An Attempt to Improve Stance Mechanics of Trans-Tibial Amputee Gait by the Design of a Modular Ankle Joint Prosthetic

摘要

A-priori research show that trans-tibial (TT) amputees display poor gait parameters when walking with passive mechanical ankle-foot prosthetics(AFP's). This has large implications for the amputee populations in the developing world, who have limited access to advanced prosthetic technologies and instead rely on baseline AFP's. Analysis of such baseline AFP's in literature indicates that the predominant issue with these devices are their inability to adequately replicate the mechanics of a normal ankle during the stance phase of a walking gait cycle. This has shown to be a contributory cause of increased energy expenditure, as well as secondary complications such as osteoarthritis and joint deterioration. This paper presents the design and analysis of a modular low-cost ankle-joint prosthetic (AJP) that serves as an attachment to existing prosthetic feet, with the intention to improve the ankle mechanics thereof. The AJP is modelled to reproduce ankle joint mechanisms, specifically controlled relative angular flexion in the sagittal plane, using only simple mechanical elements (i.e. compression springs instead of electronics). Initial results were positive, indicating that the AJP improves the stance phase mechanics of the baseline AFP in a simulated TT amputee gait cycle. During forefoot dorsiflexion rollover, an 80%-132% (p < 0.001) increase in joint angle and a 42-56% decrease in ankle stiffness (p < 0.001 for all but one participant) is observed. Following heelstrike a 22%-77% (p < 0.001) increase in joint angle is observed. However equipment and methodology errors left the moment response of this phase unverifiable. The overall conclusion of this paper is that the introduction of the AJP to baseline AFP's supplies evidence of improved rollover shapes, easier phase transitions, and the facilitation of footflat during mid-stance.