Introduction

The canine and feline humerus is a complex bone, having an “S‐shape” from the lateral perspective and terminating distally with the humeral condyle, which is divided into medial and lateral components. It should be noted that there is only one humeral condyle with medial and lateral portions; there are no separate medial and lateral humeral condyles. The medial part of the humeral condyle is termed the trochlea and articulates with the ulna, while the lateral part of the humeral condyle is termed the capitulum and articulates mainly with the radial head. Caudally, the olecranon fossa articulates with the anconeal process of the ulna and provides important medial‐lateral stability when the elbow is extended. Two prominent bony landmarks, the medial and lateral epicondyles, are present on the medial and lateral aspects of the humeral condyle and serve as the origin for the flexor and extensor muscle groups, respectively, along with the medial and lateral collateral ligaments of the elbow. The distal metaphysis, proximal to the condyle, is divided by the supratrochlear foramen.¹ It should be noted that, in cats, the supratrochlear foramen is not perforated as it is in the dog. Therefore, condylar fractures in the cat are less common. However, in cats, there is a supracondylar (i.e., epicondylar) foramen just proximal to the medial epicondyle, through which the median nerve and brachial artery pass. Caution should be taken when making surgical approaches and when placing implants for fracture fixation in this region.

The maturation of the distal part of the humerus entails the formation of both the trochlea and the capitulum, which arise from separate centers of ossification. These centers typically fuse by roughly 85 days (3 months), followed by fusion of the entire condyle to the metaphysis by 5.5–6 months of age.² Weight‐bearing of the antebrachium is directed from the radial head through the capitulum and lateral epicondylar crest. The lateral epicondylar crest is smaller and weaker than the medial epicondylar crest. In the skeletally immature dog, prior to the fusion of these centers and the metaphysis, the softness of the bone in the lateral epicondyle in conjunction with the forces applied through the radial head during weight‐bearing to the humeral capitulum predispose dogs to Salter–Harris type IV fractures that involve the articular surface of the condyle (Figure 44.1). In dogs, lateral condylar fractures are the most common (~70%), with complex T/Y fractures involving both components of the condyle (~20%) and medial condylar fractures (10%) being significantly less common (Figure 44.2).^2,3 Patient signalment is an important consideration when evaluating fusion of the humeral condyle. Humeral intracondylar fissure (HIF), previously referred to as incomplete ossification of the humeral condyle (IOHC), is characterized by a fissure in the sagittal plane bisecting the humeral condyle that persists past the normal age of ossification (Figure 44.3). English Springer Spaniels, French Bulldogs, and other breeds have been reported to be at a higher risk for this condition.^4,5

The neurovascular structures surrounding the distal aspect of the humerus are robust and intricate, and they must be accounted for when considering the surgical approach and implantation for fracture repair. Laterally, the radial nerve traverses the humerus from caudoproximal to craniodistal approximately 2/3 of the way distally along the diaphysis, superficial to the brachialis muscle. This nerve crosses the elbow joint cranial to the lateral epicondyle before sending a deep branch to the extensor carpi radialis and terminates by innervating the underside of the supinator muscle on the radius and continuing distally in the interosseous space. This nerve innervates muscles that control both elbow and carpal extension. The median nerve lies on the craniomedial surface of the humerus, while the ulnar nerve courses caudomedially prior to crossing the elbow joint. The median nerve runs adjacent to the brachial artery and vein cranially, while the collateral ulnar artery and vein follow the course of the ulnar nerve caudally.⁶

Indications and Preoperative Considerations

As with all fracture patients, a comprehensive evaluation is crucial to rule out concurrent effects of trauma on the body as a whole. Patients presenting with a history of significant trauma should have a complete physical exam (including both orthopedic and neurologic evaluation), baseline bloodwork (typically, a complete blood count and serum chemistry panel), three‐view chest radiographs, and evaluation of the abdominal cavity, usually either via abdominal‐focused assessment of ultrasonographic trauma (AFAST) or abdominal radiographs. This evaluation is important for patients who have sustained significant trauma, such as from vehicular trauma, or who have a complex T‐Y condylar fracture. For skeletally immature patients that suffer lower velocity trauma, such as a fall from an elevated surface, and have a Salter–Harris type IV lateral condylar fracture, a complete physical examination and baseline bloodwork are typically sufficient. Following the establishment of patient stability, two‐view radiographs of the affected limb are performed. It is often useful to obtain contralateral humeral radiographs both for interpretation of the fracture site and for surgical planning. Patients who present with a lack of significant trauma with a humeral condylar fracture should be carefully evaluated for the presence of underlying HIF, particularly in predisposed breeds. This screening involves two‐view radiographs of the affected and contralateral humerus, and/or 10° obliqued craniolateral‐caudomedial radiographs, and/or a CT scan (Figure 44.3).⁷ Neurologic evaluation of the affected limb(s) should involve careful evaluation of radial nerve function, as this nerve crosses the distolateral aspect of the humerus and is, at times, compromised by the initial trauma or by the fracture itself.

After orthopedic and neurologic evaluation, analgesics should be administered. Most commonly, this involves a full mu opioid, such as fentanyl, hydromorphone, or methadone, if the patient is to remain hospitalized. Nonsteroidal anti‐inflammatories (NSAIDs) may be administered judiciously, but caution should be used in patients with significant trauma, hypotension, renal compromise, or other preexisting conditions that increase the risk for side effects. In the absence of open wounds, antibiotics are not necessary to administer to fracture patients upon admission to the hospital. If a patient is confirmed or suspected to have an open fracture, broad‐spectrum antibiotics should be administered as soon as possible, as this has been shown to improve outcomes in this population.⁸

Prior to the definitive correction, the limb may be temporarily stabilized in a Spica splint. It is crucial that external coaptation immobilizes both the elbow and the shoulder to appropriately protect the fracture site and the adjacent soft tissue structures. A common error is to place a soft‐padded bandage that stops at the level of the axilla proximally. This will act as a fulcrum on the fracture site, increasing patient discomfort and the likelihood of additional trauma. Alternatively, the limb may be left without a bandage, as most patients will protect the fracture site by reducing or eliminating weight‐bearing on the affected limb.

Treatment options for humeral condylar fractures are numerous and are based on multiple factors, including fracture configuration, fracture chronicity, patient age, presence of HIF, and others. As with any articular fracture, anatomical reconstruction of the joint surface is critical with the avoidance of any steps or gaps. In general, medial or lateral humeral condylar fractures are treated with a transcondylar screw placed either in a lag or positional fashion. Following articular reconstruction, adjunctive fixation is needed to achieve fracture stability. This can be completed with a bone plate on the ipsilateral epicondylar region of the distal humerus or with an anti‐rotational K‐wire placed from the humeral epicondyle and driven proximally through the epicondylar crest to exit the contralateral cortex. However, recent evidence suggests adjunctive K‐wire fixation is more prone to complications compared to plating, as an epicondylar plate is biomechanically stronger than an adjunctive K‐wire.⁹

Stay updated, free articles. Join our Telegram channel

Join