Development of a finger biomechanical model

Abstract

Forces in hand tendons due to various hand functions have been of great interest to surgeons and researchers. The knowledge on tendon forces could help surgeons to restore patient’s tendon during rehabilitation period. This leads to the development of this project which is to determine the tendon forces at the wrist due to various hand functions.

This study utilizes a biomechanical model of the index finger to replicate the middle, ring, little finger and thumb. The orthogonal reticular ligament (ORL) and the effect of tissue compression were identified as critical factor in the movement of fingers. The principle of non-optimizing technique was used with the aid of Matlab to estimate the tendon forces. A simulation programme was developed to allow the user to input anatomical parameters such as sex, age, weight and applied forces on the finger. The results are presented graphically for three case studies: external loading; pinch force; and power grip.

The previously developed model of the index finger was found to contain errors and the Matlab programme was evaluated and corrected. From the simulation results obtained in case study one, flexor digitorum profundus (FDP) and extrinsic digitorum communis (EDC) of the middle, ring and little finger have similar force profile with the index finger while flexor digitorum superficialis (FDS) exhibits zero force. The simulation for case study two also demonstrated corresponding force profiles for each finger. Lastly, the simulation for case study three suggested a significant increase in flexor and extensor forces above 42 mm and the associated handle sizes should be avoided.