Interaction of Flexor Tendons and Pulleys in Sport Climbing (P6)

Abstract

The most common injury in sport climbing is the disruption of a flexor tendon pulley of the middle or ring finger, mostly the A2 pulley, during the so called crimp grip position, where the proximal interphalangeal joint is flexed about 90 and the distal interphalangeal joint is hyperextended. This study aimed to investigate the frictional properties of the interaction of the flexor tendons and pulleys in vitro. Eight fresh frozen cadaver fingers were used. After dissection of the flexor tendons the fingers were fixated at the proximal phalanx and mounted on a isokinetic movement device (centre of rotation through the proximal interphalangeal joint, kinetic device/resistance at the finger tip, flexor tendons loaded with 20-100N) simulating the crimp grip position. Maximum flexion torque was at 85° of flexion. Strength applied at the flexor tendons was 3 times higher as at the tip of the finger. The highest amount of eccentric-concentric strength deficit of 12% (SD 0.8) was also at 85° of flexion which indicates that there is a substantial amount of friction. Strength deficit showed a rise of up to 28% when the tension of the superficial flexor tendon was increased. This indicates a synergism of both flexor tendons (superficial surrounds profundus tendon) during eccentric work. There was no correlation of friction and speed of motion up to 210°/s when smooth tendon gliding became an interrupted staggering movement. There was a proportional linear increase of friction with increasing load to flexor tendons from 20–100N. An interesting “memory effect” of the tendon pulley interaction was found. Static flexion torque was influenced by the preceding movement and was substantially higher (11%, SD 2.2) after an eccentric movement compared to a concentric movement. The difference did almost not level out even after several minutes which indicates an elastic tendon internal energy saving mechanism or static friction.