A proposal for the pre‐evaluation protocol of below‐knee socket design - integration pain tolerance with finite element analysis

Abstract

Abstract The design of a fitted socket is a fundamental critical issue in ameliorating the disability of an amputee. In this study, an evaluation protocol integrated finite element analysis with the pain‐pressure‐tolerance (PPT) of soft‐tissue, is proposed to provide a quantitative socket design guideline prior to the socket being fabricated. A subject using a Kondylen‐Bettung‐Münster socket was selected in this study. Two FE models (the original Kondylen‐Bettung‐Münster and a newly designed total‐surface bearing socket) were established based on computer tomography images. The surface‐ to‐surface contact elements were employed to simulate the contact and sliding behaviors at the stump‐socket interface. The PPT of the soft‐tissue was measured by a hand‐held indentor system. Comparing the simulated peak interface pressure with the PPT, both sockets demonstrated a safe margin (PPT / peak interface pressure) greater than two. These large safe margin values were consistent with the subjective assessment, as acceptable, of the amputee on both sockets. To conclude, using a nonlinear contact finite element simulation integrated with the PPT of each individual, it is possible to evaluate the socket fitness prior to the fabrication of the socket. Based on the results, for a fitted socket design the peak interface pressure under single leg standing should be much less than the PPT value. The acceptable range of safe margin value for a fitted socket should further be justified by more subjects.