Characterization of Prosthetic Liner Products for People with Transtibial Amputation

Introduction Typical practitioners choose from among only two to three products when selecting liners for their patients. A lack of comparable objective information about similarities and differences among elastomeric liner products may be part of the reason. Methods Commonly used, commercially available polyurethane, silicone, and thermoplastic elastomer (TPE) liners were tested for their compressive, shear, tensile, and volumetric elasticities as well as their coefficients of friction (CoFs) and thermal conductivities. Results Polyurethane and silicone liners tended to be stiffer in compression and shear than TPE liners. Fabric backings contributed primarily to increased tensile elasticity (and thus reduced pistoning). Polyurethane liners demonstrated relatively low CoFs, whereas silicone and TPE liners had higher CoFs and wider ranges. All materials tested were essentially incompressible. Thermal conductivities of all materials were comparable and similar to that of leather. Conclusions Polyurethane liners are softer and less sticky than 16 years ago, and TPE liners have higher tensile stiffness than previously. A stiff fabric backing can increase tensile stiffness by more than 200%. Compressive stiffness may be used to characterize a liner’s ability to flow. Elastomeric liners move heat almost exclusively via conduction.