Accuracy of Pedicle Screw Placement in the Thoracic and Lumbosacral Spine Using Conventional Intraoperative Fluoroscopy Placement Technique: A Single-Center Analysis of 1236 Consecutive Screws
Aims: Pedicle screw placement is a very common procedure to stabilize all three columns of the thoracic and lumbar spine. Since the introduction of the free-hand method in posterior spinal fixation various techniques have been proposed to increase the accuracy of placement. The purpose of this study was to evaluate the incidence of screw misplacement and its complications in patients who underwent fluoroscopy-guided transpedicular screw fixation in thoracic and lumbar posterior spine fusion.
Methods: We retrospectively reviewed consecutive cases that underwent transpedicular screw fixation in the thoracic and lumbosacral spine with conventional open technique and intraoperative fluoroscopy from January 2007 to May 2011. All patients had postoperative computed tomography (CT). Accuracy of pedicle screw placement was assessed by an independent radiologist in reconstructed axial, sagittal, and coronal plane. Displacement was classified as minor (≤ 2 mm), moderate (2.1 to 4 mm or less than screw thread diameter), and severe (>4 mm or >1 screw diameter).
Results: A total of 1236 pedicle screws were placed in 273 consecutive patients (137 males and 136 females) in the thoracic and lumbar spine. Indications for surgery were degenerative disease (37.4%), spondylolisthesis (42.5%), trauma (8.1%), tumor (1.5%), infection (0.4%) and revision-surgery (9.9%). 90.1% of all screws were found to be within accuracy level 1 (no pedicular violation and minor violation). A total of 247 (20%) screws were identified to breach the pedicle; thereof 135 (10.9%) minor violation, 65 (5.3%) moderate violation and 47 (3.8%) severe violation. 18 (6.6%) patients developed nerve root symptoms directly attributable to screw misplacement. All of them were identified to be in the subgroup of severe screw displacement. 72.2% of the symptomatic screw misplacements were localized medial, 22.2% inferior and 5.6% superior.
Conclusion: The presented data confirm that transpedicular screw fixation remains a technically demanding procedure. Although most breaches to the pedicle are minor, severe medial screw displacement is associated with a high likelihood of neurological symptoms. Gain in accuracy beyond that of conventional intraoperative fluoroscopy placement technique may be achieved by using intraoperative CT reconstructions.