Lower Residual Limb for Prosthetic Socket Design - Computational Biomechanics of the Musculoskeletal System - page 153

13 Lower Residual Limb for

Prosthetic Socket Design

Winson C.C. Lee and Ming Zhang

ContentS
Summary ........................................................................................................................................ 153
13.1 Introduction .......................................................................................................................... 153
13.2 Model Development .............................................................................................................. 154
13.2.1 Geometries ................................................................................................................ 154
13.2.2 Material Properties ................................................................................................... 155
13.2.3 Boundary Conditions and Pre-Stress Simulations ................................................... 156
13.2.4 Analysis of the Effects of Pre-Stress on Full Weight Bearing ................................. 157
13.2.5 Prediction of Interface Stress throughout a Gait Cycle ............................................ 157
13.3 Model Findings ..................................................................................................................... 157
13.3.1 Pre-Stress Effects on Full Weight Bearing ............................................................... 157
13.3.2 Interface Stress throughout a Gait Cycle .................................................................. 160
13.4 Applications .......................................................................................................................... 160
References ...................................................................................................................................... 162

Summary
Comfort is among the most important issues when fitting a prosthesis. However, high stress applied
to the residual limb, which is not particularly tolerant to loading, can cause discomfort, pain, and
tissue breakdown. In an attempt to improve prosthesis it, it is important to study the stress distri-
bution at the residual limb-prosthetic socket interface. Computational finite element (FE) model-
ing allows for efficient parametric analysis and is a useful tool for investigating the load transfer
mechanics at the limb-socket interface. Due to the complicated frictional and sliding actions at the
interface, however, simulation of the mechanical interaction between the limb and socket is chal-
lenging. In addition, a prosthetic socket is usually shape-rectified so as to redistribute the load to
load-tolerant regions of the residual limb. After donning the shape-rectified socket, some mechani-
cal stresses known as pre-stresses are produced. Many previous models have incorporated some
simplifying assumptions when simulating the friction-slip and pre-stresses. This chapter illustrates
a technique that simulates the contact at the limb-socket interface, considering both the friction/slip
and pre-stress conditions, by using an automated contact method.

13.1 IntroduCtIon
A lower-limb prosthesis can improve physical appearance and, more importantly, restore the lost
functions of individuals with lower-limb amputations. To be effective, however, it should not pro-
duce any discomfort or pain. Prosthetic socket design is the most important factor in determining
the comfort of using a prosthesis. To achieve a successful it, it is important to understand the
mechanical interaction between the prosthetic socket and the residual limb. FE modeling is a use-
ful tool to understand the load transfer mechanics at the limb-socket interface. FE analyses have

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