The influence of concentric and eccentric loading on the finger pulley system

I. Schoffl a, , K.Oppelt b, J.Jungert c, A.Schweizer d, T.Bayer e, W.Neuhuber a, V.Schoffl b,e

a Institute of Anatomy 1,Friedrich-Alexander University Erlangen-Nuremberg,FRG
b Department of Trauma Surgery,Friedrich-Alexander University Erlangen-Nuremberg,FRG
c Department of Pediatrics,Friedrich-Alexander University Erlangen-Nuremberg,FRG
d Department of Orthopaedics, Balgrist, University of Zurich,Switzerland
e Department of Orthopaedic and Trauma Surgery,Klinikum Bamberg,FRG

Journal of Biomechanics 42(2009)2124–2128

Abstract:
In this study we investigated the influence of the loading condition (concentric vs. eccentric loading) on the pulley system of the finger. For this purpose 39 cadaver finger (14hands,10donors) were fixed into
an isokinetic loading device. The forces in the flexor tendons and at the finger tip were recorded. In the concentric loading condition A2 and A4 ruptures as well as alternative events such as fracture of a phalanx or avulsion of the flexor tendons were almost equally distributed, whereas the A2 pulley rupture was the most common event (59%) in the eccentric loading condition and alternative events were rare (23.5%). The forces in the deep flexor tendon, the finger tip and in the pulleys were significantly lower in the eccentric loading condition. As the ruptures occurred at lower loads in the eccentric than in the concentric loading condition it can be concluded that friction maybe an advantage for climbers, supporting the holding force of their flexor muscles but may also increase the susceptibility to injury.