Study on wear reduction mechanism of artificial joints grafted with hydrophilic polymer membranes

The effective life of artificial joints is approximately 15 years and it is necessary to extend this effective life. Previously, the use of graft-polymerized 2-methacryloyloxyethyl phosphorylcholine (MPC) was proposed for this purpose. However, the mechanism underlying the wear reduction in ultra-high molecular weight polythene (UHMWPE) by hydrophilic polymers such as MPC polymers remains unexplained. Therefore, this study investigates the characteristics of the MPC polymer membrane grafted onto the surface of a UHMWPE plate. The investigation clearly revealed that the MPC polymer membrane has a finely porous inner structure with a diameter of approximately 100 nm, and hence the membrane has a high water-retention capacity. Furthermore, a 2-axis pin-on-plate sliding test of a UHMWPE pin sample with an MPC polymer grafted on its surface revealed that the water-retention capacity of the porous MPC membrane plays an important role in wear reduction.