Santosh Zachariah, Ph.D.
Department of Bioengineering, Prosthetic Engineering Lab
"Shape, Interface Mechanics, and Things to come"


ABSTRACT

A lower-limb prosthesis (artificial leg) must satisfy three requirements:  It must look right;  It must restore, at least partially, the lost function of the foot, ankle, and (possibly) knee joint;  And it must transfer force from the skeleton to the ground, *without* causing pain or injury to the tissues.  It is this last requirement that interests us at the Prosthetic Engineering Laboratory, in the Dept. of Bioengineering.

At present, the soft tissues of the amputated limb are between a rock and a hard place.  On one side is the bone, to or from which force has to be transferred.  On the other side is the prosthetic socket, which must be durable enough to withstand the applied loads and provide stability.  External force from the base of the socket flows as interface stress between the socket and the skin, and then as internal stresses within the soft tissues to the bone.

The interface stresses - the ones that cause most pain and damage - can be visualized as pressure (a normal stress) and shear (a tangential stress governed by friction.  In my talk, I will discuss how we try and understand these stresses - by measurement and modeling.  I will elaborate on why we focus on shape as the one of the most significant parameters modulating interface stresses.  And finally, I will introduce the concept of a shape adaptable socket.