Precoating of ultrahigh molecular weight polyethylene with polymethylmethacrylate: Interfacial strength

Abstract

Fixation of polymeric implants, especially an ultrahigh molecular weight 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 aseptic loosening; the mobile loosened particles further contribute to the progression of aseptic loosening. Although the obvious fixation problems lie in the bone-bone cement interface, little work has been done to reduce the loosening by improving the acetabular components as a whole in cemented procedures. Most of the grooved outer surface, external fixation devices, and metal backings have been introduced to avoid problematic fixation of the cup to bone cement; nevertheless, the designs themselves to some degree became the source of the loosening problems. One possible way to improve the adhesion of acrylic bone cement to the UHMWPE acetabular cup is precoating the surface with polymethylmethacrylate (PMMA). This study successfully precoated the UHMWPE surface with PMMA, showing good chemical and mechanical stability, and suggests the optimal conditions of variables involved in the newly developed 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 chemical analysis and mechanical testing are in progress, yet the present result of the mechanical tensile strength test showed that the precoating process for the UHMWPE surface could be a viable means toward stable fixation of the polymeric implants by using PMMA bone cement.

Chemical surface treatment of ultrahigh molecular weight polyethylene for improved adhesion to methacrylate resins

“…Recently, improved adhesion, as measured by lap shear testing, and improved mechanical properties were obtained for acrylic bone cement bonded to UHMWPE by precoating the surface of the latter with polymethylmethacrylate (PMMA) 11. This was achieved by diffusing MMA monomer into the UHMWPE with xylene as the cotransporting agent.…”

“…Surface modification was achieved by (1) diffusion of reactive molecules (adhesion promoters) near the surface of UHMWPE after swelling of UHMWPE; (2) deposition of a PE‐silane; or (3) deposition of SiO 2 from alsoxysilane/O 2 plasmas, followed by silanization with a reactive methacrylate. The adhesion promoters included MMA, PMMA, camphorquinone (CQ), and functional silanes; the first three molecules were previously used 11–13. The effect of the surface treatments on the interfacial shear strength was measured using a microbond shear strength test.…”

Stress–strain behavior of low‐density polyethylene/poly(methyl methacrylate) blends with modulated interfaces with a hydrogenated polybutadiene‐block‐poly(methyl methacrylate) diblock copolymer

“…Although selected for this investigation for a model blend, LDPE and PMMA are mass homopolymers used in a very large number of applications of low added value. However, their biocompatible nature is progressively enabling their employment in products of high added value in medical applications 11–13. This blend can be considered a polymer–polymer composite in analogy to filled polymer composites.…”

Investigation of interfacial strength and its structure on the development of a new design of UHMWPE acetabular component

“…Chemical adhesion between PMMA (bone cement) and polyethylene has been made possible in this laboratory by swelling a bulk, solid UHMWPE at high temperature with xylene, a solvent, and then treating it with a PMMA/MMA solution 26, 27. This technique, however, was abandoned because of the uncertainty of completely removing the xylene component from the UHMWPE matrix.…”