Analysis of the zigzag movement of the human finger under influence of the extensor digitorum tendon and the deep flexor tendon

Abstract

For the unresisted zigzag movement of the finger (defined as metacarpophalangeal extension and interphalangeal flexion) effected by the deep flexor and the extensor digitorum tendons, the tendinous system of the finger must meet certain requirements. This movement has been theoretically analysed according to two methods. The first method is based on relations between tendon displacements and joint rotations and leads to conditions for the derivatives of tendon lengths with respect to joint angles, which derivatives can be approximated by the distances from tendons to joint axes. The second method is based on relations between tendon forces and moments about joint axes and leads to conditions for the moment arms of the tendon forces at the joints, which moment arms can be approximated by the distances from the tendons to the joint axes. The two methods and more in particular their zigzag conditions are compared with each other. © 1976.