Medio-lateral function in a computer-aided-design of a flexible foot prosthesis

The authors present a new concept in flexible keel design. The advantages of sagittal energy storage shortly after heel-strike and release at push-off of the prior energy storing feet are integrated with a medio-lateral control and propulsion functions. This is achieved by a totally asymmetrical shaped keel having three main curvatures. The heel has a complex shape consisting of a composite curvature in the sagittal and frontal planes. The mid-portion of the keel is arched and acts as a leaf-spring. The last curvature is located at the forefoot where the toe-end is internally rotated. A geometric model of the keel was developed to ensure that no shape interferences were occurring with a physical model of the entire foot. From the geometric model a finite element model was developed and validated. Preliminary results indicate that the heel deforms itself medially by about 1 mm and the fore-foot raises when a load at representing the heel-strike contact is applied. Maximum deflection occurs when the push-off load is applied