Polyethylene wear in metal-backed tibial components in unicompartmental knee prostheses

The utilization of unicompartmental knee arthroplasty (UKA) has increased worldwide and has become a favourable alternative to total knee arthroplasty (TKA) in patients with isolated single-compartment knee osteoarthritis. With the increase in UKA utilization, there has been an increase in the number of revisions. The two most common causes of revision are the progression of osteoarthritis in other compartments and aseptic loosening with polyethylene wear, with other common causes for revision including periprosthetic fracture, bearing dislocation, infection, instability and unexplained pain. This narrative review will outline how UKA implant design has evolved and specifically outlines important differences in wear biomechanics, survival and clinical outcomes between the most commonly employed implant designs: metal-backed (MB) versus all-polyethylene (AP) and fixed-bearing (FB) versus mobile-bearing (MoB) MB tibial components.