Comparing the symmetry of walking in transtibial amputees: biomechanical differences of prosthetic heel lifts

Abstract

Prosthetic devices provide an avenue to accommodate transtibial amputees and mechanically restore some of their walking functionality. The loss of a lower limb results in significant mobility changes for these individuals’ prosthetic gait patterns, which are commonly characterized by asymmetry and changes in force distribution, leading to an increased risk of secondary musculoskeletal injuries. Shock absorbing shoe materials seem to provide a potential solution for improving functional outcomes in lower limb amputees to restore symmetrical walking patterns. Based on this evidence, this study examined the effect of two different types of shoe materials on restoring some of the symmetrical characteristics of a normal walking pattern for transtibial amputees. The type of shoe materials included thermoplastic polyurethane (TPU) and a conventional foam heel lift commonly used with prosthetic devices, to observe changes in symmetry of force, energy, and power. The researcher performed static compression tests to observe changes in the properties of the material and identify its energy absorption capabilities. Dynamic impact tests were also performed to examine the effect of heel lift types (TPU heel lift, conventional heel lift, and no heel lift) on measures of force and energy absorption when combined with a passive prosthetic foot and flat-soled shoe during a simulated heel-strike. Finally, the researcher conducted dynamic human participant testing to examine the effect of the shoe material in the symmetry of walking between the amputated and non-amputated limbs of transtibial amputees during the braking and propulsion phases of gait for measures of ground reaction force (GRF), energy, and power. The results of this study revealed that the TPU heel lift, when compared to the conventional heel lift, had a significantly higher capacity for energy absorption during both static compression testing and dynamic impact testing, and generated significantly less force than the conventional heel lift during dynamic testing. This study also found that the TPU had a significantly increased symmetry ratio for measures of energy during propulsion when compared a no heel condition. No other significant differences were found for the TPU heel lift. The findings of this study may have implications for the design of footwear and insoles that are used with lower limb prosthetic devices and suggest avenues for future research.