Biomechanics of walking with silicone prosthesis after midtarsal (Chopart) disarticulation

Currently accepted understanding is that silicone foot prostheses have little influence on biomechanics of walking; however clinical observations suggest several beneficial effects. The objective of this study was to characterize biomechanics of gait in a group of subjects with disarticulation through the talonavicular (T-N) and calcaneocuboid (C-C) (midtarsal) joints wearing two different prosthetic solutions: silicone prostheses and conventional prostheses.

Four subjects that underwent Chopart partial foot amputation were included in the study. Silicone prosthesis was custom manufactured for each individual subject. Instrumented gait analysis was performed in each subject in four experimental conditions: barefooted, barefooted and wearing silicon prosthesis, wearing footwear with conventional prosthesis and wearing footwear with silicon prosthesis. Comparisons and statistical analysis were made between both barefooted conditions and both foot-wearing conditions.

Our results show that silicone prosthesis without reinforced sole increases gait velocity, improves generation of ankle plantarflexion moment throughout the stance phase and enables greater power generation at push-off. The most important changes, however, occur in the frontal plane, where improved hip adduction angles and higher hip abduction moment in the stance enable more normal pelvic movement and consequently also less trunk inclination toward amputated side.

We conclude that silicone prostheses are not solely for cosmetic reasons but may be also biomechanically superior over other prosthetic solutions, especially for walking barefoot.