Range of Motion of Upper Limb Joint Angles During Two Tasks for Transradial Prosthetic Design

During wartime, the numbers of amputees will likely increase adding to the need for progress in upper limb prosthetic design. Improvement of prostheses often requires knowledge of how the body adapts. Added weight and fatigue are complaints of upper limb prostheses users. Current improvements in the design of a transradial prosthesis include advanced technology in control systems and electronics that improve its functions. However, these improvements often require excess mass distally along the prosthesis. A transradial prosthesis without a dynamic wrist component may cause awkward compensatory motion in the shoulder and elbow. This work analyzes the ranges of joint movement of shoulder and elbow during two tasks: drinking from a cup and lifting a box. The main purpose of this study was to determine if simulating a basic transradial prosthesis by limiting motion of the forearm and wrist using a brace, would cause significant changes in the compensatory motion of the shoulder and elbow during the tasks. The second purpose of the study was to determine if the location of added mass of 96 g (mass of an electrical wrist rotator) would affect shoulder and elbow angles during these same tasks. A group of able-bodied participants were asked to complete the tasks during the following conditions: (1) no intervention (2) while wearing a brace that restricted forearm and wrist motion of their dominant arm (right) (3) wearing the same brace with a 96 g mass added near the elbow, (4) with the same brace and a 96 g mass added near the wrist. Subject movements were captured using a motion capture system and ranges of movement of shoulder and elbow, as well as degree of asymmetry (DoA) during the box lift were calculated for each subject. Three trials were collected for each test condition and were averaged as a representative for each subject. Statistical analysis of the results concluded that during drinking elbow flexion was significantly different in case 1 from the other 3 levels. Statistical analysis of lifting found significant differences in the dominant (right) shoulder and elbow flexion between all 4 levels, while their relative degree of symmetry was found to be statistically different between level 1 and 3–4. The study concludes that bracing limits forearm and wrist affects shoulder and elbow flexion and their relative DoA. The position of a 96g mass did not cause any statistical differences in the movements observed or in their DoA. Further testing will examine the transradial amputee population as well as the effects of position of added mass on joint torques during common tasks.