Perioperative testing for persistent sepsis following resection arthroplasty of the hip for periprosthetic infection

Eighty-seven hips with an infected total hip arthroplasty were treated with an antibiotic spacer and 6 weeks of antibiotics. The erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) measurements were repeated before attempted reimplanation, and a synovial fluid white blood cell (WBC) count was obtained intraoperatively. Nine hips (10.1%) had persistent infections. The mean ESR, CRP, and synovial fluid WBC count and differential decreased significantly (P < .001) between stages; however, the ESR remained elevated (>30 mm/h) in 50 patients (62.5%) and the CRP remained elevated (>10 mg/L) in 22 patients (27.5%) in whom the infection had been eradicated. The synovial fluid WBC count was the best test for identifying persistent infection, with an optimum cutoff of 3528 WBCs/microL(sensitivity, 78%; specificity, 96%) and an area under the curve of 0.91. The ESR and CRP were not sufficiently rigorous to aid in diagnosis and frequently failed to normalize even in patients without persistent infection.