Nonunion and Malunion of Distal Humerus Fractures

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CHAPTER 23 Nonunion and Malunion of Distal Humerus Fractures

INTRODUCTION

Nonunion and malunion are two of the most common and challenging complications of distal humerus fractures. Newer internal fixation principles and techniques have improved our ability to achieve stable fixation of complex distal humerus fractures18 (see Chapter 22, Current Concepts in Fractures of the Distal Humerus). However, some fractures will fail to unite, leaving the patient with an unstable, dysfunctional, and oftentimes painful upper extremity requiring additional surgery. Distal humeral malunion is well characterized in the pediatric population after supracondylar fractures (see Chapters 14 and 15) but has not been analyzed as extensively in the adult population.4,8 This chapter reviews the prevalence, risk factors, pathology and treatment options for distal humeral nonunions and the clinical relevance and treatment options for distal humeral malunion.

DISTAL HUMERAL NONUNION

PATHOLOGY

Distal humeral nonunions share a constellation of pathologic findings that need to be addressed at the time of surgery (Fig. 23-1). 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.7 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. Not uncommonly, ulnar nerve excursion is compromised by scarring, especially when there has been previous surgery. Excessive motion at the nonunion site may further compromise the function of the ulnar nerve by stretching. Attention should be paid to the ulnar nerve at the time of surgery.

EVALUATION AND TREATMENT OPTIONS

INTERNAL FIXATION

Internal fixation is the treatment of choice for the majority of patients presenting with a distal humerus nonunion. The goals of internal fixation are (1) to achieve an adequate reduction and stable internal fixation, (2) stimulate bone healing with bone graft or substitutes, (3) release the associated joint contracture to help achieve a functional range of motion and decrease the stresses on the fixation, and (4) protect the ulnar nerve.

Surgical Technique

Surgical Approach and Ulnar Nerve Decompression

Most patients with previous surgery will have a posterior midline skin scar that may be used for the revision procedure. If the previous fixation was attempted through separate lateral and medial incisions, most of the time, it is better to ignore those and create a new posterior midline skin incision, unless the skin quality is compromised and wound problems are anticipated. Next, the ulnar nerve should be identified; when a previously transposed ulnar nerve is asymptomatic, additional nerve dissection should be avoided as long as the procedure can be performed without further nerve exposure and the ulnar nerve can be protected and reassessed at the end of the procedure. The nerve should be formally isolated and transposed when it was left in situ during previous surgeries.7 Neurolysis should be considered in patients with a previously transposed symptomatic ulnar nerve.

Several deep exposures may be used. A nonunited previous olecranon osteotomy should be used for exposure whenever present. Similarly, when a triceps-reflecting or triceps reflecting anconeus pedicle (TRAP) approach was used for previous surgeries, the same approach should be used if incomplete healing of the extensor mechanism to the olecranon is found at the time of surgery.11 For extra-articular nonunions with an intact extensor mechanism, the so-called bilaterotricipital approach (working on both sides of the triceps without violating the extensor mechanism) provides good exposure while preventing complications such as olecranon nonunion or triceps weakness (Fig. 23-3).2 Olecranon osteotomy provides an excellent exposure and is used by many surgeons for fixation of distal humerus nonunion (Fig. 23-4).15 Alternatively, a triceps-reflecting (Bryan-Morrey or Mayo-modified extensile K├╝cher) or TRAP approach is selected when the decision to proceed with fixation versus arthroplasty will be taken intraoperatively.3 Once the deep exposure is complete, tissue should be sent routinely for pathology and microbiology.

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