Physical Examination
The injured thumb should be evaluated for swelling and pain at the ulnar aspect of the metacarpophalangeal (MCP) joint. Ecchymosis is frequently seen. A palpable mass on the ulnar aspect of the MCP joint may represent the retracted ulnar collateral ligament (UCL) stump that is displaced proximally and dorsally relative to the adductor aponeurosis. The uninjured thumb should be evaluated first to assess its range of motion (ROM) and valgus stability in both extension and 30º flexion.
The range of flexion and extension of the thumb MCP joint varies considerably. The variation of normal joints can include ROMs of 5-115º of flexion and extension. In full extension, valgus laxity averages 6º and increases to an average of 12º in 15º of flexion.
The accessory collateral ligament may remain intact, and gross instability may be absent. The thumb should be placed in 30° flexion and tested for valgus instability in this position. However, this maneuver should be performed only after radiographic findings rule out a gamekeeper's fracture.
Although a gamekeeper's fracture is a contraindication for stress testing, a nondisplaced avulsion fracture is not. If the patient's pain is severe, the joint may be anesthetized with a lidocaine injection before the stress testing.
A laxity of 30º or one that is 15º more than that on the uninjured side represents a ruptured proper collateral ligament in this position (the proper collateral ligament runs from the metacarpal head to the volar aspect of the proximal phalanx). [16, 10] A supination deformity of the MCP joint, which may be visualized, can be associated with the volar subluxation of the MCP joint and suggests instability.
A Stener lesion can be present only when both the proper collateral ligament and the accessory collateral ligament are ruptured. In more than 80% of complete ruptures of the UCL, a Stener lesion is present, whether it is palpable or not. Stress testing with the thumb in the extended position is the best test for determining the competence of the accessory collateral portion of the UCL.
Again, valgus laxity of more than 30º or a laxity that is 15º more than that on the uninjured side suggests rupture of this portion of the ligament. [16, 10] If valgus laxity of the MCP joint is present in both the flexed and extended positions, complete UCL rupture should be suspected.
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Anteroposterior radiograph displaying gamekeeper's fracture.
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Lateral radiograph displaying gamekeeper's fracture.
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Radiograph displaying stress test of torn ulnar collateral ligament.
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Stress testing of metacarpophalangeal joint of thumb in flexion.
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Stress testing of metacarpophalangeal joint of thumb in extension.
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Anterior view of hand in thumb spica splint.
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Lateral view of hand in thumb spica splint.
