Impact testing of the residual limb: System response to changes in prosthetic stiffness

Abstract

Currently, it is unknown whether changing prosthetic limb stiffness affects the total limb stiffness and influences the shock absorption of an individual with transtibial amputation. The hypotheses tested within this study are that a decrease in longitudinal prosthetic stiffness will produce (1) a reduced total limb stiffness; and (2) reduced magnitude of peak impact forces and increased time delay to peak force. Fourteen subjects with a transtibial amputation participated in this study. Prosthetic stiffness was modified by means of a shock-absorbing pylon (SAP) that provides reduced longitudinal stiffness through compression of a helical spring within the pylon. A sudden loading evaluation device (SLED) was built to examine changes in limb loading mechanics during a sudden impact event. No significant change was found in the peak force magnitude or timing of the peak force between prosthetic limb stiffness conditions. Total limb stiffness estimates ranged Institutional Review: This study was approved by the Northwestern University Institutional Review Board. Written informed consent was obtained from each subject prior to participation. Participant Follow-Up:The authors do not plan to inform participants of the publication of this study. However, participants have been encouraged to check our Web site for updated publications. Disclaimer:The opinions contained in this publication are those of the grantee and do not necessarily reflect those of the Department of Education. U.S. Department of Veterans Affairs VA Author ManuscriptVA Author Manuscript VA Author Manuscript from 14.9 -17.9 kN/m and was not significantly different between conditions. Thus, the prosthetic-side total limb stiffness was unaffected by changes in prosthetic limb stiffness. The insensitivity of the total limb stiffness to prosthetic stiffness may be explained by the mechanical characteristics (i.e., stiffness and damping) of the anatomical tissue within the residual limb.

A systematic review of shock-attenuating componentry for lower limb amputees

“…In total, the studies included 78 participants (mean = 8.67). Although the details of these studies were unclear in a number of cases, many were performed within a laboratory or rehabilitation facility, [48][49][50][51] with the assistance of a certified prosthetist to undertake the fitting and alignment of prostheses. [48][49][50][52][53][54][55] Despite observations of minor trends, the vast majority of studies were suggestive that SAPs show no strong effect for a difference in the ability to attenuate shock as compared to rigid pylons among transtibial amputees while undertaking different modes of activity, including walking, running and stepping down from an elevated platform.…”

“…Although the details of these studies were unclear in a number of cases, many were performed within a laboratory or rehabilitation facility, [48][49][50][51] with the assistance of a certified prosthetist to undertake the fitting and alignment of prostheses. [48][49][50][52][53][54][55] Despite observations of minor trends, the vast majority of studies were suggestive that SAPs show no strong effect for a difference in the ability to attenuate shock as compared to rigid pylons among transtibial amputees while undertaking different modes of activity, including walking, running and stepping down from an elevated platform. [47][48][49][50][53][54][55] Some studies did report isolated but significant differences in group variables, including a reduction in knee flexion upon initial contact when fitted with a SAP and while walking at a controlled speed, 48 as well as differences in select variables among individual participants.…”

“…[48][49][50][52][53][54][55] Despite observations of minor trends, the vast majority of studies were suggestive that SAPs show no strong effect for a difference in the ability to attenuate shock as compared to rigid pylons among transtibial amputees while undertaking different modes of activity, including walking, running and stepping down from an elevated platform. [47][48][49][50][53][54][55] Some studies did report isolated but significant differences in group variables, including a reduction in knee flexion upon initial contact when fitted with a SAP and while walking at a controlled speed, 48 as well as differences in select variables among individual participants. 51,55 These findings, however, were not consistent with the overall trend of the included studies.…”

“…Means of participant recruitment were also often left unreported, with the exception of one study which utilised a convenience sampling process. 49 Types of intervention. Four different models of SAP were examined throughout the nine studies: the Endolite Teletorsion Pylon, [49][50][51][52]55 Seattle Airstance, 47,54 Mercury Telescopic Torsion Pylon 48 as well as the Reflex VSP foot module with integrated SAP.…”

“…Although not always specified, there was a great variability in suspension systems, including suprapatella cuffs, neoprene sleeves and shuttle locks, 51,52,54 as well as prosthetic feet, ranging from SACH feet to energy storage and return (ESAR) feet. [48][49][50][51][52][53][54][55] There were six studies [48][49][50][53][54][55] which controlled for the prosthetic foot between participants and two which controlled for the footwear. 49,50…”