Proteins bound to polyethylene components in patients who have aseptic loosening after total joint arthroplasty - A preliminary report

Background: Immunological responses to proteins that adhere to ultra-high m olecular weight polyethylene have not, to our knowledge, been examined prev iously in patients who have aseptic loosening. In the current study, polyet hylene components from forty-nine failed prostheses recovered during revisi on procedures were examined for the presence of antibodies that were bound to the polyethylene surface or that were reactive,vith other proteins that were bound to the polyethylene surface. Methods: The polyethylene components consisted of thirty acetabular cups re covered during revision total hip arthroplasties and nineteen tibial compon ents recovered during revision total knee arthroplasties, After extensive w ashing, bound proteins were extracted from the polyethylene components with use of 0.1-molar glycine-hydrogen chloride solution followed by four-molar guanidine hydrochloride solution. Results: Sufficient protein for analysis was recovered from forty-two polye thylene components. Polyacrylamide gel electrophoresis demonstrated a minim um of one and a maximum of twelve protein bands,,vith molecular weights ran ging from thirteen to 231 kilodaltons, Immunoblotting revealed the presence of type-I collagen in most (thirty-four) of the forty-two explants, wherea s aggrecan proteoglycans were detected in eight samples. Immunoglobulin als o was detected in most (thirty-three) extracts, whereas type-II collagen wa s consistently absent, The presence of autologous antibodies directed again st polyethylene-bound proteins in sera drawn at the time of the revision wa s investigated. Antibodies that were reactive against the ultra-high molecu lar weight polyethylene-bound proteins were detected in twenty-six of the f orty-two patients with use of the Western blot technique. The number of rea ctive bands ranged from one to six, and the strongest binding was directed against a 103-kilodalton protein. Assays for specificity revealed that thes e sera autologous antibodies were reactive against the type-I collagen that was present in the explant solutions. Conclusions: We hypothesize that immunoglobulin complexed with polyethylene may fix complement and that the complement cascade may in turn attract inf lammatory cells to the polyethylene surface, Our data support the hypothesi s that an immunological response to antigens bound to the polyethylene surf ace may contribute to aseptic loosening. Clinical Relevance: Despite improvements in materials and designs of prosth eses, aseptic loosening is the most common complication of total joint repl acement, frequently leading to revision operations. We examined the immunol ogical response to proteins that bind to ultra-high molecular weight polyet hylene in patients who had aseptic loosening and discovered a high prevalen ce of antibodies to polyethylene-bound proteins. This immunological respons e may contribute to an inflammatory reaction in the periprosthetic tissue, ultimately leading to increased bone resorption around the prosthesis.