Influence of prosthetic foot selection for load carriage on prosthetic limb mechanical work.

BACKGROUND

Prosthetic foot selection may influence gait biomechanics in individuals with transtibial amputation, particularly during load carriage. While prior work often emphasizes intact limb compensation, this study examined prosthetic limb mechanics to directly assess device-user interaction. We compared five commercially available feet: a clinically prescribed foot, a stiffer category of the same foot, the same foot with a heel-stiffening wedge, a dual-keel foot, and a powered ankle-foot, across five load conditions: unloaded, anterior, posterior, intact side, and prosthetic side.

METHODS

Twelve participants performed overground walking trials at self-selected speed with each foot-load combination. Net positive and negative joint work at the prosthetic limb ankle, knee, and hip was calculated over the gait cycle and specific gait subphases via inverse dynamics. Linear mixed-effects models evaluated foot effects within load conditions.

RESULTS

Ankle joint work differed significantly between feet within all load conditions. The powered ankle-foot generated the highest net positive ankle work in late stance, suggesting enhanced propulsion. The clinically prescribed and heel-wedge feet produced the highest negative ankle work in early stance, indicating increased energy absorption. The stiffer and dual-keel feet reduced both positive and negative ankle work. Knee and hip joint work did not differ significantly across feet within load conditions.

CONCLUSIONS

Prosthetic foot type primarily modulates prosthetic ankle mechanics without altering proximal joint work under moderate load carriage. The powered ankle-foot may benefit users seeking propulsion, while non-powered designs may support energy absorption and stability. Prosthetic prescription should align with user mobility goals and expected load demands.