Simulation of Physiological Loading in Total Hip Replacements

[+] Author and Article Information
A. Ramos

Departamento de Engenharia Mecânica Universidade de Aveiro, 3810-193 Aveiro, Portugal

F. Fonseca

Faculdade de Ciências da Saúde Universidade da Beira Interior, 6201-001 Covilhã, Portugal

J. A. Simões1

Departamento de Engenharia Mecânica Universidade de Aveiro, 3810-193 Aveiro, Portugalsimoes@mec.ua.pt


Corresponding author.

J Biomech Eng 128(4), 579-587 (Jan 02, 2006) (9 pages) doi:10.1115/1.2205864 History: Received May 05, 2005; Revised January 02, 2006

The determination of biomechanical force systems of implanted femurs to obtain adequate strain measurements has been neglected in many published studies. Due to geometric alterations induced by surgery and those inherent to the design of the prosthesis, the loading system changes because the lever arms are modified. This paper discusses the determination of adequate loading of the implanted femur based on the intact femur-loading configuration. Four reconstructions with Lubinus SPII, Charnley Roundback, Müller Straight and Stanmore prostheses were used in the study. Pseudophysiologic and nonphysiologic implanted system forces were generated and assessed with finite element analysis. Using an equilibrium system of forces composed by the Fx (medially direction) component of the hip contact force and the bending moments Mx (median plane) and My (coronal plane) allowed adequate, pseudo-physiological loading of the implanted femur. We suggest that at least the bending moment at the coronal plane must be restored in the implanted femur-loading configuration.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

CAD models of Charnley Roundback, Lubinus SPII, Stanmore and Müller Straight cemented prostheses

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Figure 2

CAD model of the intact femur; moments and forces transmitted (Mz-horizontal plane; My-coronal plane, and Mx-median plane) due to loading; x (medially), y (anteriorly), and z (proximally)

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Figure 3

Geometric and dimensional variables of the implanted femur

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Figure 4

Strain distribution at the medial aspect of the implanted femur: (a) intact femur load system; (b) implanted femur load (Case_4) system

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Figure 5

Maximum strain error measurement (intact femur strain minus implanted femur strain for load Case_4)



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