Diagnosing Infection in the Setting of Periprosthetic Fractures

Abstract The diagnosis of periprosthetic joint infection (PJI) is particularly challenging in patients with periprosthetic fractures. The purpose of this study was to investigate the utility of commonly used diagnostic tests for PJI in patients with a periprosthetic fracture. Of 121 patients treated with a periprosthetic fracture (97 hips, 24 knees, mean age 72.9), fourteen (11.6%) met MSIS criteria for infection. The synovial white blood cell count (WBC) and differential were the best diagnostic tests, with good test performance (AUC 84%) and optimal cutoffs of 2,707 WBC/uL and 77% polymorphonuclear cells. The ESR and CRP were found to have overall lower test performance but remained relatively sensitive at standard cut-off values of 30mm/hr and 10 mg/L respectively. The synovial fluid WBC count and differential are the best tests with optimal cutoff values that are similar to those used for patients without a periprosthetic fracture.