Feedforward control strategies of subjects with transradial amputation in

The rate of upp er-limb ampu tations is in creasing, and the rej ection rate of prosth etic devices remains high. People with upper-limb amputation do not fully incorporate prosthetic devices into t heir acti vities of d aily li ving. By understanding the reaching beha viors of prosthesis us ers, researchers can alter pros thetic devices and develop training protocols to improve the acceptan ce of prosthetic limbs . By observing the reaching characteristics of the nondisabled arms of people with amputation, we can begin to understand how the brain alters its motor commands after amputation. We asked subjects to perform rapid reach ing movements to two targets with and without visual feedback. Subjects performed the tasks with both their prosthetic and nondisabled arms. We calculated endpoint error, trajectory error, and variability and compared them with those of nondisabled control subjects. We found no significant abnormalities in the p rosthetic l imb. However, we found an abnormal leftward trajectory error (in right arms) in the nondisabled arm of prosthetic users in the vision condition. In th e no-vision cond ition, th e nond isabled arm displ ayed abnormal leftward endpoint errors and abnormally higher endpoint variabi lity. In t he vi sion condition, p eak vel ocity w as lower and movement duration was longer in both arms of subjects with amputation. These abnormalities may reflect the cortical reorganization associated with limb loss.