Wrist and tendon dynamics as contributory risk factors in work-related musculoskeletal disorders

Many studies have shown that repetitive wrist motion is a major risk factor for work-related musculoskeletal disorders (WMSDs). Specific contributory factors include wrist and tendon dynamics. The authors present recent methodological advances, epidemiological studies, and biomechanical models estimating the effects of wrist dynamics on internal tendon force as a theoretical basis for the risk of incurring a WMSD. These biomechanical models utilize either the reduction method or the optimization method to solve the indeterminate problem resulting from too many internal variables. Generally, the optimization methods show the best agreement with direct in vivo tendon force studies. For the models of pinch grips, the average ratio of tendon forces to external forces ranges from 1.8 to 3.5, while for direct tendon measurements, the ratio ranges from 1.73 to 7.92. Similarly, high contributions of flexor tendons for pinches and grasps are found in both the models and direct tendon measurements. These high tendon forces combined with wrist dynamics may be a significant factor in the development of WMSDs.