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

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.

The 20 most important questions for novices of full-endoscopic spinal surgery in China: a mixed-method study protocol

IntroductionThe full-endoscopic spinal surgery (FESS) procedure is widely accepted and welcomed in China. With the continuous development of minimally invasive surgery, the further expansion of indications and the greater diversity of techniques, spinal endoscopic surgery currently accounts for more than 10% of spinal surgery in China, ranking among the top in the world. However, the admission system and standardised training system for spinal endoscopic surgery are not perfect, which presents a challenge and disadvantage for novices.Methods and analysisExploratory mixed methods are applied for designing this study. First, we will collect questions from novices by allowing them to openly list their concerns to those who have completed FESS. These qualitative questions will be categorised using NVivo software. To produce the qualitative results, a questionnaire for the sequential two-round Delphi approach will be developed to identify the 20 most important questions from novices. This study is planned to be started at April 2021, and completed at March 2022.Ethics and disseminationThe Research Ethics Committee of Peking University Third Hospital provided a waiver for this Delphi protocol. We expect that the findings will be published in a clinical journal and presented at conferences. Furthermore, we hope that the results can contribute to answering the questions raised by novices of spinal endoscopy in the form of books and to improving the training system for spinal endoscopy surgery.

Full-Endoscopic Decompression with the Application of an Endoscopic-Matched Ultrasonic Osteotome for Removal of Ossification of the Thoracic Ligamentum Flavum

Background: Resection of the ossification of the thoracic ligamentum flavum (OTLF) with a high-speed burr may cause a high rate of perioperative complications, such as dural laceration and/or iatrogenic spinal cord injury. Objectives: The aim of this study was to investigate the safety and feasibility of the endoscopicmatched ultrasonic osteotome in full-endoscopic spinal surgery for direct removal of OTLF. Study Design: Retrospective study. Setting: All data were from Honghui Hospital in Xi’an. Methods: This study conducted between December 2017 and December 2018, included 27 consecutive patients who met the study criteria, had single-level OTLF, and underwent fullendoscopic decompression under local anesthesia. The postoperative follow-up was scheduled at 1, 3, 6, and 12 months postoperatively. Outcomes evaluations included the Visual Analog Scale (VAS) score for lower extremity pain and the modified Japanese Orthopaedic Association (mJOA) score and improvement rate for the assessment of thoracic myelopathy. Removal of OTLF was measured by comparing the pre- and postoperative computed tomography (CT) and magnetic resonance imaging (MRI) scans. Results: The operation was completed in all patients without conversion to open surgery. The operation time ranged from 65 to 125 minutes (average, 83.7 ± 12.3 minutes). All patients were followed up for 12 to 18 months, with an average follow-up of 14.3 ± 1.3 months. Satisfactory neurologic decompression was confirmed by postoperative CT and MRI, and no revision surgery was required. The VAS and mJOA scores showed statistically higher improvement at the 1-month follow-up and the last follow-up compared with the preoperative assessment (P < 0.05). According to the improvement rate at the final follow-up, 20 cases were classified as good, 6 cases were fair, and 1 case remained unchanged. Limitations: A single-center, noncontrol study. Conclusions: The endoscopic-matched ultrasonic osteotome can be considered quite safe and feasible for direct removal of OTLF during full-endoscopic spinal surgery in strictly selected patients, as this allows for effective direct decompression of OTLF while minimizing trauma and instability. In addition, because of the design characteristics of the ultrasonic osteotome, surgical complications, especially dural tears and spinal cord injury, can also be effectively controlled. Key words: Percutaneous endoscopic spinal surgery, ultrasonic osteotome, ossification of thoracic ligamentum flavum, microsurgery, thoracic myelopathy, minimally invasive procedures