Dynamics of Below-Knee Child Amputee Gait: A Comparative Analysis of the Flex-Foot and SACH Foot
T. J. HART, M.S., K. SCHNEIDER, Dr. rer. nat.,Y. SETOGUCHI, M.D., R. F ZERNICKE, Ph.D. ANDW. L. OPPENHEIM, M.D.
The ability to run, jump, and play games is important for the general wellbeing of limb-deficient youngsters. In the past, prosthetic foot designs such as the SACH (Solid Ankle Cushioned Heel) were designed principally for walking and did not fulfill the special mobility and functional demands of children. With the advent of space-age materials that are light, strong and durable a new generation of prosthetic feet has evolved. The Flex-Foot" is one of those state-of-the-art prothestic feet that proportedly has a potential for energy storage to enhance propulsion of the artificial limb during gait. The hypothesis of the enhanced energy-return has yet to be investigated systematically.
The purpose of this project was to quantify the gait mechanics of unilateral below-knee BK) amputee children while they wore either the Flex-Foot" or the SACH foot during slow and fast walking. Ten BK child amputees were fit with a new SACH foot prosthesis, allowed to ambulate freely for two months, and their gait was subsequently tested. Each child was then given a FlexFoot" prosthesis, allowed two months to acclimate to the prosthesis, and retested. The movements of the children's normal and prosthetic limbs were recorded in three dimensions using a WATSMART motion analysis system, and the ground reaction forces were recorded from a force platform. Dynamic equations of motion quanified muscle torques and joint power.
The results demonstrated that during fast walking, the Flex-Foot" joint power profiles more-closely approximated those of the normal limb than did the SACH profiles. During early stance the Flex-Foot" deflected under the child's body weight and during push off a portion of this stored energy assisted propulsion. For an "active" child, the Flex-FootTM may approximate more closely the normal gait dynamics than does the SACH foot.
Funded by Shriner's Hospital for Crippled Children (15952).
Department of Kinesiology, UCLA, 2859 Slichter Hall, Los Angeles, CA 90024-1568