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Factors Influencing Initial Cup Stability in Total Hip Arthroplasty

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journal contribution
posted on 02.03.2015 by Farid Amirouche, G. Solitro, S. Broviak, M. Gonzalez, W. Goldstein, R. Barmada
Background: One of the main goals in total hip replacement is to preserve the integrity of the hip kinematics, by well positioning the cup and to make sure its initial stability is congruent and attained. Achieving the latter is not trivial. Methods: A finite element model of the cup-bone interface simulating a realistic insertion and analysis of different scenarios of cup penetration, insertion, under reaming and loading is investigated to determine certain measurable factors sensitivity to stress-strain outcome. The insertion force during hammering and its relation to the cup penetration during implantation is also investigated with the goal of determining the initial stability of the acetabular cup during total hip arthroplasty. The mathematical model was run in various configurations to simulate 1 and 2 mm of under-reaming at various imposed insertion distances to mimic hammering and insertion of cup insertion into the pelvis. Surface contact and micromotion at the cup-bone interface were evaluated operative loading conditions. Findings: The results suggest a direct correlation between under-reaming and insertion force used to insert the acetabular cup on the micromotion and fixation at the cup-bone interface. Interpretation: while increased under-reaming and insertion force result in an increase amount of stability at the interface, approximately the same percentage of surface contact and micromotion reduction can be achieved with less insertion force. We need to exercise caution to determine the optimal configuration which achieves a good conformity without approaching the yield strength for bone.

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Publisher Statement

This is the author’s version of a work that was accepted for publication in Clinical Biomechanics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Clinical Biomechanics,Dec.29(10) 2014 DOI: 10.1016/j.clinbiomech.2014.09.006

Publisher

Elsevier Inc.

issn

0268-0033

Issue date

29/12/2014

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