Acute injuries of the ulnar collateral ligament of the thumb metacarpophalangeal joint have received much attention in the literature.3,8,9,15,17,20,24,25 The term skier's thumb has been coined to describe these injuries due to their common occurrence in skiing accidents.6,8,9,13 Injury to the ligament results from forceful abduction of the thumb and may also occur from simple falls and from a variety of sporting activities including football, basketball, hockey, wrestling, and cycling.5,12,17,21,23,25
This paper deals specifically with avulsion fractures of the ulnar collateral ligament of the thumb metacarpophalangeal joint. It discusses anatomy, clinical and radiographic evaluation, and treatment including the options for surgical fixation as well as rehabilitation.
The metacarpophalangeal joint of the thumb is a diarthrodial hinged joint that flexes, extends, abducts, and adducts. The range of flexion and extension varies greatly and, to a lesser extent, so does abduction and adduction.22 This variation is secondary to differences in metacarpal head configuration and collateral ligament tightness.
Stability of the metacarpophalangeal joint is determined by the joint capsule, the volar plate, and the collateral ligaments. The proper ulnar collateral ligament originates from the dorsal ulnar metacarpal head and inserts into the volar ulnar base of the proximal phalanx. It is at this site of attachment where avulsion fractures most commonly occur. The accessory collateral ligament runs volar and parallel to the proper collateral ligament and inserts into the volar plate (Fig 1). When stressing the ulnar collateral ligament complex, the proper ulnar collateral ligament is taut in flexion while the accessory collateral ligament is relaxed. The reverse is true in extension. This is of importance in the evaluation of joint stability.
Dynamic stability of the metacarpophalangeal joint is provided by the intrinsic muscles of the thumb, particularly the adductor pollicis, which resists active abduction. It has 3 points of insertion: into the ulnar base of the proximal phalanx, into the ulnar sesamoid, and into the extensor expansion via the broad adductor aponeurosis.
CLINICAL AND RADIOGRAPHIC EVALUATION
The mechanism of injury is forced abduction of the thumb. Patients present with pain, swelling, and tenderness on the ulnar side of the metacarpophalangeal joint.
Before performing stress testing, anteroposterior, oblique, and lateral radiographs of the thumb are obtained. Collateral ligament avulsion fractures vary in location, size, displacement, rotation, and the presence or absence of comminution. Rarely, the avulsion will be from the metacarpal head. Louis et al18 have described an avulsion fracture of the volar plate, which should be distinguished from ulnar collateral ligament avulsion fractures, because it is a stable injury and 1 that should be treated conservatively. Skeletally immature patients may have a Salter-Harris Type III fracture.10
When the degree of fracture displacement or rotation or both requires surgical treatment, stress testing is unnecessary. When there is a question of instability, stress testing should be performed. A median and radial nerve block at the wrist helps eliminate pain and allows for a more accurate examination. It has been reported that small, minimally displaced fragments may be detached from the ligament with instability, and consequently stress testing has been recommended for these fractures.13 This is, however, controversial and may carry with it the risk of converting a stable fracture into an unstable 1.
Given that the proper collateral ligament is taut in flexion and lax in extension, the authors perform stress testing at 30 ° metacarpophalangeal flexion. If the metacarpophalangeal joint angulates 35 ° or more with the radially applied stress, or 15 ° greater than the opposite side, then it is considered unstable and surgery is recommended.12,22
Properly performed stress testing has eliminated the need for stress radiographs in the majority of patients. Ultrasound11 and magnetic resonance imaging (MRI) have been used to evaluate ligamentous injuries, but are not indicated for bony skier's thumb injuries.
Undisplaced or minimally displaced fractures with no joint instability are managed nonoperatively (Fig 2). Previous reports, however, have failed to define clearly what represents significant displacement or rotation. Generally, displacement of 1 mm or less, joint stability, and the absence of articular incongruity are indications for conservative treatment.
After the initial swelling subsides, the patient is fitted either with a short arm thumb spica cast or a custom made forearm based thumb spica splint with the interphalangeal joint included. Active range of motion (ROM) exercises can be started in most cases approximately 3 weeks after injury with discontinuation of all splinting 3 to 4 weeks later. The patient continues with ROM and is instructed in strengthening exercises. Formal hand therapy usually is unnecessary. A return to unrestricted activities often is possible as early as 6 weeks after injury.
Radiographically, most patients demonstrate progressive fracture healing, although some will have a persistent, but stable and pain free, fibrous nonunion. Those patients who develop instability or arthritis may ultimately require surgical reconstruction.
Inappropriate treatment of bony skier's thumb injuries has been reported to result in chronic painful instability, weakness of pinch, and arthritis.7,17,20,23 Therefore, surgical treatment is recommended for those fractures with 2 mm or more of displacement, or significant articular involvement with incongruency or rotation. The goal of surgery is restoration of anatomy with stable fixation. Ideally, surgery should be performed within 2 weeks of injury.21
The authors prefer to use a chevron incision with its apex at the volar ulnar aspect of the metacarpophalangeal joint. This incision allows for adequate exposure-volarly where the fracture is located and dorsally where a constant sensory nerve to the thumb must be identified and protected (Fig 3). After completion of the superficial dissection, a bony Stener lesion occasionally may be identified at the proximal edge of the adductor aponeurosis. The ulnar side of the joint is exposed by taking down the adductor aponeurosis, taking a small margin of the extensor pollicis longus to allow for easier repair (Fig 4).
If a capsular tear is not present, adequate visualization of the joint is obtained by incising the capsule longitudinally dorsal to the ulnar collateral ligament. The joint and fracture site are inspected and cleared of hematoma. The choice of fracture fixation technique depends on several factors, including the size of the fragment, the presence of comminution, and the experience and preference of the surgeon. For a large, single fragment, the authors prefer to use a 1.5-mm minifragment screw (Fig 5). This technique is technically demanding because the joint and fracture line cannot be visualized once the fracture is reduced. Therefore the starting point and direction of screw insertion must be chosen carefully. The proximal fragment is overdrilled to allow for interfragmentary compression. Due to the relatively small size of the fracture, the surgeon typically has only 1 chance to place the screw. On occasion, the fragment will break into 2 or more pieces making fixation even more difficult. This situation can be salvaged by using a pullout wire, or, as the authors prefer, a small suture anchor. The fragments are excised, 1 or 2 suture anchors are placed in the base of the fracture in the proximal phalanx and the ulnar collateral ligament is advanced into the defect and secured there (Fig 6).
Tension band wiring10,14,16 is particularly appropriate for those fractures that are too small for screw fixation. The initial dissection and reduction are the same as for screw fixation. Additional dissection is carried onto the proximal phalanx where a hole is drilled in a dorsal to volar direction 1 cm distal to the joint. In a figure of 8 configuration, a 26-gauge wire is passed through the drill hole and then through the collateral ligament using a 20-gauge needle as a guide. If fragment size permits, a small Kirschner wire (K wire) may be used to stabilize the fracture, otherwise the fragment is held reduced with a forceps while the figure of 8 wire is tightened (Fig 7).
For smaller or comminuted fractures, screw and tension band fixation often are inappropriate. These injuries can be treated successfully using a conventional pullout wire6,25 or small bone anchors as described above.
On rare occasions, a combined injury with ligament avulsion from the fracture fragment may exist.13 In this situation the authors have combined fracture fixation and ligament repair using a pullout wire. Smaller fragments may be excised and the ligament advanced and secured in the defect using suture anchors.
The capsule and the adductor aponeurosis are repaired with 4-0 nonabsorbable suture. A bulky thumb spica plaster dressing, including the interphalangeal joint, is applied with the thumb slightly adducted. The authors do not stabilize the metacarpophalangeal joint with a temporary K wire.
Assuming that stable fixation has been achieved, the initial splint is removed within 1 week of surgery, a forearm based thumb spica splint is fabricated, and the patient begins flexion and extension exercises. If a pullout suture or suture anchors are used for the repair, immobilization is continued for 6 weeks. At 6 weeks after surgery, the fracture has usually healed, strengthening is started, and splinting is discontinued.
Injuries to the ulnar collateral ligament have for many years been referred to as gamekeeper's thumb. Campbell2 described this injury in Scottish gamekeepers in whom ulnar collateral instability developed due to chronic stress and attrition of the ligament. The majority of ulnar collateral ligament ruptures, however, occur with an acute abduction injury to the thumb. This injury commonly has been referred to as a skier's thumb reflecting the preponderance of this injury in downhill and cross country skiing accidents.1,4,9,19 Avulsion fractures of the ulnar collateral ligament account for approximately ⅓ of skier's thumb injuries,4,9,13,19,23 and the authors think the term bony skier's thumb more accurately reflects the acute nature of this condition.
Radiographs must be evaluated to determine fragment size, displacement, and rotation. One must differentiate volar plate avulsion fractures from ulnar collateral ligament avulsions, as the former can be satisfactorily treated nonoperatively.18
The following points concerning evaluation and management of bony skier's thumb deserve emphasis: (1) If there is any doubt about joint stability, stress testing should be performed under a median and radial nerve wrist block with the thumb at 30 ° metacarpophalangeal joint flexion. If the joint opens 35 ° or more with radial deviation stress, then surgery is indicated. (2) Undisplaced, stable fractures are managed with 3 to 4 weeks of immobilization and early ROM exercises. A custom made thumb spica splint is recommended in compliant patients for convenience and to allow early motion. (3) Displaced and rotated fractures require open reduction and internal fixation to prevent chronic instability with pain and weakness. (4) The choice of fracture fixation depends on the size of the fracture fragment along with surgeon experience and preference. For larger fractures, it is preferable to use 1.5-mm minifragment screws with interfragmentary compression. Tension band wiring is a useful technique for those fragments not large enough to support a screw, whereas the use of suture anchors is recommended for the smaller and comminuted fractures. The goal of surgery is stable fixation permitting early motion.
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