LAUSR

BACKGROUND The aim of this study was to evaluate and to compare the cross-sectional area (CSA) of flexor digitorum tendons and the thickness of A1 pulleys between contralateral normal digits and trigger digits at positions of finger flexion and extension using a noninvasive ultrasound system. METHODS Seventeen affected fingers of 17 patients (6 men and 11 women) with trigger digits in one hand, and 17 contralateral normal digits without trigger finger symptoms were examined. The sonographic appearances of flexor digitorum tendons and A1 pulleys were observed at two positions of metacarpophalangeal (MCP) joint flexion: 0° and 60°. RESULTS The findings of this study indicate that CSA of flexor digitorum tendons and A1 pulley thickness were significantly larger in both positions of 0° and 60° flexion of MCP joint compared to contralateral normal digits (p < 0.01). In trigger digits, there was a significantly thicker A1 pulley at 60° flexion of MCP joint than that at 0° flexion (p < 0.01), but no significant change on CSA of flexor tendons. CONCLUSION Our results suggested that trigger digits lead to the thicker A1 pulley and larger CSA of the flexor digitorum tendons. The mismatch in volume change between CSA of flexor digitorum tendons and A1 pulley thickness during MCP flexion may lead to the trigger phenomenon.