[1] and
metal-on-polymer [2]. In the latter case the polymeric acetabular cup was initially made from
polytetrafluoroethylene (ptfe/teflon), a bearing material with the lowest known coefficient of friction, but
it soon emerged that its wear resistance was inadequate and so an alternative polymer, ultra high
molecular weight polyethylene (UHMWPE) was adopted. The Charnley total hip replacement dominated
the next half century or so and is still the first choice for many surgeons. In due course interest arose in
alternative material combinations including;