Case 4: Ulnar Collateral Ligament (UCL) injury (Skier’s or Gamekeepers Thumb)
The UCL is typically 4-8mm wide and 12-14mm long and gives lateral and dorsal stability to the metacarpophalangeal joint of the thumb. The ligament arises from the medial tubercle of the metacarpal and inserts into the base of the proximal phalanx distally.
The UCL is composed of the proper collateral ligament which resists valgus load with thumb in flexion, the accessory collateral ligament and the volar plate which resists valgus load with thumb in extension. A marked valgus laxity in both flexion and extension is indicative of a complete rupture of both components of the UCL.
Testing should be carried out both in 30° flexion and neutral to assess both the ligament proper and accessory ligament respectively.
Injury to the UCL usually follows a forced abduction injury and may result in a partial tear (usually at the articular side of the ligament) or a complete tear. Both partial and complete tears may be associated with or without a bony avulsion.
A Stener lesion occurs when the adductor aponeurosis becomes interposed between the ruptured ends of the UCL. Such an interposition prevents healing and on US is seen as a
The video clip demonstrates dynamic stressing of the UCL with a valgus force. The ligament appears thickened and there is an avulsion fracture noted to the left of the image. The avulsion fragment does however appear stable and the ligament patent with this dynamic test. (Click on link below for video)