Design and Qualitative Testing of a Prosthetic Foot With Rotational Ankle and Metatarsal Joints to Mimic Physiological Roll-Over Shape

Abstract

This paper presents the analysis, design, and preliminary testing of a prototype prosthetic foot for use in India. A concept consisting of a rigid structure with rotational joints at the ankle and metatarsal with rotational stiffnesses provided by springs is discussed. Because literature suggests that prosthetic feet that exhibit roll-over shapes similar to that of physiological feet allow more symmetric gait, the joint stiffnesses were optimized to obtain the best fit between the roll-over shape of the prototype and of a physiological foot. Using a set of published gait data for a 56.7 kg subject, the optimal stiffness values for roll-over shape that also permit the motion required for natural gait were found to be 9.3 N·m/deg at the ankle and 2.0 N·m/deg at the metatarsal. The resulting roll-over shape has an R2 value of 0.81 when compared with the physiological roll-over shape. The prototype was built and tested in Jaipur, India. Preliminary qualitative feedback from testing was positive enough to warrant further development of this design concept.