For the young child, stable and independent gait represents a significant milestone in motor skill development. The ability to locomote freely requires careful coordination of many body segments. For the child with amputation, the development of walking is more challenging, as the child must adopt movement strategies to compensate for the lost limb and prosthesis. With the development of "energy-storing" prostheses, the conventional functional requirements of prosthetics are being reassessed, but few studies have examined the benefits of this new generation of prostheses, and no investigation to date has addressed their benefits for children. Thus, the current study described the kinematic and kinetic profiles of below-knee amputee children as they walked at normal and fast speeds wearing either a conventional prosthetic foot (SACH foot) or a new energy-storing foot (Flex-Foot).

Kinematic and kinetic performance profiles were analyzed for eight below-knee (BK) amputee children. Motion data were synchronized with ground reaction forces to quantify the strategies used by the BK children to compensate for the partial loss of the lower extremity and to differentiate between the SACH and the Flex-Foot. Kinematic and kinetic parameters measured during the stance phase of gait included joint ranges of motion, peak ground reaction forces and center of pressure, joint muscle moments, and joint power and energy.

The results indicated that the Flex-Foot absorbed and generated significantly more energy than the SACH foot. The Flex-Foot had a greater potential for reducing the energy cost of walking for the BK child by providing a significant push-off force near toe-off and thus, compensated for decreased hip flexor moment at toe-off. Significant asymmetries were noted in the force, moment and power profiles of the prosthetic limb as compared to the natural limb. Although the natural limb primarily was responsible for maintaining stable gait, the capabilities of the Flex-Foot decreased the demands on the natural limb. Thus, the Flex-Foot may provide benefits to the BK child at a variety of locomotor speeds.