Comparison of wear in a total knee replacement under different kinematic conditions

A six station ProSim (Manchester, UK) knee simulator was used to assess the wear of six PFC (DePuy) fixed bearing total knee replacements under two di fferent kinematic conditions defined as low and high kinematic inputs. The high kinematics displacement and rotation inputs were based on the kinemati cs of the natural knee with ISO standards used for the axial load and flexi on. Low kinematics were defined as approximately half the magnitude. The si x specimens were run for three million cycles under low kinematics and thre e million cycles under high kinematics. The mean wear rate found during the low kinematics phase was 7.7 +/- 2mm(3) per million cycles. This then incr eased significantly to an average wear rate of 41 +/- 14mm(3) during the hi gh kinematics input phase. The wear areas were characterized by a predomina nt damage mode of burnishing with some abrasive wear occurring during the h igh kinematics phase. This study supports the findings that introduction of cross-shearing of the polyethylene by introducing both rotational and ante rior/posterior displacement increases the wear rate. This has implications for younger patients with higher levels of activity that need knee replacem ents. (C) 2001 Kluwer Academic Publishers.