Integrated F18 NaF PET/CT scanning for the evaluation of patients with chronic pain after spinal surgery

Objectives To evaluate the utility of F18 NaF PET/CT scanning for identifying a source of pain or hardware failure in patients who have continued pain after spinal arthrodesis or spinal fixation surgery.

Methods 20 patients with intractable back pain after spinal surgery were prospectively enrolled to undergo NaF PET/CT for evaluation. In all 20 patients, prior physical exam and MRI had failed to pinpoint a specific source of pain. Scanning occurred at least 8 months after most recent surgery. Clinical interpretation was based on semi-quantitative SUV measurements, lesion focality, and the location of suspected foci with CT co-registration to sites of surgical hardware (e.g. screws, rods, cages, and grafts). After results were communicated to the orthopedist, the patient then underwent surgical exploration and revision, local anesthetic blockade, or watchful waiting.

Results Abnormal foci were found in 17/20 patients. 12/20 patients underwent surgical exploration of areas with abnormal NaF foci, 4/20 patients underwent a local anesthetic nerve blockade directed at sites of abnormal foci, and 4/20 patients were followed conservatively without intervention. In total, 24 abnormal foci were identified at the following sites: screws (8/24), cages (6/24), rods (4/24), bone grafts (6/24). 16/24 abnormal foci were confirmed by surgical exploration to have hardware failure (e.g. screw, rod, cage loosening) or failure of bone graft. 4/24 abnormal foci led to successful alleviation of symptoms by local anesthetic nerve block and considered a true positive. 1/24 abnormal foci were shown to be a false positive by surgery (no abnormality found at exploration), 3/24 abnormal foci were shown to be a false positive from alleviation of clinical symptoms without aggressive intervention. The PPV was 83% in pinpointing the exact site of pain.

Conclusions In patients with chronic back pain after spinal surgery, F18 NaF PET/CT has excellent potential for identifying the source to help direct surgical revision or therapeutic nerve blockade