Contact pressure dependence of wear rates of ultra high molecular weight polyethylene.

Wear rates of orthopaedic polyethylene in 37 degrees C water are not very contact stress dependent below 1000 psi (6.9 MPa) but above that level they accelerate substantially. The pressure dependence overall follows an exponential function. Creep in the contact pressure range of 3--17 MPa and above is a much larger factor than wear in indentation effects. For accurate measurement of wear rates by depth measurements it is necessary to permit creep to proceed under static load until it ceases before beginning the wear test.