The problem of surface damage in polyethylene total knee components.

Observations of surface damage on retrieved total knee polyethylene components have been combined with experimental and analytical studies of the contact problem to identify important clinical and design factors. The amount and severity of damage occurring on the articulating surfaces of knee components increases significantly with patient weight and with the length of time the component is implanted. The design variables that affect the amount of damage are component thickness, the conformity of the articulating surfaces, and the type of polyethylene material used. Surface damage will be more severe in thin (less than 4-6 mm) components and in components with relatively flat tibial articulating surfaces. Surface damage is also expected to be more extreme for carbon-reinforced polyethylene components than for components made from plain polyethylene.