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 the first metacarpal and the proximal phalanx and functions as a major stabilizer of the first metacarpophalangeal joint. Acute or chronic injury of this ligament is referred to as gamekeeper's thumb. The objectives of this study were to (1) determine the MR appearance of the ulnar collateral ligament of the thumb in cadavers and volunteers and (2) analyze the MR findings in patients with gamekeeper's thumb, especially with regard to the value of MR in detecting clinically significant displacement 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 injury. In the patients, the mechanism of injury was an abrupt abductive force on the thumb resulting in rupture of the ulnar collateral ligament. The diagnosis was confirmed by surgery in five patients and by clinical follow-up in the remaining six. Cryomicrotome sectioning of the cadaveric tissue blocks was performed to correlate pathologic and NIR findings. Images were interpreted by one radiologist. RESULTS. MR images showed rupture of the ulnar collateral ligament in all 11 patients. Prospectively, Stener lesions (n = 3) could be differentiated from non-Stener lesions (n = 8) in eight of 11 patients. Retrospectively, the correct 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 ligament and adductor aponeurosis to good advantage. It can also accurately show tears of the ulnar collateral ligament and thus be used to differentiate a rupture without significant retraction from a Stener lesion. This information is important in determining whether surgical or conservative management is indicated.