Prosthetic foot roll-over shapes with implications for alignment of trans-tibial prostheses

Roll-over shape is introduced as a significant characteristic of prosthetic feet. The roll-over shapes of the Flexwalk, Quantum, SACH, and SAFE prosth etic feet were determined using three methods; two involving quasi-static l oading and one dynamic loading. The results show that foot roll-over shape properties obtained by quasi-static and by dynamic methods are similar. Relationships between foot roll-over shape and the alignment of trans-tibia l prostheses are introduced that suggest ways to align trans-tibial prosthe ses without walking trials and iterations. The relationships may explain wh at prosthetists attempt to accomplish when they dynamically align a trans-t ibial limb. They also explain why prosthetic feet with different mechanical properties usually necessitate different alignments, and may explain why a number of gait studies of trans-tibial amputees do not show major gait dif ferences when walking is executed on various kinds of prosthetic feet.