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.