A new measuring technique for determining the forces acting on the pulley system of the finger

Abstract

In this study, a new force measuring technique was employed for determining the forces acting on the pulley system of the finger. An index and a ring finger of two separate cadavers (76 and 75 years of age) were placed in an isokinetic loading device in which the fingertip was fixed and loading was applied by pulling the two flexor tendons separately with increasing strength, while recording the forces occurring at the fingertip and in each of the two tendons. At the same time, we recorded the pressure underneath the pulleys using special sensors developed for this purpose. The fingers were loaded until a pulley rupture or an alternative event (fracture, tendon rupture) occurred. The whole loading process was recorded by digital camera. An A2 pulley rupture occurred in the index finger, while the ring finger fractured at the middle phalanx. The forces measured underneath the pulleys were smaller than the ones calculated by a mathematical model described in the literature. However, the forces measured and calculated showed the same characteristics during the loading process. More data is needed for validating the forces measured with these new pressure sensors. However, this pressure measuring technique represents a first approach for analyzing high forces in very confined spaces.

Keywords:

• pulley
• biomechanics
• pliance sensor
• finger
• model
• climbing

Notes

Institute of Anatomy 1, Friedrich‐Alexander University, Erlangen‐Nürnberg, Krankenhausstrasse 9, Erlangen 91054, Germany. E‐mail: [email protected]‐erlangen.de