A Computational Tool to Enhance Clinical Selection of Prosthetic Liners for People with Lower Limb Amputation

Abstract

People with transtibial amputation experience a loss of mobility that results from the removal of propulsive and load bearing anatomy. The more delicate soft tissues of the residual limb are coupled to a hard prosthetic socket, and this results in regular instances of skin breakdown. Soft and flexible prosthetic liners worn between the limb and socket are a common method of reducing these interface stresses. Advances in materials and manufacturing technics over the previous two decades has led to the development of over 70 liner products on the clinical market. The aims of this dissertation were to (1) design a set of benchtop protocols to accurately measure clinical relevant liner characteristics, (2) use the design characteristics to measure a selection of liner products and evaluate assumptions on their use in clinical practice, (3) develop a finite element model (FEM) that simulates a modern prosthetic design, and (4) use the developed FEM to assess the effect of liner product and socket size. Six protocols were used to assess 24 liner products available on the clinical market. Results showed that liner products demonstrated significant variability, even when products were formulated from a common base polymer (e.g., polyurethane or silicone). This emphasized the need for a tool to facilitate liner selection in a clinical setting. The developed FEM produced results that were reasonable with the context of literature reported interface mechanics, and showed focused stresses in locations that corresponded with incidences of skin breakdown experienced by participants in their as-prescribed prosthesis. Further evaluations showed that a change in liner product could result in 15-25% change in interface stresses, while a 1–2% change in limb volume could correspond to a 15–30% increase in interface stresses.