The role of bone SPECT/CT in the evaluation of lumbar spinal fusion with metallic fixation devices.

Purpose: It is difficult to evaluate the stability of the lumbar spondylodesis with metallic fixation devices by conventional imaging methods such as radiography or magnetic resonance imaging. It is unknown whether single photon emission computed tomography/computed tomography (SPECT/CT) may be useful to detect a lack of fixation of the pedicle screws and hence to predict instability of the fused vertebral segments. Materials and Methods: A retrospective analysis of 9 patients who were referred to bone scintigraphy, including combined SPECT/CT, due to persistent pain or discomfort after stabilizing lumbar surgery with metallic implants. The SPECT/CT findings were compared with observations from subsequent surgical reexploration. Results: In 6 of 9 patients, the SPECT/CT fully or partially detected the vertebral level of loose pedicle screws. Of 9 cases, 2 were considered inconclusive, whereas in 1 case loose pedicle screws were detected at a wrong vertebral level. Conclusion: SPECT/CT may be useful to detect a lack of fixation of the metallic implants, and hence instability of the spondylodesis by evaluating the focal bone mineralization activity in relation to the pedicle screws.