Sonographic diagnosis of acute injuries of the ulnar collateral ligament of the metacarpophalangeal joint of the thumb

Purpose. To evaluate the significance of the ultrasonographic appearance of the aponeurosis for deciding the best treatment for ulnar collateral ligament (UCL) injuries of the thumb metacarpophalangeal joint. Methods. Fourteen patients (11 men, 3 women; mean age, 41 years; range, 15–66 years) who had an acute UCL tear were included. All patients were examined by ultrasonography (US) with a 7.5‐MHz transducer and subsequently underwent surgery. The ultrasonographic findings were compared to the intraoperative findings. Results. UCL injuries were classified into two types by US according to the appearance of aponeurosis and its spatial relationship with the UCL: the intra‐aponeurosis type (5 patients) and the extra‐aponeurosis type (9 patients). In the 5 patients with intra‐aponeurosis, ultrasonographic findings were well consistent with intraoperative findings. In contrast, extra‐aponeurosis cases contained two different pathologies: of the 9 patients, 7 had so‐called ‘Stener lesions’, one showed folding of a ruptured capsule, and one showed a ruptured aponeurosis. Conclusions. Because US is highly reliable in differentiating intra‐aponeurosis from extra‐aponeurosis types of injuries, the aponeurosis is a more reliable reference than Stener lesion for treatment decision by US. © 2006 Wiley Periodicals, Inc. J Clin Ultrasound, 2007.