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

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.

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.

FIGURE 23-3 A, Antero-posterior radiograph showing an extra-articular distal humerus nonunion. B, These injuries can be fixed working on both sides of the triceps.

FIGURE 23-4 Most complex distal humerus nonunions require a more extensile approach such as an olecranon osteotomy for fixation.

Capsular Release

Capsular contracture is a constant feature of distal humerus nonunions. Failure to release the contracture will limit final range of motion and increase the stress transmitted to the nonunion site, which may contribute to fixation failure. The posterior capsule and posterior band of the medial collateral ligament can been accessed and resected easily through any of the posterior approaches mentioned earlier. The anterior capsule may be released through the nonunion site (Fig. 23-5). Care should be taken to identify and protect the radial and median nerves at the time of the anterior capsular release. The anterior band of the medial collateral ligament and the lateral collateral ligament complexes should be preserved, along with the muscular attachments on the medial and lateral epicondyles, which are responsible for most of the blood supply to the distal segments.

FIGURE 23-5 The anterior elbow capsule may be resected through the nonunion site to avoid residual stiffness and decrease stress on the fixation construct.

Fixation Technique and Bone Grafting

The fixation technique that we recommend for internal fixation of distal humerus nonunions follows the same principles, objectives, and steps described for fixation of acute distal humerus fractures in the previous chapter (see Chapter 22).¹⁸ However, bone reabsorption at the nonunion site usually makes it difficult to apply compression at the supracondylar level if the reduction is anatomic, and the concept of metaphyseal shortening (see Chapter 22) often needs to be applied.¹²

Correct orientation of the distal fragment relative to the diaphysis may be difficult, especially in cases with more extensive bone loss. Care should be taken to avoid excessive flexion, extension, valgus, varus, or malrotation when the distal portion is aligned with the diaphysis. After reduction and provisional fixation of the nonunion with Kirschner wires, the quality of the reduction may be assessed under fluoroscopy, if necessary. Correct rotational alignment will place the forearm in roughly symmetrical positions with shoulder internal and external rotation. Excessive flexion or extension will shift the elbow arc into more flexion or more extension respectively. If shortening at the nonunion level is needed to achieve adequate bone contact and compression, the distal segment should be translated anteriorly to provide room for the coronoid and radial head in flexion; extension will be limited until a new olecranon fossa is recreated by excavating bone at the posterior aspect of the diaphysis. Once the reduction is considered satisfactory, the need for structural bone graft should be assessed and dealt with accordingly. Tricortical iliac crest bone graft may be needed to reconstruct large areas of bone loss.

Two parallel plates are then applied medially and laterally, and fixed with multiple distal long screws, which most of the time will interdigitate and interlock, increasing the stability of the construct (Fig. 23-6). Compression at the nonunion site is achieved by a combination of maneuvers including the use of a large reduction clamp, proximal screw insertion in the compression mode, and slight undercontouring of the plates. Cancellous bone autograft or a bone graft substitute is then placed at the nonunion site to promote bone healing. Our preference is to fashion two thin corticocancellous plates from the iliac crest and fix them with one or more screws across the nonunion site on the medial and lateral columns (Figs. 23-6 and 23-7).

FIGURE 23-6 Parallel-plating internal fixation provides satisfactory stability even in cases with severe bone loss. Note the posterior to anterior screws on the lateral radiograph to fix iliac crest bone graft.

FIGURE 23-7 Intraoperative photograph showing iliac crest bone graft fixed posteriorly with screws.

ELBOW ARTHROPLASTY

Elbow arthroplasty has emerged as a safe and effective treatment option for selected patients with distal humerus nonunion. The details regarding total elbow arthroplasty for the salvage of distal humerus nonunion are described in Chapter 59.

EVALUATION

Most patients with malunion after a distal humerus fracture present with a combination of pain and stiffness. In the absence of associated degenerative changes or other pathology, stiffness is usually much more prominent than pain. However, pain and stiffness may be present in patients with a previous distal humerus fracture complicated by capsular contracture, heterotopic ossification, post-traumatic osteoarthritis, infection, or avascular necrosis. The evaluation of patients with a distal humerus malunion should help determine to what extent correction of the malunion is needed in order to improve pain and function.

Plain radiographs are useful mostly to assess the status of the articular cartilage and identify associated pathology (Fig. 23-8). In addition, marked deformity is easily identified in plain radiographs, but computed tomography with three-dimensional reconstruction represents the ideal imaging modality to understand the deformity and determine if there is an associated nonunion of part of the articular surface, because some patients will present with a combination of nonunion on one side of the joint and malunion on the other side of the joint.⁸ The malunion may be mostly extra-articular, mostly intra-articular, or a combination of the two. The evaluation should be completed with studies to identify infection in patients with previous surgery, risk factors or suspicious findings on the history and physical exam.

FIGURE 23-8 Anteroposterior (A) and lateral (B) radiographs of a patient with pain and decreased motion secondary to distal humerus malunion.

TREATMENT

Patients with symptomatic distal humerus malunion may be offered several alternatives (Box 23-1). Osteotomy for correction of extra-articular and intra-articular deformities is appealing because it provides the potential to preserve the native joint and improve pain and motion. However, some patients may present with severe joint destruction not amenable to osteotomy. Arthroplasty may represent a good alternative for older patients willing to limit their upper extremity use and prevent mechanical failure. When moderate extraarticular deformity limits motion secondary to impingement of the proximal ulna and radius with the deformed distal humerus, recontouring of the distal humerus by selective removal of bone provides a reasonable alternative with relatively low morbidity. Joint fusion may be considered for patients with severe pain who are not candidates for other surgical alternatives, but most patients with limited motion secondary to a distal humerus malunion are reluctant to have their elbow fused.

Osteotomy

Patients with an extra-articular malunion of the distal humerus may benefit from extra-articular osteotomy. Correction of the malunion may improve range of motion and cosmesis. In addition, varus malunion may be associated with progressive ulnar neuropathy as well as gradual attrition of the lateral collateral ligament complex and tardy posterolateral rotatory instability.¹³ Closing-wedge osteotomies are usually preferred because humeral shortening is relatively well tolerated. Medial or lateral translation of the distal fragment should be considered to avoid a serpentine aspect of the distal humerus. Usually, extra-articular osteotomies are performed through a bilaterotricipital approach and fixed with medial and lateral plates (Fig. 23-9). Capsular release and ulnar nerve transposition may be associated as needed.

FIGURE 23-9 A, Extra-articular nonunion may be corrected with a supracondylar osteotomy. B, Intra-articular fluoroscopy showing the planned osteotomy. C, Healed osteotomy after internal fixation with two parallel plates.

Intra-articular osteotomies may be indicated when intra-articular malunion is thought to be responsible for pain or limited motion and joint salvage is not compromised by the severity of joint destruction, avascular necrosis or secondary degenerative changes. Intra-articular osteotomies usually require a more ample approach, such as olecranon osteotomy or reflection of the extensor mechanism. Care should be taken to protect the articular cartilage and bone graft is usually required to fill the defects created by correction of the deformity. Whenever an intra-articular osteotomy is performed, an alternative salvage procedure, such as interposition arthroplasty or joint replacement should be available because the degree of joint destruction is difficult to fully appreciate before surgery.

OUTCOME

There is very limited information about the outcome of surgical correction of distal humerus malunion. Cobb et al⁴ reported on three patients treated with an intra-articular derotational opening-wedge osteotomy for a distal humerus malunion. Motion was improved in all three patients, but one required conversion to interposition arthroplasty.

More recently, McKee et al.⁸ reported on a heterogeneous group of 13 patients with intra-articular distal humerus malunion or nonunion following fracture. Six fractures had healed in a malunited position, two elbows presented a combination of lateral malunion and medial nonunion, and the remaining five presented a nonunion. An intra-articular osteotomy was performed in the eight patients with malunion; results were rated as satisfactory in seven patients.

The results of arthroplasty in patients with distal humerus malunion are difficult to dissect out of the studies analyzing arthroplasty for the sequelae of trauma (see section on arthroplasty). As noted, the main concern is the increased rate of polyethylene wear found in patients with preoperative angular deformity.