Comparison of Foot-Ankle Biomechanics During Treadmill Walking with Commercially Available and Corresponding Emulated Prosthetic Feet

Background            A robotic prosthetic foot emulator (PFE) programmed to emulate different prosthetic feet could allow individuals with lower limb loss to quickly ‘test-drive’ different prosthetic feet and provide input to prosthetic foot prescription. While a previous study validated the mechanical properties of the PFE against those of corresponding prosthetic feet, no studies have compared the foot-ankle biomechanics of prosthesis users walking with ‘actual’ and corresponding ‘emulated’ prosthetic feet. Methods            Ten unilateral transtibial prosthesis users walked on an instrumented treadmill with three actual and three corresponding emulated prosthetic feet in a randomized order, while masked to foot type. Kinetic and kinematic data collected during steady-state walking were used to calculate prosthesis ankle push-off power, push-off work, effective forefoot length, rollover radius, and step length/time asymmetry. Findings            Ankle push-off power and work were greater with the emulated versions of the two stiffer prosthetic feet compared with the corresponding actual feet. The stiffest emulated foot had a longer effective forefoot length than the corresponding actual foot. The least stiff emulated prosthetic foot had a shorter rollover radius than its actual version, while the stiffest emulated prosthetic foot had a longer rollover radius than its actual version. Despite these differences, nine of ten participants correctly identified all three emulated feet; all correctly identified at least one emulated foot. Interpretation            These findings suggest that while there are some differences in foot-ankle biomechanics, the PFE accurately simulates the spatiotemporal and perceived aspects of walking with corresponding actual feet.