Background/Objectives: This is a retrospective study. We aimed to identify an optimal biportal endoscopic spine surgery (BESS) technique that maximizes facet joint preservation while achieving sufficient decompression for central to extraforaminal lumbar stenosis across all spinal levels. Methods: We retrospectively analyzed the data of 46 patients who underwent surgery and assessed clinical outcomes (visual analogue scale scores for pain; pregabalin usage) and radiological changes (using computed tomography/magnetic resonance imaging) in the spinal canal; intervertebral foramen area expansion; facet joint preservation; and degenerative change. Results: Using interlaminar and transforaminal approaches (two-way BESS decompression technique), the mean facet joint volume preservation ratio was 87%, and the mean facet joint length maintenance ratio was 90%, indicating a successful anatomical preservation compared with previous studies. Radiological outcomes revealed effective decompression (178% in the spinal canal; 245% in intervertebral foramen expansion). Additionally, all clinical outcome parameters significantly improved (p < 0.001). Conclusions: To the best of our knowledge, this study is the first to accurately estimate the degree of facet joint preservation using different methods after endoscopic surgery. The two-way BESS decompression technique maximized facet joint preservation with sufficient decompression and clinically improved central to extraforaminal stenosis across all lumbar levels. Therefore, this technique can sufficiently preserve facet joints to prevent rapid degenerative change after surgery.

Advancements in expandable cage technology may overcome limitations such as narrow working corridor, continuous irrigation, and endplate injury risk in biportal endoscopic transforaminal lumbar interbody fusion (BE-TLIF). We evaluate sagittal realignment, fusion rates, and clinical outcomes over one year using a single bullet-type expandable cage. This retrospective study included 29 patients (38 levels) who underwent BE-TLIF with a single expandable cage and were followed for at least 12 months. Radiological assessments included disc height (DH), segmental lordosis (SL), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), PI-LL mismatch, and cage subsidence. Clinical outcomes were evaluated using back and leg Visual Analog Scale (VAS), Oswestry Disability Index (ODI), 36-Item Short Form Survey (SF-36), and EuroQol-5 Dimension (EQ-5D). Fusion was evaluated using CT based Bridwell classification at 6 and 12 months. At 12 months, the fusion rate was 92.1%, with significant subsidence (≥ 2 mm) in 3 levels. Anterior and posterior DH increased by 3.97 mm and 4.22 mm, while SL and LL improved by 3.01° and 5.00°, respectively. Back and leg VAS and ODI decreased by 3.0, 5.0, and 12.76 points, while EQ-5D increased by 5.81 points. Greater PI-LL correction correlated with higher fusion rates and better functional recovery. Patients with preoperative sagittal malalignment showed significant improvements. Cage size and type had limited effect on outcomes. BE-TLIF using a single bullet-type expandable cage achieved favorable outcomes at one year, with meaningful sagittal correction and fusion rates, supporting the non-inferiority of this construct in short-segment lumbar fusion..

Methods or RF probe usage time between the two groups. Also, as explained in the reference, there is no significant increase in temperature in coagulation or ablation probe use, and sufficient saline inflow and outflow are maintained during surgery, so we don't think there is anything problem with the author concerns. Finally, the letter points out about useful of warm saline with temperature similar to human body. We also agree about this opinion, and we will consider adding that to further study. In conclusion, we believe this letter will inspire future research that addresses these critical points, also we hope that this study will serve as an opportunity to provide a better prognosis for patients in endoscopic spinal surgery in the future. Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Dear Editor, First of all, we thank the authors for their constructive criticism and insightful inquiries. The letter points out that there is a selection bias about randomization. We agree with what the authors pointed out, and it can also be included in the limitation of this study. However, this study is designed as a retrospective study, it is difficult to have a randomization protocol. In addition, since this is the first study to compare the effects of saline irrigation in BESS, we are planning a prospective study including also group randomization and controlling the variables of the selected patients based on this study. Therefore, we think that if further study proceeds, the question of the authors will be resolved. Next, the letter points out about temperature change of epidural space by using radiofrequency probe. We are fully sympathetic about author's concerns but, this study was performed by a single expert endoscopic spine surgeon. Because of this reason, there is no difference in surgical

To evaluate the clinical outcomes associated with epidurally applied acellular dermal matrix (ADM) soaked with dexamethasone or fentanyl following biportal

Background Biportal endoscopic spinal surgery (BESS) for the treatment of spinal stenosis provided favorable clinical outcomes in many studies. They reported that interlaminar BESS decompression achieved favorable effects in patients with central spinal stenosis. However, many patients still experienced radiating pain even after conventional interlaminar BESS decompression. Therefore, a more reliable BESS decompression method for traversing root and lateral recess areas is necessary. Hence, we investigated a method to better decompress both lateral recess areas while preserving both facet joints as much as possible with bilateral radiculopathy. Methods We retrospectively analyzed the data of 48 patients undergoing interlaminar BESS decompression; 24 patients underwent decompression using the conventional BESS technique (group A), and the other 24 patients underwent a both facet joint preserving BESS technique (group B). The following steps are the characteristics of a better decompression technique: using a 30° endoscope at ipsilateral side decompression, enough decompression through traversing root pathway, and enough removal of fibrotic tissue. Clinical outcomes (visual analog scale scores for pain, pregabalin usage, and modified MacNab criteria) and radiological changes (using magnetic resonance imaging) in the spinal canal expansion, lateral recess angle, and facet joint preservation were evaluated. Results In radiological outcomes, there were significant differences in ipsilateral facet joint preservation ratio and contralateral lateral recess increasing ratio (ipsilateral facet joint preservation ratio 92.15% ± 2.62% vs 90.96% ± 2.88%, P value 0.041 and contralateral lateral recess increasing ratio 155.22% ± 15.99% vs 165.39% ± 22.07%, P = 0.0136). In clinical outcomes, there were significant differences between the 2 groups over time in leg visual analog scale score and pregabalin medication use. Conclusion The BESS technique for preserving both facet joints was an effective treatment option in long-term follow-up; it achieved favorable clinical outcomes while preserving both facet joints and making as much decompression space as possible. Level of Evidence 3.