Background: Noninvasive diagnosis continues to present a challenge in chronic bone infections. Positive intraoperative microbiological and/or histological results are regarded as the gold standard for confirmation of the diagnosis. The aim of the present study was to evaluate the value of F-18 FDG-PET in the diagnosis of chronic osteitis in the patients of a department devoted specifically to septic orthopaedic surgery. In particular, the study was intended to answer the question of whether the results of FDG-PET correlate with those found in intraoperatively removed biopsy specimens (microbiology, histology) and what value this method of investigation has relative to computed tomography (CT) and magnetic resonance imaging (MRI).
Methods: An F-18 FDG-PET examination was performed preoperatively in each of 50 patients with a suspected diagnosis of "chronic osteitis of bone/s in a limb". All these patients had a history of an open fracture and/or a previous operation on the affected limb. The FDG-PET results were analysed blind. All patients enrolled in the study were subsequently operated on. After surgery, the results of histological and microbiological examination of the biopsy specimens taken intraoperatively were compared with the results of the FDG-PET and of CT (n=22) and MRI (n=18). Finally, the sensitivity, specificity and accuracy of each method were determined.
Results: Postoperatively the biopsy specimens from 37 patients yielded positive results in the microbiological and/or histological tests. According to this gold standard, then, osteitis was not present in 13 patients. In the preoperative FDG-PET report 34 of the patients whose microbiological and/or histological results were positive were correctly diagnosed as infection positive. In addition, 4 false-positive results were observed. False-negative results were recorded in 3 patients and true-negative results, in 9. The sensitivity and specificity were 92% and 69%, respectively, for the entire group of patients. The accuracy was 86%. The sensitivity, specificity and accuracy were 47%, 60% and 50%, respectively, for CT and 82%, 43% and 67%, respectively, for MRI.
Conclusion: F-18 FDG-PET is a promising diagnostic imaging method with high sensitivity and accuracy in the investigation of chronic osteitis. If the result of FDG-PET is negative chronic osteitis can be virtually excluded. The results presented suggest that it is superior to CT and MRI in sensitivity and accuracy. A definitive diagnosis of chronic osteitis will continue to require an invasive method in the future, in the form of removal of biopsy specimens for microbiological and histological tests.