PRECOATING OF ULTRAHIGH MOLECULAR-WEIGHT POLYETHYLENE WITH POLYMETHYLMETHACRYLATE - INTERFACIAL STRENGTH

Fixation of polymeric implants, especially an ultrahigh molecular weig ht polyethylene (UHMWPE) acetabular cup, to a host bone site has been a challenge since its first conception from the Charnley low friction total hip arthroplasty, Destabilization of the acetabular cup, similar to the well-documented cases of femoral stems, is caused mainly by as eptic loosening; the mobile loosened particles further contribute to t he progression of aseptic loosening, Although the obvious fixation pro blems lie in the bone-bone cement interface, little work has been done to reduce the loosening by improving the acetabular components as a w hole in cemented procedures, Most of the grooved outer surface, extern al fixation devices, and metal backings have been introduced to avoid problematic fixation of the cup to bone cement; nevertheless, the desi gns themselves to some degree became the source of the loosening probl ems. One possible way to improve the adhesion of acrylic bone cement t o the UHMWPE acetabular cup is precoating the surface with polymethylm ethacrylate (PMMA), This study successfully precoated the UHMWPE surfa ce with PMMA, showing good chemical and mechanical stability, and sugg ests the optimal conditions of variables involved in the newly develop ed precoating process, The highest interfacial tensile strength was 11 .51 +/- 0.65 MPa, which is stronger than those of UHMWPE and metal in metal-backed cups (6.3 MPa) and bone-bone cement (8.5 MPa), Further ch emical analysis and mechanical testing are in progress, yet the presen t result of the mechanical tensile strength test showed that the preco ating process for the UHMWPE surface could be a viable means toward st able fixation of the polymeric implants by using PMMA bone cement. (C) 1998 John Wiley & Sons, Inc.