Is the wear factor in total joint replacements dependent on the nominal contact stress in ultra-high molecular weight polyethylene contacts?

Abstract

The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Is the wear factor in total joint replacements dependent on the nominal contact stress in ultra-high molecular weight polyethylene contacts?K Vassiliou* and A Unsworth Centre for Biomedical Engineering, University of Durham, UK Abstract: The exact dependence of wear factor on contact stress, load and apparent contact area is much disputed in the literature. This study attempts to solve this dispute. Pin-on-plate studies of ultra high molecular weight polyethylene against stainless steel were conducted under di erent combinations of load (33-250 N ), nominal stress (0.56-12.73 MPa) and face diameter, as well as two tests where both stress and load were kept constant, while the diameter was changed. For these tests the centre of the pin face was bored out to create four di erent average pin diameters with similar face areas. Diameter and load were found to have no signi cant e ect on the wear factor, while the wear factor decreased with increasing contact stress according to the relation K=2×10Õ 6sÕ 0.84.Keywords: ultra high molecular weight polyethylene wear, contact stress, load, pin-on-plate set-up NOTATION ness term has been incorporated into the wear factor. Archard assumed Hertzian contact theory for a at K wear factor (mm3/N m) non-deformable surface in contact with a nominally at deformable surface with spherical asperities evenly L load (N ) R a surface roughness parameter (ím) distributed in depth. UHMWPE ultra high molecular weight polyethylene V wear volume (mm3) 1.2 E ect of stress and load on wear factor x sliding distance (m) Although the Lancaster equation suggests that the wear volume is dependent only on the particular combination of materials, the load and the distance slid, the situation 1 INTRODUCTION may not be quite so simple. The literature is divided as to the exact e ect of load and stress on the wear rate of 1.1 Wear ultra high molecular weight polyethylene ( UHMWPE ). The simple model of wear, according to the Lancaster This is made more di cult by the di erent operating equation [1] states that V =KLx, where V is the wear conditions in each study, including di erences in apparvolume (mm3), L is the load (N ), x is the sliding disatus and lubricants. tance (m) and K is the wear factor (mm3/N m). This Barbour et al. [4], using pin-on-plate apparatus, indicates that the wear volume is dependent on the load indicated that the wear factor decreases with increasing and the sliding distance for any given con guration. The nominal contact stress. Wang et al. [5 ] s...

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“…To our knowledge, the impact of the patient height on wear rate is rarely mentioned in the literature, despite the fact that height directly influences the body weight which, in turn, leads to greater forces applied to the hip [31]. Archard's equation predicts that the volume of wear per unit of sliding distance will increase in direct proportion to the load [32,33], (i.e. with the cube of patient height).…”

Modifying and Expanding the Simulation of Wear in the Spherical Joint With a Polymeric Component of the Total Hip Prosthesis

“…But, for example, in [10], the wear factor was proposed in a variable form as an empirical relationship with normal contact pressure:…”

“…In [5], the polymer wear in terms of cumulative linear and volume wear when the wear factor is chosen to be a function of contact pressure was first evaluated. Herewith, various known wear factor dependencies on the contact pressure were investigated as contained in [9,10,11]. Since the contact pressure in the above formulae is a power function with a negative degree, these relations give a decrease in wear factor depending on the increase of a contact pressure, which means a reduction of wear values that are not uniquely consistent with the physics of the process.…”

Conventional and Highly Crosslinked Polyethylene in Total Knee Arthroplasty—A Design-Independent Wear Investigation

“…The amplitude of the change inside the molecular structure of the UHMWPE is nonetheless of a lower extent, which could in theory lead to a decrease of wear, analogous to what was shown for femoral lift-off-which is an extrapolation of vertical force alteration-inside TKA systems [25]. Additionally, any change of stress, an increase as well as decrease, can lead to enhanced production of wear [26].…”