Greater external negative mechanical work is accompanied by a greater metabolic cost of walking for socket-suspended versus bone-anchored prosthesis users with transfemoral limb loss.

BACKGROUND: Bone-anchored prostheses may address the high metabolic cost of walking in transfemoral (i.e., above-knee) amputees if they mitigate the mechanical energy dissipated due to socket use, reflecting a lower metabolic cost of walking than socket-suspended prosthesis users. Therefore, we compared external mechanical work between socket-suspended and bone-anchored transfemoral prosthesis users during walking and identified if these differences are accompanied by those in their metabolic costs of walking. We hypothesized that socket users would perform more net and negative external mechanical work in their prosthetic limb over the gait cycle and exhibit a higher metabolic cost of walking than bone-anchored prosthesis users.

METHODS: High-functioning (Medicare K-level ≥ 3, no dysvascular limb loss) transfemoral amputees with a socket-suspended or bone-anchored prosthesis were recruited (N = 12 per group). Participants walked at 1.0 m/s on a treadmill as pulmonary gases were measured for metabolic cost estimates and overground as ground reaction forces were measured to calculate net and negative external mechanical work across the gait cycle. Metabolic cost and prosthetic-limb external mechanical work outcomes were compared between groups using independent samples t-tests (α < 0.05) corrected for multiple comparisons.

FINDINGS: Net mechanical work done by the prosthetic limb was not significantly different between groups (p = 0.93, g = 0.64). However, socket users showed greater external negative mechanical work (p = 0.005, g = 1.17), which was accompanied by a 10.13 % greater metabolic cost of walking than bone-anchored prosthesis users (p = 0.03, g = 0.54).

INTERPRETATION: Bone-anchored prostheses may address the high metabolic costs of transfemoral amputee walking by mitigating socket-related energy loss.