Morphometric analysis of lumbar nerve root takeoff in the lumbar spine

Study Design: Retrospective cohort study. Purpose: The purpose of this study was to quantify lumbar nerve root takeoff height and assess its clinical relevance in patients with lumbar spine pathology. Overview of Literature: Although lateral recess and foraminal stenosis are known causes of radiculopathy, the vertical origin (takeoff height) of lumbar nerve roots has not been quantitatively assessed. A higher nerve root origin from the thecal sac, or root takeoff, may be of clinical relevance, as a more proximal takeoff will consequently result in a greater length of neural tissue traversing the lateral recess. This study aims to characterize variability in lumbar nerve root takeoff height using computed tomography (CT) myelography in patients with lumbar spinal pathology. Materials and Methods: Retrospective review of CT myelograms from patients with lumbar pathology with measurements of the vertical origin (root takeoff height) of L4 and L5 nerve roots relative to total interpedicular height, producing a takeoff ratio (h/H). Clinical records were reviewed to categorize symptom distribution as leg-dominant, back-dominant, or mixed. Statistical analyses included interrater reliability (κ), intrarater reliability, group comparisons, correlation testing between takeoff ratio and symptom type, and a priori power analysis. Results: A total of 75 patients were included in the study. Nerve root takeoff height showed substantial interindividual variability at both L3-4 and L4-5 levels. Conclusion: Lumbar nerve root takeoff height demonstrates meaningful variability across patients, representing an anatomical parameter not typically considered in conventional imaging assessments. In this study, we observed that such variability may influence how nerve roots traverse the lateral recess. We speculate that a higher root takeoff could predispose patients to radicular symptoms; however, further investigation is needed to confirm this relationship.