Extended physiological proprioception is affected by transhumeral Socket-Suspended prosthesis use.

The objective of this study was to define targeted reaching performance without visual information for transhumeral (TH) prosthesis users, establishing baseline information about extended physiological proprioception (EPP) in this population. Subjects completed a seated proprioceptive targeting task under simultaneous motion capture, using their prosthesis and intact limb. Eight male subjects, median age of 58 years (range 29-77 years), were selected from an ongoing screening study to participate. Five subjects had a left-side TH amputation, and three a right-side TH amputation. Median time since amputation was 9 years (range 3-54 years). Four subjects used a body-powered prosthetic hook, three a myoelectric hand, and one a myoelectric hook. The outcome measures were precision and accuracy, motion of the targeting hand, and joint angular displacement. Subjects demonstrated better precision when targeting with their intact limb compared to targeting with their prosthesis, 1.9 cm2 (0.8-3.0) v. 7.1 cm2 (1.3-12.8), respectively, p = 0.008. Subjects achieved a more direct reach path ratio when targeting with the intact limb compared to with the prosthesis, 1.2 (1.1-1.3) v. 1.3 (1.3-1.4), respectively, p = 0.039 The acceleration, deceleration, and corrective phase durations were consistent between conditions. Trunk angular displacement increased in flexion, lateral flexion, and axial rotation while shoulder flexion decreased when subjects targeted with their prosthesis compared to the intact limb. The differences in targeting precision, reach patio ratio, and joint angular displacements while completing the targeting task indicate diminished EPP. These findings establish baseline information about EPP in TH prosthesis users for comparison as novel prosthesis suspension systems become more available to be tested.