Surgically Relevant Morphological Parameters of the L5-S1 Interlaminar Window: A Statistical Analysis Based on 3D Reconstruction of CT Data

Abstract

Abstract Study design: Retrospective study. Objectives: The interlaminar window is the most important anatomical corridor for posterior approach of lumbar procedures. Three-dimensional (3D) reconstruction of the L5-S1 interlaminar window may benefit the accurate measurement and assessment of surgical considerations. The aim of this study was to measure surgical relevant parameters of the L5-S1 interlaminar window based on 3D reconstruction of lumbar CTs. Methods: 50 thin-layer CT data were retrospectively collected, segmented, and reconstructed. Surgical relevant parameters included the width, left height, right height, interpedicular distance, area, and operable area of the L5-S1 interlaminar window. Morphological measurements were performed independently by two experienced experts. Patients with radiologic abnormalities at L5-S1 level were regarded as group A (n=28), while those without L5-S1 disc herniation were regarded as group B (n=22). Results: The average left height, right height, width, and area of the L5-S1 interlaminar window were 9.14±2.45mm, 9.55±2.56mm, 23.55±4.91mm, and 144.57±57.05mm2. The average interpedicular distance (IPD) at superior, middle, and inferior pedicle level were 29.29±3.39mm, 27.96±3.38mm and 37.46±4.23mm, with significant differences among these three parameters (P<0.05). The average operable areas of the L5-S1 interlaminar window were: left-axilla 24.52±15.91mm2, left-shoulder 27.14±15.48mm2, right-axilla 29.95±17.17mm2, and right-shoulder 31.12±16.40mm2 (P>0.05). There were no significant differences between group A and B in these parameters (P>0.05), except the inferior IPD (36.69±3.73mm vs 39.23±3.01mm, P=0.017<0.05). Conclusion: The morphological measurement of the L5-S1 interlaminar window based on 3D reconstruction provided accurate and reliable reference data for epidural puncture approach and posterior approach of lumbar surgery. Moreover, it could also assist the placement of endoscopic working channel in percutaneous endoscopic interlaminar discectomy (PEID) and might be useful for further studies of anatomical and surgical consideration of unilateral biportal endoscopic spinal surgery (UBE) procedures. Key words: Interlaminar window; percutaneous endoscopic interlaminar discectomy (PEID); unilateral biportal endoscopy spinal surgery (UBE); 3D reconstruction.