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RATIONALE AND BASIC SCIENCE
Painless rotation of the forearm is vital for the function of the upper extremity and is the result of complex interactions of the proximal radioulnar joint, interosseous membrane, forearm musculature, and the distal radioulnar joint (DRUJ). Pathologic instability of the DRUJ can be painful, limit the range of pronation and supination of the forearm, and cause significant disability. It can be secondary to osseous or soft tissue injury or a combination of both, and it can be acute or chronic. The direction of instability may be dorsal, volar, or multidirectional.
The normal DRUJ is inherently unstable. The joint is formed at the distal end of the forearm by the cylindrical ulnar head and the concave sigmoid notch of the radius. There is a significant mismatch of the radius of curvature of the two surfaces, which results in decreased bony constraints to translation of the radius on the ulna.
Given the lack of osseous constraint, the stability of the joint is highly dependent on the arrangement of soft tissues surrounding the distal ulna, the most important being the triangular fibrocartilage complex (TFCC). The TFCC consists of a number of confluent structures. The triangular fibrocartilage is cartilaginous in its central portion and serves a weight-bearing function, whereas its peripheral portion is more vascular and confluent with the dorsal and palmar radioulnar ligaments.
The contribution of these ligaments to DRUJ stability has been debated in the past. af Ekenstam and Hagert demonstrated that the dorsal radioulnar ligament tightens with supination and the palmar radioulnar ligament tightens with pronation in cadaver specimens. In sharp contrast, Schuind and colleagues, using stereophotogrammetry on cadaveric specimens, demonstrated that the dorsal radioulnar ligament tightens with pronation whereas the palmar radioulnar ligament tightens with supination, seemingly the opposite conclusion of af Ekenstam and Hagert. Hagert later resolved the inconsistency. In the af Ekenstam and Hagert study, the methodology required disruption of the superficial radioulnar ligaments that attach distally on the ulnar styloid process. Therefore, only the deep radioulnar ligaments attaching at the fovea, or base of the ulnar styloid, were observed. In Schuind’s study, phosphorescent markers were placed on the surface of the TFCC. As a consequence, only the superficial radioulnar ligaments attaching to the ulnar styloid process were observed. Hagert concluded that in pronation, both the deep palmar fibers and the superficial dorsal fibers tighten, while in supination the deep dorsal fibers and the superficial palmar fibers tighten. Further scrutiny of the arrangement of the deep and superficial fibers shows that the deep fibers are aligned more appropriately to provide a vector of force that resists sagittal plane motion of the radius. Thus, the deep palmar and dorsal radioulnar ligaments, which insert into the fovea, function as checkreins to translation of the radius on the ulna and are the primary stabilizers of the DRUJ.
In addition, the ulnolunate ligament, ulnotriquetral ligament, interosseous membrane, and the deep portion of the extensor carpi ulnaris (ECU) sheath act as secondary static stabilizers of the DRUJ. The ECU and pronator quadratus provide dynamic stability to the joint. Injury to a combination of these structures may lead to disruption of the biomechanical balance of the DRUJ and cause instability.
Acute instability of the DRUJ may result from a variety of traumatic mechanisms. Acute dislocations are most commonly dorsal but may be palmar. A dorsal dislocation may be the result of a fall on an outstretched hand in pronation and hyperextension. Palmar dislocations occur less frequently and result from a fall onto a supinated hand or from exertional lifting in supination. These injuries usually are associated with gross instability, complete avulsion of the TFCC from its ulnar foveal insertion, and possibly a locked ulnar head—either dorsally or volarly.
Various fracture patterns are associated with injuries to the DRUJ as well. The Galeazzi fracture, a radial diaphyseal fracture usually in the distal third of the bone, is associated with DRUJ dislocation or subluxation and TFCC disruption ( Fig. 52-1 ). Occasionally, the ECU can be interposed in the DRUJ and may prevent reduction.
Essex-Lopresti injuries are usually caused by a fall onto an outstretched hand with axial loading. These are severe injuries that disrupt the entire forearm axis. Consisting of a radial head fracture with proximal migration of the radius and disruption of the interosseous membrane and TFCC, Essex-Lopresti injuries are associated with DRUJ instability. The primary stabilizer of the radius that prevents proximal migration is the radial head with the interosseous membrane and TFCC acting as secondary stabilizers.
Fractures of the distal radius occasionally have concomitant DRUJ instability.
Ulnar styloid fractures may be overlooked in the treatment of distal radius fractures. Type 1 fractures of the ulnar styloid are fractures of the tip at a point distal to the deep radioulnar ligament insertion and have a stable DRUJ. Type 2 fractures, however, occur at the base of the styloid and may disrupt the insertion site of the deep dorsal and palmar radioulnar ligaments, resulting in instability of the DRUJ ( Fig. 52-2 ).
Trauma may cause isolated tears of the TFCC. These tears have been classified into four types by Palmer ( Table 52-1 ). Type 1B tears occur in the peripheral region of the TFCC, representing an avulsion of the insertion of the deep dorsal and palmar radioulnar ligaments and thus may result in DRUJ instability.
|1A||Small flap tear near the radius; the flap itself may or may not be unstable|
|1B||Avulsion from the base of the ulnar styloid; may include a fleck of the ulnar insertion|
|1C||Tear of the ulnocarpal ligament complex that exposes the pisiform|
|1D||Avulsion from the ulnar border of the sigmoid notch|
Chronic instability may follow injuries to the DRUJ that have not been recognized and treated in the acute phase. Osseous malalignment may lead to chronic DRUJ instability with resultant pain and limitation of motion. Examples include malunited distal radius fractures with more than 20 degrees of loss of volar tilt or more than 5 mm of shortening and pediatric fractures that lead to growth disturbances with subsequent malalignment of the DRUJ.
The proliferative chronic synovitis associated with rheumatoid arthritis may destroy cartilage, bone, and ligaments, which in turn may destabilize the DRUJ. Finally, distal ulnar resection (Darrach procedure), performed for a variety of reasons, may result in instability of the distal ulnar stump and create a challenging reconstructive problem.
Instability may occur in conjunction with other causes of ulnar-sided wrist pain such as ECU tendon subluxation, ulnar abutment syndrome, and DRUJ arthritis. These conditions must be considered before attributing the patient’s symptoms solely to instability.
Clinical evaluation should start with a thorough history. The mechanism of injury may suggest the cause of instability. Patients with TFCC tears or acute dislocations typically present with a history of a fall onto an outstretched hand or a torque injury with axial load. Patients may find that specific activities involving pronation and supination are painful, or they may have a limited range of motion. Occasional clunking, catching, and snapping of the wrist are also common complaints. Subjective mechanical instability may be sensed by the patient. A history of distal radius fracture or childhood fracture is important to determine, as is a history of surgery or rheumatoid arthritis.
Physical examination of the wrist is the next step in clinical evaluation. Palpation of the ulnar styloid is performed by following the ulnar shaft distally with the wrist in pronation. Tenderness in this location may indicate an ulnar styloid fracture or TFCC tear. Limitation of the pronation-supination arc of motion is noted. Excessive dorsal prominence of the distal ulna in pronation is indicative of a dorsal dislocation. The ulnar head is palpable volarly with palmar dislocations; patients present with the forearm held in supination and have pain with pronation. Increased anteroposterior translation with ballottement of the ulna is indicative of instability ( Fig. 52-3 ). This maneuver is performed with the elbow held in 90 degrees of flexion and the forearm in neutral rotation. It is then repeated and compared with the opposite side.
The press test is a simple but useful test. Ask the patient to push up from the seated position using the symptomatic wrist. The maneuver places an axial ulnar load on the wrist and has high sensitivity for detecting TFCC tears when painful.
Other sources of ulnar-sided wrist pain are evaluated. With loss of volar tilt in a malunited distal radius fracture, the ulna appears more prominent dorsally. Ulnar impaction syndrome can be tested by placing the wrist in ulnar deviation to load the ulnar side of the wrist and passively pronating and supinating the wrist. Pain with this maneuver may indicate a central tear of the TFCC and ulnar impaction syndrome.
Plain radiographs should be routinely obtained to assess for signs of instability and rule out other causes of ulnar-sided wrist pain such as DRUJ arthritis and ulnar impaction syndrome. A true lateral with the forearm in neutral rotation may demonstrate either volar or dorsal subluxation of the ulna. However, it is important that the lateral is performed with a tolerance of less than 10 degrees of rotation from the neutral position to ensure accuracy of the examination. On the posteroanterior radiograph, look for a fleck fracture at the base of the ulnar styloid indicating an avulsion of the TFCC. Also, a type 2 ulnar styloid fracture, nonunion of the styloid process, and DRUJ widening should be sought. Other radiographic signs of DRUJ instability include more than 20 degrees of loss of volar tilt or more than 5 mm of radial shortening. Obtain bilateral ulnar variance views that are posteroanterior x-rays with the elbow in 90 degrees of flexion, the shoulder forward flexed to 90 degrees, and the forearm in neutral rotation to ensure standard positioning. The variance is calculated by drawing a transverse line at the level of the lunate fossa and the ulnar head and measuring the distance between them. Both sides should then be compared. Positive ulnar variance may be evidence of ulnar impaction syndrome.
Magnetic resonance imaging (MRI) combined with arthrography (MRA) is valuable in assessing the integrity of the TFCC ( Fig. 52-4 ). Arthroscopy, however, remains the gold standard for evaluating the condition of the TFCC. Computed tomography (CT) scanning may be used to evaluate the congruency of the DRUJ. Several methods exist for assessing for subluxation on CT scans or MRI, including the congruency method, the epicenter method, the radioulnar ratio method, and the technique described by Mino and associates ( Fig. 52-5 ). These methods require that images are obtained in neutral, pronation, and supination.
Considering the variety of pathology that may lead to DRUJ instability, the plethora of procedures recommended for its treatment is not surprising. The primary pathology, the acuteness of the condition, and the status of the osseous and soft tissue components of the joint all influence the decision-making process in treating this condition.
Acute dislocations usually are associated with gross instability and complete avulsion of the TFCC from its ulnar insertion. A dorsal dislocation is reduced by applying a volarly directed force on the distal ulna with simultaneous supination of the forearm and is subsequently immobilized for 6 weeks. Some authors recommend immobilization in neutral forearm rotation, whereas others recommend full supination. If the joint is not reducible by closed means or if residual incongruity in any plane is seen radiographically, an open reduction with open TFCC repair should be performed. We use the technique of open TFCC repair described by Hermansdorfer and Kleinman to treat the grossly unstable, dorsally dislocated DRUJ.
A similar approach may be used in treating volar dislocations. Closed reduction is attempted by applying a dorsally directed force on the ulnar head with forceful pronation of the forearm. Immobilization may be in neutral to slight pronation for 6 weeks. Failure of reduction is an indication for open reduction via a volar approach.
Galeazzi fractures should be treated by open reduction and internal fixation. After reduction and fixation of the radius fracture are achieved, the DRUJ should be checked for stability through a full range of motion. If stable, early motion can be started postoperatively. If the DRUJ is unstable, the wrist should be immobilized in slight supination for 4 to 6 weeks. Associated type 1 ulnar styloid fractures should be fixed as well. Occasionally, the DRUJ is not reducible. The presence of an interposed ECU warrants removal of the ECU from the joint. If the joint is still irreducible, open reduction and repair of the TFCC should be performed.
Treatment for an Essex-Lopresti injury consists of open reduction and internal fixation of the radial head fracture. Comminuted fractures may require radial head replacement with a metal prosthesis. Postoperatively, immobilization should be done with the forearm in slight supination. Pinning of the DRUJ can be considered, but pin breakage may make it difficult to remove the pin after healing. If you elect to pin the joint, make sure it completely passes to the radial cortex of the radius so if it does break, both ends can be retrieved.
Triangular Fibrocartilage Complex Tears
Isolated TFCC tears in the peripheral region (type 1B) may cause subtle instability and painful range of motion of the wrist. The peripheral TFCC is well vascularized compared with the central portion and consequently has much better healing potential. When such a lesion is suspected based on clinical evaluation, diagnostic arthroscopy may show the lack of the usual trampoline effect of the TFCC, which is the main indication for surgical repair. Open repair has been historically advocated, but many authors have had success with arthroscopic repair. Minimal incisions, less soft tissue dissection, and faster recovery are advantages of arthroscopic repair. Many techniques exist, and new ones are continually evolving. We recommend an outside-in suture repair technique. However, it is important to recognize that arthroscopic repair addresses the peripheral vascular superficial fibers of the TFCC and not the deep fibers that insert into the fovea.
Distal Radius Malunion
Chronic instability associated with osseous malalignment of the DRUJ may occur with malunion of distal radius fractures or growth disturbance after pediatric radius fractures. We recommend that all patients with symptomatic osseous malalignment undergo correction of the deformity. A soft tissue procedure may be needed secondarily, but it will fail if the bony deformity is not corrected first.
The type of operative intervention chosen depends on the deformity and condition of the TFCC. The TFCC should be evaluated using MRA or arthroscopy before operative realignment. Treatment should be tailored to the individual patient with careful preoperative planning. For correcting distal metaphyseal deformities, we use an intercalated corticocancellous iliac crest autograft to achieve longitudinal and angular correction. Fixation is accomplished with a volar distal radius locking plate. More proximal deformities may be corrected using a dome osteotomy with iliac crest autograft and dynamic compression plate fixation. This is useful when a closing wedge osteotomy or opening wedge osteotomy would cause unwanted relative shortening or lengthening of the radius ( Fig. 52-6 A–D). If the DRUJ is unstable after the corrective osteotomy, open repair of the TFCC should be considered if the tissues appear repairable. Nonrepairable lesions should be stabilized with a tendon graft as described in the text that follows or can potentially be treated with closed bracing techniques.