Biomechanical study of tendon excursion of thumb muscles related to interphalangeal and metacarpophalangeal joint motion.

Abstract

A biomechanical study of tendon excursion versus interphalangeal and metacarpophalangeal (MCP) joint motion relationships on extrinsic and intrinsic thumb muscles has been carried out. Continuous recording of excursion related to joint motion was obtained using a rotary potentiometer and an electrogoniometer. Functional activities of individual muscles were defined based on the excursion data. Moment arms of tendons were also derived. Flexor pollices longus and extensor pollices longus (EPL) tendons have a constant and linear relationship with flexion of the MCP joint. Extensor pollices brevis and flexor pollices longus contribute minimally in abduction-adduction. Extensor pollices longus is a secondary adductor of the joint. Abductor pollices brevis and adductor pollices transverse head are important in dynamic stabilization of the MCP joint and to keep EPL tendon in proper position through the balance of dorsal aponeurosis. This information enables pre-operative planning for functional reconstruction of the thumb, such as in tendon transfers, opponensplasty. MCP joint collateral ligament reconstruction and post-operative management after flexor tendon repair.