Influence of resting periods on polyethylene wear in a knee simulator study.

BACKGROUND Knee wear simulator studies are performed to evaluate the wear behavior of implants. These wear studies simulate in vivo situations as closely as possible. Simulation of the human gait cycle is often carried out continuously according to international standards. However, implants are not loaded continuously in vivo, so it might be advisable to implement resting periods in which no motion occurs. MATERIAL/METHODS In the present study the influence of resting periods on the wear behavior of a commercial implant was analyzed using a force-controlled AMTI knee simulator. RESULTS The wear rates were 2.27+/-0.23 mg/10(6) cycles for a simulation with resting periods and 2.85+/-0.27 mg/10(6) cycles for a reference simulation without resting periods. There was no significant difference (p=0.22) in wear behavior between these two tests. CONCLUSIONS The present study shows that continuous simulation without the implementation of resting periods is a valid approach for assessing the wear of knee implants.