Polyethylene Damage in Total Knees and Use of Highly Crosslinked Polyethylene

Tibial inserts and patellar components used in total knee arthroplasty (TKA) are made of ultra-high molecular weight polyethylene. (In the present article, “UHMWPE” and “polyethylene” terminology will be used interchangeably to refer to the same polymer, i.e., ultra-high molecular weight polyethylene.) The mechanisms of damage at the tibiofemoral and patellofemoral articulations consist of delamination, adhesive wear, and abrasive wear of the polyethylene component. These damage mechanisms contribute to the formation of a visible scar on the articular surfaces of the tibial insert and the patellar component. Creep and plastic deformation, both of which induce permanent deformation, also contribute to the scar on the articular surfaces and on the backside of modular polyethylene components. Creep accumulates for approximately the first two years of in vivo use and then reaches a steady state. Plastic deformation occurs rapidly due to the yielding of the polyethylene surface when the joint is loaded.