of normal joint function.
Surgical options for UAP are its removal, reattachment to the ulna, and osteotomy/partial ostectomy of the ulna with or without surgical fixation of the anconeal process to the ulna.7,8,11,13,17,25,29, 30,32,33,34,37,39
Surgical Removal of the Anconeal Process
(Table 56-1)
Initially, the recommendation was that all UAPs be surgically removed.2,5,14,21,28,34 However, due to the inherent instability of the elbow following removal of the anconeal process,41 the prognosis associated with this procedure has been variable. The lack of the anconeal process causes an unstable joint, reliably leading to a decreased range of motion of the elbow joint, increased osteoarthritis and a high incidence of post-operative clinical dysfunction.9,10,18,21 One study reported that even though 70% of patients improved clinically following removal of the UAP, only 50% were free of lameness9 whereas in another retrospective study, surgical removal resulted in good to excellent long term function.29 Long-term results with excision are generally considered unsatisfactory because patients are not free of lameness. Removal of the anconeal process may still be an appropriate decision when it is misshapen and its preservation would not restore joint congruity or if the dog has advanced osteoarthritis.
Reattachment of the Anconeal Process
(Table 56-2)
In an attempt to improve outcome, a technique was described whereby a compression screw is utilized to stabilize the ununited anconeal process.10,25,26 This can be done from either the anconeal process into the ulna, or vice versa, though the latter is preferred because no implants are left within the joint. Results were encouraging and showed the stability afforded the joint by preserving the anconeal process.7 Compression of the cleavage plane utilizing a screw placed in lag fashion stabilizes the anconeal process in a normal anatomic position and encourages bony fusion. By preserving the anconeal process, elbow joint stability is maintained, decreasing the potential for future development of osteoarthritis.7 However, a complication encountered with any compression screw fixation is breakage of the screw.31 This most likely occurs secondary to continued shear forces across the cleavage plane between the anconeal process and the ulnar metaphysis when the underlying elbow incongruity is not corrected. Stabilizing the anconeal process in an obviously incongruent joint may actually increase the forces acting on the articular cartilage of the anconeal process and the humeral trochlea, resulting in increased cartilage wear and potential screw failure. Continued incongruity will cause osteoarthritis to progress.
Reestablishment of Joint Congruity (Ulnar Osteotomy/Partial Ostectomy)
(Table 56-2)
An ulnar osteotomy or partial ostectomy is advocated to allow dynamic repositioning of the radius, relative to the ulna, thereby improving elbow congruity. It also lessens the pressure directed against the anconeal process, encouraging ossification of the cleavage plane.20,33,34 Radiographic union of the anconeal process to the ulnar metaphysis has been variable with this technique,34,39 but this appears to be dependent on the age of the dog at the time of surgery as well as whether or not the anconeal process is firmly attached to the ulna by fibrous tissue or is loose. Patients in whom the anconeal process is firmly fixed to the ulna appear to be more likely to proceed to bony union with only an ulnar osteotomy/partial ostectomy than those in which the anconeal process is loose at the time of surgery.17 Failure to observe fusion of an ununited anconeal process after only an ulnar osteotomy/ partial ostectomy is more prevalent when the age of the dog at the time of surgery is greater than seven to eight months.11,39 These patients should have combination fixation (see below). A more favorable outcome is achieved with an ulnar osteotomy or partial ostectomy compared to surgical excision of the anconeal process.34 Any time an intra-articular step with the ulna being shorter than the radius is evident within the joint at the time of surgery an ulnar osteotomy/partial ostectomy is indicated.
Overall, ulnar osteotomy or partial ostectomy alone should be performed in cases where the anconeal process is stable at the time of surgery or in animals 6 months of age or less. Additional fixation (lag screw) is indicated in any animal whose anconeal process is not stable at the time of surgery regardless of age.17,38
Combination Fixation Approach
(Table 56-2)
Combining both the ulnar osteotomy/partial ostectomy with lag screw fixation of the anconeal process has shown the most consistently promising results,11,17 likely because it addresses the underlying cause (elbow incongruency) as well as the resultant pathology (UAP). The ulnar osteotomy improves the underlying elbow incongruency and relieves pressure directed against the anconeal process. Placement of the compression screw achieves the stability necessary to encourage fusion of the cleavage plane between the ununited anconeal process and ulna. In the long term, maintaining joint stability (preserving the anconeal process) and improving joint incongruency (osteotomy) should result in optimal clinical outcome.11 Excellent long-term outcome with no to minimal OA progression has been achieved. Of 39 joints reported in the literature, radiographic fusion was achieved in over 97% of cases.11,17 In another study, 13 of 20 dogs with UAP treated with the combination of an AP fixation and ulnar osteotomy/ostectomy were re-examined clinically and radiographically at a mean of two and a half years later. Nine (69%) had no lameness, four (31%) had no arthrosis, and 80% (16/20) of owners were satisfied with the outcome.12 Best results are expected in dogs less than 6 months of age at the time of surgery.16
Surgical Techniques
Surgical options for UAP are its removal, reattachment to the ulna, and osteotomy/ partial ostectomy of ulna with or without surgical fixation of the anconeal process to the ulna.7,8,11,13, 17,25,29,30,32,33,34,39
Anconeal Process Removal
Anconeal process removal can be performed via a caudomedial or caudolateral approach,22 though the caudolateral approach is preferred due to the smaller size of the lateral humeral condyle making visualization, surgical manipulation, and fragment removal easier. Surgical removal using arthroscopy has also been described.40
Arthrotomy
The dog is placed in lateral recumbency with the affected limb up. During surgical manipulation, the elbow can be stabilized by placing a roll of towels or other padding underneath it. Two different surgical approaches have been described, one based on a procedure by Snavely and Hohn35 (described here), and another based on a procedure by Chalman and Slocum.
Based on the procedure of Snavely and Hohn (Figure 56-23A-D): A curvilinear skin incision is made over the caudolateral aspect of the joint, centering over the lateral humeral epicondyle (Figure 56-23A). The incision extends from just proximal to the lateral epicondylar crest to several centimeters distal to the radial head. The subcutaneous fascia is incised along the same line, exposing the brachial fascia (Figure 56-23B). The radial nerve may be encountered if the incision is made too far proximally. The brachial fascia is then incised just cranial to the lateral head of the triceps brachii muscle where it inserts on the olecranon. The triceps brachii muscle is then elevated and retracted caudally to visualize the anconeus muscle underneath (Figure 56-23C). The anconeus muscle is incised at its periosteal origin at the lateral epicondylar crest and subperiosteally elevated (Figure 56-23D). Retracting the anconeus muscle caudally exposes the caudolateral joint compartment of the elbow and the anconeal process. Gelpi retractors can be used to maintain exposure. For closure, absorbable sutures are recommended in a simple interrupted or continuous pattern. The anconeus muscle is sutured to the origin of the antebrachial extensor muscles. The brachial and subcutaneous fasciae are closed in separate layers, followed by the skin closure.
Anconeal Process Removal
With the anconeal process exposed, the joint is placed in maximum flexion. The anconeal process can be removed with tissue or towel forceps. Usually fibrous attachments between the anconeal process and the ulna need to be severed.
Ulnar Osteotomy
In chondrodystrophic and short-legged breeds, a distal ulnar ostectomy is recommended to prevent the creation of a painful nonunion that may occur after proximal or midshaft ulnar transection, while in long-legged dogs and non-chondrodystrophic breeds a proximal osteotomy or partial ostectomy is preferred.15,38 Placing an intramedullary Kirschner wire is recommended for the fixation of proximal ulnar osteotomies or ostectomies to prevent caudal “kicking” of the proximal ulnar segment due to the pull of the triceps brachii muscle. Anconeal process removal or further fixation may be necessary if fusion is not observed 12 to 18 weeks after ulnar ostectomy and clinical signs remain.38
Proximal Ulnar Osteotomy/Partial Ostectomy
The skin is incised caudolaterally directly over the proximal ulna, followed in the same line by an incision in the underlying deep fascia. Periosteal incisions are then made in the origin of the flexor carpi ulnaris muscle medially and the ulnaris lateralis muscle laterally. The ulna is freed from its surrounding muscular attachments using a periosteal elevator. The ostectomy or osteotomy is performed 2 to 3 cm distal to the radial joint surface. The amount of dissection depends on whether a partial ostectomy or osteotomy is chosen. Hohmann retractors can be used to protect the soft tissues surrounding the ulna during the osteotomy. A sagittal saw is generally used for the ulnar cut(s). It is essential to ensure that the osteotomy penetrates the entire ulna in order for joint congruity to be reestablished. The osteotomy may be straight or oblique at a 45° angle to the long axis of the ulna (caudoproximal to craniodistal) to minimize caudal angulation of the proximal piece and encourage rapid healing. In dogs in which this is the only method of UAP treatment, an ostectomy may be indicated as the oblique osteotomy may result in healing prior to restoration of joint congruence.34 For the ostectomy, approximately 5 mm of bone and the surrounding periosteum are removed. The intramedullary pin can be applied normograde or retrograde. Normograde insertion is more difficult due to the small diameter of the target, but it will result in it exiting the ulna at a site amenable to surgical removal should that be needed. The surgical site is closed using absorbable sutures. The ulnaris lateralis and the flexor carpi ulnaris are sutured to each other over the caudal border of the ulna. The deep fascia, subcutaneous tissues and skin are closed routinely.
The intramedullary pin may cause discomfort, presumably due to interference with triceps muscle tendon of insertion. Once ulnar osteotomy or ostectomy site has healed, the intramedullary pin can easily be removed through a small incision.
Distal Ulnar Ostectomy
A skin incision is made directly over the distal lateral surface of the ulna, from the midshaft to the styloid process. Subcutaneous tissues are incised along the same line, exposing the underlying tendon of the ulnaris lateralis muscle over the distal ulna or slightly caudal to it and the tendon of the lateral digital extensor muscle is immediately cranial to the ulna. After identification of these tendons, the fascia between them is incised and retracted. The surrounding tissues, including part of the origin of the abductor pollicus longus if needed, are elevated from the ulna and protected from the sagittal saw using Hohmann retractors. The ostectomy is performed as above. Closure is routine: the fascia is closed, followed by the subcutaneous tissues and the skin.
Lag Screw Fixation of the Anconeal Process
The original procedure described screw placement from the anconeal process into the ulna, countersinking the screw head into the articular cartilage.10 This has since been modified by placing the screw in the opposite direction, preventing the presence of an implant within the joint, creating a smaller hole in the anconeal process, and removal (if necessary) is easier and does not involve an arthrotomy.25 A further modification is the addition of K-wires as a visual guide for screw placement and for anti-rotational purposes.7
The surgical approach to the joint for this procedure is as described above based on Snavely and Hohn (see Anconeal process removal). Once the anconeal process and the cleavage plane are visualized, a Kirschner wire (K-wire) is inserted into the anconeal process passing perpendicular to the cleavage line. It enters the caudal surface of the ulna, passes through the proximal quadrant of the anconeal process and exits 1mm beyond the articular margin. This allows visualization of the wire to assure its proper placement. A second K-wire and a compression screw are inserted sequentially using a drill guide. An aiming device can be used to facilitate proper K-wire and screw placement. The screw should be aimed towards the tip of the anconeal process. Either an appropriate length of partially threaded cancellous screw or a fully threaded cortical screw placed in lag fashion can be used. It is very important that there is no screw purchase within the ulnar metaphysis for both the lag screw and the partially threaded cancellous screw in order to ensure maximal compression of the cleavage plane. To achieve this with a fully threaded screw, a glide hole must be drilled through the existing thread (guide) hole to the cleavage plane. Its depth can be estimated by measuring the distance from the caudal aspect of the ulna to the cleavage plane along the line of the proposed screw placement. Screw sizes vary depending on the size of the anconeal process to be purchased, but 2.7 and 3.5 mm cortical screws and 4.0 mm partially threaded cancellous screws are most commonly used. After satisfactory screw placement, the initially placed K-wire is backed out until it is in the subchondral bone of the anconeal process, cut and bent in order to prevent migration into the joint. Its ideal position is 10 to 20 degrees divergent from the screw.17 Post-operative radiographs are indicated (See Figure 56-24).
Proximal Ulnar Osteotomy and Lag Screw Fixation of the Anconeal Process
The combination of an ulnar osteotomy and lag screw fixation is used to address the underlying cause of the problem (elbow incongruity) and its resultant pathology (UAP). The procedure is performed as described above in the sections for lag screw fixation of the anconeal process and ulnar osteotomy/partial ostectomy. The general order of procedures is as follows: caudolateral arthrotomy, evaluation of the anconeal process and the tightness of its attachment, evaluation of joint incongruity, and lag screw fixation of the anconeal process followed by the ulnar osteotomy/partial ostectomy (Figure 56-24). It is thought that oblique ulnar osteotomy cuts may result in healing which is too rapid to allow for restoration of joint congruency.34 This author concurs with that premise if the ulnar osteotomy is the only method of treatment for the UAP. If placing a lag screw in addition, the sliding oblique proximal ulnar osteotomy with an intramedullary pin appears to be adequate and comfortable for the patient. If in doubt, the joint should be evaluated for congruence after the ulnar osteotomy. If a large step remains, a partial ostectomy may be indicated. In dogs less than 6 months of age at the time of surgery that have minimal anconeal process instability, fixation using two K-wires is often sufficient.16 This should always be combined with ulnar osteotomy or partial ostectomy in order to prevent continued incrongruency resulting in implant failure. In basset hounds, dachshunds and other chondrodystrophic breeds, a distal ulnar osteotomy/partial ostectomy is performed because the proximal procedure carries a higher risk of pseudoarthrosis formation in these breeds.16 In dogs with longer legs, a proximal ulnar osteotomy/partial ostectomy is performed for better correction of joint incongruity, though it is associated with greater morbidity.16
Post-operative Care
Most surgeons recommend that the animal be placed in a soft support wrap for 2 to 5 days to decrease the immediate post-op swelling and minimize seroma formation. Exercise is generally restricted for 2 to 4 weeks8,10,32 following anconeal process removal and until bony union has occurred in all other procedures. Passive range of motion exercise, heat and cold therapy, and non-steroidal anti-inflammatory drugs usually are implemented during the healing phase. Controlled walking on the limb is also encouraged. Removal of implants can be performed after bony healing is complete (Figure 56-25).
Complications
All surgeries described above carry a risk of infection, seroma formation, and bleeding. Osteoarthritis of the elbow may also continue after any of these procedures. Anconeal process removal itself does not carry any other major complications other than the probable increase in osteoarthritis. If only an ulnar osteotomy/partial ostectomy is performed, complications may include failure of the anconeal process and ulna to proceed to bony union, continued elbow incongruency, non-union of the ulnar osteotomy, chronic post-operative pain, and pin migration (Figure 56-26). Lag screw fixation of the ulna carries the possible complications of implant failure, failure of the anconeal process to undergo bony union with the ulnar metaphysis, and penetration of the joint surface with the screw or K-wire. When a combined treatment approach is used, all of the complications listed above are possible. Use of combined treatment does, however, appear to increase the likelihood of a positive outcome.
Prognosis
Currently, there is no clinical trial definitively comparing all of the previously mentioned techniques, though some generalizations can be made based on the literature: Removal results in an increase of osteoarthritis in 93% of animals reported in the literature, though some lamenesses may temporarily improve, probably secondary to removal of the loose fragment. This procedure is likely indicated in those cases presenting as adults with severe osteoarthritis. The reported outcome with only lag screw fixation of the anconeal process has been disappointing with only 38% of reported cases achieving bony union. In one study, all dogs which did not achieve bony union had implant failure. Of the cases reported in the literature treated solely with an ulnar osteotomy, the overall rate of progression to bony union was 51%. Patient selection appeared to be important. If a fragment was firmly attached at surgery and the dog was less than 7 months of age, it is reasonable to expect radiographic union and a good to excellent clinical outcome with only an ulnar osteotomy. If the animal is over 7 months of age or if the fragment is loose, combination fixation with a lag screw and ulnar osteotomy/ostectomy is recommended. Ninety-seven percent of cases which had this type of fixation continued to radiographic fusion (See Figure 56-26). Normal function even after strenuous exercise can be achieved in 82% of these dogs.
References
- Breit S, Kunzel W, Seiler S: Variation in the ossification process of the anconeal and medial coronoid processes of the canine ulna. Res Vet Sci 77:9, 2004.
- Brinker WO, Piermattei DL, Flo GL: Handbook of small animal orthopedics and fracture treatment. Philadelphia: Saunders, 1990, p 502.
- Cook JL: Forelimb lameness in the young patient. Vet Clin North Am Small Anim Pract 31:55, 2001.
- Cross AR, Chambers JN: Ununited anconeal process of the canine elbow. Comp Cont Ed Pract Vet 19:349-361, 1997.
- Denny HR: A guide to canine and feline orthopedic surgery. London: Blackwell, 1993, p 229.
- Evans HE: Miller’s anatomy of the dog. 1993.
- Fox SM, Burbidge HM, Bray JC, et al: Ununited anconeal process: Lag-screw fixation. J Am Anim Hosp Assoc 32:52, 1996.
- Goring RL, Bloomberg MS: Selected development at abnormalities of the canine elbow: Radiographic evaluation and surgical management. Comp Cont Ed Pract Vet 5:178-192, 1983.
- Guthrie S: Some radiographic and clinical aspects of ununited anconeal process. Vet Rec 124:661, 1989.
- Herron MR: Ununited anconeal process in the dog. Vet Clin North Am 1:417, 1971.
- Krotscheck U, Hulse DA, Bahr A, et al: Ununited anconeal process: Lag-screw fixation with proximal ulnar osteotomy. Vet Comp Ortho Trauma 13:212, 2000.
- Kurzbach T: Retrospektive langzeituntersuchung von operativ versorgten ellbogen- und schultergelenkfrakturen bei hund und katze. Vet Med Diss Munich 2000.
- Lewis R, Leighton RL: Surgical stabilization of the ununited anconeal process in the dog using cerclage wire. Calif Vet 49:10, 1995.
- Loeffler K: Der isolierte processus anconaeus beim deutschen schaeferhund. Dtsch Tieraerztl Wochenschr 71:291, 1963.
- Matis U. Lag screw fixation of ununited anconeal process, in Surgical Fixation of Fractures, 24th annual advanced canine course in AO/ASIF Technique 2001.
- Matis U. Management of the UAP by internal fixation, in 10th ESVOT Congress 2000.
- Meyer Lindenberg A, Fehr M, Nolte I: Short- and long-term results after surgical treatment of an ununited anconeal process in the dog. Vet Comp Ortho Trauma 14:101, 2001.
- Meyer-Lindenberg A, Fehr M, Nolte I: Der isolierte processus anconaeus des hundes - vorkommen, behandlung, und ergebinsse. Kleintierpraxis 36:671, 1991.
- Olsson SE: Pathophysiology, morphology, and clinical signs of osteochondrosis in the dog. In Bojrab MJ, ed.: Disease Mechanisms in Small Animal Surgery. Philadelphia: Lippincott Williams & Wilkins, 1993, p 778.
- Olsson SE, Jerre S, Kasstrom H. Pathogenesis of ununited anconeal process, fragmented medial coronoid process, and OCD of the canine elbow, in 9th Congress of the Society for Veterinary Radiology 1991.
- Parrisius A: Detached anconeal process in the dog. treatment and results between 1975 and 1983. 1985.
- Piermattei DL, Johnson KA: Atlas of surgical approaches to the bones and joints of the dog and cat. 2004.
- Presnall K: Ununited anconeal process of the elbow. In Bojrab MJ, ed.: Current Techniques in Small Animal Surgery. Philadelphia: Lea and Febiger, 1990, p 778.
- Preston CA, Schulz KS, Kass PH: In vitro determination of contact areas in the normal elbow joint of dogs. Am J Vet Res 61:1315, 2000.
- Pritchard DL: Anconeal process pseudoarthrosis: Treated by lag-screw fixation. Canine Pract 3:18-23, 1976.
- Punzet G: Ellbogengelenksdysplasie mit isoliertem processus anconaeus - eine neue moeglichkeit der chirurgischen behandlung. Kleintierpraxis 18:121, 1973.
- Remy D, Neuhart L, Fau D, et al: Canine elbow dysplasia and primary lesions in german shepherd dogs in france. J Small Anim Pract 45:244, 2004.
- Renegar WR, Farrow CS: OsteochondrosisIn Whittick WG, ed.: Canine orthopedics. Philadelphia: Febiger, 1990, p 620.
- Roy RG, Wallace LJ, Johnston GR: A retrospective long-term evaluation of ununited anconeal process excision on the canine elbow. Vet Comp Ortho Trauma 7:94, 1994.
- Sikkema DA, Roush JK: Unusual presentation of an ununited anconeal process in a 6-year-old great dane. Vet Comp Ortho Trauma 7:177, 1994.
- Sinibaldi KR: Ununited anconeal process in the dog. In Bojrab MJ, ed.: Current Techniques in Small Animal Surgery. Philadelphia: Lea and Febiger, 1983, p 719.
- Sinibaldi KR, Arnoczky SP: Surgical removal of the ununited anconeal process in the dog. J Am Anim Hosp Assoc 11:192, 1975.
- Sjostrom L: Ununited anconeal process in the dog. Vet Clin North Am Small Anim Pract 28:75, 1998.
- Sjostrom L, Kasstrom H, Kallberg M: Ununited anconeal process in the dog. pathogenesis and treatment by osteotomy of the ulna. Vet Comp Ortho Trauma 8:170, 1995.
- Snavely DA, Hohn RB: A modified lateral surgical approach to the elbow of the dog. J Am Vet Med Assoc 169:826, 1976.
- Stevens DR, Sande RD: An elbow dysplasia syndrome in the dog. J Am Vet Med Assoc 165:1065, 1974.
- Thomson MJ, Robins GM: Osteochondrosis ot the elbow, a review of the pathogenesis and a new approach to treatment. Aust Vet J 72:375, 1995.
- Trostel CT, McLaughlin RM, Pool RR: Canine elbow dysplasia: Anatomy and pathogenesis. Comp Cont Ed Pract Vet 25:754, 2003.
- Turner BM, Abercromby RH, Innes J, et al: Dynamic proximal ulnar osteotomy for the treatment of ununited anconeal process in 17 dogs. Vet Comp Ortho Trauma 11:76, 1998.
- van Bree HJJ, van Ryssen B: Diagnostic and surgical arthroscopy in osteochondrosis lesions. Vet Clin North Am, Small Animal Practice 28:161, 1998.
- Wind AP: Elbow dysplasia. In Slatter D, ed.: Textbook of Small Animal Surgery. Philadelphia: WB Saunders Co, 1993, p 1966.
- Wind AP, Packard ME: Elbow incongruity and developmental elbow diseases in the dog: Part II. J Am Anim Hosp Assoc 22:725, 1986.
Surgical Treatment of Fragmented Coronoid Process
Ursula Krotscheck
Anatomy
See previous section on ununited anconeal processes.
Pathogenesis
In dogs, the medial coronoid process (MCP) develops exclusively by appositional ossification. The normal radioulnar articulation is a smooth transition between the ulnar trochlear notch and the proximal articular surface of the radial head.58 During a dog’s growth phase, the relatively early development of a trabecular pattern within the MCP reflects significant mechanical loading at an early age. It is loaded primarily in a direction perpendicular to the humeroulnar surface during normal weight bearing as evidenced by the primary axis of its trabecular orientation, while the tensile stress from the annular ligament forms a secondary axis.62 Initially, a fragmented medial coronoid process (FCP) was believed to be a form of osteochondrosis (OCD),39,40 but it has since been suggested that mechanical overload at an early age may lead to this condition.17 The histologic and ultrastructural appearance of an FCP is more consistent with mechanical failure of the cartilage, its associated subchondral bone, and subsequent unsuccessful fibrous repair17,22 than an osteochondrosis type of lesion. The characteristic osteochondral fissures or fractures associated with an FCP may be due to excessive loads experienced by the developing MCP secondary to conformational abnormalities, such as elbow incongruity.17,58-60 Elbow incongruity is speculated to result from underdevelopment of the ulnar trochlear notch8,15,58,59,61 or asynchronous growth of the radius and ulna (short radius, long ulna).30,59,61
In large, heavy-set breeds of dogs, the ulnar trochlear notch may not be large enough to accommodate the relatively big humeral condyle. When evaluating lateral radiographs of the elbow, the proximal ulna is significantly longer in breeds commonly affected with FCP compared to other breeds.59,61 Additionally, heavy-set breeds have a slightly wider, larger, and less steeply sloping MCP than sight hounds.58 When comparing the radius of the curvature of the ulnar notch in rottweilers and greyhounds, a significant and consistent difference was found, with greyhounds having a significantly greater mean radius of curvature at the end of the medial coronoid process, in comparison to rottweilers. The significance of these findings for dogs with FCP is unclear.12
As with an ununited anconeal process, the rate of growth of the radius and ulna in relation to each other is speculated to be part of the pathogenesis of FCP. Necropsies of dogs with FCPs have revealed that the MCP and the distal edge of the ulnar trochlear notch are often positioned slightly proximal to the adjacent articular surface of the radial head.59,61 This incongruity then places excessive load on the developing MCP during weight-bearing and is implicated as the cause of fragmentation.58-61 This agrees with the ultrastructural appearance of the FCP.22 The most likely cause of this is a genetic predisposition to elbow incongruency leading to subsequent mechanical overload of the MCP.18,50 Worsening of the phenotypic expression may be caused by caloric oversupplementation58,61,65 and excessive calcium intake.44
Both osteochondritis dissecans and FCP have a polygenic mode of inheritance.41 The heritability estimates vary from 0.27 to 0.7721,48,49 and it is not recommended to breed dogs with this disorder, dogs producing offspring with this disorder, as well as phenotypically normal dogs with first degree relatives with this disorder.41
Clinical Presentation
FCP is one of most frequent canine developmental orthopedic disorders8,26,34 and can occur in conjunction with OCD in the same joint. Often, the disease is bilateral.30
The age of presentation for clinical signs consistent with FCP in retriever-type dogs has two peaks: 5.9 months and 4.5 years.31 Dogs bilaterally affected seem to present later because the lameness may be more difficult to recognize.8 Male dogs account for 65 to 75% of cases in some studies,19,28 while in a controlled breeding study to determine the inheritance of FCP and OCD males and females were equally affected.41
Clinical signs often consist of stiffness and a stilted gait or lameness occurring between four to seven months of age.28,39 When the patient is standing, inward rotation of the elbow and external rotation, or supination, of the paw may be present. Pain on hyperextension or hyperflexion of the elbow is common and joint effusion of variable degree is usually present in more advanced cases. The development of osteoarthritis (OA) associated with FCP is influenced by the size of the fragment, its mobility, and the amount of time it has been present.39 These fragments can be single or multiple and may involve only a small section of the MCP or its majority. It is interesting to note that the boxer is one of most frequently affected breeds presenting over 18 months of age, but radiographic evidence of OA in the affected joint is either absent or mild for unknown reasons.34
Diagnosis
Definitive diagnosis of FCP can be difficult. Techniques which have been used include plain film radiography, xeroradiography, linear tomography,14 arthrography,29 CT,9,11 MRI and arthroscopy.55,56
Visualizing or definitively diagnosing an FCP using plain film radiography can be challenging. The MCP is a small ulnar projection obscured in normal dogs by the radial head and the ulnar shaft on standard views. The cleavage line cannot be seen if it is at all oblique to the x-ray beam. In young dogs radiographs can appear normal (Figure 56-27) while in older dogs only secondary OA changes are seen (Figure 56-28). Radiographic changes characteristic of secondary OA include periarticular osteophytosis of the dorsal aspect of the anconeal process (AP), the cranial articular margin of the radial head, the medial humeral epicondyle, and the MCP, as well as bony sclerosis of the ulnar trochlear notch.5,28 The most significant radiographic lesion of FCP is osteophyte formation on the proximal margin of the AP.24,36,57 Most osteophytes associated with FCP do not appear until the dog is 7 to 8 months of age.2 Often, the radiographic diagnosis of FCP is based on these secondary OA changes.4,6,18, 39,45,57 The accuracy and sensitivity of survey radiographs in detection of FCP is 56.7% and 23.5%, respectively.11 Several alternative radiographic projections have been evaluated for their ability to definitively diagnose FCP. In one study, the MCP was best visualized on a mediocaudal-laterocranial 15° oblique (extended and supinated mediolateral) radiographic projection when compared to the standard mediolateral and flexed mediolateral views.36,57 Another study agreed with these findings, stating that the Cr15L-CdMO provided greatest sensitivity (62%) for definitive identification of an FCP when it existed and the greatest agreement among evaluators.64 A more recent study compared the Cr15L-CdM oblique and the Di35M-PrL oblique views (in addition to standard radiographic views) and found that a normal MCP was best identified on the Di35M-PrL oblique view, concluding that the Di35M-PrL oblique view enhances the identification of anomalies and fragmentation of MCP compared to other views.23
Because of the inherent difficulty with the definitive diagnosis of FCP on plain radiographs, other imaging modalities have been evaluated. Using arthroscopy as the definitive diagnostic method for FCP, computed tomography (CT) had the highest accuracy (86.7%) and sensitivity (88.2%) and negative predictive value (84.56%) when compared to standard radiographs, linear tomography, and xeroradiography.11 Other advantages of CT are the ability to not only evaluate the MCP, but also other aspects of the articular surfaces for defects and incongruities (Figure 56-29A and B). Sagittal reconstruction of CT images can be helpful in evaluating joint incongruity. Magnetic resonance imaging (MRI) is also more accurate than conventional radiography for FCP detection in dogs.46 Magnetic resonance arthrography permits classification of an FCP into 2 categories: completely loose fragments and fragmented processes that are still attached to the ulna by a cartilaginous bridge, but this did not provide substantial additional information about changes on MCP compared to MRI without contrast.47 In general, CT and MRI have higher accuracy, sensitivity and specificity than plain radiographs.11,46 Regardless, no noninvasive imaging modality currently available to veterinary medicine can make a diagnosis of an FCP with 100% certainty.53 It was recently proposed that arthroscopy is the best diagnostic technique for determining the cause of elbow disease when there is no radiographic proof of FCP.34 Comparison of standard radiographs, CT and arthroscopy in lame dogs elucidated that only arthroscopy allows consistent definitive diagnosis of elbow lesions before the development of OA.56
Treatment Options and Indications
Osteoarthritis is expected to progress in most dogs with FCP. Because of this, all dogs with FCP should be started on conservative medical management regardless of surgical intervention. This consists of dietary control of growth, weight management, exercise moderation, non-steroidal anti-inflammatory drugs, and chondroprotective agents. Early surgical removal of an FCP has been the treatment of choice.31,42,43,54 This may have a better outcome than conservative medical management; especially if the dog is a companion animal and the surgery is performed prior to 2 years of age. According to owner questionnaires, 78% of dogs which had surgery at less than two years of age returned to apparent soundness.31 Traditionally, in older dogs with severe OA secondary to FCP, medical management has been recommended over surgical FCP removal.4,6,18,39 Evidence suggests that with only conservative therapy, elbow OA progresses significantly and the duration of lameness increases,6,18,35,62 thus leading to the recommendation for surgery even in older patients with chronic OA.33 Over half of patients followed radiographically after FCP removal did not increase in OA grade, suggesting that surgery may prevent worsening of the secondary OA.19
On the other hand, there are studies documenting a lack of positive influence of surgical intervention on the progression of secondary OA.7 Part of the lack of improvement after surgical intervention and continued OA may be explained by remaining elbow incongruity. If present at the time of surgery, it can be addressed with an ulnar ostectomy/osteotomy.30,37 It has been recommended that this surgery should be performed early to prevent changes to other ulnar structures. When combining FCP removal with a proximal ulnar osteotomy, the average time to improvement was 8.6 weeks. Nine of 10 dogs had a good to excellent clinical outcome with almost full range of motion (ROM), absence of pain and crepitation in the elbow, and no signs of lameness. Late follow-up radiographs showed mild caudomedial rotation of proximal ulna: 10 to 15 degrees caudally and zero to five degrees medially compared to the pre-operative images, with the author commenting that the fear of excessive rotation of the proximal ulnar fragment is unfounded.38 OA did progress in most of these dogs. It has been recommended not to stabilize the osteotomy even though this might speed recovery and reduce callus formation. The risk of maintaining the fragment in an inappropriate location is minimized with an unstable osteotomy and optimizes the chance of achieving good functional elbow joint anatomy.38 Along these lines, it has been hypothesized that with an early ulnar osteotomy/ostectomy, the removal of an FCP may be unnecessary because it could consolidate following relief of the excessive pressures it is subjected to in an incongruous elbow.
Several surgical approaches to the elbow for FCP removal have been described: triceps tenotomy,6 olecranon osteotomy,6 proximal ulnar diaphyseal osteotomy,27 osteotomy of the medial epicondyle,24 muscle separation with tenotomy of the pronator teres and/or in combination with tenotomy of the flexor carpi radialis,16,32 muscle separation between the pronator teres and flexor carpi radialis muscles,13,18,42 muscle separation between the flexor carpi radialis and flexor digitorum profundus muscles,18 and longitudinal myotomy of the flexor carpi radialis muscle.1 Adequate exposure to the medial compartment of the elbow joint for medial humeral condylar OCD and FCP evaluation and treatment can be obtained with either medial epicondylar osteotomy or a muscle separation technique with or without tenotomy of pronator teres or flexor carpi radialis muscle(s).8 Significantly increased complications requiring additional surgery have been reported with the osteotomy approach and multiple authors suggest using one of the muscle separation techniques instead.28,52 There are no other significant differences between the muscle separation and epicondylar osteotomy techniques in gait, range of motion, joint thickness or joint pain, but muscle mass measurements were significantly greater in the osteotomy group.52
Surgical Treatment by Arthrotomy
(Figure 56-30A-D)
The muscle separation approaches provide adequate exposure and a medial humeral epicondylar osteotomy is generally not needed. The approach described here is one of the more commonly used, varying from others only by which muscles are separated. The dog is placed in dorsal recumbency with the affected limb suspended for surgical preparation and draping. The limb is abducted once draped and the elbow is stabilized by placing a roll of towels or other padding underneath it.
A curvilinear skin incision is made over the medial aspect of the joint, centering on the medial humeral epicondyle and extending along the proximal ulna. The ulnar nerve crosses the medial epicondyle of the humerus just proximal to the origin of the humeral head of the superficial digital flexor and then continues on under the ulnar head of the flexor carpi ulnaris muscle. It should be protected during the fascial incision. The antebrachial fascia is incised along the same line as the skin and retracted, exposing the flexor muscle group. The muscular septum between the flexor carpi radialis and the deep digital flexor muscles or the pronator teres and flexor carpi radialis muscles is identified and bluntly separated (Figure 56-30A). The median artery and nerve will be visible in most dogs when dissection is complete. Hemostasis from intermuscular vessels is achieved with cautery and ligation. The muscles can now be separated by retraction, exposing the underlying joint capsule (Figure 56-30B). Desmotomy of the medial collateral ligament can be performed to increase exposure, though it is generally not needed for FCP removal. The joint capsule is carefully incised either along the same line as the muscles or horizontally along the joint line. It is then tagged and retracted to expose the articular surfaces of the humerus and ulna (Figure 56-30C). In order to completely visualize the MCP, the incision may need to be extended parallel to the ulnar trochlear notch, being careful not to sever the medial collateral ligament. Pronation and abduction of the antebrachium opens the medial joint surface; the previously placed towels or padding under the elbow facilitate this maneuver (Figure 56-30D). A fair amount of pressure may be required for adequate visualization. The FCP can then be removed using rongeurs, curettes, or hemostatic forceps depending on its soft tissue attachments, size, location and remaining bony attachments. After fragment removal, the joint is flushed profusely and closed in a simple interrupted pattern using absorbable suture material. Following this, the intermuscular septum, brachial fascia, and subcutaneous tissues are closed in separate layers, followed by the skin closure.
Treatment by Arthroscopy
Arthroscopy is rapidly becoming a common method of FCP removal and joint exploration. Advantages include the minimally invasive approach, a greater area of visualization within the joint, and lower risks of complications usually associated with an arthrotomy. Its main disadvantages are the equipment requirements and the time needed to become proficient at arthroscopy.
The following is adapted from Beale et al,3 and the reader is referred to this resource for a more in depth discussion. The arthroscopic procedure for evaluation of the elbow joint was originally described using a 2.7 mm, 30° rigid arthroscope. Beale et al recommend a 1.9 mm, 30° short scope because it causes less cartilage trauma in small joint such as the elbow.
Fluid inflow
For larger joints gravity inflow can be used, however small joints need a fluid pump due to higher pressures required to keep the joint open. It is recommend using 60 to 70 mm Hg pressure with a relatively low flow rate (10 to 20%) to avoid sudden surges.
Instrumentation
Power instruments are not required for elbow arthroscopy, but they can make surgery quicker, especially if large fragments are to be removed. An aggressive power shaver and a burr can be used. Arthroscopic cautery units or radiofrequency instrumentation are not recommended as they may pose a risk to the median and ulnar nerves.
Patient Preparation
The patient is prepared for open elbow surgery as if using the standard medial approach (see above) in case arthroscopy is unsuccessful and an arthrotomy must be pursued. The dog is placed in dorsal recumbency, especially if bilateral arthroscopy is planned, but can be placed in lateral recumbency with the affected limb down if only one side is affected. The surgery table, custom-made braces or towels can be used as a fulcrum for joint distraction.
Procedure
The assistant surgeon maintains the leg in a normal standing angle, positions the joint over the fulcrum, and places moderate downward (lateral) pressure on the antebrachium to open the medial compartment of the joint. Internal rotation also enlarges the joint space. For arthroscopic treatment of an FCP, 3 portal sites are generally used.
Egress
(Figures 56-31 and 56-33)
The egress is established first. Insert a needle craniodistal and slightly lateral, starting just proximal or adjacent to the anconeus, directing the needle so it sits in the joint pouch just proximal to the anconeus. A syringe is attached to aspirate joint fluid in order to ensure proper placement within the joint. If the needle is not within the joint space and fluid is injected, the difficulty of the procedure rises due to obscured landmarks, and external fluid pressure can cause the joint space to collapse. Lactated ringers solution may cause less damage to cartilage than saline. The joint is filled until moderate backpressure is felt in the syringe plunger. Underfilling makes scope portal establishment difficult and more traumatic, while overfilling may cause rupture of the joint capsule and loss of the fluid into the periarticular soft tissues. The assistant surgeon maintains pressure on the syringe to maintain joint pressurization during the arthroscope portal insertion.
Arthroscope Portal
(Figures 56-32 and 56-33)
A blunt obturator is usually used within the arthroscope cannula. To determine the appropriate site for portal insertion, a line is drawn from the medial epicondyle distal to the level of the joint line, and then approximately 5 mm caudally. A needle is placed to ensure the appropriate location, after which a proximodistal incision is made through the skin and soft tissues. It is imperative not to incise into the joint capsule, otherwise joint distention is lost and fluid can extravasate. Having the assistant maintain the valgus force on leg, the scope cannula is inserted into the joint through this incision. Removing the obturator, fluid will rush out if the cannula is placed correctly.
Instrument Portal
Once the joint has been examined with the arthroscope, the instrument portal is established. A needle is inserted into the joint at the level of the medial collateral ligament at the same level and angle as the arthroscope. Triangulate the needle and arthroscope until the needle tip is visualized within the joint. Once the needle is visualized, use a blade to make an incision directly adjacent to the needle. Immediately remove the needle and insert a blunt trocar if planning to work through a soft tissue tunnel, or a cannula with trocar if planning to work through an instrument cannula.
FCP Assessment and Removal
(Figure 56-34A and B)
A probe can be used to assess the cartilage texture. If chondromalacia is present, the cartilage should be debrided and the underlying bone assessed. Removal of avascular bone is always indicated, even if it is palpably stable. Care must be taken not to injure the normal articular cartilage.
Ulnar Osteotomy
The use of an ulnar osteotomy has been reported both with and without fragment removal. The osteotomy is performed in a craniodistal oblique direction or transversely as described in the previous section of Chapter 56 (Surgical Treatment of Ununited Anconeal Process of the Elbow).
Postoperative Care
Most surgeons recommend that the animal be placed in a soft support wrap for 2 to 5 days to decrease immediate post-op swelling and minimize seroma formation. Exercise is generally restricted for 2 to 4 weeks following FCP removal. Passive range of motion exercise, heat and cold therapy, and non-steroidal anti-inflammatories usually are implemented during the healing phase. Controlled walking on the limb is also encouraged.
Prognosis
Surgical outcome is strongly dependent on several preoperative conditions. It tends to worsen with increasing age, a longer pre-operative duration of lameness, an increase in elbow incongruence, and an increasing OA grade. It is also negatively influenced by presence of a UAP and/or OCD lesions.1,4,6,10,18,39,60,62 Other factors that affect prognosis are the age at which elbow dysplasia develops, the rate of disease progression, and the breed.8 OA is expected to progress in all dogs, regardless of surgical intervention or not, though the severity seems less in operated patients.33 Some studies do not show a difference between surgical and conservative medical management of FCP,7,25 but most studies do. Surgical treatment of FCP seems to have a favorable result at both 6 weeks and 6 months post-operatively, despite progression of OA.51 Interestingly, the severity of “kissing lesion” in the medial humeral condyle and the OA grade did not predict surgical outcome in one study.51
A better outcome is expected with a lower pre-operative OA grade10,18,19,61 and the progression of OA appears slower in dogs that are surgically managed (4.9 Guthrie points/month for FCP excision and ulnar osteotomy, 6.7 Guthrie points/month for FCP excision only) than those that received only conservative management (9.7 Guthrie points/month). It is important to note that these groups can not be directly compared due to variations in age.20 Overall, a good outcome can be achieved in up to 75%of the cases operated at 4-6 months of age, decreasing to 42% in older dogs. Pre-existing OA seems to be the major determining factor: in one study animals without OA accounted for 60% of the cases with a good outcome.10
References
- Anderson SM, Lippincott CL, Schulman AJ: Longitudinal myotomy of the flexor carpi radialis: A new approach to the medial aspect of the elbow joint. J Am Anim Hosp Assoc 25:499, 1989.
- Bardet JF: Arthroscopy of the elbow in dogs. part II: The cranial portals in the diagnosis and treatment of the lesions of the coronoid process. Veterinary and Comparative Orthopaedics and Traumatology 10:60, 1997.
- Beale BS, Hulse DA, Schulz KS, et al: Arthroscopically assisted surgery of the elbow jointIn Small Animal Arthroscopy. Philadelphia: Saunders, 2003, p 51.
- Bennett D, Duff SR, Kene RO, et al: Osteochondritis dissecans and fragmentation of the coronoid process in the elbow joint of the dog. Vet Rec 109:329, 1981.
- Berry CR: Evaluation of the canine elbow for fragmented medial coronoid process. Veterinary Radiology and Ultrasound 33:273, 1992.
- Berzon JL, Quick CB: Fragmented coronoid process: Anatomical, clinical, and radiographic considerations with case analyses. J Am Anim Hosp Assoc 16:241, 1980.
- Bouck GR, Miller CW, Taves CL: A comparison of surgical and medical treatment of fragmented coronoid process and osteochondritis dissecans of the canine elbow. Veterinary and Comparative Orthopaedics and Traumatology 8:177, 1995.
- Boulay JP: Fragmented medial coronoid process of the ulna in the dog. Veterinary Clinics of North America, Small Animal Practice 28:51, 1998.
- Braden TD, Stickle RL, Dejardin LM, et al: The use of computed tomography in fragmented coronoid disease: A case report. Veterinary and Comparative Orthopaedics and Traumatology 7:40, 1994.
- Brunnberg L, Allgoewer I: Age-related results of the treatment of elbow dysplasia (FCP) in the bernese mountain dog. Veterinary and Comparative Orthopaedics and Traumatology 9:65, 1996.
- Carpenter LG, Schwarz PD, Lowry JE, et al: Comparison of radiologic imaging techniques for diagnosis of fragmented medial coronoid process of the cubital joint in dogs. J Am Vet Med Assoc 203:78, 1993.
- Collins KE, Cross AR, Lewis DD, et al: Comparison of the radius of curvature of the ulnar trochlear notch of rottweilers and greyhounds. Am J Vet Res 62:968, 2001.
- Denny R: Surgical treatment of osteochondritis dissecans and ununited coronoid process of the ulna in the elbow joint of the dog. Kleintierpraxis 25:343, 1980.
- Fox SM, Roberts RE: Linear tomography in diagnosing fragemented coronoid process in canine elbows. Comp Cont Ed Pract Vet 9:60, 1987.
- Fox SM, Walker AM: Identifying and treating the primary manifestations of osteochondrosis of the elbow. Vet Med 88:132-146, 1993.
- Goring RL, Bloomberg MS: Selected development at abnormalities of the canine elbow: Radiographic evaluation and surgical management. Compendium on Continuing Education for the Practicing Veterinarian 5:178-192, 1983.
- Grondalen J: Arthrosis in the elbow joint of young rapidly growing dogs. 1981.
- Grondalen J: Arthrosis in the elbow joint of young rapidly growing dogs. III. ununited medical coronoid process of the ulna and osteochondritis dissecans of the humeral condyle. surgical procedure for correction and postoperative investigation. Nord Vet Med 31:520, 1979.
- Gutbrod F, Festl D: Surgical treatment of a fragmented medial coronoid process of the ulna in dogs and the clinical results. Kleintierpraxis 44:405, 1999.
- Guthrie S: Use of a radiographic scoring technique for the assessment of dogs with elbow osteochondrosis. J Small Anim Pract 30:639, 1989.
- Guthrie S, Pidduck HG: Heritability of elbow osteochondrosis within a closed population of dogs. J Small Anim Pract 31:93, 1990.
- Guthrie S, Plummer JM, Vaughan LC: Aetiopathogenesis of canine elbow osteochondrosis: A study of loose fragments removed at arthrotomy. Res Vet Sci 52:284, 1992.
- Haudiquet PR, Marcellin Little DJ, Stebbins ME: Use of the distomedial-proximolateral oblique radiographic view of the elbow joint for examination of the medial coronoid process in dogs. Am J Vet Res 63:1000, 2002.
- Henry WB,Jr: Radiographic diagnosis and surgical management of fragmented medial coronoid process in dogs. J Am Vet Med Assoc 184:799, 1984.
- Huibregtse BA, Johnson AL, Muhlbauer MC, et al: The effect of treatment of fragmented coronoid process on the development of osteoarthritis of the elbow. J Am Anim Hosp Assoc 30:190, 1994.
- LaFond E, Breur GJ, Austin CC: Breed susceptibility for developmental orthopedic diseases in dogs. J Am Anim Hosp Assoc 38:467, 2002.
- Lenehan TM, Nunamaker DM: Lateral approach to the canine elbow by proximal ulnar diaphyseal osteotomy. J Am Vet Med Assoc 180:523, 1982.
- Lewis DD, Parker RB, Hager DA: Fragmented medial coronoid process of the canine elbow. Compendium on Continuing Education for the Practicing Veterinarian 11:703-715, 734, 1989.
- Lowry JE, Carpenter LG, Park RD, et al: Radiographic anatomy and technique for arthrography of the cubital joint in clinically normal dogs. J Am Vet Med Assoc 203:72, 1993.
- MacPherson GC, Lewis DD, Johnson KA, et al: Fragmented coronoid process associated with premature distal radial physeal closure in four dogs. Veterinary and Comparative Orthopaedics and Traumatology 5:93, 1992.
- Meij BP, Geertsen KMK, Hazewinkel HAW: Results of FCP [fragmented coronoid process] treatment in retrievers: A follow-up study at the utrecht university small animal clinic. Veterinary and Comparative Orthopaedics and Traumatology 9:64, 1996.
- Meij BP, Hazewinkel HAW: Treatment of canine elbow dysplasia. Veterinary and Comparative Orthopaedics and Traumatology 9:61, 1996.
- Meyer Lindenberg A, Fehr M, Brunnberg L, et al: Detachment of the medial ulnar coronoid process in dogs. occurrence and results of therapy in 101 cases. Monatsh Veterinarmed 48:457, 1993.
- Meyer Lindenberg A, Langhann A, Fehr M, et al: Prevalence of fragmented medial coronoid process of the ulna in lame adult dogs. Vet Rec 151:230, 2002.
- Meyer-Lindenberg A, Fehr M, Nolte I: Der isolierte processus anconaeus des hundes - vorkommen, behandlung, und ergebinsse. Kleintierpraxis 36:671, 1991.
- Miyabayashi T, Takiguchi M, Schrader SC, et al: Radiographic anatomy of the medial coronoid process of dogs. J Am Anim Hosp Assoc 31:125, 1995.
- Nap RC: Pathophysiology and clinical aspects of canine elbow dysplasia. Veterinary and Comparative Orthopaedics and Traumatology 9:58, 1996.
- Ness MG: Treatment of fragmented coronoid process in young dogs by proximal ulnar osteotomy. J Small Anim Pract 39:15, 1998.
- Olsson SE: The early diagnosis of fragmented coronoid process and osteochondritis dissecans of the canine elbow joint. J Am Anim Hosp Assoc 19:616, 1983.
- Olsson SE: [New type of elbow joint dysplasia in the dog; preliminary report]. Svensk Veterinartidning 26:152, 1974.
- Padgett GA, Mostosky UV, Probst CW, et al: The inheritance of osteochondritis dissecans and fragmented coronoid process of the elbow joint in labrador retrievers. J Am Anim Hosp Assoc 31:327, 1995.
- Probst CW, Flo GL, McLoughlin MA, et al: A simple medial approach to the canine elbow for treatment of fragmented coronoid process and osteochondritis dissecans. J Am Anim Hosp Assoc 25:331, 1989.
- Read RA, Armstrong SJ, O’Keefe JD, et al: Fragmentation of the medial coronoid process of the ulna in dogs: A study of 109 cases. J Small Anim Pract 31:330, 1990.
- Richardson DC, Zentek J: Nutrition and osteochondrosis. Vet Clin North Am Small Anim Pract 28:115, 1998.
- Robbins GM: Some aspects of the radiographic examination of the canine elbow joint. J Sm Anim Pract 21:417, 1980.
- Snaps FR, Balligand MH, Saunders JH, et al: Comparison of radiography, magnetic resonance imaging, and surgical findings in dogs with elbow dysplasia. Am J Vet Res 58:1367, 1997.
- Snaps FR, Park RD, Saunders JH, et al: Magnetic resonance arthrography of the cubital joint in dogs affected with fragmented medial coronoid processes. Am J Vet Res 60:190, 1999.
- Studdert VP, Lavelle RB, Beilharz RG, et al: Clinical features and heritability of osteochondrosis of the elbow in labrador retrievers. J Small Anim Pract 32:557, 1991.
- Swenson L. incidence-selection-heritability-sex-age related factors on elbow arthrosis, in Third Int Elbow Working Group Meeting 1991.
- Swenson L, Audell L, Hedhammar A: Prevalence and inheritance of and selection for hip dysplasia in seven breeds of dogs in sweden and benefit: Cost analysis of a screening and control program. J Am Vet Med Assoc 210:207, 1997.
- Theyse LFH, Hazewinkel HAW, Brom WEvd: Force plate analyses before and after surgical treatment of unilateral fragmented coronoid process. Veterinary and Comparative Orthopaedics and Traumatology 13:135, 2000.
- Tobias TA, Miyabayashi T, Olmstead ML, et al: Surgical removal of fragmented medial coronoid process in the dog: Comparative effects of surgical approach and age at time of surgery. J Am Anim Hosp Assoc 30:360, 1994.
- van Bree H, Van Ryssen B. Arthroscopy in the diagnosis and treatment of front leg lameness. Vet Q. 17: sippl. 1:532-534, 1995.
- Van Ryssen B, van Bree H: Arthroscopic findings in 100 dogs with elbow lameness. Vet Rec 140:360, 1997.
- Van Ryssen B, van Bree H, Simoens P: Elbow arthroscopy in clinically normal dogs. Am J Vet Res 54:191, 1993.
- Van Ryssen B, van Bree P. Elbow Arthroscopy, in ECVS Proceedings 1995.
- Voorhout G, Hazewinkel HAW: Radiographic evaluation of the canine elbow joint with special reference to the medial humeral condyle and the medial coronoid process. Vet Radiol 28:158, 1987.
- Wind AP: Elbow dysplasiaIn Slatter D, ed.: Textbook of Small Animal Surgery. Philadelphia: WB Saunders Co, 1993, p 1966.
- Wind AP: Elbow incongruity and developmental elbow diseases in the dog: Part I. J Am Anim Hosp Assoc 22:711, 1986.
- Wind AP: Incidence and radiographic appearance of fragmented coronoid process. California Veterinarian 36:19, 1982.
- Wind AP, Packard ME: Elbow incongruity and developmental elbow diseases in the dog: Part II. J Am Anim Hosp Assoc 22:725, 1986.
- Winhart S: Fracture of the medial coronoid process of the ulna in dogs. 1991.
- Wolschrijn CF, Weijs WA: Development of the trabecular structure within the ulnar medial coronoid process of young dogs. Anat Rec A Discov Mol Cell Evol Biol 278:514, 2004.
- Wosar MA, Lewis DD, Neuwirth L, et al: Radiographic evaluation of elbow joints before and after surgery in dogs with possible fragmented medial coronoid process. J Am Vet Med Assoc 214:52, 1999.
- Zentek J, Meyer H, Dammrich K: The effect of a different energy supply for growing great danes on the body mass and skeletal development. 3. Clinical picture and chemical studies of the skeleton. Zentralbl Veterinarmed A 42:69, 1995.
Total Elbow Replacement in the Dog
Michael G. Conzemius
The Causes and Frequency of Elbow Osteoarthritis
Elbow osteoarthritis (OA) secondary to fragmentation of the medial coronoid process (FCP), osteochondrosis (OCD), ununited anconeal process (UAP), intra-articular fracture, and elbow luxation is the most common cause of forelimb lameness in the dog.1 Collectively, these conditions represent the cause of lameness for nearly 8% of all dogs that present to university hospitals for lameness.1 The above conditions can be separated, based upon etiology, into either developmental (FCP, OCD, and UAP) or acquired (fracture and luxation) conditions. In addition, the developmental elbow abnormalities frequently occur bilaterally.
Treatment Alternatives and their Efficacy
The goal of nonsurgical and/or surgical management of the developmental abnormalities is to slow the progression OA in the joint and reduce lameness in the patient. Nonsurgical management includes using nonsteroidal anti-inflammatory medications (NSAIDs), weight reduction (if the patient is overweight), and moderate daily exercise. Surgical management is dependent upon diagnosis. Historically, FCP and OCD are treated with fragment removal via arthrotomy or arthroscopy. An UAP is treated by removal of the process, internal stabilization of the process, proximal ulnar osteotomy or by a combination of therapies. In addition to the surgical treatments listed, procedures to address cartilage defects, such as curettage of a subchondral defect, are commonly performed.
Unfortunately, nonsurgical and surgical management of developmental conditions of the elbow joint frequently lead to unsatisfactory results. Huibregtse et al. studied 22 dogs with forelimb lameness caused by a FCP and provided evidence that elbow OA progressed radiographically in dogs following nonsurgical or surgical treatment.2 In addition, they performed force platform gait analysis and found that there was no difference in limb function between groups and the pet owners reported a recurrence of lameness in 78% of dogs treated without and 69% of dogs treated with surgery.2 Bouck et. al. studied 19 dogs diagnosed with FCP and/or OCD that were treated medically or surgically using physical, radiographic and force platform gait evaluations and found similar results: regardless of treatment, OA progressed radiographically and range of motion decreased over time.3 Using force platform gait evaluations they did determine that dogs in both groups improved but there was no difference in the amount of improvement between treatments.3 Read et al. studied the largest groups of dogs, reporting on 130 episodes of FCP in 109 dogs with 62 managed nonsurgically and 68 surgically.4 In this retrospective study owners reported that the severity of lameness improved to some degree in 59% of dogs, regardless of treatment.4 Lameness, however, persisted in 75.9% of all dogs studied.4 Tobias et al. performed a long-term evaluation of 35 dogs that had surgery for FCP.5 After evaluating an owner questionnaire, physical and radiographic findings they concluded that nearly 65% of dogs still had lameness, 80% had joint pain, and over 95% had joint thickening and a reduced range of motion at follow-up examination.5 In addition, OA significantly increased in 100% of the cases.5 Caplan et al. studied the radiographic progression of OA in 24 dogs treated non-surgically and 26 treated surgically for lameness because of a FCP provided and reported that, regardless of treatment, OA progressed in 100% of cases and that the progression of OA was similar regardless of treatment.6 How prognosis is affected by a growing list of more recent procedures (arthroscopy, medial coronoidectomy, radial head lengthening, humeral osteotomy, etc.) will only be known after thorough investigation and speculation is beyond the scope of this chapter.
The goal of treatment of the acquired conditions is to restore normal anatomy. Conditions that frequently cause elbow OA include intra-articular fracture and luxation.1,7-11 In addition, fracture of the radius or ulna can lead to OA in the elbow by two mechanisms. First, fracture of the one of the growth plates of the radius or ulna can cause asynchronous growth between the two bones leading to incongruity in the elbow.12 Second, fracture and subsequent callus formation can cause synostosis between the radius and ulna which, in a growing animal can lead to incongruity in the elbow.13 Although, treatment for these conditions can lead to a good prognosis, long-term complications are common. In one study, 45% of all cases that had surgery for traumatic luxation had an unacceptable clinical outcome.11 Similarly, Gordon et al. reported that following surgery for humeral condylar fracture 50% of dogs had visible lameness and 100% had developed OA.14
Treatment Alternatives for Dogs with established OA
Treatment alternatives for dogs with moderate to severe elbow OA include nonsurgical management, debridement arthroplasty (removing loose bodies and osteophytes from the joint), and arthrodesis.8,15,16 In a clinical report, one dog with severe elbow OA had surgery to remove fragmented medial coronoid processes and a fractured anconeal process; this dog returned to near normal function after surgery.8 This case may be the exception, however, because the dog became acutely lame because of an intra-articular fracture. There are no reports in the peer-reviewed literature addressing debridement arthroplasty for moderate to severe OA in dogs. However, in one abstract it was suggested that this procedure provided good long-term results.15 deHann et al. retrospectively investigated results after arthrodesis of the elbow and found that although pain in the joint was eliminated, function of the limb was limited.16 In a review article addressing the surgical treatment of OA, it was stated that debridement was the primary and arthrodesis the secondary option for OA in the elbow. They also stated that total elbow arthroplasty was likely to be the best future option.17
Total Elbow Arthroplasty as an option in the Dog
Improvements in implant design and surgical techniques have made total elbow arthroplasty a satisfactory treatment for arthritic disorders of the elbow in man since the mid-1970s.18 In two separate evaluations, 91% of total elbow arthroplasty cases had excellent long-term (~4 years) outcomes.19,20 It is important to note that limb use in man after successful total elbow arthroplasty is far from normal. Limb functions that are possible include such activities as opening a door, using a fork, and bringing the hand to the back of the head.19,20 The success that veterinarians have had in total joint replacement has mirrored that of physicians when it comes to hip and knee. In the dog, 90 to 95% of patients will have a good or excellent outcome after total hip replacement.21 Current implant designs and surgical techniques for total knee replacement in man are commonly developed in canine models.22 The similarities in implant design and surgical success found in the hip and knee are likely because of similarities in anatomy and joint mechanics.
The anatomy and mechanics of the elbow joint, unfortunately, are dramatically different between man and dog. The first and most obvious difference is that the dog is a quadruped, and the elbow is a load bearing joint during motion. In fact, the forelimbs have ground reaction forces (GRF) that are 75% greater than the rear limbs at a trot (velocity of 1.5 to 2.0 m/s).23 Anatomically, the radius is the primary load bearing bone in the dog. In contrast, the ulna seems to be the primary load bearing bone in man. The difference is most likely explained by the fact that dogs almost exclusively load the elbow when in extension, whereas man generally loads the elbow when in flexion.24 These differences in mechanical demands have led to differences in anatomy. The ulna of the dog is comparatively smaller and the radial head larger. These differences are reflected by the fact that radial head excision arthroplasty can be successfully performed in man.25 Given an understanding of canine anatomy and joint mechanics, it is easy to understand why radial head excision is not even reported in the dog. This point is further reflected in designs of total elbow components for humans. Many currently used total elbow designs (Coonrad/Morrey elbow replacement prosthesis, GBS II design, Capitello-Condylar design, HSS-Osteonics Linked Semiconstrained Total Elbow Prosthesis, etc.) utilize a humeral and an ulnar component. The radial head is removed during the surgical procedure.18-20,25,26 These design concepts, although successful for the human elbow, seem inadequate for the canine elbow.
Total elbow arthroplasty has been reported in the dog. To the author’s knowledge, Dr. Ralph Lewis was the first to report on experience with total elbow arthroplasty in the dog.27 He used constrained (hinge-like) components and although he had some successful outcomes he concluded that because of a high complication rate the system needed to be redesigned. Vasseur et al., at the University of California at Davis designed a nonconstrained system and tested it in three dogs with naturally occurring elbow OA. Although their results are not reported it was suggested, via personal communication, that the dogs in that study had poor short-term and long-term results and the project was abandoned.
Conzemius et al. designed and reported on a semiconstrained, two component (humeral and radioulnar) system, based on a morphometric study in Greyhounds and tested it in six Greyhounds.28 (Figure 56-35) The design was based on the rationale that a total elbow replacement for the dog should reflect the anatomy of a breed that is not predisposed to developmental elbow diseases. A semiconstrained design was selected because constrained (hinge-like) designs do a poor job of sharing load with intact ligamentous structures. Load is principally absorbed by the implant and concentrated at the implant-bone interface. This type of design has not withstood the test of time in load bearing joints; the best example being the human knee. Constrained total knee designs have a comparatively high rate of aseptic loosening and are reserved for use in revision surgeries of the knee when no ligamentous structures remain intact.29,30 In addition, semiconstrained and nonconstrained designs can include shorter stem lengths relative to constrained designs. A feature that was appealing because of assumed anatomic differences that would be present amongst dog breeds. Cement fixation was used because it allows for a greater variability in implant design and positioning (Figure 56-36). Cement fixation allows the stems of the implant to be virtually anywhere within the confines of the medullary canal as long as there is room remaining for a cement mantle with a thickness of at least 2.0 mm.31 Press-fit and porous in-growth designs require a near perfect fit between existing bone anatomy and implant. A two piece design was used to limit the number of working pieces. This minimizes manufacturing costs and makes it technically simpler for the surgeon. For example, the radial and ulnar components were made as a single component instead of two or three. Although post-operative complications occurred in 4 of 6 dogs many beneficial things came from this study. First, two dogs had a fair outcome with peak vertical force (PVF) reaching 82% four months after surgery (Figure 56-37). Thus, it was concluded that elbow replacement was possible, just not with the exact design and technique used. In an evaluation of limb use in normal Greyhounds after femoral head and neck excision and total hip replacement limb function improved for the first six months after surgery.32,33 Second, it was apparent that lateral luxation occurred in two dogs from lateral instability after transection of the lateral collateral and insufficient stabilization. An alternative approach needed to be considered. Third, the cement-bone interface of the radioulnar component was loose in all dogs (See Figure 56-37). This was likely because the snap fit components were too constrained and the 1 cm pegs of the radioulnar component (designed so it could be used in either the left or right limb) were too short. These short pegs provided limited surface area for the cement interface thus increasing stress. Fourth, the humeral component was consistently stable even after a stabilization screw was removed. Finally, radio-ulnar synostosis was incomplete in all dogs and the screw placed between the radius and ulna was loose in 5 of 6 dogs. Radio-ulnar synostosis is necessary when a single component has stems that enter the medullary canal of multiple bones. It was concluded that the ulnar osteotomy was too proximal, the radio-ulna screws were insufficient and that cancellous autograft should be used to encourage fusion.
This was followed by an in vivo study evaluating the efficacy of a modified system in six normal dogs.34 The system and surgical technique evaluated included several modifications as compared to the initially reported design.28 The humeral component had been angled in a cranial direction by 5° to reduce the probability of bone contact, dove-tail grooves in the sides of the component were included that were deeper and did not communicate with the load-bearing surface of the humeral component and all articulating surfaces were made with a larger radius. The radioulnar component now had two, 3 cm stems (radial and ulnar), it was designed for either left or right limbs with stem angles and an inter-stem distance that matched that of the anatomy of the a Labrador retriever and the proximal aspect of the component was removed and all articulating surfaces were made with a larger radius. Changes in surgical technique included removal of the lateral collateral ligament at its insertion from the radius, distal ulnar ostectomy (~1 cm of bone), no screws were used with the humeral component or between the radius and ulna and a generous amount of autogenous cancellous bone graft was placed between the radius and ulna just distal to the radioulnar component on the lateral side. Six, healthy, adult medium and large breed dogs ranging from 25 to 38 kg were used in the study. Each dog underwent an orthopedic, radiographic, and force plate gait evaluation before surgery and surviving dogs were reevaluated at 8, 16, 24 and 52 weeks after surgery. Dogs were sacrificed 6, 10, and 20 weeks after surgery, leaving three dogs for long-term evaluation. Treated limbs from the sacrificed animals were harvested and the components were examined. The results from this study were mixed. Post-operative complications occurred in 3 of 6 dogs and included one dog that never used the operated limb, a dog that developed proximal ulnar fracture 9 weeks after surgery and a dog that developed osteomyelitis. Limb function in the remaining 3 dogs consistently improved over the course of the 52 week study to the point that PVF and vertical impulse (VI) were the same as the unoperated, normal limb at 1 year. These dogs were adopted and continue to do well over 5 years after surgery. Important conclusions from this study were that the components could be made even less constrained, a corner on the caudal aspect of the radioulnar component needed to be removed, a hole in the humeral component to simulate a foramen needed to be removed, synostosis between the radius and ulna could be achieved using only the distal ostectomy and bone graft, multiple component sizes were needed and that limb function could return to normal when elbow replacement was performed in a normal dog.34
Although that study did not demonstrate that total elbow arthroplasty could yield consistent results or that it would be successful in naturally occurring elbow OA, it provided evidence that it would likely be successful in at least some cases.
Given the frequency of elbow OA in the dog, the poor prognosis provided by other available treatments, and the encouraging preliminary data it was thought to be reasonable to attempt total elbow arthroplasty in severely affected cases. Prior to clinical use, several design changes were made to enhance the nonconstrained total elbow arthroplasty components. First, the corners at the articulating surface of the humeral and radioulnar component were softened. This made the articulation less constrained which should reduce the formation of particulate wear debris. Second, the hole in the humeral component was eliminated. Third, the surface area for the component-cement interface was increased. Fourth, the caudal peg of the radioulnar component was angled to better fit the ulnar metaphysis. Fifth, the caudal non-articulating surface that rests on the ulna was made semicircular. This will preserve ulnar bone stock and reduce the chance of ulnar fracture. Finally, three were made available, with a 10% increase in size from small to medium to large.
This implant system was tested in twenty, adult, client owned dogs with elbow OA that were treated with nonsurgical management unsuccessfully for at least 1 year.35 Following inclusion into the study dogs were evaluated clinically, radiographically and by force platform gait analysis before surgery and at 3, 6, and 12 months after surgery. At 1 year it was concluded that 16 of the 20 dogs had a satisfactory outcome, as defined by an improvement in quality of life and a reduction in pain and lameness. On average, 1 year ground reaction forces were 25% greater on the operated limb when compared to preoperative function. Unsatisfactory outcomes were associated with infection, lateral luxation and an iatrogenic humeral condylar fracture. Similar to previous investigations potential improvements in component design and surgical technique were identified. The humeral component had large proximal shoulders that required removal of an unnecessarily large amount of bone. These shoulders have been removed. It was nearly impossible to establish a good cement mantle at the interface between the sides of the humeral component and the remaining bone of the humeral condyle. The sides of the humeral component have been beaded for porous ingrowth fixation. Although no problems were identified with the articulating surface in this 1 year study, it was thought that a surface that was similar to that or a human knee component would be ideal. Technical challenges that remained were development of drill and cutting guides that would allow for a more reproducible outcome and provision for lateral stabilization to reduce the probability of lateral luxation. These changes and an additional component have been implemented into a total elbow replacement system (Figure 56-38) that is commercially available and taught to surgeons in training courses.
Surgical Procedure
Dogs are placed in lateral recumbancy and standard aseptic preparation of the affected forelimb is performed. A caudolateral approach to the elbow through the anconeus muscle that is extended proximally along the triceps and distally along the ulna is made. The insertion of the lateral collateral ligament on the radius is identified and removed close to its bony attachment. The elbow is luxated laterally (this can be difficult in many cases that have severe periarticular fibrosis or a large osteophyte on the cranial aspect of the radius). A 5 mm access hole is made in the humeral diaphysis. The humeral mounting pin is placed into the humerus and the humeral cutting guide mounted. The arthritic, articular aspect of the condyle is removed using the cutting guide and a trial component is implanted. (Figure 56-39) A 3.5 mm hole is drilled from proximal to distal down the radius diaphysis. The radial cutting guide is mounted and the cut started on the radius. The radial cutting guide is removed and the radial cut completed. The ulnar cutting guide is then mounted and used to drill multiple holes along the proximal ulnar metaphysis (Figure 56-40). The cutting guide is removed and the drill holes are connected with a high speed bur which results in removal of the ulnar trochlea and the medial and lateral coronoid processes. The diaphysis of the radius and ulna are then prepared to accept the component and cement. A trial radioulnar component is positioned and the joint is reduced to ensure that both components are positioned correctly. A distal ulnar ostectomy (1 cm) is performed. The components are cemented in position and the joint is reduced. As the cement polymerizes an autogenous, cancellous bone graft harvested from the removed bone is placed between the proximal aspects of the radius and ulna just below the body of the lateral aspect of the radioulnar component. Prior to closure, two suture anchors are placed (one in the lateral aspect of the humeral condyle and one between the proximal radius and ulna) to provide additional lateral stability during the early postoperative period. Following closure a splint is applied and postoperative radiographs are taken (Figures 56-41 and 56-42). Postoperative management generally should include removal of the splint 2 to 3 days after surgery, restriction to short leash walks for 8 weeks and a re-exam at 8 weeks. At this time more aggressive postoperative rehabilitation for the joint can be considered.
In the author’s experience with this commercially available system, an outcome that is satisfactory to the surgeon and owner(s) can be expected 80 to 85% of the time. The most common complications that can be expected include infection, luxation, and fracture of the ulna. In 5% of humans undergoing total elbow replacement, fracture of the olecranon has been reported as a major complication.36 Since perpendicular bone cuts create a stress riser in the ulna and have been identified as a predisposing factor for an olecranon fracture,37 it is hoped that the technical modifications in place will reduce this problem. Again, in the author’s experience, the majority of complications occur in the first 8 weeks after surgery.
References
- Johnson JA, Austin C, Breur GJ. Incidence of canine appendicular musculoskeletal disorders in 16 veterinary teaching hospitals from 1980 through 1989. Vet Comp Orthop Traumotol 7:56, 1994.
- Huibregtse BA, Johnson AL, Muhlbauer MC, Pijanowski GJ. The effect of treatment of fragmented coronoid process on the development of osteoarthritis of the elbow. JAAHA 30:190, 1994.
- Bouck GR, Miller CW, Taves CL. A comparison of surgical and medical treatment of fragmented coronoid process and osteochondrosis dissecans of the canine elbow. Vet Comp Orthop Traumotol 8:177, 1995.
- Read RA, Armstrong SJ, O’Keefe JD, Eger CE. Fragmentation of the medial coronoid process of the ulna in dogs: A study of 109 cases. J Small An Prac 30:330, 1990.
- Tobias TA, Miyabayashi T, Olmstead ML, Hedrick LA. Surgical removal of fragmented medial coronoid process in the dog: Comparative effects of surgical approach and age at time of surgery. JAAHA 30:360, 1994.
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Elbow Arthrodesis
Arnold S. Lesser
Indications
Arthrodesis of the elbow or any midlimb joint is some what controversial. There are some surgeons that believe that the result after fusion of the elbow or stifle is not good enough to warrant the procedure. Certainly pancarpal or pantarsal arthrodesis gives better and more consistent results but there are dogs that can function fairly well after fusion of the elbow, especially smaller patients that tend to walk with a stiff gait. The decision to fuse a joint is only made when other alternatives are not feasible or successful. The indication for arthrodesis of the elbow is any condition that leaves the elbow chronically painful and nonfunctional. These can be divided into traumatic and developmental. Traumatic includes fractures that cannot be repaired or that have failed to heal or healed as painful malunions. The elbow’s configuration can make primary repair difficult especially in miniature breeds. Highly comminuted articular fractures or gun shot trauma with bone loss are examples of fractures that may not be repairable or lead to painful malunions. In the majority of cases a primary repair should be attempted first but there may be situations where finances allow only one procedure to be performed and then it is the surgeon’s judgment whether to go right to the arthrodesis or attempt the repair. With non unions the question also arises as to whether to attempt another osteosynthesis or go right to an arthrodesis. If a malunion cannot be revised to allow for good function or has led to severe DJD and the patient is not using the limb then fusing the elbow is indicated. Also the elbow joint is especially susceptible to loss of motion after difficult fracture repair and if the joint becomes ankylosed in too flexed a position the dog will not use the leg due to the physiologic shortening. Arthrodesis of the joint at the proper angle is then indicated.
The other major indication for elbow arthrodesis is severe arthritis, most commonly secondary to elbow dysplasia (ununited anconeal process or fragmented coronoid process). When conservative therapy is no longer giving sufficient relief then surgery is indicated. Recently a Total Elbow prosthesis has become available and where applicable would be the first choice. There are size restrictions and the presence of infection affects the use of a prosthesis more than arthrodesis, but this is a promising alternative and further clinical use will be needed to fully evaluate its potential.
Procedure
Plate fixation along the caudal aspect of the humerus and ulna is by far the best method (Figure 56-43). This places the plate on the tension band side. It is necessary to perform an olecranon osteotomy to provide a smooth transition and bed for the plate. Part of the olecranon can be sacrificed for graft (all fusions should be grafted) and the remainder reattached to the bone next to the plate. The angle of the cut can be determined by placing the leg in the desired angle (reported from 110 to 130 degrees) and running a line off the caudal edge of the humerus onto the ulna (Figure 56-44). The lateral collateral ligament is transected and the extensor muscles are elevated to provide exposure for the removal of cartilage from the radial head, coronoid process and humeral condyle. These surfaces should be shaped to create good contact. The ulnar and median nerves should be identified and protected on the medial aspect of the joint. Once the angle has been determined from the standing angle of the normal leg, the joint is held with a pin driven from the ulna into the medial humeral condyle. A goniometer or an old plate prebent can be used to measure this angle at surgery. If there has been bone loss then the angle is increased (straighter). However, there is more of an acute angle at the elbow than appears from looking at the leg because of the thick muscle caudal to the humerus and the curvature of the radius, so there is a tendency to make the leg too straight. Be sure to measure the bone and not the leg when determining the angle of arthrodesis (Figure 56-45). A sterile preparation of the controlateral leg provides a quick reference. The triceps muscles can be elevated to allow placement of the plate. A minimum of 3 screws are used in the humerus and ulna respectively, with additional intervening screws crossing the joint under compression. A 9 or 10 hole, self compressing or locking plate is sufficient for a 30 kg dog.
Screw fixation has been advocated for elbow arthrodesis and may have a place in smaller patients when combined with an external skeletal fixator(Figure 56-46), With the availability the small 2.0 mm cuttable plates, I would recommend staying with plate fixation. These plates can be doubled for greater stiffness. External fixators can be used but are more difficult to adapt in this area due to the presence of the body wall medial to the humerus. Modified type 1b fixators can be used but are more complicated to construct. Fixators can also be used as a secondary fixation rather then a bulky spica where the primary fixation is suspect. If the plate fixation is sufficient only a padded bandage is used for a few weeks.
Suggested Readings
Piermattei DL, Flo GL: Brinker, Piermattei, and Flo’s Handbook of Small Animal Orthopedics and Fracture Repair 3rd Edition. W.B. Saunders. Philadelphia. 1997.
Lesser: Arthrodesis. In Slatter: Textbook of Small Animal Surgery. Saunders. Philadelphia. 2003 Humerus and Elbow Joint p 929.
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