The wear of ultra-high molecular weight polyethylene, the most commonly use
d bearing material in prosthetic joints, is often substantial, posing a sig
nificant clinical problem. For a long time, there has been a need for simpl
e but still realistic wear test devices for prosthetic joint materials. The
wear factors produced by earlier reciprocating and unidirectionally rotati
ng wear test devices for polyethylene are typically two orders of magnitude
too low, both in water and in serum lubrication. Wear is negligible even u
nder multidirectional motion in water. A twelve-station, circularly transla
ting pin-on-disc (CTPOD) device and a modification of the established biaxi
al rocking motion hip joint simulator were built. With these simple and ine
xpensive devices, and with the established three-axis hip joint simulator,
realistic wear simulation was achieved. This was due to serum lubrication a
nd to the fact that the direction of sliding constantly changed relative to
the polyethylene specimen. The type and magnitude of load was found to be
less important. The CTPOD tests showed that the subsurface brittle region,
which results from gamma irradiation sterilization of polyethylene in air,
has poor wear resistance. Phospholipid and say protein lubrication resulted
in unrealistic wear. The introduction of devices like CTPOD may boost wear
studies, rendering them feasible without heavy investment.