In this study the tribological analysis of Al 2 O 3 nanocomposites/Al 2 O 3 pair; proposed as a candidate material to fabricate hip prostheses was carried out. Nanopowders of Al 2 O 3 (AKP 50, 300 nm), TiO 2 (PS-25, 50 nm) and Co metallic powder (Nilaco, 28 nm) were mixed and hot pressed. Wear test was carried out in a pin-on-plate tribometer, with a frequency of 1 Hz, a load of 49 N, for 4h; the counterface used was Al 2 O 3 . Mechanical properties as Vickers hardness, fracture toughness and Young’s modulus were estimated using the indentation method. Distilled water and fetal bovine serum solution (FBSS) were used as environment. It was found that the specific wear rate of Al 2 O 3 nanocomposites was about 10 −8 mm 3 /N*m and the coefficients of friction were around 0.3–0.5 for FBSS. Worn surfaces were observed using SEM.

The long term stabilization and durability of cemented total hip replacement (THR) depends on not only the bulk properties of the components but also the interfaces through which they interact. The stem-cement interface has been consistently considered as a weak link in the stem-cement-bone system, being a transitional zone between two materials with significantly different mechanical properties. Previous research concerning this interface has been limited to investigation of interfacial shear strength through in vitro test and finite element analysis (FEA). Until now, a deep insight into the contact characteristics at this interface, especially the interaction between femoral stems with various surface finishes and bone cement, has not been established. In addition, it is still an area of debate whether a permanent fixation can be achieved by utilizing a matt femoral stem, and furthermore it is another matter of concern that a matt femoral stem would cause much more damage to the cement mantle, resulting in an acceleration of aseptic loosening of the femoral stem. This present study investigated the surface topography of stainless steel rods and Simplex P bone cement obtained from a series of pull out tests in order to gain a better understanding of the interaction at the stem-cement interface.

In this study, a new developed tribological multi-function simulator system, SHU-MFS is firstly introduced. By changing of the holder, a hip joint simulator and a POD tester can be generated in the new system. The simulator is designed not only for wear tests of the total hip prostheses, but also applicable in common tribological study. As to the module of hip joint simulator, this design can be described as having the basic motion components in human hip joints. A frequency control system is developed to offer a wide range of rotation frequency so as to provide proper experiments towards different groups. In the POD part, eight precision-made pins are generated and an advanced computer system is built up to measure the friction coefficient of the test samples.

Polyethylene (PE) debris has been examined in total hip replacements from clinical retrievals and laboratory simulator studies, but little is known about PE debris from total knee replacements. In this study we investigated the effects of crosslinking PE and the counterface material. Mildly and highly crosslinked PE were studied in combination with CoCr and Zirconia femoral components. Wear was determined by gravimetric measurements and the wear debris was isolated and morphologically characterized. Although the zirconia counterface with 7 Mrad PE did not exhibit measurable wear, wear debris was found. This indicated that wear occurred below the limits of the gravimetric approach. This study showed that the amount of crosslinking of PE and the counterface material were important factors in the wear of PE in a knee simulator model.

This paper describes an experimental method, Bio-Ferrography, to separate ultra high molecular weight polyethylene (UHMWPE) wear debris, generated in hip simulators, from bovine serum lubricating fluid. A total of 54 experiments were performed in which an enzyme digestion “cocktail” was developed and used to clean the bovine serum samples of extraneous sugars, proteins and lipids that interfere with the UHMWPE particle separation. Erbium chloride was used to marginally magnetize particles in the fluid prior to passing through the ferrographic device. The particles were captured and separated from the fluid by traversing the treated serum across a magnetic gap of a bio-ferrograph. Morphology of the captured and separated wear debris was compared with particles from samples of fluid filtered through a paper sieve arrangement with pores of 0.05 micrometers in diameter. The UHMWPE wear debris collected using the described experimental method, were found to be between 0.1 and 20 micrometers in diameter with spherical and pill-shaped particles. The filtered UHMWPE particles were also in the same size range as the debris separated using bio-ferrography, 0.1 to 20 micrometers. To show that the experimental method captured UHMWPE particles, the spectra of the chemical composition of UHMWPE from an acetabular cup insert of a hip implant and of UHMWPE particles separated using Bio-Ferrography were compared and found to be the same. To further demonstrate that polyethylene could be captured and separated through the experimental method, manufactured polyethylene microspheres in the diameter range of 3 to 45 micrometers, were captured and separated using the bio-ferrographic process.