Mobile-bearing total knee arthroplasty: design factors in minimizing wear

Premature polyethylene wear is a major cause of total knee arthroplasty (TKA) failure. It has been attributed to numerous factors including poor surgical technique, reduced polyethylene thickness, poor locking mechanisms of modular fixed bearing tibial components, gamma irradiation sterilization techniques in the presence of oxygen, and low conformity implant designs. The incidence of implantation of TKA into younger patients who have increased activity requirements and longevity expectations is increasing. This requires continued analysis of design features lessening polyethylene wear. The purpose of this manuscript is to review clinical and basic scientific studies of factors influencing polyethylene wear, focusing on the potential benefits of mobile bearing TKA which potentially reduce long-term polyethylene wear by providing increased implant conformity and reduced polyethylene contact stresses. In vivo kinematic studies have shown self-alignment of the polyethylene bearing with the femoral component typically occurs in rotating platform TKA designs which should hypothetically lessen polyethylene surface stresses, minimize stabilizing post impingement, and increase the potential for enhanced polyethylene longevity.