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The spectrum of effects leading to the bone loss observed around failing implants is explained by means of a wear-debris-activated, macrophagic osteolytic mechanism. This concept is presented as the universal failure mechanism for all arthroplasty components, irrespective of fixation mode. The early descriptions of this bone-destruction process can be traced back to various clinical reports in the early 1950s which described failure of polymeric hemiarthroplasty implants, such as nylon and polyethylene cup arthroplasties, and the early polymethyl methacrylate, short-stem, Judet implants. Thus, polymeric debris and macrophages appear to be particularly reactive agents in the bone lysis phenomenon seen around contemporary total hip designs, but any particulate material small enough to be phagocytosed may contribute to this mechanism (metallics or ceramics). In addition to wear at the articulating surfaces, micromotion at any interface also has the potential to produce wear particles, thereby adding to the osteolytic process. Thus, the three potential sources of wear debris in contemporary total joints are (1) metal/ultrahigh-molecular-weight polyethylene (UHMWPE) joint articulation, (2) implant/coating interfaces, and (3) implant/bone interfaces. Present and future designs of joint replacement components must emphasize material and design combinations that will reduce the incidence of debris formation. Such designs will extend the survival time of the implant and also preserve bone stock in the eventuality that revision becomes necessary.
particulates, implants, debris, osteolysis, bone lysis
Bioengineering Research Institute, Newbury Park, CA
Hip Research Center, Orthopedic Hospital, Los Angeles, CA
Biomaterials Bioreactivity Characterization Laboratory, Department of Pathology, University of California at Los Angeles, Los Angeles, CA