99mTc ciprofloxacin imaging for the diagnosis of infection in the postoperative spine.

Abstract

The non-invasive assessment of postoperative spinal infections can pose a substantial diagnostic challenge, especially in the presence of orthopaedic devices. In contrast to white blood cell scanning, which is of limited use in the spine, the low uptake of 99mTc ciprofloxacin into normal bone marrow, combined with its claimed bacterial specificity, makes it, theoretically, an ideal candidate for evaluating postoperative spinal infections. This study aimed to evaluate 99mTc ciprofloxacin planar and single photon emission tomography (SPET) imaging in relation to microbiological diagnosis in the postoperative spine. Only patients with a microbiologically confirmed diagnosis were included in this analysis. Planar imaging was performed at 1, 3 and 24 h, and SPET was performed at 3 h post-injection of 370 MBq 99mTc ciprofloxacin. Images were scored by two independent, certified, nuclear medicine physicians, blinded for the final diagnosis. Within the first 22 consecutive patients with microbiological diagnosis, there were nine deep infections. Sensitivity, specificity and accuracy at visual scoring were, respectively, 67%, 77%, 73% (1 h), 78%, 69%, 73% (3 h), and 56%, 92%, 77% (24 h) for planar imaging, and 100%, 54%, and 73% for SPET. In contrast to white blood cell scanning, SPET with Tc ciprofloxacin is sensitive in evaluating infections in the postoperative spine. Sensitivity is higher for SPET than for planar imaging. However, the results presented prove that its specificity is limited, especially in patients who have recently (< 6 months) undergone surgery. Taken this limitation into account, we advise planar and SPET imaging at 3 h post-injection and at an interval of at least 6 months after surgery to minimize the chance for false positives.