Development of Standardized Material Testing Protocols for Prosthetic Liners

Abstract

A set of protocols was created to characterize prosthetic liners across six clinically relevant material properties. Properties included compressive elasticity, shear elasticity, tensile elasticity, volumetric elasticity, coefficient of friction (CoF), and thermal conductivity. Eighteen prosthetic liners representing the diverse range of commercial products were evaluated to create test procedures that maximized repeatability, minimized error, and provided clinically meaningful results. Shear and tensile elasticity test designs were augmented with finite element analysis (FEA) to optimize specimen geometries. Results showed that because of the wide range of available liner products, the compressive elasticity and tensile elasticity tests required two test maxima; samples were tested until they met either a strain-based or a stress-based maximum, whichever was reached first. The shear and tensile elasticity tests required that no cyclic conditioning be conducted because of limited endurance of the mounting adhesive with some liner materials. The coefficient of friction test was based on dynamic coefficient of friction, as it proved to be a more reliable measurement than static coefficient of friction. The volumetric elasticity test required that air be released beneath samples in the test chamber before testing. The thermal conductivity test best reflected the clinical environment when thermal grease was omitted and when liner samples were placed under pressure consistent with load bearing conditions. The developed procedures provide a standardized approach for evaluating liner products in the prosthetics industry. Test results can be used to improve clinical selection of liners for individual patients and guide development of new liner products.

Synthesis and characterization of a silver nanoparticle-containing polymer composite with antimicrobial abilities for application in prosthetic and orthotic devices

“…The mechanical results presented in this study may not generate any inconvenience, as the values obtained were within the acceptable ranges of hardness (0 -20 on the Shore A scale) [66], density (1.0 -2.5 g/cm 3 ) [67], deformation by compression (8 -59%) [68], ultimate tensile, and rupture strength (0.030 -0.248 MPa) [69] and modulus of elasticity (0.124 -3.45 MPa) [70], for lower limb orthotic and prosthetic devices.…”

Using mechanical testing to assess texturing of prosthetic sockets to improve suspension in the transverse plane and reduce rotation

“…Despite pre-compression of the socket and mock residual limb, additional settling of the mock residual limb inside the socket occurred during the first trial, hence only five trials of data from each socket were included in the final analysis. We avoided testing the same liner and the same mock residual limb more than once per day in order to avoid any unwanted motion that may occur due to flow characteristics of the elastomeric materials used in the mock residual limb and liner [36,37].…”

Developing an Analogue Residual Limb for Comparative DVC Analysis of Transtibial Prosthetic Socket Designs

“…The tests were performed on an Instron 5569 mechanical test machine (Instron Corp, Norwood, MA, USA) with a 2kN load cell, in ramped displacement-controlled compression up to 60% strain at 5%/sec, between flat plates lubricated with bicycle oil to allow transverse expansion. The compressive force was used to calculate engineering-and estimated true stress, assuming incompressibility [36], and plotted against strain calculated from the loading plate displacement, which was corrected for machine compliance. These data were used to estimate linear tangent moduli.…”