Fractures of the humerus are relatively common in the dog and cat with approximately half of all humeral fractures occurring in the distal portion of the bone.
The overwhelming majority of distal humeral fractures involve the elbow joint and are classified according to their anatomic location. Lateral condylar fractures are common and may occur from either minor or severe trauma in dogs and cats of all ages. Because of the close proximity of the thoracic cavity, additional injuries such as pneumothorax, hemothorax, pulmonary contusion, traumatic myocarditis, diaphragmatic hernia, and thoracic wall trauma can occur concurrently with humeral fractures. These potential injuries should be identified and treated appropriately prior to repair of the humeral fracture.
The severity of the trauma sustained has been shown to influence the resulting fracture type. While severe trauma has been shown to result in simple lateral condylar fractures and the associated injuries previously mentioned, the majority of lateral condylar fractures result from minor trauma. The high incidence of condylar fractures resulting from minor trauma in immature animals may be explained by the relative weakness of the fusion zones of the principal centers of ossification of the developing distal humerus. A substantial number of condylar fractures, however, occur in adult animals. One study found an increased risk for male Cocker Spaniels over two years of age fracturing their humeral condyle with only minor loading forces. The findings of this study suggest that certain breeds of dogs may be predisposed to distal humeral condylar fractures after sustaining minor trauma equal to or only slightly greater than the loading forces generated by the normal activity. Distal humeral condylar fractures are far more common in dogs than in cats. The rarity of condylar fractures in cats may be partially explained by their straighter condyles and relatively wider and thicker epicondylar crests.
Fractures of the lateral humeral condyle (capitulum) occur as abnormal compressive forces are directed upward through the radius. The condyle shears off the intercondylar area through the supratrochlear foramen and the lateral supracondylar ridge. Several factors are associated with the higher incidence of lateral versus medial condylar fractures. The capitulum is the major weight-bearing surface because of its articulation with the radial head. As forces are directed through the radius, they are transmitted directly to the capitulum. Fractures of the medial condyle (trochela) are less common because of its less frequent weight bearing position. In addition, the shape of the distal humerus is such that the capitulum sits off the midline of the central axis of the body, predisposing itself in injury. Finally, the lateral supracondylar ridge is smaller and biomechanically weaker than its medial counterpart.
Treatment of lateral condylar fractures should be directed at complete restoration of joint anatomy and function. Because these fractures are intraarticular, perfect reduction with interfragmentary compression is required for optimal postoperative function. Closed methods of reduction and external fixation cannot usually reduce the fracture fragments perfectly and prolonged immobilization of the joint, which is necessary for fracture healing may lead to joint stiffness. Closed reduction and stabilization using a condyle clamp to place a transcondylar screw through a stab incision is possible. The results obtained with this technique depend on the length of time since the injury occurred, the expertise and experience of the surgeon, the amount of swelling and edema present, and the amount of soft tissue interposed at the fracture site.
Open reduction and internal fixation are indicated for optimal alignment and stabilization of lateral condylar fractures and an early return to function. An early return to function will help alleviate elbow stiffness and degenerative joint disease. While several surgical approaches may be used to expose lateral condylar fractures, excellent exposure with minimal soft tissue dissection is achieved via a lateral or craniolateral approach to the elbow. The most common method employed for repair of lateral condylar fractures is a transcondylar lag screw with or without an additional crosspin for increased rotational stability.
Once the fracture site is adequately exposed, fibrin, clots, blood, and interposed soft tissue should be removed to allow perfect anatomic reduction of the articular surface. With the fracture reduced, a transcondylar hole is drilled beginning at a point just cranial and ventral to the palpable lateral epicondylar crest. The drill hole is tapped, the later condylar fragment is over-drilled to create a gliding hole, and transcondylar lag screw is placed. In order to ensure central placement of the lag screw through the condyle, an alternate technique may be employed. The lateral condylar fragment is outwardly rotated and the gliding hole is drilled from the intercondylar fracture surface out through the lateral side of the condyle. The fracture is then reduced, the medial condyle is appropriately drilled, and tapped and a lag screw is placed. An anti-rotational Kirshner wire or Steinman pin is then driven from the lateral condyle and seated into the medial cortex of the distal humeral shaft. The elbow joint should be put through a full range of motion to assess stability and to check for crepitus.
I prefer to place the limb in a modified Bobby Jones dressing to help control swelling during the immediate post-operative healing period. The owners are advised to restrict the animal’s exercise for the first 6-8 weeks after surgery while employing gentle, passive physiotherapy to help prevent elbow stiffness. When early surgical intervention, accurate anatomic reduction, and rigid internal fixation are employed a good to excellent result should be expected.