[Skier's thumb. Sonographic clarification of retracted ruptures].

Rupture of the ulnar collateral ligament (LCU) is the result of traumatic abduction of the metacarpophalangeal joint of the thumb ("skier's thumb"). If the ligament becomes retracted superficially to the adductor aponeurosis, surgical treatment is advocated, non-displaced tears can be treated by immobilization. Differentiation between displaced and non-displaced tears by radiography is not possible. We examined 45 patients to assess whether sonography was of help in this respect. The retracted LCU appeared as a hypoechogenic, mostly round structure medial to the metacarpal head. Using this criterion, 86% of retracted ruptures could be diagnosed correctly. Although intact LCU and nondisplaced tear cannot be differentiated consistently by sonography, high sensitivity in diagnosis of retracted ruptures seems promising, as it enables specific planning of therapeutic decisions.