Abstract
Introduction
Coronal plane alignment is one of the contributing factors to polyethylene wear in total knee arthroplasty (TKA). The goal of this study was to evaluate the wear and damage patterns of retrieved tibial polyethylene inserts in relationship to the overall mechanical alignment and to the position of the tibial component.
Materials and methods
Based on full-length radiographs, ninety-five polyethylene inserts retrieved from primary TKA's with a minimum time in-vivo of five years were analysed for wear and damage. Four alignment groups were compared: valgus, neutral, mild varus and moderate varus. Varus and valgus positioning of the tibial component was analysed for damage score for the neutral and varus aligned groups.
Results
A progression in the angle of wear was observed with progressively mechanical varus alignment. The valgus group was thinner laterally and the neutral, mild varus, and moderate varus groups were progressively thinner medially. The lateral compartment had greater damage in the mild and moderate varus group compared to the valgus group. There was a progression of increased lateral damage with increasingly varus HKA. No difference in damage was seen between groups for tibial component positioning.
Conclusion
While greater wear of the lateral compartment in valgus aligned implants and progressively greater medial compartment wear in varus aligned implants was observed, greater damage scores were observed in the lateral compartment in the mild and moderate varus aligned TKAs compared to the valgus group. This observation is unique and might by explained by lateral condylar lift-off inducing impact and shear loading in the varus group.
