The influence of implant design and limb alignment on in vivo wear rates of fixed‐bearing and rotating‐platform knee implant retrievals

Abstract

Analysis of polyethylene wear in knee implants is crucial for understanding the factors leading to revision in total knee arthroplasty. Importantly, current experimental and computational methods for predicting insert wear can only be validated against true in vivo measurements from retrievals. This study quantitatively investigated in vivo polyethylene wear rates in fixed‐bearing (n=21) and rotating‐platform (n=53) implant retrievals. 3D surface geometry of the retrievals was measured using a structured light scanner. Then, a reference surface that included the deformation, but not the wear that the retrievals had experienced in vivo, was constructed using a fully automatic surface reconstruction algorithm. Finally, wear volume was calculated from the deviation between the worn and reconstructed surfaces. The measurement and analysis techniques were validated and the algorithm was found to produce errors of only 0.2% relative to the component volumes. In addition to quantifying cohort‐level wear rates, the effect of mechanical axis limb alignment on mediolateral wear distribution was examined for a subset of the retrievals (n=14+26). Our results show that fixed‐bearing implants produce significantly (p=0.04) higher topside wear rates (24.6±10.1 mm3/year) than rotating‐platform implants (15.3±8.0 mm3/year). This effect was larger than that of limb alignment, which had a smaller and non‐significant influence on overall wear rates (+4.5±11.6 mm3/year, p=0.43). However, increased varus alignment was associated significantly with greater medial compartment wear in both the fixed‐bearing and rotating‐platform designs (+1.7±1.3 %/° and +1.8±1.6 %/°). Our findings emphasize the importance of implant design and limb alignment on wear outcomes, providing reference data for improving implant performance and longevity.This article is protected by copyright. All rights reserved.

Effect of novel polyethylene insert configurations on bone-implant micromotion and contact stresses in total ankle replacement prostheses: a finite element analysis

“…Ensuring the perfect combination of flexible layers and nonflexible layers, which poses a new challenge to the manufacture of improved inserts. Dreyer et al, 2023 indicated that the wear rate of fixed-insert was higher than rotating-platform insert, and the influence of insert structure on wear was greater than limb alignment. Favorable conformity can increase the contact area, reduce wear in the weight-bearing region.…”