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

BACKGROUND: The interlaminar window is the most important anatomical corridor during the posterior approach for lumbar and lumbosacral pathologies. Three-dimensional (3D) reconstruction of the L5-S1 interlaminar window including accurate measurements may be beneficial for the surgeon. The aim of this study was to measure relevant surgical parameters of the L5-S1 interlaminar window based on 3D reconstruction of lumbar computed tomography (CT). METHODS: Fifty thin-layer CT data were retrospectively collected, segmented, and reconstructed. Relevant surgical parameters included the width, left height, right height, interpedicular distance (IPD), area, and suitable approach area of the L5-S1 interlaminar window. Morphological measurements were performed independently by two experienced experts. Patients with disk herniation at L5-S1 were regarded as group A (n = 28) and those without L5-S1 disk 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 ± 2.45 mm, 9.55 ± 2.46 mm, 23.55 ± 4.91 mm, and 144.57 ± 57.05 mm2, respectively. The average IPD at the superior, middle, and inferior pedicle levels was 29.29 ± 3.39, 27.96 ± 3.38, and 37.46 ± 4.23 mm, respectively, with significant differences among these three parameters (p < 0.05). The average suitable approach areas of the L5-S1 interlaminar window were the following: left axilla-24.52 ± 15.91 mm2; left shoulder-27.14 ± 15.48 mm2; right axilla-29.95 ± 17.17 mm2; and right shoulder-31.12 ± 16.40 mm2 (p > 0.05). There were no significant differences between groups A and B in these parameters (p > 0.05), except the inferior IPD (36.69 ± 3.73 vs. 39.23 ± 3.01 mm, 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 posterior microsurgical and endoscopic approaches as well as percutaneous infiltrations.

Deep learning-based lumbosacral reconstruction for difficulty prediction of percutaneous endoscopic transforaminal discectomy at L5/S1 level: A retrospective cohort study.

BACKGROUND: Deep learning has been validated as a promising technique for automatic segmentation and rapid three-dimensional (3D) reconstruction of lumbosacral structures on CT. Simulated foraminoplasty of percutaneous endoscopic transforaminal discectomy (PETD) through the Kambin triangle may benefit viability assessment of PETD at L5/S1 level. MATERIAL AND METHODS: Medical records and radiographic data of patients with L5/S1 lumbar disc herniation (LDH) who received a single-level PETD from March 2013 to February 2018 were retrospectively collected and analyzed. Deep learning was adopted to achieve semantic segmentation of lumbosacral structures (nerve, bone, disc) on CT, and the segmented masks on reconstructed 3D models. Two observers measured the area of the Kambin triangle on 6 selected deep learning-derived 3D (DL-3D) models and ground truth-derived 3D (GT-3D) models, and intraclass correlation coefficient (ICC) was calculated to assess the test-retest and interobserver reliability. Foraminoplasty of PETD was simulated on L5/S1 lumbosacral 3D models. Patients with extended foraminoplasty or stuck canula occurs on simulations were predicted as PETD-difficult cases (Group A). The remaining patients were regarded as PETD-normal cases (Group B). Clinical information and outcomes were compared between the two groups. RESULTS: Deep learning-derived 3D models of lumbosacral structures (nerves, bones, and disc) from thin-layer CT were reliable. The area of the Kambin triangle was 161.27 ± 40.10 mm2 on DL-3D models and 153.57 ± 32.37 mm2 on GT-3D models (p = 0.206). Reliability test revealed strong test-retest reliability (ICC between 0.947 and 0.971) and interobserver reliability of multiple measurements (ICC between 0.866 and 0.961). The average operation time was 99.62 ± 17.39 min in Group A and 88.93 ± 21.87 min in Group B (P = 0.025). No significant differences in patient-reported outcomes or complications were observed between the two groups (P > 0.05). CONCLUSION: Deep learning achieved accurate and rapid segmentations of lumbosacral structures on CT, and deep learning-based 3D reconstructions were efficacious and reliable. Foraminoplasty simulation with deep learning-based lumbosacral reconstructions may benefit surgical difficulty prediction of PETD at L5/S1 level.

Concentric Stereotactic Technique of Percutaneous Endoscopic Transforaminal Discectomy and Radiation Exposure to Surgeons.

OBJECTIVE: In percutaneous endoscopic transforaminal discectomy (PETD), surgeons are exposed to intraoperative radiographic radiation over a long-term career, which may be correlated with high risk of iatrogenic radiation hazards. The purpose of this prospective cohort study was to assess the impact of concentric stereotactic technique on radiation exposure to surgeons in PETD. METHODS: Patients who underwent conventional PETD were regarded as group A, whereas those undergoing PETD with concentric stereotactic technique were considered as group B. The primary outcomes were cumulative radiation dose to the surgeon's eye, thyroid gland, and breast. RESULTS: A total of 34 patients were treated in group A and 30 patients were treated in group B. The cumulative radiation dose of the eye per operation was 0.017 (0.58/34) mSv in group A and 0.010 (0.31/30) mSv in group B, which meant a reduction of 41.18%. The cumulative radiation dose of the thyroid gland per operation was 0.018 (0.60/34) mSv in group A and 0.011 (0.33/30) mSv in group B, which meant a reduction of 38.89%. The cumulative radiation dose of the chest per operation was 0.039 (1.33/34) mSv in group A and 0.023 (0.70/30) mSv in group B, which meant a reduction of 41.03%. There were no significant differences in hospital stay, visual analog scale score of waist and leg pain, Oswestry Disability Index score, MacNab satisfaction, and complications between the 2 groups (P > 0.05). CONCLUSIONS: The concentric stereotactic technique can effectively reduce radiation exposure to surgeons by about 40%.