Gamekeeper thumb: differentiation of nondisplaced and displaced tears of the ulnar collateral ligament with MR imaging. Work in progress.

Ulnar collateral ligament (UCL) injury of the first metacarpophalangeal joint (gamekeeper thumb) is common. If the UCL becomes displaced superficially to the adductor pollicis aponeurosis, surgical treatment has been advocated. Radiography cannot help differentiate between displaced and nondisplaced tears. The authors investigated the use of magnetic resonance (MR) imaging in the evaluation of UCL injury. Ten displaced and six nondisplaced UCL tears were surgically created in 16 nonembalmed cadaveric specimens. Twelve unaltered specimens served as controls. Coronal MR images were obtained and interpreted by two observers. The MR images were compared with corresponding anatomic slices. MR imaging depicted UCL displacement in all 10 specimens with displaced tears. A displaced tear was interpreted in one control specimen. Non-displaced tears were diagnosed in four control specimens. Although MR imaging was only 67% specific for all tears, it was 100% sensitive and 94% specific for depicting UCL displacement and, therefore, may be useful for evaluating gamekeeper thumb.