Use of modern magnetic resonance imaging technology for lumbar screw planning

Introduction: Preoperative screw planning enables the use of modern technologies such as navigation and robotics. To reduce radiation exposure to patients, there is growing interest in Magnetic Resonance Imaging (MRI) technologies. Research question: This study assesses the use of isotropic MRI and synthetic Computed Tomographies (sCT) for planning lumbar screws. Methods: Two 3D T1-weighted scans were performed on 22 patients, one isotropic fast spin-echo sequence, and one multi-echo gradient echo sequence for generating sCTs. A total of 200 screws were planned equally split across the isotropic MRIs and sCTs. All scans were then fused to an intraoperative scan for evaluation. Each screw was evaluated by three surgeons using Gertzbein-Robbins classification and a qualitative survey. Results: A mean interrater agreement of 94.5 % (83 %–100 %) was observed. A significant difference was identified in the Gertzbein-Robbins classification (P = 0.04) where sCT had the most A and B rated screws. The qualitative survey identified differences in screw length and screw positioning but not in screw diameter. Discussion and conclusion: Nearly 75 % of cases can use modern MRI sequences for planning of lumbar screws. Where the MRI sequence alone is insufficient for total confidence, sCT can be used to supplement the scan and enable effective planning in approximately 90 % of patients without the need for ionizing radiation.