Chondrocortical Closing Wedge Osteotomy of the Ulna for Impaction Syndrome

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INTRODUCTION

Ulnar impaction is a common degenerative cause of ulnar-sided wrist pain. The ulnocarpal joint sustains a significant force transmission through a relatively small surface contact area and is therefore susceptible to degeneration over time. The degeneration of the ulnocarpal joint has been correlated with a positive ulnar variance. The location and severity of degenerative changes of the triangular fibrocartilage complex (TFCC), ulnar head, ulnocarpal bones, and lunotriquetral interosseous ligament have been classified by Palmer and Palmer and associates.

A variety of surgical options are available for patients who fail conservative management. Each surgical option has its inherent risks and benefits. Each patient’s pathology and anatomy should help guide the hand surgeon in choosing an appropriate procedure. The cause of an ulnar-positive variance includes congenital, dynamic, and pathologic radial shortening. If the primary cause of ulnar-positive variance is from a distal radius malunion or radial head excision after an Essex-Lopresti injury, it may be more appropriate to consider correction of the malunion or radial head replacement to restore the radial length. Patients with evidence of lunotriquetral interosseous ligament rupture may have a greater benefit from a traditional diaphyseal ulnar-shortening osteotomy by the tightening effect on the ulnocarpal ligaments.

DIAGNOSIS

Patients with ulnar impaction typically present with ulnar-sided wrist pain, which is exacerbated by gripping with the wrist in pronation and ulnar deviation (e.g., turning a doorknob, twisting a towel, or swinging a racquet or club). Ulnar-sided wrist pain has a large differential diagnosis and requires a detailed history and physical examination. Typically, on examination, wrist flexion and ulnar deviation with supination and pronation produces ulnolunate impaction mimicking the patient’s symptoms. Wrist radiographs typically show a static or dynamic positive ulnar variance. Ulnar variance is measured by measuring the distance between a line drawn parallel with the distal radial articular surface and a line drawn parallel with the distal ulnar articular surface. The variance is positive when the line parallel with the ulnar articular surface is distal to the radial line as measured on a standard neutral posteroanterior radiograph. Magnetic resonance imaging (MRI) may demonstrate ulnar-sided marrow edema of the proximal lunate or cystic changes in the ulna, lunate, or triquetrum. Arthrography may identify TFCC tears or lunotriquetral interosseous ligament tears.

LITERATURE REVIEW

In 1941, Milch recognized that a positive ulnar variance from radial shortening due to a malunited distal radius fracture was a cause of wrist pain. He proposed ulnar shortening as an alternative method to excision of the distal ulna for treatment of the distal radioulnar derangement. Milch performed an ulnar-shortening osteotomy in his patient, leading to relief of symptoms. Since then, the principle of surgical treatment of idiopathic and acquired ulnar impaction has been to perform an ulnar recession. Both biomechanical and clinical studies confirm the association of an increased ulnar-positive variance with degenerative changes of the ulnocarpal articulation and a resolution of patients’ symptoms after ulnar shortening. Cadaveric biomechanical studies have shown that a 2.5-mm increase in ulnar length increases the load on the ulnar side of the wrist to 42% from the normal of 18%, whereas shortening by 2.5 mm decreases the loading to 4.3%. Since Milch’s original description, there have been many modifications of the ulnar-shortening osteotomy, especially with the surgical advancements in rigid internal fixation. Despite all the advancements, the ulnar-shortening osteotomy has been plagued with complications, such as second operations for painful hardware, refracture, tendinitis, and variable nonunion and delayed union rates.

In 1992, Feldon and associates described a partial (“wafer”) excision of the distal ulna as an alternative to ulnar shortening for treatment of ulnar impaction syndrome. The Feldon wafer procedure consists of resecting the distal 2 to 4 mm of the ulnar dome with its articular cartilage via a dorsal approach. The TFCC is preserved and repaired if necessary. The efficacy of the wafer procedure has subsequently been validated by multiple authors with favorable results. A retrospective comparison of the wafer procedure and the ulnar-shortening osteotomy procedure showed comparable results but without the complications associated with ulnar-shortening osteotomies (i.e., hardware removal and delayed union). More recently, Wnorowski and associates described an arthroscopic-assisted wafer procedure. In patients with a degenerative central TFCC tear (Palmer class 2C), they advocated resecting the distal ulna arthroscopically using a 2.9-mm arthroscopic burr. Tomaino and Elfar have proposed the use of arthroscopic ulnar recession through an intact TFCC for ulnar impaction by first excising the central disk. Although the wafer procedure, either open or arthroscopic, has been reported as yielding good results without the hardware-related complications that are attendant with an ulnar-shortening osteotomy, it has also been associated with a relatively prolonged recovery period of up to 6 months.

The prolonged recovery period often seen after the wafer procedure potentially may be a result of a persistent hemarthrosis. The distal articular cartilage and subchondral bone are resected in the wafer procedure, leaving exposed metaphyseal trabecular bone, which results in bleeding into the distal radioulnar, ulnocarpal, and radiocarpal joints. In vitro and in vivo studies have shown that prolonged or recurrent hemarthrosis can be toxic to joints, leading to iron deposition in the synovium, to synovitis, to inhibition of cartilage proteoglycan synthesis, and to chondrocyte apoptosis.

We have previously reported a new surgical technique for treating patients with ulnar impaction that preserves the distal ulna’s articular surface via a chondral metaphyseal shortening osteotomy that is fixed with a headless compression screw. This method of rigidly fixing a metaphyseal closing wedge osteotomy should not only decrease the ulnar variance but also decrease any postoperative hemarthrosis while providing high union rates and lead to a faster recovery. It also preserves the articular cartilage and therefore the natural cushion and articulating surfaces. Another author has also recently described the same technique except without using internal fixation. In their case series of seven patients, all seven osteotomies progressed to union without internal fixation. The patients regained a full range of wrist motion by 3 to 5 weeks after the procedure, with an improvement in their pain levels as assessed with a visual analog scale (VAS). Similar to the senior author’s technique (JS), these authors performed the distal ulnar osteotomy just beneath the articular dome via a dorsal approach through the floor of the fifth extensor compartment. In this way, the stability of the distal radioulnar joint (DRUJ) and TFCC remain intact. Patients typically have minimal postoperative pain and are usually fully recovered. Moreover, they have achieved an excellent range of wrist motion within the first 2 months postoperatively.

RATIONALE

Metaphyseal bone has a richer blood supply than diaphyseal bone and should therefore be expected to have a shorter time to union. The shortest time to union of a distal ulna-shortening osteotomy reported in the literature was in a series of 11 patients, with an average time to union of 4.3 weeks after a step-cut osteotomy at the distal ulnar metaphysis that was held with a wire suture fixation. Good results have even been reported in osteochondritis dissecans lesions in the knee that were treated with internal fixation with headless compression screws, despite the inherent poor blood supply and high load stress in this condition. This experience combined with the excellent blood supply of the distal ulna provides a rationale for use of a headless compression screw for the dome osteotomy. In the paper by Barry and Macksoud, the patients had an average 1.29-mm decrease in the ulnar variance with a mean postoperative variance of –0.43 mm (range 0 to 1 mm). However, their mean long-term (range 14 to 38 months) postoperative ulnar variance was –0.2 mm (range +1 to –1 mm). Thus, at least one of these patients experienced a healed osteotomy with a positive ulnar variance. For this reason, we recommend fixation of the osteotomy with a compression screw, since our belief is that it is more reliable in maintaining the ulnar variance that was achieved at the time of surgery, even with the attendant risk of hardware complications.

INDICATIONS

Surgery is indicated in patients who have been diagnosed with ulnar impaction without DRUJ arthritis and who have failed to improve with nonoperative methods, such as activity modification, nonsteroidal anti-inflammatory medications, corticosteroid injections, and/or splinting. The goal of surgical treatment is to decrease the ulnocarpal load transmission.

SURGICAL TECHNIQUE: ULNAR OSTEOCHONDRAL SHORTENING OSTEOTOMY

Preoperative measurement of the ulnar variance from a standard posteroanterior radiograph of the wrist in neutral rotation is necessary to determine the amount of bone to be resected ( Fig. 18-1 ).The DRUJ must be critically analyzed to ensure that there are no signs of DRUJ arthritis and that the proposed osteotomy will not lead to an incongruous joint.

Either regional or general anesthesia can be used. A standard wrist arthroscopy is performed to both stage and treat any ulnocarpal arthrosis or TFCC tears that may need debridement or repair. The radiocarpal, midcarpal, and ulnocarpal joints should be inspected for pathology. Classic arthroscopic findings of ulnar impaction syndrome include a central TFCC tear, lunate impaction with chondromalacia, and lunotriquetral interosseous ligament tear. Mild TFCC wearing may be the only arthroscopic finding of impaction in early stages of the disease process.

The wrist is placed in a neutral position on an arm table with a mini-fluoroscopy unit perpendicular to the wrist ( Fig. 18-2 ). Care is taken to identify and protect the dorsal sensory branch of the ulnar nerve. A scalpel is then used to incise the extensor retinaculum overlying the extensor digiti quinti (EDQ) tendon. This incision is carried down through the floor of the fifth extensor compartment, creating an L-shaped dorsal capsulotomy. The longitudinal arm is the floor of the fifth dorsal compartment, and the transverse arm is proximal to the dorsal radioulnar ligament of the TFCC, which preserves the stability of the DRUJ. After completing the capsulotomy, retractors are placed around the distal ulna to deliver the distal head into the surgical wound and protect the volar capsule and the ulnar neurovascular structures that lie just volar to the capsule. This provides an excellent exposure of the distal ulnar metaphysis and the DRUJ. Depending on the preoperative ulnar variance, a 2- to 5-mm wafer of bone is resected with a microsagittal saw at the level of the DRUJ, leaving the distal ulnar articular surface and the TFCC foveal attachments intact ( Figs. 18-3 A and B and 18-4 ). The osteotomy is reduced and compressed with a hemostat and temporarily held in place by a Kirschner (K) wire ( Figs. 18-5 A and B and 18-6 ). Intraoperative fluoroscopy is used to identify the level of the osteotomy, confirm the reduction, guide the placement of the K wires and compression screw, and measure the postosteotomy ulnar variance ( Fig. 18-7 ). More bone can be resected if the patient remains ulnar-positive; however, excessive bony resection could lead to DRUJ instability or impingement. Rigid fixation is achieved using headless compression screws. Screw length is determined by using two wires of equal length.