Duration of postoperative antibiotic therapy following revision for infected knee and hip arthroplasties

In the period from 1990 to 1998 28 patients (14 males and 14 females) were treated for infected hip (19 cases) and knee (9 cases) arthroplasties. The median age at index operation was 72 y (range 31-82 y) and at revision surg ery 74 y (range 36-83 y). The primary diagnosis was osteoarthritis (16 case s), rheumatoid arthritis (5 cases), failed femoral neck fracture (6 cases) and arthritis secondary to congenital hip dislocation (1 case). Nine cases were infected early i.e. within 3 months postoperatively, and 19 had late i nfections. The median interval from index operation to diagnosis of me infe cted arthroplasty was 18 months (range 1-156 months). Postoperatively, all patients received antibiotics based on susceptibility studies of the causat ive organism according to culture specimens. The erthrocyte sedimentation r ate and CRP level were controlled twice a week during hospitalization and a ntibiotics were continued until normalization of CRP. The indication for th e shift from intravenous to oral antibiotics was a rapid fall in CRP. Antib iotic therapy was terminated when CRP was close to or below 10 mg/l and the re was evidence of clinical recovery. Based on the screening of ESR and CRP in this study we believe that CRP is a valuable parameter in deciding,when to stop antibiotic therapy. However, it is not clear whether a shorter tre atment period is effective or not.