Background. Some reports have suggested that debris generated from the head neck taper junction is more destructive than equivalent doses from metal bearing surfaces. Methods. Part 1. We examined the relationship between the source (taper/bearing) and volume of metal debris on Cr and Co concentrations in corresponding blood and hip synovial fluid samples and the observed agglomerated particle sizes in excised tissues using regression analysis of prospectively collected data at a single revision unit. Part 2. We investigated variables most strongly associated with macroscopic soft tissue injury as documented at revision surgery using ordinal logistic regression. Independent variables included source and volume of CoCr exposure, Cr and Co joint fluid concentrations, joint fluid grade, ALVAL (Aseptic Lymphocytic Vasculitis Associated Lesion) grade, presence of vascular hyalinisation, agglomerated particle size, implant type, patient sex and age. Results. A total of 199 explanted MoM hips were analysed. Multiple regression statistical modelling suggested that a greater source contribution of metal debris from the taper junction was associated with smaller aggregated particle sizes in the local tissues and a relative reduction of Cr ion concentrations in the corresponding synovial fluid and blood samples. There was an association between increasing Co concentrations in the joint fluid and an increasing ALVAL score (p<0.001). In contrast, higher Cr concentrations were inversely related to ALVAL (p<0.001). The ALVAL response was itself strongly associated with larger fluid collections (p<0.001). Vascular hyalinisation and larger fluid collections were significantly associated with macroscopic
