Effect of lubricant on the wear of prosthetic joint materials

The wear of ultra-high molecular weight polyethylene (UHMWPE) in prosthetic hip and knee joints is a significant clinical problem. The wear particles cause inflammatory tissue reactions which may lead to osteolysis and loosening of the implant fixation. The effect of lubricant on the wear of polyethylene was studied with a reciprocating pin-on-flat (RPF) apparatus, uniaxial (HUT-2) and three-axis (HUT-3) hip joint simulators, circularly translating pin-on-disk (CTPOD) device, biaxial rocking motion (BRM-1 and BRM-2) hip wear simulators, and a three-axis ball-on-flat (BOF) knee wear simulator. The aim was to produce wear similar to that known to occur clinically. To accomplish this, the basic criteria for the lubricant were: 1) no polyethylene transfer layer should form on the metal counterface, 2) the bearing surface of the polyethylene should become burnished, 3) the wear particle size should be of the order of 1 μm, and 4) the wear factor should be of the order of 1 x 10-6 mm3/Nm. The lubricants studied were human prosthetic joint fluid, bovine and calf serum, bovine albumin and gamma-globulin, soybean lecithin, dipalmitoylphosphatidylcholine (DPPC), soy protein, and distilled water. The counterfaces of polyethylene were CoCr, stainless steel, alumina, and diamondlike carbon (DLC). All the criteria were met by bovine and calf serum, albumin and gamma-globulin. Hence, albumin and gamma-globulin proved to be the crucial fractions of serum and synovial fluid with respect to producing clinically relevant wear of polyethylene. In conclusion, realistic wear was produced when the direction of sliding constantly changed relative to the polyethylene specimen, and a protein-based lubricant was used.reviewe