Characterization of Compensatory Trunk Movements During Prosthetic Upper Limb Reaching Tasks

Metzger AJ, Dromerick AW, Holley RJ, Lum PS. Characterization of compensatory trunk movements during prosthetic upper limb reaching tasks.ObjectiveTo characterize the compensatory movements of the trunk during functional reaching tasks performed by upper limb prosthesis users.DesignSurvey.SettingClinical laboratory at a national rehabilitation hospital.ParticipantsTranshumeral and transradial prosthesis users (n=10) and uninjured control subjects (n=10).InterventionsNot applicable.Main Outcome MeasuresThree-dimensional motion analysis data were collected during simulated reaching tasks, such as donning a cap, placing a nut, and sorting clothes. The metrics were range of motion of the trunk in the 3 anatomical directions and elbow and shoulder path distance.ResultsProsthesis users had significantly larger truncal movements than controls during all 3 reaching tasks in all 3 directions (P≤.03). Shoulder path distance in persons with amputation was larger than in controls in all 3 tasks (P<.01). Elbow path distance in persons with amputation was larger than in controls in the nut and clothes tasks (P≤.02). The subgroup of transradial prosthesis users displayed these abnormal movements despite the presence of an intact elbow.ConclusionsThe altered physiologic structure of the arm caused the individuals to develop a different motor control strategy than an intact arm. Functional limitations, such as the loss of distal degrees of freedom, required persons with amputation to use trunk displacement in place of arm/hand movement. These compensatory movements during reaching tasks may be a cause of prosthesis rejection and, in some cases, may be resolved with proper rehabilitative training. Analysis of compensatory trunk movements may also provide a useful endpoint for evaluating new prosthesis designs.