The pathology of failed McKee-Farrar implants: correlation with modern metal-on-metal-implant failure

The McKee-Farrar (MF) prosthesis was the first widely used total hip replacement (THR) to employ a metal-on-metal (MoM) articulation. These implants had a high rate of early aseptic loosening but a number achieved good long-term implant survival, stimulating the reintroduction of second and third generation implants of this type. In this study we analysed archival histopathology of periprosthetic tissues in twenty cases of MF aseptic implant failure to determine if there was evidence of an innate and adaptive immune response similar to that seen in modern MoM implants. The presence of macrophages, the extent of necrosis and the ALVAL response were graded semi-quantitatively. Variable but in most cases extensive tissue necrosis was associated with a heavy macrophage response to Cobalt-Chrome (Co-Cr) wear particles in periprosthetic tissues; most cases also contained evidence of a predominantly lymphocyte response which in eight cases was moderate or heavy (Oxford Grade 2/3). Our findings show that inflammatory and necrotic changes to deposition of Co-Cr wear particles are found in periprosthetic tissues of failed MF implants, indicating that there is an innate and adaptive response similar to that noted in second/third generation MoM implants; they also suggest that the pathobiological response to metal wear particles is likely to have contributed to MF implant failure in these cases

Ab Initio Modelling of the Structure and Properties of Crystalline Calcium Carbonate

Many biominerals occur as crystalline materials, and their formation often involves steps where metastable crystalline phases appear. The latter can correspond either to intermediate species that then transform into more stable phases or to the final mineral crystal. Because of their instability and rare occurrence, the structure and properties of such intermediate metastable phases may not always be fully understood from experiment alone. Vaterite (CaCO3) is one such phase, and recent advances in understanding its complex structure were achieved through ab initio modelling techniques. This chapter will highlight the importance of achieving a comprehensive understanding of the atomic details of the crystalline phases involved in biomineralisation. Examples will be focused on calcium carbonate, and especially on vaterite, and ab initio methods based on density functional theory (DFT) will be proposed as the main tool to undertake this kind of investigation, together with more traditional techniques such as spectroscopic methods, microscopies and X-ray and neutron diffraction