Objective: To investigate the clinical efficacy and imaging outcomes of unilateral biportal endoscopy (UBE) with unilateral laminotomy for bilateral decompression (ULBD) in the treatment of severe lumbar spinal stenosis (SLSS).Methods: We retrospectively analyzed 50 patients with SLSS treated with UBE-ULBD from October 2018 to March 2021. Visual analog scale (VAS) for back and legs pain, Oswestry disability index (ODI), modified Macnab criteria, complications, hospital stay, preoperative and postoperative dural sac cross-sectional area (DSCA) and Schizas grade, mean angle of facetectomy and osseous lateral recess decompression rate were examined.Results: The mean follow-up period was 10.7 months. The mean hospital stay was 2.76 ± 1.02 days. At the final follow-up, VAS for back pain and legs pain decreased from 7.22 ± 0.95 to 1.26 ± 0.44 and from 7.88 ± 0.69 to 1.18 ± 0.39, respectively; ODI decreased from 69.88 ± 6.32% to 14.96 ± 2.75%. According to the modified Macnab criteria, the results were excellent in 24 (48%), good in 22 (44%), and fair in 4 (8%). Excellent or good results (a satisfactory outcome) were obtained in 92% of the patients. There were 2 cases of complications of dural sac tear. The postoperative DSCA was significantly enlarged compared with that before surgery, from 44.74 ± 9.85 to 126.86 ± 14.81 mm². According to Schizas grade, the stenosis grade changes from preoperative grade C in 16 cases, grade D in 34 cases, to postoperative grade A in 40 cases, and grade B in 10 cases. The mean angle of facetectomy of the ipsilateral facet joint was 70.87 ± 5.68∘, contralateral was 65.07 ± 4.98∘. The decompression rate was 70.81 ± 4.43% (ipsilateral side) and 71.22 ± 3.68% (contralateral).Conclusions: UBE-ULBD has a good clinical effect in the treatment of SLSS, and has achieved satisfactory results in spinal canal enlargement, undercutting of facet joints, and decompression effect. It is a safe and effective surgical for SLSS.

Background Cervical spondylotic myelopathy (CSM) caused by multi-segment cervical stenosis is a common spinal surgery disease with severe neurological dysfunction. The surgical goal was to achieve full canal decompression while minimizing damage to the normal structures. Unilateral biportal endoscopy (UBE), due to its good visualization, independent view-working portals, and wider instrument availability, can be utilized to efficiently and safely complete a laminectomy under endoscopy. Objective This study was to determine the efficiency and safety of a novel cervical laminectomy technique and introduce some new endoscopic anatomic concepts. Methods We report on 3 cases of multi-segment of cervical stenosis. The author attempted combinations of "laminectomy", "hemilaminectomy", and "ligamentum flavum resection" under UBE for different cervical cases. The postoperative neurological improvement and perioperative complications were used to determine the efficiency and safety. Results All 3 patients got significant improvement after surgery. And no complication was observed. This study described in detail the surgical steps and introduced new anatomic concepts that "infraspinous absence range (IS-AR)" and "ligamentum flavum-interspinous space (LF-IS space)". Conclusion Central laminectomy for bilateral decompression (CLBD) under UBE is an effective surgical method for the treatment of CSM caused by multi-segment cervical spinal stenosis. It can achieve the same decompression effect as traditional open cervical laminectomy while protecting the paraspinal muscles and posterior ligament complex which can avoid postoperative axial symptoms and cervical stiffness. However, due to the small size of the spinal canal and the small perturbation tolerance of the cervical spinal cord, the learning curve will be slightly high. China Clinical Trial registration number：ChiCTR2200065144.