The Study of Compensatory Motions While Using a Transradial Prosthesis

Improvement of prostheses requires knowledge of how the body adapts. A transradial prosthesis without a dynamic wrist component may cause awkward compensatory motion leading to fatigue, injury or rejection of the prosthesis. This work analyzed the movements of shoulder, elbow and torso during four tasks: drinking from a cup, opening a door, lifting a box and turning a steering wheel. The main purpose of this study was to determine if using a basic transradial prosthesis that lacks motion of the forearm and wrist would cause significant compensatory motion of the shoulder, elbow and torso during the tasks. The second purpose of the study was to determine if the location of added mass would affect compensatory movements during these tasks. A group of able-bodied participants were asked to complete the tasks, without and with a brace, simulating a basic transradial prosthesis to determine if bracing is an appropriate way to study prosthetic use. Transradial prosthesis wearers also completed the tasks without and with added mass at the elbow or at the wrist to determine if distribution of mass has an effect on the motions. Using a motion capture system movements of the shoulder, elbow and torso were analyzed. For the bilateral tasks, the degree of asymmetry (DoA) was calculated for each subject. Statistical analysis was completed within subject comparing the mass interventions and between subjects comparing the control, braced and prosthesis wearing groups. While opening a door and lifting a box, prosthesis users compensated predominantly by bending the torso sideways toward affected side. During the steering wheel task, amputees used more elbow flexion to accommodate for the lack of forearm rotation. While drinking from a cup, compensation occurred by bending the cervical spine, although this was not measured. Adding mass increased the joint forces and moments during the box lift. This research can be used for transradial prosthesis design improvements as well as improving methods of prosthesis fitting and therapeutic training by providing quantitative data of compensatory motion. The data from this study is being used to develop a model for an upper limb prosthesis