Histological and microbiological findings in non-infected and infected revision arthroplasty tissues

An assessment of clinical and laboratory findings is generally required to distinguish between septic and aseptic loosening of a hip implant. In order to evaluate the diagnostic utility of histological and microbiological investigative techniques to differentiate between these two conditions, we analysed their results in 617 patients with hip implant loosening. Histology and microbiology study confirmed the clinical diagnosis of septic loosening in approximately 98% and 89%, respectively. The clinical diagnosis of aseptic loosening was confirmed by histology in 99% of cases. In all but 2 of 81 cases of septic loosening, in which an organism was isolated on microbiological culture, the histological diagnosis of septic loosening was made on the basis of the degree of the acute inflammatory infiltrate (i.e. the presence of 1 or more neutrophil polymorphs per high power field (x 400) on average after examination of at least 10 high power fields) in periprosthetic tissues. In 10 patients for whom there was a strong clinical suspicion of septic loosening but no organisms were isolated on microbiological culture, the histological findings, using the above criteria, were in keeping with the clinical diagnosis of septic loosening. As almost 11% of cases of septic loosening would not have been diagnosed by microbiological investigation alone, our findings indicate that histological examination of periprosthetic tissues should form part of the investigative protocol to distinguish between aseptic and septic loosening.