ULNAR COLLATERAL LIGAMENT OF THE THUMB - MR FINDINGS IN CADAVERS, VOLUNTEERS, AND PATIENTS WITH LIGAMENTOUS INJURY (GAMEKEEPERS THUMB)

OBJECTIVE. The ulnar collateral ligament bridges the ulnar aspect of t he first metacarpal and the proximal phalanx and functions as a major stabilizer of the first metacarpophalangeal joint. Acute or chronic in jury of this ligament is referred to as gamekeeper's thumb. The object ives of this study were to (1) determine the MR appearance of the ulna r collateral ligament of the thumb in cadavers and volunteers and (2) analyze the MR findings in patients with gamekeeper's thumb, especiall y with regard to the value of MR in detecting clinically significant d isplacement of the ligament (Stener lesion). MATERIALS AND METHODS. MR imaging of the first metacarpophalangeal joint was performed in three volunteers, two cadaveric specimens, and 11 patients with acute injur y. In the patients, the mechanism of injury was an abrupt abductive fo rce on the thumb resulting in rupture of the ulnar collateral ligament . The diagnosis was confirmed by surgery in five patients and by clini cal follow-up in the remaining six. Cryomicrotome sectioning of the ca daveric tissue blocks was performed to correlate pathologic and NIR fi ndings. Images were interpreted by one radiologist. RESULTS. MR images showed rupture of the ulnar collateral ligament in all 11 patients. P rospectively, Stener lesions (n = 3) could be differentiated from non- Stener lesions (n = 8) in eight of 11 patients. Retrospectively, the c orrect diagnosis could be made in all 11 patients once the importance of determining the position of the ulnar collateral ligament relative to the adductor aponeurosis was understood. CONCLUSION. MR imaging of the first metacarpophalangeal joint depicts the ulnar collateral ligam ent and adductor aponeurosis to good advantage. It can also accurately show tears of the ulnar collateral ligament and thus be used to diffe rentiate a rupture without significant retraction from a Stener lesion . This information is important in determining whether surgical or con servative management is indicated.