Use of positron emission tomography to detect infection around antibiotic-loaded cement spacers in patients with high C-reactive protein levels

In patients who have antibiotic-loaded cement hip spacers in the interim period, the correct diagnosis of infection eradication is the major determinant before reimplantation arthroplasty. Diagnosis is usually based on clinical findings and serum C-reactive protein (CRP) levels. However, diagnosis can be challenging when the clinical findings are normal but the CRP level is high. From March 2007 to January 2008, fluorodeoxyglucose positron emission tomography (FDG-PET) was used to detect infection around antibiotic-loaded cement spacers in 13 patients (mean age, 60 years). Although patients' clinical conditions were deemed suitable for reimplantation, their serum CRP levels were persistently elevated (mean, 54 mg/L) an average of 120 days (range, 28-413 days) after the first-stage operation. Reimplantation total hip arthroplasty (THA) was subsequently performed in 7 patients based on the negative findings of FDG-PET. In 6 patients, FDG-PET was positive for infection. The persistence of infection was confirmed in 3 of these patients by another debridement surgery. Staged reimplantation THA was delayed in 1 patient who underwent repeat debridement and in 3 patients who were treated with extended periods of oral antibiotics. Of the 11 staged reimplantation THAs, only 1 reinfection was noted at an average follow-up of 48 months. The success rate of 91% suggests FDG-PET could help in the differential diagnosis of infection around cement spacers, especially in patients with normal clinical findings but elevated CRP levels.