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, fluorodeoxy-glucose 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.