DYNAMICS OF BELOW-KNEE CHILD AMPUTEE GAIT - SACH FOOT VERSUS FLEX FOOT

Gait kinematics and dynamics during stance of unilateral, below-knee c hild amputees were analyzed for self-selected, comfortable (0.9 ms-1) and fast (1.3 m s-1) speeds with the SACH foot and the energy-storing Flex-foot prostheses. The three-dimensional movements of the lower lim bs were recorded and synchronized with ground reaction forces for 12 s ubjects (7 girls and 5 boys, ages 6-16 yr). Each lower limb was modele d as a set of interconnected rigid links (thigh, leg, and foot) with f rictionless joints (hip, knee, and ankle) to calculate moment and join t power profiles. Marked asymmetries were noted in ground reaction for ce, joint moment, and power profiles for the prosthetic versus the nat ural limb, but with the Flex foot the asymmetries were less pronounced than with the SACH foot. For the amputee wearing the Flex foot, great er moments and power were generated by the natural limb at the comfort able pace as compared to the SACH foot, but during fast walking, the S ACH foot required greater output from the natural limb. With both pros theses, for the prosthetic limb the amputees used similar force, momen t, and power patterns, but with significantly different amplitudes. At both speeds of walking, the Flex foot returned significantly more ene rgy (66 % at comfortable and 70 % at fast walking) than the SACH foot (21 % at comfortable and 19 % at fast walking). Thus, the Flex foot ha d a greater potential for reducing the energy cost of walking at comfo rtable and fast speeds for the below-knee child amputee.