Slideshow
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Figure 1. Anteroposterior radiograph of the right thumb.
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Figure 2. Lateral radiograph of the right thumb.
An 11-year-old girl presents with pain in her right thumb following an injury sustained during soccer practice 2 days earlier. The girl was playing goalie when the ball struck her thumb. Physical examination reveals tenderness to palpation over the ulnar side of the metacarpophalangeal (MCP) joint. When the ulnar collateral ligament (UCL) is stress tested, mild laxity and pain are identified, and the injured thumb opens 10° further than the contralateral thumb. Anteroposterior and lateral radiographs of the thumb are obtained (Figures 1 and 2).
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The UCL is the primary stabilizer against valgus force to the MCP joint and is made up of 2 components: the proper collateral ligament and the accessory collateral ligament. Injury to the UCL is often referred to as “skier’s thumb” or “gamekeeper’s thumb,” but any fall or impact to the thumb can cause this injury. Sprain or tear of the UCL can be disabling and make grasping objects such as a door knobs or pencils difficult.
If a UCL injury is suspected, the MCP joint should be stressed with radial deviation in a neutral position (to test the integrity of the accessory collateral ligament) and with 30° of flexion (to test the integrity of the proper collateral ligament). The goal of stress testing is to determine if the ligament is partially (grade 1 or 2) or completely (grade 3) torn. Radial deviation of the proximal phalanx on the metacarpal head >35° of flexion or >20° of side-to-side variation is considered an unstable injury or indicative of a UCL tear. Laxity is best appreciated when comparing the examination to the contralateral thumb.
Routine use of magnetic resonance imaging for diagnosing partial UCL tears is not recommended because a clinical examination can accurately diagnose the severity of the injury. Grades 1 and 2 injuries can be treated with thumb spica immobilization for 4 to 6 weeks. Gripping and thumb opposition is allowed at 6 weeks. Grade 3 injuries usually require surgical repair.1,2
Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor-in-chief of the Journal of Orthopedics for Physician Assistants (JOPA).
References
1. McKeon KE, Gelberman RH, Calfee RP. Ulnar collateral ligament injuries of the thumb: phalangeal translation during valgus stress in human cadavera. J Bone Joint Surg Am. 2013;95(10):881-887.
2. Pulos N, Shin AY. Treatment of ulnar collateral ligament injuries of the thumb: a critical analysis review. JBJS Rev. 2017;5(2).
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