PRE-OPERATIVE SERUM INFLAMMATORY MARKERS IN THE DIAGNOSIS OF INFECTION IN REVISION HIP SURGERY.

Abstract

Introduction: Serum inflammatory markers are routinely used as pre assessment investigation before the revision hip surgery. Various investigations are used to aid in diagnosis of infection in the revision prosthetic hip replacement including aspiration, broad range PCR, bone scan and serum interleukin- 6.

Materials and Methods: 256 consecutive revision total hip replacements were assessed for the value of pre operative ESR and c-reactive proteins (CRP) in predicting the deep infections.

All patients were evaluated prior to surgery. The patients with coexisting inflammatory disease or peri-prosthetic fracture were also evaluated.

A hip was diagnosed as infected on the basis of positive intra operative microbiology samples three or more out of five and or histological evidence.

Results: Using the values of ESR > 35 mm/1^st hour and CRP> 10mg/l, the positive predictive value (either /or) was 56% and the negative predictive value was 96%. 14 patients had an underlying inflammatory arthritis and 5 were peri prosthetic fractures. The inflammatory markers tended to be elevated in these patients. Excluding these 19 patients and using the same criteria, the positive predictive value was 65% and the negative predictive value was 97%

Discussion: We conclude that a CRP< 10 mg/l and ESR < 35 mm/1^st hour are very useful in excluding infection (negative predictive value of 97%, excluding peri-prosthetic fractures and inflammatory joint disease), but raised inflammatory markers are less accurate in predicting infection.