Date of Award

Summer 1999

Document Type

Thesis

Degree Name

Master of Science in Mechanical Engineering - (M.S.)

Department

Mechanical Engineering

First Advisor

Taiming Chu

Second Advisor

Micheal W. Dudasik

Third Advisor

J. Russell Parsons

Abstract

A Finite Element Analysis was conducted to determine the effect of a plug on the performance of the critical section of a femoral implant coupled with a trochanter cable grip system. The critical section was defined near the proximal end of the stem where a hole was designed for the purpose of attaching the cable grip system. Two models were generated for the analysis. One consisted of the critical section with the grip cables and a plug filled in the hole and the other was without the plug. The models were based on design specifications provided by Howmedica Incorporated. Two types of simulations were performed on each model. The static simulation represented the instant the hip is subjected to ftill "heel strike" loading conditions during a normal walking cycle. The quasi-dynamic simulations represented two critical subphases of stance ("heel strike" and "foot flat") where the maximum loads were exerted on the implant. A normal walking speed of 4 km/h was used in the analysis. The cables around the hole were pre-tensioned. Both static and quasi-dynarnic results showed that the von Mises stress concentrations in the plugged model were lower than those in the non-plugged model. That is, a plug added to the hole of a femoral implant adjoined with a cable grip system reduced the critical stress around the hole. In addition, stress distributions within the implant were also altered due to the plug: it shifted the stress concentration away from the hole. Thus, these led to an enhancement in the performance of the implant.

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