Aim

Septic arthritis of the hip is a rare entity among the adult population, but with a potential severe repercussion. The most accepted treatment is the hip debridement, even though a notorious proportion of the cases need further hip replacement owing to the cartilage destruction. The aim of this study is to analyse all our cases of septic arthritis of the hip treated with a 2-stage strategy using an antibiotic-loaded cement spacer.

Introduction: The histology of prosthetic tissue is a gold standard for the diagnosis of prosthetic joint infection. However, the specificity and sensitivity of histology has never been 100% and this could be due to several causes. A possible cause for inconsistencies in histological results could be the type of specimen submitted to laboratory. The majority of authors obtain specimens from pseudocapsule, interface membrane and any tissue area suspicious of infection.

Aim: The objective of our study was to elucidate which is the most accurate specimen for histological diagnosis of prosthetic joint infection.

Methods: Prospective study including all revision arthroplasties performed in Hospital Clinic of Barcelona (Spain) from January 2007 to June of 2009. Specimens from pseudocapsule and from interface membrane were obtained from each patient. Definitive diagnosis of infection was considered when ≥2 cultures were positive for the same microorganism or the presence of pus around the prosthesis. Patients were classified in two groups:

patients submitted to hip revision arthroplasty due to an aseptic loosening in whom cultures (at least 5) obtained during surgery were negative and

Results: A total of 69 revisions were included in the study; 57 were classified in the group A and 12 were classified in the group B. The percentage of positive interface membrane histology in patients with prosthetic joint infection (group B) was significantly higher than the percentage of positive pseudocapsule histology (83.3% vs 41.6%, p=0.04, Fisher exact test).

Conclusion: The results suggest that the best specimen of periprosthetic soft tissue for histological study to diagnose the chronic periprosthetic infection in a revision total hip arthroplasty is the periprosthetic interface membrane.