Aim. Ceramic-ceramic coupling is currently used in Orthopaedics in younger patients with longer life expectance, for the high biocompatibility of these materials. More recently new ceramic materials have been developed with better mechanical properties in comparison to Alumina, as the Alumina Matrix Composites by Transformation Toughened and in situ Plateled Reinforcement (ZPTA). The aim of the study was to analyze the biological properties of this material in comparison to Alumina and Zirconia. Materials and methods. Cylinders of different ceramic materials were inserted into surgical created defect of proximal metaepiphysis of New Zealand White adult rabbits to analyze the bone response to ceramics. Percentage of bone ceramic contact was measured. Massive inflammatory response was analyzed by intraarticullar injection of powders of different materials; while chronic low grade response as the one observed in long term well functioning implants was tested by implantation of low cohesive ceramic pellets under patellar tendons of rabbits: thank to leg movements few particles were released in time. Systemic host response was tested analyzing peripheral organs of animals. Results. Connective tissue was present at bone ceramic interface whatever materials used: no statically differences were observed in term of bone ceramic contact among Alumina, Zirconia and ZPTA. Inflammatory response with new vessels was observed around powders, especially with small diameter; while low cohesive pellets did not elicited inflammatory response neither systemic toxicity. Discussion and conclusion. Our results confirm that Alumina Matrix Composites by Transformation Toughened and in situ Plateled Reinforcement, as well as Alumina and Zirconia ceramics, induces a low inflammatory reaction in periprosthetic tissues without any systemic toxicity, due to massive or chronic release. So thank to its higher mechanical properties than Alumina and Zirconia, it should be indicated for ceramic to ceramic coupling in Orthopaedic Surgery.

We studied factors contributing to the initiation of fracture and failure of a zirconia ceramic femoral head. The materials retrieved during a revision total hip replacement were submitted to either visual, stereomicroscopic and scanning electron microscopy (SEM) or SEM and energy-dispersive x-ray analysis. X-ray diffraction was performed in order to investigate the extent of tetragonal to monoclinic phase transition. Histological examination was performed on the periprosthetic tissues.

The results showed that failure was due to the propagation during clinical use of defects which may have been introduced into the material during the processing of the ceramic, rather than those intrinsic to zirconia. The literature relating to previous failures of zirconia components is reviewed.