Nonunion and Malunion of Distal Humerus Fractures

Prevalence and Risk Factors

Distal humerus nonunion with hardware failure and fracture redisplacement usually presents within the first few months after surgery. The prevalence of hardware failure is difficult to determine, because in some cases, hardware failure may allow ultimate fracture healing with residual secondary displacement. In addition, some potential failures of fixation may be avoided by prolonged postoperative immobilization, leading to fracture healing but very limited motion. Nonunion or hardware failure have been reported in approximately 8% to 25% of recent series on distal humerus fractures.

In our experience, poor initial fracture fixation is the most common risk factor for fracture nonunion. Stable fixation is difficult to achieve, especially in fractures with extensive comminution or when suboptimal fixation techniques are used. However, other risk factors for fracture nonunion have been reported to be common by some authors, including smoking, use of immunosuppressive medications, severe associated soft tissue injuries, osteopenia, diabetes, and poor compliance with postoperative instructions.

Pathology

Distal humeral nonunions share a constellation of pathologic findings that need to be addressed at the time of surgery ( Fig. 50.1 ). The nonunion is usually located at the supracondylar level; most of the time, the distal fragments heal in a more or less anatomic position. Progressive bone reabsorption at the nonunion site may lead to severely compromised bone stock. Previously placed hardware may compromise bone stock even further, especially when screw loosening results in a windshield-wiper effect.

Additionally, severe stiffness develops, and when the patient tries to flex and extend the elbow, most motion occurs through the nonunion site, not through the joint. Failure to release the associated elbow contracture at the time of fixation of the nonunion may contribute to failure; otherwise, when elbow motion is rehabilitated, excessive loads are transmitted through the nonunion site. Alternatively, patients with a very complex nonunion can be managed in a staged fashion: the first procedure is aimed to achieve union, but motion restoration is not attempted; a few months later, once union is achieved, a planned second stage contracture release may be performed.

A third element of many distal humerus nonunions involves compromised ulnar nerve excursion by scarring, especially when there has been previous surgery. Excessive motion at the nonunion site may further damage the ulnar nerve by stretching. Careful attention should be paid to the ulnar nerve at the time of surgery to avoid iatrogenic injury and also to release any scar tissue that may result in worsening ulnar neuropathy once motion is restored.

Evaluation and Treatment Options