Enhanced wear resistance of modified cross‐linked polyethylene by grafting with poly(2‐methacryloyloxyethyl phosphorylcholine)

Abstract

We developed a cross-linked polyethylene (CLPE) modified with a phospholipid polymer in order to address the serious problem of osteolysis caused by wear particles derived from the polyethylene components of artificial hip joints. Our goal of preventing aseptic loosening could be achieved by avoiding any formation of CLPE wear particles or suppressing the activation of cell systems by the wear particles. We investigated the surface and wear resistance properties of 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer grafted onto the surface of CLPE (CLPE-g-MPC). The relative density of MPC polymer chains was determined by the P-O group index. Generally, polymerization times correspond to the number of polymer chains in radical polymerization. After 3.0 x 10(6) cycles in a hip joint simulator test, the steady wear rates of the untreated CLPE and CLPE-g-MPC cups with a low P-O group index were as high as 4 mg/10(6) cycles; those of the CLPE-g-MPC cups with high P-O group indexes, that is, 0.46 and 0.48, markedly decreased to -1.12 and 0.16 mg/10(6) cycles, respectively. Therefore, the grafting of an MPC polymer with high density would be essential in order to maintain the long-term wear resistance of CLPE-g-MPC as an orthopedic bearing material.

Cell membrane-inspired phospholipid polymers for developing medical devices with excellent biointerfaces

“…The surface showed high lubricity, which was similar to fluidic friction. The wear of the poly(MPC)-grafted CLPE was significantly reduced compared with that of bare CLPE and of CLPE grafted with other hydrophilic polymers, as shown in figure 15 [150,151]. Furthermore, the PMPC-modified polyethylene particles did not stimulate osteoclast cells, whereas non-modified polyethylene particles generated from friction and wear of artificial joints did induce osteolysis in artificial hip joints [149].…”

Update on UHMWPE research From the bench to the bedside

“…Another nanoscale modification uses photo-induced polymerization of radicals to graft 2-methacryloyloxyethyl phosphorylcholine polymer onto the polyethylene surface (Moro et al 2006, Kyomoto et al 2007b. Innovations to potentially improve mechanical properties using composite materials have been reported, where multiwalled carbon nanotubes are added as a reinforcing component for different polymers and fibrous materials (Polizu et al 2006, Cao et al 2007).…”

Cartilage-mimicking, High-density Brush Structure Improves Wear Resistance of Crosslinked Polyethylene: A Pilot Study

“…Recently, we developed an artificial hip based on a new concept by using poly(2-methacryloyloxyethyl phosphorylcholine (PMPC) grafted onto the surface of CLPE (PMPC-grafted CLPE) [23][24][25][26][27][30][31][32]. This implant was designed to suppress wear and thus suppress bone resorption [23][24][25][26][27][30][31][32]. 2-Methacryloyloxyethyl phosphorylcholine (MPC), a methacrylate monomer, is a novel biomaterial that mimics the neutral phospholipids of cell membranes [11].…”