Effect of brightness in the evaluation of lumbar pedicular screws position: clinical study

Abstract

Artifact may lead to confusion when evaluating postoperative CT scans of lumbar pedicle screws. The aim of our study was to develop a specific metal artifact reduction image protocol, in order to reduce metal artifact caused by titanium pedicular screw in patients undergoing lumbar pathology by lumbar fusion. Therefore, the reduction in metal artifacts in lumbar pedicle screws allows surgeons to do an accurate diagnosis of the exact placement of inserted pedicle screws, minimizes false reexploration, and maximizes proper and prompt treatment of misplaced screw. In a first step, we performed a retrospective study of 103 titanium alloy pedicle screws in patients undergoing a lumbar instrumented fusion for treatment for degenerative disease. CT scan was performed postoperatively evaluating the possible overdimension caused by artifact. In a second step, a prospective study was performed using a 64-slice multidetector-row computed tomography (MDCT) in 104 titanium alloy pedicle screws in patients undergoing a lumbar instrumented fusion for treatment for degenerative disease. Our results show that on the group of sequential CT scan, mean overdimension (on each side) due to brightness was 1.045 mm (SD 0.45). On the group of 64-slice multichannel CT, mean overdimension (on each side) due to brightness was 0.005 mm at the proximal part of the screw and 0.025 mm at the distal part of the screw. The results observed suggest that beam-hardening artifacts caused by the screw on CT after lumbar fusion are dramatically reduced by using specific metal artifact reduction image protocol in a 64-slice MDCT.

Potential risk factors in development of the “halo sign” in patients performed transpedicular screw fixation through the posterior spinal approach.

“…Although CT scan is frequently used to evaluate the transpedicular screw loosening, image distortion (artefact) caused by metal instrumentation material is a major disadvantage and can lead to false negative or false positive results (11,12). However, CT scan is still the only accepted method in literature to evaluate osseous progression after spinal fusion surgery, to determine screw positions, to confirm the integrity of instrumentation elements, to detect suspicious complications, to investigate new disease and / or disease progression (5,8,13,14).…”