Analysis of Energy Storage and Return foot stiffness by Coupling Musculoskeletal and Finite Element Simulation

Abstract

Transtibial amputees currently have numerous prostheses in the market which are aimed at improving the control, cosmetics and comfort. Each of the three categories of prosthetic feet namely; conventional, energy storage and return, and bionic feet have different characteristics. Current studies reveal that energy storage and return feet offer better performance as compared with conventional prostheses. In this study, evolution of the prosthesis and the significance of mimicking human ankle-foot biomechanics is highlighted. Lower limb amputations occur due to Peripheral Vascular Disease, Diabetes, War and accidents .It is associated with mortality, morbidity, and disability. Transtibial amputees exhibit loss of plantar flexor musculature [1, 7] resulting in greater intact leg stance times [12]and asymmetrical gait comorbidity in their residual and intact legs [2, 7].Below-knee amputees lose the functional use of the ankle muscles, which are critical during walking to provide body support, forward propulsion, leg-swing initiation and mediolateral balance [3, 7]. During early and pre-swing, amputees exhibit increased hamstring and rectus femoris activity on residual leg [12].Prosthetic foot do not allow sufficient dorsiflexion even on levelterrain and possess inertia asymmetry. Further improvements ought to be incorporated to adjust the degree of dorsiflexion [4], absorb shock on impact [10], and improve inertia gait. Unilateral, transtibial amputees’ clinical efficacy is dependent on appropriate prosthetic foot stiffness [6].Proper prosthetic foot selection with appropriate design characteristics is critical for successful amputee rehabilitation. Use of laminated composites in the manufacture of prostheses is vital due to their high stiffness and low density.Many researchers have reported that unilateral below-knee amputees (BKA) walk asymmetrically and differently from able-bodied people [1-10, 17].Researchers have given varied reasons. It is generally believed that socket fit, prostheticalignment, and prosthetic components (including prosthetic parts' weight and design) can all influence the gait of amputees [2-7,12,18-19].Others argue that due to loss of plantar flexor muscles, there would be greater intact leg stance times and asymmetrical gait comorbidity in their residual and intact legs. Moreover, degenerative changes in the lumbar spine and knees would occur due to the asymmetrical walking that overloads the musculoskeletal system [7, 12].This research will come up with an analysis of the energy storage and return foot coupling musculoskeletal and finite element analysis with aim of improving amputee gait. The analysis of the foot is performed using the boundary conditions of ISO-10328 and ISO-22675.The prosthetic foot serves to substitute the loss of tendons and muscles of the intact foot due to amputation. Further series of computer simulation of ESAR foot is performed using Altair Hyper works 14.0 to investigate the effect of stiffness on the tibia section of foot, muscleactivity, residual and intact ground reaction forces with aim of coming up with an optimal design.The results of this study would add to the core knowledge regarding prosthetic feet features and their effects on gait, making them directly relevant to prosthesis design and prescription.