Forced radial deviation (abduction) of the thumb can cause a rupture of the ulnar collateral ligament (UCL) known as “gamekeeper’s” or “skier’s” thumb. The tear usually occurs at the proximal phalanx insertion and can be associated with volar plate and dorsal capsule injury. Pain and swelling are present over the ulnar aspect of the proximal phalanx and thumb metacarpal.
Radiographs may reveal a small avulsion fracture of the proximal phalanx. Abduction stress testing (stabilizing the metacarpal with one hand while applying radial stress on the proximal phalanx) may provide additional clinical information, especially in patients with normal radiographs. Classically, more than 30 to 40 degrees radial angulation indicates complete rupture. Stress testing should be done on both sides in extension and 30 degrees of flexion while feeling for a firm endpoint.
Management and Disposition
Apply a thumb spica splint and provide analgesia. Patients with pincer function weakness, point tenderness at the volar-ulnar aspect of the thumb MCP joint, a bony fragment of greater than 15% of the articular surface, avulsed fragment displacement of greater than 5 mm, or significant angulation on stress testing should prompt hand surgery referral. Complete tears need repair within 1 week. A sprain without instability is commonly treated with thumb spica casting or splinting for 4 to 6 weeks followed by range of motion exercises.
Gamekeeper’s Thumb. Laxity of 30 to 40 degrees more than the uninjured thumb, measured in neutral and 30 degrees of flexion, is strongly suggestive of a complete ulnar collateral ligament tear. There is no “endpoint” to the radial deviation of the phalanx. (Used with permission from Brunicardi FC, Anderson DK, Billar TR, et al. Schwartz’s Principles of Surgery. 8th ed. New York, NY: McGraw Hill; 2005. © 2005 by McGraw Hill.)
Radial collateral ligament rupture can also occur with forced adduction but is uncommon.
Skier’s thumb refers to an acute injury, whereas gamekeeper’s has classically been associated with repetitive trauma.
Thumb MCP joint laxity is highly dysfunctional, painful, and may lead to late arthritis.
Complete UCL tears put patients at risk for developing a Stener lesion, which occurs when the aponeurosis of the adductor pollicis becomes interposed between the ends of the torn ligament and prevents healing. MRI is the gold standard for diagnosis.
Gamekeeper’s Thumb. Stress x-ray of a thumb with a complete ulnar collateral ligament tear demonstrates marked instability of the ulnar side of the MCP joint and radial deviation of the proximal phalanx. (Used with permission from Brunicardi FC, Anderson DK, Billar TR, et al. Schwartz’s Principles of Surgery. 8th ed. New York, NY: McGraw Hill; 2005. © 2005 by McGraw Hill.)