A Dynamic Biomechanical Model of the Wrist Joint

This paper describes a biomechanical model of the wrist joint that incorporates the dynamic component of angular acceleration. Repetition, which has been found to be a risk factor for cumulative trauma disorders (CTDs), is essentially cyclic angular acceleration and velocity. The objective of the dynamic model presented here, which is based on Armstrong's and Chaffin's (1979) static model, is to explain how the component of angular acceleration could increase a worker's risk of developing CTDs. When the wrist is accelerated in the flexion/extension plane, the resultant reaction force on the tendons and median nerve from the carpal bones and flexor retinaculum increases. This increase in reaction force is due solely to the acceleration of the wrist without any external grasp or pinch force. External grasp or pinch forces would increase the resultant reaction force even more.