Nonunion and Malunion of Distal Humerus Fractures

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CHAPTER 23 Nonunion and Malunion of Distal Humerus Fractures

Joaquin Sanchez-Sotelo

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 fractures ¹⁸ (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

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.^6,^9,^14,^19,²⁰

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. Other risk factors for fracture nonunion include smoking, use of immunosuppressive medications, severe associated soft tissue injuries, osteopenia, 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. 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.

FIGURE 23-1 Anteroposterior radiograph of a patient with a distal humerus nonunion after failed internal fixation. Bone stock is compromised by the nature of the initial injury and the effects of loose hardware.

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

History and Physical Examination

The history and physical examination should help delineate the details of the initial injury and subsequent treatment attempts. Risk factors for bone nonunion should be identified, including smoking and use of medications that may inhibit bone formation. It is also important to document the location and status of previous skin incisions, identify the location and ulnar nerve, and examine the neurovascular function of the upper extremity. Patients should be specifically questioned about symptoms or signs of infection after previous surgeries.

Imaging Studies

Simple Radiographs

When possible, sequential radiographs should be evaluated to understand the initial fracture pattern, assess the quality of the initial fixation when previously attempted, and determine the amount of bone loss. Recent radiographs will help determine the feasibility of repeated internal fixation versus arthroplasty and the need for structural bone graft and special tools for hardware removal.

Computed Tomography

Computed tomography with three-dimensional reconstruction is an invaluable tool when repeated internal fixation is planned (Fig. 23-2), because it provides a better understanding of the remaining bone stock and any degree of associated malunion, and facilitates planning of plate and screw placement in order to achieve the maximum anchorage of the fixation devices.

FIGURE 23-2 A, Computed tomography represents an excellent imaging modality for understanding and surgical planning in distal humerus nonunion. B, Three-dimensional reconstruction may help understand rotational and angular deformities and assist in proper reduction at the time of surgery.

Aspiration and Laboratory Studies

Every patient presenting with a distal humerus nonunion and previous surgery or suspicious findings in the history or physical examination should be evaluated for infection. An abnormal cell blood count and elevated sedimentation rate and C-reactive protein should raise the possibility of infection. Aspiration of the elbow joint and the nonunion site provide invaluable information; the aspiration may be performed under fluoroscopy when access is difficult. Ideally, patients on antibiotics should discontinue their treatment between 2 and 4 weeks before the aspiration. Samples should be sent for cell count, gram stain, cultures and sensitivities.

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 Kücher) 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.