One hundred and twenty-nine Charnley acetabular components were acquired at the time of revision surgery and a tribological investigation undertaken. The relative occurrence of pitting in the unworn and worn regions of the sockets suggest that most of the cement ingress occurs during the early part of the service life. The penetration depth of the explanted sockets was determined using the shadowgraph technique. Observation of the profiles in the wear planes suggest that, in general, the creep component was not a significant proportion of the overall change in the inner bore of the socket. Using weighted ordinary least squares regression, in which the intercept was not assumed to be zero, mean penetration and wear volume rates of 0.20 (SE = 0.02) mm/year and 55 (SE = 5) mm³/year, respectively, were recorded and are in agreement with other retrieval studies. In neither case was the intercept found to be significantly different from zero. A mean clinical wear factor, k_clinical, equal to 2.1 (SE = 0.2) × 10-⁶ mm³/N m was calculated which is considerably larger than that found in laboratory experiments which purport to reflect in vivo conditions. In this analysis, a significant positive intercept was observed [96 (SE = 36) mm³] and may be evidence of the small initial penetration due to creep reported in simulator experiments. A strong positive association between k_clinical and the arithmetical mean roughness, R_a, of the femoral head was also demonstrated although the rate of change was not as great as that cited for laboratory experiments.

Hip and knee joint replacements are common and largely successful procedures that utilise implants to restore mobility and relieve pain for patients suffering from e.g. osteoarthritis. However, metallic ions and particles released from both the bearing surfaces and non-articulating interfaces, as in modular components, can cause hypersensitivity and local tissue necrosis, while particles originating from a polymer component have been associated with aseptic loosening and osteolysis. Implant coatings have the potential to improve properties compared to both bulk metal and ceramic alternatives. Ceramic coatings have the potential to increase scratch resistance, enhance wettability and reduce wear of the articulating surfaces compared to the metallic substrate, whilst maintaining overall toughness of the implant ensuring a lower risk of catastrophic failure of the device compared to use of a bulk ceramic. Coatings can also act as barriers to inhibit ion release from the underlying material caused by corrosion. This review aims to provide a comprehensive overview of wear-resistant coatings for joint replacements – both those that are in current clinical use as well as those under investigation for future use. While the majority of coatings belong predominantly in the latter group, a few coated implants have been successfully marketed and are available for clinical use in specific applications. Commercially available coatings for implants include titanium nitride (TiN), titanium niobium nitride (TiNbN), oxidized zirconium (OxZr) and zirconium nitride (ZrN) based coatings, whereas current research is focused not only on these, but also on diamond-like-carbon (DLC), silicon nitride (SiN), chromium nitride (CrN) and tantalum-based coatings (TaN and TaO). The coating materials referred to above that are still at the research stage have been shown to be non-cytotoxic and to reduce wear in a laboratory setting. However, the adhesion of implant coatings remains a main area of concern, as poor adhesion can cause delamination and excessive wear. In clinical applications zirconium implant surfaces treated to achieve a zirconium oxide film and TiNbN coated implants have however been proven comparable to traditional cobalt chromium implants with regards to revision numbers. In addition, the chromium ion levels measured in the plasma of patients were lower and allergy symptoms were relieved. Therefore, coated implants could be considered an alternative to uncoated metal implants, in particular for patients with metal hypersensitivity. There have also been unsuccessful introductions to the market, such as DLC coated implants, and therefore this review also attempts to summarize the lessons learnt.

Entative of the dynamic canal occlusion and associated neurological damage that occurs during the fracture event....

The spinal cord is an integral component of the spinal column and is prone to physical injury during trauma or more long-term pathological insults. The development of computational models to simulate the cord-column interaction during trauma is important in developing a proper understanding of the injury mechanism. Such models would be invaluable in seeking both preventive strategies that reduce the propensity for injury and identifying specific treatment regimes. However, these developments are hampered by the limited information available on the structural and mechanical properties of this soft tissue owing to the difficulty in handling this material in a cadaveric situation. The purpose of the present paper is to report the rapid deterioration in the quality of the tissues once excised, which provides a further challenge to the successful elucidation of the structural properties of the tissue. In particular, the tangent modulus of the tissue is seen to increase sharply over a period of 72 h.