| The rate of upper-extremity amputations is increasing, and the rejection rate of prosthetic devices remains high. Amputees have difficulty incorporating prosthetic devices into their daily activities due to limited functionality, difficulty during usage, and limited sensory feedback. By understanding the patterns of motor control of prosthesis users, prosthetic devices can be altered and training protocols can be developed to improve performance and increase the usage of prosthetic limbs. Three studies were performed to characterize and evaluate the reaching behavior of prosthesis users during common tasks. First, compensatory trunk and arm movements were characterized during functional activity of daily living tasks. Second, the accuracy of goal-directed reaching was measured during planar ballistic movements with and without the presence of visual feedback. Thirdly, motor control associated with grasping was analyzed as prosthesis users were required to grasp and lift objects of unknown weight.;Compensatory movements were observed in the form of truncal flexion and excessive shoulder and elbow path distance. No significant abnormalities were observed during planar, goal-directed reaching when performed with the prosthetic limb. However, abnormal trajectory error was observed during reaching of the intact arm of prosthesis users. Excessive grip force was observed in new prosthesis users during grip and lift tasks. However, the formulation of an internal model of grasping with a prosthesis may be possible with an appropriate level of training, which would decrease the amount of unnecessary grip force. Upper extremity prosthesis users demonstrate abnormal characteristics of movement in various forms, including the trunk, shoulder, elbow, and hand, but future research in prosthesis design and rehabilitative training may improve overall motor control and increase prosthesis usage. |
