Does use of pre-operative low-dose CT-scan in adolescent idiopathic scoliosis improve accuracy in screw placement? Results of a retrospective study

Purpose: To evaluate the efficacy of pre-operative low-dose radiation computed tomography (CT) in optimizing screw placement in patients with adolescent idiopathic scoliosis (AIS). Methods: 49 patients with AIS who required correction and posterior fusion between January 2018 and December 2019 were included in this retrospective study. All patients underwent surgery performed by the same team of experienced surgeons. Patients were divided in two groups. The study group received a pre-operative low-dose CT scan (CT group, n = 25), differently from the control group (CG, n = 24). Patients of both groups received a post-operative low-dose CT scan. The primary outcome measure was the accuracy of screw placement on the Gertzbein–Robbins scale (grades A and B were considered acceptable). Secondary outcome measures included a comparison of perioperative complications. Results: A total of 1045 screws were placed. In CT group (n = 25, screws = 528) and CG (n = 24, screws = 517), trajectories were grade A or B in 94.5% and 93.6% of screws, respectively. Two screws (one for each group) were removed because of intra-operative-evoked potentials alteration and one screw required revision after post-operative imaging. No correlation was found between the malpositioning rate and the proximity to the apex of the curve, conversely a significative peak of misplacements was observed at T3 (p < 0.01). No neurological and vascular complications related to screw placement were recorded. There was not intergroup difference neither in screw accuracy (Chi-Square, 2-tailed Fisher’s exact, p = 0.63), nor in complications rate. Conclusion: Pre-operative low-dose CT scan as surgical plan does not contribute in reducing pedicle screw misplacement rate. Study design: Retrospective comparative cohort study. Level of evidence: III.