Acute ulnar collateral ligament injuries of the thumb metacarpophalangeal joint: an anatomical and clinical study.

Treatment of acute injuries of the ulnar collateral ligament of the metacarpophalangeal joint of the thumb remains controversial owing to the difficulty involved in establishing an accurate diagnosis. Conservative treatment may be successful in sprains, but surgical repair has been advocated when the ligament is completely torn. The authors performed a comparative study of the anatomical lesions of the metacarpophalangeal joint of the thumb with respect to degrees of instability. The study was conducted on fresh specimens and retrospectively in surgically treated patients. Instabilities greater than 30 degrees were found to correspond to complete rupture of the ulnar collateral ligament of the metacarpophalangeal joint of the thumb, and the stump of the ligament was found on the adductor aponeurosis in 5 out of 20 cases. In 2 out of 9 cases of avulsion-fractures, the fragments were rotated 90 degrees although on x-rays they appeared slightly displaced. It is concluded that surgical repair is the treatment of choice for instabilities greater than 30 degrees and for avulsion-fractures.