A Natural Anatomical Channel for Percutaneous Transforaminal Endoscopic Surgery: Concept and Initial Outcomes of the BEIS Technique

A Natural Anatomical Channel for Percutaneous Transforaminal Endoscopic Surgery: Concept and Initial Outcomes of the BEIS Technique | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article A Natural Anatomical Channel for Percutaneous Transforaminal Endoscopic Surgery: Concept and Initial Outcomes of the BEIS Technique Hongchen Wang, Shuai Xu, Hongyu Wei, Shipeng Xiao, Liwen Wang, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7974947/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 21 You are reading this latest preprint version Abstract Objective To introduce the Broad Easy Immediate Surgical (BEIS technique) technique, a novel transforaminal endoscopic approach that utilizes a natural anatomical corridor through the superior foraminal zone, and to evaluate its initial clinical outcomes. Methods This retrospective case-series study included 392 patients. The BEIS technique is characterized by a working cannula trajectory that enters the spinal canal dorsally to the exiting nerve root via the upper foramen, requiring only minimal resection of the superior articular process (SAP) apex. With the patient in a lateral position, the puncture needle was advanced under fluoroscopy along the ventral aspect of the SAP apex (the BEIS point) to the posterior-superior edge of the vertebral body. A midline-directed channel was established using a TOMshidi needle and graduated bone drills (Ø4-9mm), followed by systematic endoscopic decompression. Results The safety of the BEIS channel was confirmed in relation to the exiting nerve root, traversing nerve root, and spinal dura. The technique demonstrated a significantly enlarged operational field and 94% patient satisfaction. Compared to conventional foraminoplasty, it achieved minimal bone resection. It also improved accessibility at the L5/S1 level in cases with a high iliac crest. Quantitative outcomes showed significant improvements in leg pain VAS (from 72.8 ± 20.9 to 22.9 ± 9.8) and ODI (from 38.3 ± 19.2 to 11.1 ± 5.2) at 1-year follow-up (P < 0.001 for both). Conclusion As an evolution of the TESSYS technique, BEIS successfully navigates the traditional "forbidden zone" of the upper foramen to establish a novel, safer anatomical corridor. Its advantages in bone preservation and surgical accessibility support its consideration as a valuable addition to the minimally invasive spine surgeon's armamentarium. Natural channel Percutaneous transforaminal endoscopic discectomy Forbidden zone Broad easy immediate surgical technique Figures Figure 1 Figure 2 INTRODUCTION Minimally invasive spinal surgery (MISS) has gained widespread acceptance as an alternative to traditional open procedures, owing to advances in surgical techniques and instrumentation 1 , 2 . Among MISS options, percutaneous lumbar endoscopic discectomy (PLED) has emerged as a promising treatment for lumbar disc herniation (LDH), offering benefits such as smaller incisions, reduced paraspinal muscle injury, minimal blood loss, shorter hospital stays, and decreased risk of iatrogenic instability 3 , 4 . Percutaneous transforaminal endoscopic discectomy (PTED), a subtype of PLED, has evolved into two principal approaches 5 : Yeung endoscopic spine system (YESS) 6 and transforaminal endoscopic spine system (TESSYS) 7 . The latter, an “outside-in” technique, has gained popularity due to its broad indications and satisfactory outcomes. It enables surgeons to perform procedures through a single-channel working cannula, extending its applicability not only to LDH but also to lumbar spinal stenosis (LSS), achieving comprehensive nerve root decompression and foraminal expansion. However, the conventional TESSYS technique is associated with several inherent limitations that warrant consideration 8 , 9 . The technique requires significant removal of the superior articular process (SAP) and offers limited working cannula mobility. Particularly challenging cases include L5/S1 disc procedures with high iliac crest or hypertrophic transverse process 10 . The need for foraminoplasty to enlarge the narrow foramen - necessitated by SAP obstruction - raises concerns about potential spinal instability and increased bleeding risk, despite facet joint preservation 11 . Furthermore, the TESSYS working cannula’s typical endpoint placement (medial foramen coronally and lower foramen region sagittally) restricts surgical visualization due to reduced instrument maneuverability 12 . The fundamental principle of optimal MISS involves achieving maximal decompression with adequate extensive surgical field while minimizing bone resection 13 . To address the aforementioned limitations of TESSYS, Professor Yibing Bai pioneered the Broad Easy Immediate Surgical (BEIS) technique in 2015 as a conceptual and technical evolution. Critically, the BEIS technique represents a potential paradigm shift by fundamentally redefining the transforaminal working corridor. In contrast to the TESSYS technique, which necessitates the creation of an artificial channel in the inferior foramen through extensive ventral SAP resection (foraminoplasty), the BEIS approach exploits a pre-existing, larger anatomical space in the superior foramen. This strategic shift from an “artificial” to a “natural” channel enables direct access to the spinal canal with minimal bone removal, primarily limited to the SAP apex. Consequently, the BEIS technique is postulated to offer a broader operational field, enhanced preservation of facet joint integrity, and a more direct working pathway to midline structures—collectively addressing the core constraints of conventional PTED. Therefore, the primary objective of this study is to present a comprehensive technical description of the BEIS approach and provide an initial evaluation of its safety and efficacy through a retrospective case-series analysis.. MATERIALS AND METHODS 1. The conception of BEIS The TESSYS technique employs gradual foraminoplasty by ventral SAP bone removal to expande lower foraminal volume, enabling the working cannula insertion through the inferior foramen to access the protrusion site. While utilizing similar instrumentation to TESSYS, the BEIS technique fundamentally differs in its anatomical approach. The BEIS cannula could directly enter the spinal canal via the upper part of foramen, positioned dorsally to exiting nerve roots within Kambin’s triangle. This strategic trajectory allows the instrument's working path to extend to the midline and potentially contralateral regions. With a broader volume in upper part of foramen, passing above the apex of SAP (BEIS point), there was much fewer or even nothing of bone removal of SAP by the natural channel (Fig. 1 ). The technical specifics of BEIS are detailed as follows. 2. Puncture localization 1) Body posture. The patient is positioned laterally with the symptomatic side superiorly oriented. The waist on the unaffected side is slightly elevated, and the torso is stabilized. using support devices to maintain strict perpendicular alignment with the horizontal plane (Supplementary Fig. 1) . 2) Radiography standardization. C-arm was adjusted to achieve: (1) the middle alignment of spinous process on the anteroposterior (AP) image. (2) Parallel alignment of the upper and lower endplates of the target disc on lateral view. This ensures optimal overlapping of bilateral superior articular processes (SAP) for maximal foraminal visualization (Supplementary Fig. 1). 3) Skin puncture point. On AP image: a reference line connects the midpoint of the posterior-superior edge of lower vertebrae and SAP vertex of the target space (The angle between this line and the horizontal line is designated α). This line intersects with a line extending from the iliac crest apex at point a. The distance from point a to the iliac crest = Distance A. Puncture point b is determined by applying a perpendicular ruler from posterior midline through point a, Simultaneously pressing a coronal-aligned ruler dorsally (Point b-to-midline = Distance B) (Supplementary Fig. 2). The distance B requires individual adjustment (about 0.5 to 1cm). 3. Working-channel (BEIS channel) establishment 1) Puncture pathway. After the initial puncture point determined, local infiltration anesthesia is administered with 0.67% lidocaine. In this process, the SAP is first identified with puncture needle under standard lateral fluoroscopy, and then the needle is advanced along the ventral aspect of the SAP apex (BEIS point) to reach the posterior upper edge of the lower vertebrae. Concurrently,, the needle tip should be located on the midline of the back on the standard AP fluoroscopy (Supplementary Fig. 3) . 2) Puncture point adjustment. For suboptimal needle trajectories, reassess distance A and B, the point b, as well as the needle’s orientation until optimal positioning is achieved. Here, the coronal inclination angle and sagittal abduction angle could be finally determined (Supplementary Fig. 2) . 3) Channel establishment. Insert a guidewire through the puncture needle, then remove the needle. Perform sequential soft tissue dilation by an expanding catheter along the guidewire. Position the TOMshidi needle to contact the BEIS point. Reinsert the guidewire and perform graduated foraminal expansion using: Nerve-protected bone drills (Ø4, 6, 7, 8, and 9 mm); maintain ventral SAP contact during drilling; partial SAP apex resection may be required for narrow foramina. Subsequently, the working cannula and endoscopy are orderly inserted to establish the operative channel (Supplementary Fig. 3) . 4. Microscopic decompression 1) Foraminal Expansion: According to the order of exposing the structure under microscope, the hypertrophic flavum and facet joints in zone III (foramen area) was repaired for further expanding the foramen, which could provide broader space for zones I and II. 2) Exiting nerve root was exposed to ensure it was free from compression. 3) Lateral Recess Decompression: After entering zone II (paracentral zone), adequate decompression on narrow lateral recess was performed by exploring cranial and caudal lateral recess, and then the outside of traversing root was exposed. When the disc protrudes in this area, the herniated nucleus pulposus could be removed. 4) Central Canal Exploration: Then the traversing root and the ventral dura were examined within zone I (central area) for further decompression such as adhesive tissue, posterior longitudinal ligament, fibrous ring, and posterior osteophytes, with meticulous search for hidden nuclear fragments ( Fig. 2 ) . RESULTS 1. The safety evaluation of BEIS 1) The exiting nerve root and foramen Since the exiting nerve root is located in the upper part of foramen, the working channel was suggested to be established in the middle and lower region of the foramen. However, the viewpoint was questionable. It is known that intervertebral foramen shaped as an inverted pear figure with a wider upper region and a narrow bottom and the exiting nerve root pierces at the anterior area of foramen on sagittal plane, close to the posterior margin of vertebrae. In that case, there was actually wider distance from nerve root to posterior margin of foramen in the upper region than the lower region, which was proved by previous publications 14 as well as the measurement of our team (Supplementary Fig. 4) . In addition, since there is a ventral and lateral traveling of exiting nerve root away from the foramen, the nearest distance between nerve root and BEIS cannula occurs exactly at the foramen plane and drifts each other away in the spinal canal (Supplementary Fig. 4) . Hence, adequate anteroposterior diameter at the foramen plane could be theoretically provided for both nerve root and cannula, the safety of channel establishment could be guaranteed. 2) The exiting nerve root and intertransverse barrier As mentioned above, the exiting nerve root travels forward outside the foramen in front of transverse and intertransverse ligament as well as musculi intertransversarii laterales, which provides natural barrier for nerve free from injury, especially by the posterior approach of BEIS (Supplementary Fig. 4) . What’s more, the transverse could be regarded as a anatomic marker for the positioning of BEIS point. 3) The safety of traversing nerve root Generally, the cannula with BEIS channel would be placed within the triangle surrounded by exiting and traversing nerve root, and the endoscopic cannula would be inserted at the outside (eg: flavum) of traversing nerve root (Supplementary Fig. 4) . 4) The safety of spinal dura There may be a misunderstanding that the spinal dura would be damaged with BEIS channel when the bone drills and cannula were placed. However, the drills and cannula would be immediately stopped when there was sense of breakthrough, which was far from the midline of posterior longitudinal ligament and ventral dura. In addition, the instruments penetrated closely to isthmus, where the dura as well as traversing root were protected by the lamina throughout the process. The safety of spatial distance could also be verified by 3D simulation derived from real-world patient with myelography (Supplementary Fig. 4) . 2. The advantages and disadvantages of BEIS The advantages brought by BEIS contrasted with TESSYS technique should be mentioned: 1) Since the angle of working-channel was more steep with BEIS than classical TESSYS, the herniation or stenosis of L5/S1 with high iliac could be operated where it was hard to be handled with TESSYS. 2) As the bony inlet of spinal canal for BEIS channel, there were wider area from upper region of foramen than TESSYS, which allowed increased swing amplitude of cannula and broaden operation field for central protrusion and prolapse disc (Supplementary Fig. 5) . 3) The scrape of little apex of SAP (BEIS point) instead of foraminoplasty with trephine preserved the maximal bone structure and lumbar stability. 4) The lateral recess was directly and effectively enlarged by removing the ventral and medial SAP. 5) The punctual landing point is stable for avoiding trackslip. 6) The exiting nerve root was easy to be exposed. 7)The length of puncture pathway to the midline was shorter. However, the disadvantages of BEIS should also be noted. Contrasted with TESSYS and YESS, more precise puncture pathway was require of BEIS since the instrument would go across and be clingy to nerve root and spinal dura. In addition, it was dangerous for traversing root squeezed outside of the lamina by this pathway. Hence, more intraoperative fluoroscopy was forced and the learning curve would be prolonged for beginners ( Table 1 ) . Table 1 The comparisons on advantages and disadvantages between YESSYS and BEIS TESSYS BEIS Technical Features Comparison Channel More artificial More natural Surgical Approach Lower 1/3 Upper 1/3 SAP removal Extensive ventral SAP Minimal SAP apex Bone removal Mainly trephine Bone drills Working-channel inclination Flatter, limited maneuverability Steeper, easier midline Length of puncture pathway Long Short (direct canal entry) Intertransverse assisted position No Yes Intraoperative fluoroscopy Less More (precision required) Exiting root exposure Sometimes hidden Easy and clear Safety Comparison Body posture Usually prone Lateral Dural Tear Risk Moderate (instrument near dura) Low (channel adjoins pedicle medially) Punctual landing point sometimes instable stable Protection by lamina No Yes Spinal Stability Potential risk Better (preserves SAP) Microscopic vision Narrower Wider Exiting root exposure Sometimes hidden Easy and clear Applicability Comparison Central Disc Herniation Limited visualization Easier midline access Operated with high iliac crest Challenging More feasible Lateral recess enlargement Difficult Direct and accessible Learning curve Short Long (precise BEIS point targeting) Therefore, considering to the superiority of BEIS, the surgical-indications could be extended to: 1) the pure lumbar disc herniation (especially for extreme external type, paracentral type and central type), 2) herniation at L4/5 level with higher iliac crest and L5/S1 disc herniation, 3) lumbar spinal stenosis, 4) degenerative spondylolisthesis (Grade I) without back pain, 5) adjacent segment disease after open surgery or revision in-situ, 6) as well as other lumbar disorders such as spinal deformities, trauma and infections. 3. Cases example and clinical efficacy evaluation Till now from December 2015, there were totally 452 patients underwent BEIS with lumbar spinal disease in our center. The study has been approved by the ethics committee of our institution and all participants have signed the consent informs. Eventually, 392 cases (M%=57.4%, mean55.0 ± 13.7(y) ) completed the follow up of 13.5 ± 2.6(m) with a rate of loss of 13.3%. The mean operation time was 97.1 ± 34.7 (min) and the most common disease was disc herniation (61.2%), followed by lumbar stenosis syndrome (34.9%). The typical cases was detailed in Supplementary Fig. 6 to Fig. 8 . According to the Odom's criteria, the proportion of patients with excellent outcomes was 60.2% and 6.7% of participants acquired unsatisfied efficacy. The pre- and post-operative visual analogue scale (VAS) of leg pain (0 ~ 100 score) and Oswestry disability index (ODI) were also evaluated for the participants. The mean VAS in leg pain significantly improved at 1-year visit (22.9 ± 9.8) compared to the baseline (72.8 ± 20.9), so was ODI (38.3 ± 19.2 at preop vs. 11.1 ± 5.2 at postop) ( Table 2 ) . The complications happened in 17 cases (4.3%), mainly included reoccurrence (5 cases), dural rupture (4 cases), injury of traversing root (3 cases), paraesthesia (3 cases) and myeloid hypertension-like syndrome (2 cases). Comparative analysis revealed that BEIS produced similar clinical efficacy to TESSYS (reported by corresponding references) in pain relief and functional recovery, but with distinct advantages: 1) minimized bleeding by eliminating foraminoplasty, 2) lower complication incidence, and 3) 4–9% higher satisfaction rates ( Table 3 ) . Table 2 The clinical efficacy of lumbar spinal disorders treated by BEIS VAS in leg pain (0 ~ 100 score) ODI (0 ~ 50 score) Preop Postop Preop Postop Mean (n = 392) 72.8 ± 20.9 22.9 ± 9.8 38.3 ± 19.2 11.1 ± 5.2 Disc herniation (L1/2 ~ L3/4) (n = 11) 77.2 ± 23.3 23.3 ± 13.5 41.1 ± 23.1 13.4 ± 8.1 Disc herniation (L4/5) (n = 161) 73.6 ± 26.0 19.8 ± 13.0 36.0 ± 22.0 10.6 ± 6.7 Disc herniation (L5/S1) (n = 62) 71.8 ± 31.1 22.2 ± 15.2 35.8 ± 29.3 10.8 ± 7.1 Lumbar spinal stenosis (n = 137) 67.3 ± 19.9 25.3 ± 11.4 42.3 ± 20.2 10.8 ± 6.2 Degenerative spondylolisthesis (n = 10) 81.8 ± 27.3 22.8 ± 11.1 43.7 ± 22.7 14.4 ± 7.7 Revision (ASD/in-situ) (n = 8) 83.8 ± 20.5 25.0 ± 16.3 41.6 ± 26.1 9.2 ± 6.6 Others (n = 3) 72.2 ± 36.7 20.6 ± 18.8 41.1 ± 25.0 13.1 ± 11.2 Footnote: VAS: visual analogue scale; ODI: Oswestry disability index; ASD: adjacent segment disease Table 3 The comparisons on clinical outcomes between YESSYS and BEIS TESSYS BEIS Operative Time 80–120 min 4, 26] 97.1 ± 34.7 min Blood Loss Foraminoplasty-related bleeding Reduced Hospital Stay 3–4 days 3–4 days Pain Relief (VAS) 70 → 25 4] Preop 72.8 → Postop 22.9 Function (ODI) 40 → 15 4] Preop 38.3 → Postop 11.1 Complication Rate 5–10% 7, 18] 4.3% (manuscript data) Patient Satisfaction 85–90% 4, 15] 94% DISCUSSION First of all, the quintessence of MISS must be emphasized, where the normal tissues would be maximally protected and the diseased tissues would be accurately removed, achieving to treat diseases with minimal cost 2 , 15 .The present study demonstrates that the BEIS technique is not merely an incremental improvement but may represent a paradigm shift in transforaminal access philosophy. Traditional PTED approaches, epitomized by TESSYS, are fundamentally based on the principle of “creating a space” by resecting the ventral SAP to access the spinal canal from the inferior foramen. In contrast, BEIS is predicated on the principle of “utilizing an existing space”—the naturally wider and more capacious superior foraminal zone. This conceptual divergence translates into tangible intraoperative differences: where TESSYS requires extensive osseous resection with trephines, BEIS accomplishes access with minimal, focused bone work using drills at a single strategic point (the BEIS point). The resulting steeper cannula inclination in BEIS not only facilitates a shorter, more direct route to central and contralateral pathologies but also inherently preserves the biomechanically critical ventral SAP to a greater extent, which may have implications for long-term spinal stability 16 , 17 . Contrasted with TESSYS, the concept of BEIS focused on the the shorter distance of direct decompression through clear visualization with wider surgical field and expansion space, where the main goal of BEIS was targeted at traversing root and ventral dura 18 . Therefore, the essence of BEIS channel could be summarized that it is a natural channel between the root of transverse process on the upper vertebrae and the SAP peak on the lower vertebrae 19 , 20 , where the instruments entered the canal through foramen and reached the midline, snugly close to the isthmus. Then, the entrance of channel was located where there was largest sagittal diameter of foramen 21 and shortest horizontal diameter of lamina, verifying a safe shortcut to enter canal. In addition, the relationship between the predetermined channel and SAP determines the amount of resection of SAP apex, as well as whether partial removal of transverse process is necessary. In the puncture process, like the tips of TESSYS, a three-dimensional puncture pathway could be simplified into two planar pathway. For example, if there was lower tilt of pathway in coronal and sagittal plane, then the increase of tilt within both planes was needed. However, it must be noted that the tilt in sagittal plane would become steeper in the X-ray although only the tilt in coronal plane was added, and vice versa. Therefore, it could be understood that the tilt should be added in the sagittal plane when the tilt of the needle was decreased for the goal in coronal plane although the tilt (in X-ray) in sagittal palne was originally proper. Similarly, the adjustment of puncture point on the skin should also be complied with this perspective principle. The skin point at L5/S1 level, in general, was determined beside the midline longer than the level of L4/5 by 2cm, and the distance at L3/4 and L2/3 was shorter than L4/5 by 2cm and 4cm, respectively 22 , 23 . In addition, the process of anesthesia also provided the chance for further adjusting and determining the puncture point. Therefore, it is unwise to purely depend on the geometric algorithms mentioned above and the combination of preoperative measurement and radiological adjustment, but also on the clinical practice, which was emphasized by the procedure with TESSYS. The meaning of BEIS point should be further strengthened. BEIS point is located at the inflection point on the posterior edge of foramen (lateral X-ray) where the it transits from the wider region to the lower narrow part in the ear-shape foramen. The foraminoplasty by grinding SAP peak at this point is considered the most effective and economical process for entering spinal canal with least bone removal, which is currently recognized as the optimal entry point. Actually, the EBIS point is a concept of “boundary” instead of a simple puncture point. The area from the BEIS point to the innermost end of the crest of SAP is called the apex of SAP 24 , 25 , within where higher safety could be guaranteed during puncture process, otherwise risk would increase. The procedure of BEIS emphasized the puncture direction should go through between SAP peak and the root of the transverse process of upper vertebrae. In this condition, the midline could be easily and accurately accessible and the nerve root and dura could acquire comprehensive relaxation. In the process, the working-cannula can swing with enlarged operation field 26 and the microscopic structures could be explored according to the “boundary”. Analogous to TESSYS, the systematic microscopic process of BEIS could be regulated as nine-steps procedure based on the concept of “boundary” ( Fig. 2 and Supplementary Fig. 9) . Similar to other approaches of MISS committing to be simpler and more convenient for learners, the nine-steps procedure of patterned BEIS would shorten the learning curve27, 28. Here, the ordered and purposeful operation could hardly leave the pressure behind and reduce ineffective works. In addition, the establishment of “boundary” could clarify the range of exploration and predict potential dangers outside the “boundary”. The natural channel and enlarged endoscopic vision of EBIS possibly make it more applicable for canal stenosis although there was gradual optimization for TESSYS 29 . Then its credibility and security could be practically confirmed with 137 cases diagnosed canal stenosis acquiring satisfied outcomes by our data. However, it was clinically difficult to determine whether the BEIS was totally superior to other technology of PLED with pure herniation although based on hundreds of cases. Admittedly, few powerful studies has demonstrated an advantage of PLED over the opening surgery such as fenestration or Love procedure in terms of operation time, projection of radiograph, incision size and decompressed range 30 . This study has several limitations that must be acknowledged. First and foremost, the evidence level is constrained by its single-arm, retrospective design. While the outcomes are promising and the cohort is substantial, the absence of a direct, concurrent control group (e.g., patients treated with TESSYS) means that comparative efficacy and safety conclusions should be drawn with caution. This work, therefore, serves as a foundational, hypothesis-generating study. Secondly, the safety of the BEIS corridor, while supported by anatomical simulations and clinical outcomes, lacks quantitative in vivo measurements of the minimum safe distances to neural structures. Future studies incorporating intraoperative neuromonitoring or neuronavigation could yield valuable quantitative data. 27 . Finally, the procedures were performed at a single center by surgeons proficient in this technique. The generalizability of these results needs validation through multi-center studies involving surgeons with varying experience levels to objectively assess the learning curve and broader applicability. CONCLUSION In conclusion, the BEIS technique fundamentally redefines the approach to percutaneous transforaminal endoscopy. Its core innovation lies in utilizing the natural, wider aperture of the superior foramen, which allows for a steeper working trajectory, significantly enlarged surgical field, and unparalleled preservation of the superior articular process compared to the TESSYS technique. Our findings, which demonstrate excellent safety and clinical outcomes, establish the feasibility of this approach and lay the groundwork for its future adoption. The BEIS technique thereby emerges as a promising and transformative advancement in the pursuit of truly minimally invasive spinal decompression. Abbreviations MISS minimally invasive spinal surgery PLED percutaneous lumbar endoscopic discectomy LDH lumbar disc herniation PTED percutaneous transforaminal endoscopic discectomy YESS Yeung endoscopic spine system TESSYS transforaminal endoscopic spine system LSS lumbar stenosis syndrome SAP superior articular process BEIS broad easy immediate surgical technique VAS visual analogue scale ODI Oswestry disability index Declarations Ethics approval and consent to participate: The study has been approved by the ethics committee of Peking University People’s Hospital (No. 2018PHC076). The ethics declaration is in accordance with the Declaration of Helsinki. All participants have signed the consent informs. Consent for publication: All the listed authors have carefully reviewed and approved this manuscript. Competing interests: The authors declare that they have no competing interests. Funding: This work was supported by (1) Clinical Medicine Plus X-Young Scholars Project Peking University, the Fundamental Research Funds for the Central Universities [grant number PKU2023LCXQ042], (2) the Beijing Natural Science Foundation [grant number 7232182], (3) Peking University Clinical Scientist Training Program (grant number BMU2024PYJH016), (4) China Association for Science and Technology: Innovative Service for Management of Scoliosis in Tibetan Adolescents (grant number: N/A). Author Contribution Conceptualization: Hongchen Wang, Shuai Xu, Hongyu Wei, Shipeng Xiao, Liwen Wang, Meng Ye, Haiying Liu, Yongping Zheng, De YangData curation: Hongchen Wang, Shuai Xu, Liwen Wang, Meng Ye, Haiying LiuFormal analysis: Shuai XuFunding acquisition: Shuai XuMethodology: Shuai Xu, Hongyu Wei, Shipeng Xiao, Liwen Wang, Meng Ye, Haiying Liu, De YangProject administration: Hongchen Wang, Shuai Xu, Hongyu Wei, Shipeng XiaoVisualization: Hongchen Wang, Shuai Xu, Hongyu Wei, Shipeng Xiao, Yongping Zheng, De YangWriting - original draft: Hongchen Wang, Shuai Xu, Shipeng XiaoWriting - review & editing: Shuai Xu, Hongyu Wei, Yongping Zheng Acknowledgement We thank Yibing Bai who contributed towards the study by making substantial contributions to the design and the acquisition of data. Data Availability The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request. References Jain D, Ray WZ, Vaccaro AR. 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08:40:42","extension":"tif","order_by":7,"title":"","display":"","copyAsset":false,"role":"supplement","size":2159096,"visible":true,"origin":"","legend":"","description":"","filename":"FigS7.tif","url":"https://assets-eu.researchsquare.com/files/rs-7974947/v1/423153083825d795aa5c61fa.tif"},{"id":96159229,"identity":"75499ccb-972a-4b87-9d09-210aa7b77f10","added_by":"auto","created_at":"2025-11-18 08:40:42","extension":"tif","order_by":8,"title":"","display":"","copyAsset":false,"role":"supplement","size":2416228,"visible":true,"origin":"","legend":"","description":"","filename":"FigS8.tif","url":"https://assets-eu.researchsquare.com/files/rs-7974947/v1/878be3509fb6f23a92df21ff.tif"},{"id":96159250,"identity":"f4178643-5b03-462d-9d4a-fa205eb7a3bc","added_by":"auto","created_at":"2025-11-18 08:40:43","extension":"tif","order_by":9,"title":"","display":"","copyAsset":false,"role":"supplement","size":2432838,"visible":true,"origin":"","legend":"","description":"","filename":"FigS9.tif","url":"https://assets-eu.researchsquare.com/files/rs-7974947/v1/ee88c6cf452ad09a437ab4bd.tif"},{"id":96159236,"identity":"43c9b343-7572-40d8-9870-3655b6793133","added_by":"auto","created_at":"2025-11-18 08:40:42","extension":"docx","order_by":10,"title":"","display":"","copyAsset":false,"role":"supplement","size":15759,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryFiglegends.docx","url":"https://assets-eu.researchsquare.com/files/rs-7974947/v1/5d8396bcade37a13b3431ddd.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"A Natural Anatomical Channel for Percutaneous Transforaminal Endoscopic Surgery: Concept and Initial Outcomes of the BEIS Technique","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eMinimally invasive spinal surgery (MISS) has gained widespread acceptance as an alternative to traditional open procedures, owing to advances in surgical techniques and instrumentation\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. Among MISS options, percutaneous lumbar endoscopic discectomy (PLED) has emerged as a promising treatment for lumbar disc herniation (LDH), offering benefits such as smaller incisions, reduced paraspinal muscle injury, minimal blood loss, shorter hospital stays, and decreased risk of iatrogenic instability\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. Percutaneous transforaminal endoscopic discectomy (PTED), a subtype of PLED, has evolved into two principal approaches\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e: Yeung endoscopic spine system (YESS)\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e and transforaminal endoscopic spine system (TESSYS)\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. The latter, an \u0026ldquo;outside-in\u0026rdquo; technique, has gained popularity due to its broad indications and satisfactory outcomes. It enables surgeons to perform procedures through a single-channel working cannula, extending its applicability not only to LDH but also to lumbar spinal stenosis (LSS), achieving comprehensive nerve root decompression and foraminal expansion.\u003c/p\u003e\u003cp\u003eHowever, the conventional TESSYS technique is associated with several inherent limitations that warrant consideration\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. The technique requires significant removal of the superior articular process (SAP) and offers limited working cannula mobility. Particularly challenging cases include L5/S1 disc procedures with high iliac crest or hypertrophic transverse process\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. The need for foraminoplasty to enlarge the narrow foramen - necessitated by SAP obstruction - raises concerns about potential spinal instability and increased bleeding risk, despite facet joint preservation\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. Furthermore, the TESSYS working cannula\u0026rsquo;s typical endpoint placement (medial foramen coronally and lower foramen region sagittally) restricts surgical visualization due to reduced instrument maneuverability\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThe fundamental principle of optimal MISS involves achieving maximal decompression with adequate extensive surgical field while minimizing bone resection\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. To address the aforementioned limitations of TESSYS, Professor Yibing Bai pioneered the Broad Easy Immediate Surgical (BEIS) technique in 2015 as a conceptual and technical evolution.\u003c/p\u003e\u003cp\u003eCritically, the BEIS technique represents a potential paradigm shift by fundamentally redefining the transforaminal working corridor. In contrast to the TESSYS technique, which necessitates the creation of an artificial channel in the inferior foramen through extensive ventral SAP resection (foraminoplasty), the BEIS approach exploits a pre-existing, larger anatomical space in the superior foramen. This strategic shift from an \u0026ldquo;artificial\u0026rdquo; to a \u0026ldquo;natural\u0026rdquo; channel enables direct access to the spinal canal with minimal bone removal, primarily limited to the SAP apex. Consequently, the BEIS technique is postulated to offer a broader operational field, enhanced preservation of facet joint integrity, and a more direct working pathway to midline structures\u0026mdash;collectively addressing the core constraints of conventional PTED.\u003c/p\u003e\u003cp\u003eTherefore, the primary objective of this study is to present a comprehensive technical description of the BEIS approach and provide an initial evaluation of its safety and efficacy through a retrospective case-series analysis..\u003c/p\u003e"},{"header":"MATERIALS AND METHODS","content":"\n\u003ch3\u003e1. The conception of BEIS\u003c/h3\u003e\n\u003cp\u003eThe TESSYS technique employs gradual foraminoplasty by ventral SAP bone removal to expande lower foraminal volume, enabling the working cannula insertion through the inferior foramen to access the protrusion site.\u003c/p\u003e\u003cp\u003eWhile utilizing similar instrumentation to TESSYS, the BEIS technique fundamentally differs in its anatomical approach. The BEIS cannula could directly enter the spinal canal via the upper part of foramen, positioned dorsally to exiting nerve roots within Kambin\u0026rsquo;s triangle. This strategic trajectory allows the instrument's working path to extend to the midline and potentially contralateral regions. With a broader volume in upper part of foramen, passing above the apex of SAP (BEIS point), there was much fewer or even nothing of bone removal of SAP by the natural channel (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The technical specifics of BEIS are detailed as follows.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003e2. Puncture localization\u003c/b\u003e\u003c/p\u003e\u003cp\u003e1) Body posture. The patient is positioned laterally with the symptomatic side superiorly oriented. The waist on the unaffected side is slightly elevated, and the torso is stabilized. using support devices to maintain strict perpendicular alignment with the horizontal plane \u003cb\u003e(Supplementary Fig.\u0026nbsp;1)\u003c/b\u003e.\u003c/p\u003e\u003cp\u003e2) Radiography standardization. C-arm was adjusted to achieve: (1) the middle alignment of spinous process on the anteroposterior (AP) image. (2) Parallel alignment of the upper and lower endplates of the target disc on lateral view. This ensures optimal overlapping of bilateral superior articular processes (SAP) for maximal foraminal visualization (Supplementary Fig.\u0026nbsp;1).\u003c/p\u003e\u003cp\u003e3) Skin puncture point. On AP image: a reference line connects the midpoint of the posterior-superior edge of lower vertebrae and SAP vertex of the target space (The angle between this line and the horizontal line is designated α). This line intersects with a line extending from the iliac crest apex at point a. The distance from point a to the iliac crest\u0026thinsp;=\u0026thinsp;Distance A. Puncture point b is determined by applying a perpendicular ruler from posterior midline through point a, Simultaneously pressing a coronal-aligned ruler dorsally (Point b-to-midline\u0026thinsp;=\u0026thinsp;Distance B) (Supplementary Fig.\u0026nbsp;2). The distance B requires individual adjustment (about 0.5 to 1cm).\u003c/p\u003e\u003cp\u003e\u003cb\u003e3. Working-channel (BEIS channel) establishment\u003c/b\u003e\u003c/p\u003e\u003cp\u003e1) Puncture pathway. After the initial puncture point determined, local infiltration anesthesia is administered with 0.67% lidocaine. In this process, the SAP is first identified with puncture needle under standard lateral fluoroscopy, and then the needle is advanced along the ventral aspect of the SAP apex (BEIS point) to reach the posterior upper edge of the lower vertebrae. Concurrently,, the needle tip should be located on the midline of the back on the standard AP fluoroscopy \u003cb\u003e(Supplementary Fig.\u0026nbsp;3)\u003c/b\u003e.\u003c/p\u003e\u003cp\u003e2) Puncture point adjustment. For suboptimal needle trajectories, reassess distance A and B, the point b, as well as the needle\u0026rsquo;s orientation until optimal positioning is achieved. Here, the coronal inclination angle and sagittal abduction angle could be finally determined \u003cb\u003e(Supplementary Fig.\u0026nbsp;2)\u003c/b\u003e.\u003c/p\u003e\u003cp\u003e3) Channel establishment. Insert a guidewire through the puncture needle, then remove the needle. Perform sequential soft tissue dilation by an expanding catheter along the guidewire. Position the TOMshidi needle to contact the BEIS point. Reinsert the guidewire and perform graduated foraminal expansion using: Nerve-protected bone drills (\u0026Oslash;4, 6, 7, 8, and 9 mm); maintain ventral SAP contact during drilling; partial SAP apex resection may be required for narrow foramina. Subsequently, the working cannula and endoscopy are orderly inserted to establish the operative channel \u003cb\u003e(Supplementary Fig.\u0026nbsp;3)\u003c/b\u003e.\u003c/p\u003e\u003cp\u003e\u003cb\u003e4. Microscopic decompression\u003c/b\u003e\u003c/p\u003e\u003cp\u003e1) Foraminal Expansion: According to the order of exposing the structure under microscope, the hypertrophic flavum and facet joints in zone III (foramen area) was repaired for further expanding the foramen, which could provide broader space for zones I and II.\u003c/p\u003e\n\u003ch3\u003e2) Exiting nerve root was exposed to ensure it was free from compression.\u003c/h3\u003e\n\u003cp\u003e3) Lateral Recess Decompression: After entering zone II (paracentral zone), adequate decompression on narrow lateral recess was performed by exploring cranial and caudal lateral recess, and then the outside of traversing root was exposed. When the disc protrudes in this area, the herniated nucleus pulposus could be removed.\u003c/p\u003e\u003cp\u003e4) Central Canal Exploration: Then the traversing root and the ventral dura were examined within zone I (central area) for further decompression such as adhesive tissue, posterior longitudinal ligament, fibrous ring, and posterior osteophytes, with meticulous search for hidden nuclear fragments \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"RESULTS","content":"\u003cp\u003e\u003cb\u003e1. The safety evaluation of BEIS\u003c/b\u003e\u003c/p\u003e\u003cp\u003e1) The exiting nerve root and foramen\u003c/p\u003e\u003cp\u003eSince the exiting nerve root is located in the upper part of foramen, the working channel was suggested to be established in the middle and lower region of the foramen. However, the viewpoint was questionable. It is known that intervertebral foramen shaped as an inverted pear figure with a wider upper region and a narrow bottom and the exiting nerve root pierces at the anterior area of foramen on sagittal plane, close to the posterior margin of vertebrae. In that case, there was actually wider distance from nerve root to posterior margin of foramen in the upper region than the lower region, which was proved by previous publications\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e as well as the measurement of our team \u003cb\u003e(Supplementary Fig.\u0026nbsp;4)\u003c/b\u003e.\u003c/p\u003e\u003cp\u003eIn addition, since there is a ventral and lateral traveling of exiting nerve root away from the foramen, the nearest distance between nerve root and BEIS cannula occurs exactly at the foramen plane and drifts each other away in the spinal canal \u003cb\u003e(Supplementary Fig.\u0026nbsp;4)\u003c/b\u003e. Hence, adequate anteroposterior diameter at the foramen plane could be theoretically provided for both nerve root and cannula, the safety of channel establishment could be guaranteed.\u003c/p\u003e\n\u003ch3\u003e2) The exiting nerve root and intertransverse barrier\u003c/h3\u003e\n\u003cp\u003eAs mentioned above, the exiting nerve root travels forward outside the foramen in front of transverse and intertransverse ligament as well as musculi intertransversarii laterales, which provides natural barrier for nerve free from injury, especially by the posterior approach of BEIS \u003cb\u003e(Supplementary Fig.\u0026nbsp;4)\u003c/b\u003e. What\u0026rsquo;s more, the transverse could be regarded as a anatomic marker for the positioning of BEIS point.\u003c/p\u003e\n\u003ch3\u003e3) The safety of traversing nerve root\u003c/h3\u003e\n\u003cp\u003eGenerally, the cannula with BEIS channel would be placed within the triangle surrounded by exiting and traversing nerve root, and the endoscopic cannula would be inserted at the outside (eg: flavum) of traversing nerve root \u003cb\u003e(Supplementary Fig.\u0026nbsp;4)\u003c/b\u003e.\u003c/p\u003e\n\u003ch3\u003e4) The safety of spinal dura\u003c/h3\u003e\n\u003cp\u003eThere may be a misunderstanding that the spinal dura would be damaged with BEIS channel when the bone drills and cannula were placed. However, the drills and cannula would be immediately stopped when there was sense of breakthrough, which was far from the midline of posterior longitudinal ligament and ventral dura. In addition, the instruments penetrated closely to isthmus, where the dura as well as traversing root were protected by the lamina throughout the process. The safety of spatial distance could also be verified by 3D simulation derived from real-world patient with myelography \u003cb\u003e(Supplementary Fig.\u0026nbsp;4)\u003c/b\u003e.\u003c/p\u003e\n\u003ch3\u003e2. The advantages and disadvantages of BEIS\u003c/h3\u003e\n\u003cp\u003eThe advantages brought by BEIS contrasted with TESSYS technique should be mentioned: 1) Since the angle of working-channel was more steep with BEIS than classical TESSYS, the herniation or stenosis of L5/S1 with high iliac could be operated where it was hard to be handled with TESSYS. 2) As the bony inlet of spinal canal for BEIS channel, there were wider area from upper region of foramen than TESSYS, which allowed increased swing amplitude of cannula and broaden operation field for central protrusion and prolapse disc \u003cb\u003e(Supplementary Fig.\u0026nbsp;5)\u003c/b\u003e. 3) The scrape of little apex of SAP (BEIS point) instead of foraminoplasty with trephine preserved the maximal bone structure and lumbar stability. 4) The lateral recess was directly and effectively enlarged by removing the ventral and medial SAP. 5) The punctual landing point is stable for avoiding trackslip. 6) The exiting nerve root was easy to be exposed. 7)The length of puncture pathway to the midline was shorter.\u003c/p\u003e\u003cp\u003eHowever, the disadvantages of BEIS should also be noted. Contrasted with TESSYS and YESS, more precise puncture pathway was require of BEIS since the instrument would go across and be clingy to nerve root and spinal dura. In addition, it was dangerous for traversing root squeezed outside of the lamina by this pathway. Hence, more intraoperative fluoroscopy was forced and the learning curve would be prolonged for beginners \u003cb\u003e(\u003c/b\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eThe comparisons on advantages and disadvantages between YESSYS and BEIS\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTESSYS\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eBEIS\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003eTechnical Features Comparison\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eChannel\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMore artificial\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eMore natural\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSurgical Approach\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eLower 1/3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eUpper 1/3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSAP removal\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eExtensive ventral SAP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eMinimal SAP apex\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBone removal\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMainly trephine\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eBone drills\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eWorking-channel inclination\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFlatter, limited maneuverability\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eSteeper, easier midline\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLength of puncture pathway\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eLong\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eShort (direct canal entry)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIntertransverse assisted position\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNo\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eYes\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIntraoperative fluoroscopy\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eLess\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eMore (precision required)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eExiting root exposure\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSometimes hidden\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eEasy and clear\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003e\u003cb\u003eSafety Comparison\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBody posture\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eUsually prone\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eLateral\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDural Tear Risk\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eModerate (instrument near dura)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eLow (channel adjoins pedicle medially)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePunctual landing point\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003esometimes instable\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003estable\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eProtection by lamina\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNo\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eYes\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSpinal Stability\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePotential risk\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eBetter (preserves SAP)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMicroscopic vision\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNarrower\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eWider\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eExiting root exposure\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSometimes hidden\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eEasy and clear\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003e\u003cb\u003eApplicability Comparison\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCentral Disc Herniation\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eLimited visualization\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eEasier midline access\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOperated with high iliac crest\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eChallenging\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eMore feasible\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLateral recess enlargement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDifficult\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eDirect and accessible\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLearning curve\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eShort\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eLong (precise BEIS point targeting)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eTherefore, considering to the superiority of BEIS, the surgical-indications could be extended to: 1) the pure lumbar disc herniation (especially for extreme external type, paracentral type and central type), 2) herniation at L4/5 level with higher iliac crest and L5/S1 disc herniation, 3) lumbar spinal stenosis, 4) degenerative spondylolisthesis (Grade I) without back pain, 5) adjacent segment disease after open surgery or revision in-situ, 6) as well as other lumbar disorders such as spinal deformities, trauma and infections.\u003c/p\u003e\n\u003ch3\u003e3. Cases example and clinical efficacy evaluation\u003c/h3\u003e\n\u003cp\u003eTill now from December 2015, there were totally 452 patients underwent BEIS with lumbar spinal disease in our center. The study has been approved by the ethics committee of our institution and all participants have signed the consent informs. Eventually, 392 cases (M%=57.4%, mean55.0\u0026thinsp;\u0026plusmn;\u0026thinsp;13.7(y) ) completed the follow up of 13.5\u0026thinsp;\u0026plusmn;\u0026thinsp;2.6(m) with a rate of loss of 13.3%. The mean operation time was 97.1\u0026thinsp;\u0026plusmn;\u0026thinsp;34.7 (min) and the most common disease was disc herniation (61.2%), followed by lumbar stenosis syndrome (34.9%). The typical cases was detailed in \u003cb\u003eSupplementary Fig.\u0026nbsp;6 to Fig.\u0026nbsp;8\u003c/b\u003e.\u003c/p\u003e\u003cp\u003eAccording to the Odom's criteria, the proportion of patients with excellent outcomes was 60.2% and 6.7% of participants acquired unsatisfied efficacy. The pre- and post-operative visual analogue scale (VAS) of leg pain (0\u0026thinsp;~\u0026thinsp;100 score) and Oswestry disability index (ODI) were also evaluated for the participants. The mean VAS in leg pain significantly improved at 1-year visit (22.9\u0026thinsp;\u0026plusmn;\u0026thinsp;9.8) compared to the baseline (72.8\u0026thinsp;\u0026plusmn;\u0026thinsp;20.9), so was ODI (38.3\u0026thinsp;\u0026plusmn;\u0026thinsp;19.2 at preop vs. 11.1\u0026thinsp;\u0026plusmn;\u0026thinsp;5.2 at postop) \u003cb\u003e(\u003c/b\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. The complications happened in 17 cases (4.3%), mainly included reoccurrence (5 cases), dural rupture (4 cases), injury of traversing root (3 cases), paraesthesia (3 cases) and myeloid hypertension-like syndrome (2 cases). Comparative analysis revealed that BEIS produced similar clinical efficacy to TESSYS (reported by corresponding references) in pain relief and functional recovery, but with distinct advantages: 1) minimized bleeding by eliminating foraminoplasty, 2) lower complication incidence, and 3) 4\u0026ndash;9% higher satisfaction rates \u003cb\u003e(\u003c/b\u003eTable\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eThe clinical efficacy of lumbar spinal disorders treated by BEIS\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003eVAS in leg pain (0\u0026thinsp;~\u0026thinsp;100 score)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003eODI (0\u0026thinsp;~\u0026thinsp;50 score)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePreop\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePostop\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ePreop\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003ePostop\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMean (n\u0026thinsp;=\u0026thinsp;392)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e72.8\u0026thinsp;\u0026plusmn;\u0026thinsp;20.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e22.9\u0026thinsp;\u0026plusmn;\u0026thinsp;9.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e38.3\u0026thinsp;\u0026plusmn;\u0026thinsp;19.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e11.1\u0026thinsp;\u0026plusmn;\u0026thinsp;5.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDisc herniation (L1/2\u0026thinsp;~\u0026thinsp;L3/4) (n\u0026thinsp;=\u0026thinsp;11)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e77.2\u0026thinsp;\u0026plusmn;\u0026thinsp;23.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e23.3\u0026thinsp;\u0026plusmn;\u0026thinsp;13.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e41.1\u0026thinsp;\u0026plusmn;\u0026thinsp;23.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e13.4\u0026thinsp;\u0026plusmn;\u0026thinsp;8.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDisc herniation (L4/5) (n\u0026thinsp;=\u0026thinsp;161)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e73.6\u0026thinsp;\u0026plusmn;\u0026thinsp;26.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e19.8\u0026thinsp;\u0026plusmn;\u0026thinsp;13.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e36.0\u0026thinsp;\u0026plusmn;\u0026thinsp;22.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e10.6\u0026thinsp;\u0026plusmn;\u0026thinsp;6.7\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDisc herniation (L5/S1) (n\u0026thinsp;=\u0026thinsp;62)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e71.8\u0026thinsp;\u0026plusmn;\u0026thinsp;31.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e22.2\u0026thinsp;\u0026plusmn;\u0026thinsp;15.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e35.8\u0026thinsp;\u0026plusmn;\u0026thinsp;29.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e10.8\u0026thinsp;\u0026plusmn;\u0026thinsp;7.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLumbar spinal stenosis (n\u0026thinsp;=\u0026thinsp;137)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e67.3\u0026thinsp;\u0026plusmn;\u0026thinsp;19.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e25.3\u0026thinsp;\u0026plusmn;\u0026thinsp;11.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e42.3\u0026thinsp;\u0026plusmn;\u0026thinsp;20.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e10.8\u0026thinsp;\u0026plusmn;\u0026thinsp;6.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDegenerative spondylolisthesis (n\u0026thinsp;=\u0026thinsp;10)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e81.8\u0026thinsp;\u0026plusmn;\u0026thinsp;27.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e22.8\u0026thinsp;\u0026plusmn;\u0026thinsp;11.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e43.7\u0026thinsp;\u0026plusmn;\u0026thinsp;22.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e14.4\u0026thinsp;\u0026plusmn;\u0026thinsp;7.7\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRevision (ASD/in-situ) (n\u0026thinsp;=\u0026thinsp;8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e83.8\u0026thinsp;\u0026plusmn;\u0026thinsp;20.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e25.0\u0026thinsp;\u0026plusmn;\u0026thinsp;16.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e41.6\u0026thinsp;\u0026plusmn;\u0026thinsp;26.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e9.2\u0026thinsp;\u0026plusmn;\u0026thinsp;6.6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOthers (n\u0026thinsp;=\u0026thinsp;3)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e72.2\u0026thinsp;\u0026plusmn;\u0026thinsp;36.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e20.6\u0026thinsp;\u0026plusmn;\u0026thinsp;18.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e41.1\u0026thinsp;\u0026plusmn;\u0026thinsp;25.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e13.1\u0026thinsp;\u0026plusmn;\u0026thinsp;11.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"5\"\u003eFootnote: VAS: visual analogue scale; ODI: Oswestry disability index; ASD: adjacent segment disease\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eThe comparisons on clinical outcomes between YESSYS and BEIS\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTESSYS\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eBEIS\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOperative Time\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e80\u0026ndash;120 min 4, 26]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e97.1\u0026thinsp;\u0026plusmn;\u0026thinsp;34.7 min\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBlood Loss\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eForaminoplasty-related bleeding\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eReduced\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHospital Stay\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u0026ndash;4 days\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3\u0026ndash;4 days\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePain Relief (VAS)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e70 \u0026rarr; 25 4]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePreop 72.8 \u0026rarr; Postop 22.9\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFunction (ODI)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e40 \u0026rarr; 15 4]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePreop 38.3 \u0026rarr; Postop 11.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eComplication Rate\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e5\u0026ndash;10% 7, 18]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.3% (manuscript data)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePatient Satisfaction\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e85\u0026ndash;90% 4, 15]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e94%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eFirst of all, the quintessence of MISS must be emphasized, where the normal tissues would be maximally protected and the diseased tissues would be accurately removed, achieving to treat diseases with minimal cost\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e.The present study demonstrates that the BEIS technique is not merely an incremental improvement but may represent a paradigm shift in transforaminal access philosophy. Traditional PTED approaches, epitomized by TESSYS, are fundamentally based on the principle of \u0026ldquo;creating a space\u0026rdquo; by resecting the ventral SAP to access the spinal canal from the inferior foramen. In contrast, BEIS is predicated on the principle of \u0026ldquo;utilizing an existing space\u0026rdquo;\u0026mdash;the naturally wider and more capacious superior foraminal zone. This conceptual divergence translates into tangible intraoperative differences: where TESSYS requires extensive osseous resection with trephines, BEIS accomplishes access with minimal, focused bone work using drills at a single strategic point (the BEIS point). The resulting steeper cannula inclination in BEIS not only facilitates a shorter, more direct route to central and contralateral pathologies but also inherently preserves the biomechanically critical ventral SAP to a greater extent, which may have implications for long-term spinal stability \u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eContrasted with TESSYS, the concept of BEIS focused on the the shorter distance of direct decompression through clear visualization with wider surgical field and expansion space, where the main goal of BEIS was targeted at traversing root and ventral dura\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. Therefore, the essence of BEIS channel could be summarized that it is a natural channel between the root of transverse process on the upper vertebrae and the SAP peak on the lower vertebrae\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e, where the instruments entered the canal through foramen and reached the midline, snugly close to the isthmus. Then, the entrance of channel was located where there was largest sagittal diameter of foramen\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e and shortest horizontal diameter of lamina, verifying a safe shortcut to enter canal. In addition, the relationship between the predetermined channel and SAP determines the amount of resection of SAP apex, as well as whether partial removal of transverse process is necessary.\u003c/p\u003e\u003cp\u003eIn the puncture process, like the tips of TESSYS, a three-dimensional puncture pathway could be simplified into two planar pathway. For example, if there was lower tilt of pathway in coronal and sagittal plane, then the increase of tilt within both planes was needed. However, it must be noted that the tilt in sagittal plane would become steeper in the X-ray although only the tilt in coronal plane was added, and vice versa. Therefore, it could be understood that the tilt should be added in the sagittal plane when the tilt of the needle was decreased for the goal in coronal plane although the tilt (in X-ray) in sagittal palne was originally proper. Similarly, the adjustment of puncture point on the skin should also be complied with this perspective principle. The skin point at L5/S1 level, in general, was determined beside the midline longer than the level of L4/5 by 2cm, and the distance at L3/4 and L2/3 was shorter than L4/5 by 2cm and 4cm, respectively\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. In addition, the process of anesthesia also provided the chance for further adjusting and determining the puncture point. Therefore, it is unwise to purely depend on the geometric algorithms mentioned above and the combination of preoperative measurement and radiological adjustment, but also on the clinical practice, which was emphasized by the procedure with TESSYS.\u003c/p\u003e\u003cp\u003eThe meaning of BEIS point should be further strengthened. BEIS point is located at the inflection point on the posterior edge of foramen (lateral X-ray) where the it transits from the wider region to the lower narrow part in the ear-shape foramen. The foraminoplasty by grinding SAP peak at this point is considered the most effective and economical process for entering spinal canal with least bone removal, which is currently recognized as the optimal entry point. Actually, the EBIS point is a concept of \u0026ldquo;boundary\u0026rdquo; instead of a simple puncture point. The area from the BEIS point to the innermost end of the crest of SAP is called the apex of SAP\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e, within where higher safety could be guaranteed during puncture process, otherwise risk would increase.\u003c/p\u003e\u003cp\u003eThe procedure of BEIS emphasized the puncture direction should go through between SAP peak and the root of the transverse process of upper vertebrae. In this condition, the midline could be easily and accurately accessible and the nerve root and dura could acquire comprehensive relaxation. In the process, the working-cannula can swing with enlarged operation field\u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e and the microscopic structures could be explored according to the \u0026ldquo;boundary\u0026rdquo;. Analogous to TESSYS, the systematic microscopic process of BEIS could be regulated as nine-steps procedure based on the concept of \u0026ldquo;boundary\u0026rdquo; \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e \u003cb\u003eand Supplementary Fig.\u0026nbsp;9)\u003c/b\u003e. Similar to other approaches of MISS committing to be simpler and more convenient for learners, the nine-steps procedure of patterned BEIS would shorten the learning curve27, 28. Here, the ordered and purposeful operation could hardly leave the pressure behind and reduce ineffective works. In addition, the establishment of \u0026ldquo;boundary\u0026rdquo; could clarify the range of exploration and predict potential dangers outside the \u0026ldquo;boundary\u0026rdquo;.\u003c/p\u003e\u003cp\u003eThe natural channel and enlarged endoscopic vision of EBIS possibly make it more applicable for canal stenosis although there was gradual optimization for TESSYS\u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e. Then its credibility and security could be practically confirmed with 137 cases diagnosed canal stenosis acquiring satisfied outcomes by our data. However, it was clinically difficult to determine whether the BEIS was totally superior to other technology of PLED with pure herniation although based on hundreds of cases. Admittedly, few powerful studies has demonstrated an advantage of PLED over the opening surgery such as fenestration or Love procedure in terms of operation time, projection of radiograph, incision size and decompressed range\u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThis study has several limitations that must be acknowledged. First and foremost, the evidence level is constrained by its single-arm, retrospective design. While the outcomes are promising and the cohort is substantial, the absence of a direct, concurrent control group (e.g., patients treated with TESSYS) means that comparative efficacy and safety conclusions should be drawn with caution. This work, therefore, serves as a foundational, hypothesis-generating study. Secondly, the safety of the BEIS corridor, while supported by anatomical simulations and clinical outcomes, lacks quantitative in vivo measurements of the minimum safe distances to neural structures. Future studies incorporating intraoperative neuromonitoring or neuronavigation could yield valuable quantitative data.\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. Finally, the procedures were performed at a single center by surgeons proficient in this technique. The generalizability of these results needs validation through multi-center studies involving surgeons with varying experience levels to objectively assess the learning curve and broader applicability.\u003c/p\u003e"},{"header":"CONCLUSION","content":"\u003cp\u003eIn conclusion, the BEIS technique fundamentally redefines the approach to percutaneous transforaminal endoscopy. Its core innovation lies in utilizing the natural, wider aperture of the superior foramen, which allows for a steeper working trajectory, significantly enlarged surgical field, and unparalleled preservation of the superior articular process compared to the TESSYS technique. Our findings, which demonstrate excellent safety and clinical outcomes, establish the feasibility of this approach and lay the groundwork for its future adoption. The BEIS technique thereby emerges as a promising and transformative advancement in the pursuit of truly minimally invasive spinal decompression.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eMISS\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eminimally invasive spinal surgery\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003ePLED\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003epercutaneous lumbar endoscopic discectomy\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eLDH\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003elumbar disc herniation\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003ePTED\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003epercutaneous transforaminal endoscopic discectomy\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eYESS\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eYeung endoscopic spine system\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eTESSYS\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003etransforaminal endoscopic spine system\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eLSS\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003elumbar stenosis syndrome\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eSAP\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003esuperior articular process\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eBEIS\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003ebroad easy immediate surgical technique\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eVAS\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003evisual analogue scale\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eODI\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eOswestry disability index\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003c/div\u003e"},{"header":"Declarations","content":"\u003ch2\u003eEthics approval and consent to participate:\u003c/h2\u003e\u003cp\u003e The study has been approved by the ethics committee of Peking University People\u0026rsquo;s Hospital (No. 2018PHC076). The ethics declaration is in accordance with the Declaration of Helsinki. All participants have signed the consent informs.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eConsent for publication:\u003c/strong\u003e\u003cp\u003e All the listed authors have carefully reviewed and approved this manuscript.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003ch2\u003eCompeting interests:\u003c/h2\u003e\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eFunding:\u003c/h2\u003e\u003cp\u003eThis work was supported by (1) Clinical Medicine Plus X-Young Scholars Project Peking University, the Fundamental Research Funds for the Central Universities [grant number PKU2023LCXQ042], (2) the Beijing Natural Science Foundation [grant number 7232182], (3) Peking University Clinical Scientist Training Program (grant number BMU2024PYJH016), (4) China Association for Science and Technology: Innovative Service for Management of Scoliosis in Tibetan Adolescents (grant number: N/A).\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eConceptualization: Hongchen Wang, Shuai Xu, Hongyu Wei, Shipeng Xiao, Liwen Wang, Meng Ye, Haiying Liu, Yongping Zheng, De YangData curation: Hongchen Wang, Shuai Xu, Liwen Wang, Meng Ye, Haiying LiuFormal analysis: Shuai XuFunding acquisition: Shuai XuMethodology: Shuai Xu, Hongyu Wei, Shipeng Xiao, Liwen Wang, Meng Ye, Haiying Liu, De YangProject administration: Hongchen Wang, Shuai Xu, Hongyu Wei, Shipeng XiaoVisualization: Hongchen Wang, Shuai Xu, Hongyu Wei, Shipeng Xiao, Yongping Zheng, De YangWriting - original draft: Hongchen Wang, Shuai Xu, Shipeng XiaoWriting - review \u0026amp; editing: Shuai Xu, Hongyu Wei, Yongping Zheng\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eWe thank Yibing Bai who contributed towards the study by making substantial contributions to the design and the acquisition of data.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eJain D, Ray WZ, Vaccaro AR. Advances in techniques and technology in minimally invasive lumbar interbody spinal fusion. Jbjs Reviews. 2020;8:e171.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePierzchajlo N, Stevenson TC, Huynh H, et al. Augmented reality in minimally invasive spinal surgery: a narrative review of available technology. World Neurosurg. 2023;176:35\u0026ndash;42.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZhang Y, Chu J, Xia Y, et al. Research trends of percutaneous endoscopic lumbar discectomy in the treatment of lumbar disc herniation over the past decade: a bibliometric analysis. J Pain Res. 2023;16:3391\u0026ndash;404.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePan M, Li Q, Li S, et al. Percutaneous endoscopic lumbar discectomy: indications and complications. Pain Physician. 2020;23:49\u0026ndash;56.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZhu K, He D. Transforaminal percutaneous endoscopic discectomy for symptomatic gas-filled discal cysts-report of three cases and literature review. J Orthop Surg Res. 2021;16:251.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eYeung AT. Minimally invasive disc surgery with the yeung endoscopic spine system (yess). Surgical Technology International-International Developments in Surgery and Surgical Research. 1999;8:267\u0026thinsp;\u0026ndash;\u0026thinsp;77.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLuan J, Wang Q, Lyu D, et al. Comparable effectiveness of transforaminal endoscopic spine system technique combined with selective nerve root block between far lateral lumbar disc herniation and central or paracentral herniation. Joint Dis Relat Surg. 2022;33:513\u0026ndash;20.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKapetanakis S, Gkasdaris G, Angoules AG, et al. Transforaminal percutaneous endoscopic discectomy using transforaminal endoscopic spine system technique: pitfalls that a beginner should avoid. World J Orthop. 2017;8:874\u0026ndash;80.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKim HS, Wu PH, Jang IT. Current and future of endoscopic spine surgery: what are the common procedures we have now and what lies ahead? World Neurosurg. 2020;140:642\u0026ndash;53.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSong QC, Zhao Y, Li D, et al. Percutaneous endoscopic transforaminal discectomy for the treatment of l5-s1 lumbar disc herniation and the influence of iliac crest height on its clinical effects. Experimental Therapeutic Med. 2021;22:866.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eYu Y, Zhou Q, Xie YZ, et al. Effect of percutaneous endoscopic lumbar foraminoplasty of different facet joint portions on lumbar biomechanics: a finite element analysis. Orthop Surg. 2020;12:1277\u0026ndash;84.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eChung AS, McKnight B, Wang JC. Scientific view on endoscopic spine surgery: can spinal endoscopy become a mainstream surgical tool? World Neurosurg. 2021;145:708\u0026ndash;11.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMomin AA, Steinmetz MP. Evolution of minimally invasive lumbar spine surgery. World Neurosurg. 2020;140:622\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eUchikado H, Nishimura Y, Hattori G, et al. Micro-anatomical structures of the lumbar intervertebral foramen for full-endoscopic spine surgery: review of the literatures. J Spine Surg. 2020;6:405\u0026ndash;14.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eJitpakdee K, Liu Y, Heo DH, et al. Minimally invasive endoscopy in spine surgery: where are we now? Eur Spine J. 2023;32:2755\u0026ndash;68.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLi J, Li H, He Y, et al. The protection of superior articular process in percutaneous transforaminal endoscopic discectomy should decreases the risk of adjacent segment diseases biomechanically. J Clin Neurosci. 2020;79:54\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLi JR, Yan Y, Wu XG et al. Biomechanical evaluation of percutaneous endoscopic posterior lumbar interbody fusion and minimally invasive transforaminal lumbar interbody fusion: a biomechanical analysis. Comput Methods Biomech BioMed Eng 2023:1\u0026ndash;11.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWiltse LL. Anatomy of the extradural compartments of the lumbar spinal canal. Peridural membrane and circumneural sheath. Radiol Clin North Am. 2000;38:1177\u0026ndash;206.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKaydu A, Andan I, Deniz MA, et al. 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Operative Neurosurg. 2021;21:S59\u0026ndash;66.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMaayan O, Pajak A, Shahi P, et al. Percutaneous transforaminal endoscopic discectomy learning curve: a cusum analysis. Spine. 2023;48:1508\u0026ndash;16.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eYang J, Guo C, Kong Q, et al. Learning curve and clinical outcomes of percutaneous endoscopic transforaminal decompression for lumbar spinal stenosis. Int Orthop. 2020;44:309\u0026ndash;17.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eJu CI, Lee SM. Complications and management of endoscopic spinal surgery. Neurospine. 2023;20:56\u0026ndash;77.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGadjradj PS, Harhangi BS, Amelink J, et al. Percutaneous transforaminal endoscopic discectomy versus open microdiscectomy for lumbar disc herniation: a systematic review and meta-analysis. Spine. 2021;46:538\u0026ndash;49.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-musculoskeletal-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmsd","sideBox":"Learn more about [BMC Musculoskeletal Disorders](http://bmcmusculoskeletdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://author-welcome.nature.com/12891","title":"BMC Musculoskeletal Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Natural channel, Percutaneous transforaminal endoscopic discectomy, Forbidden zone, Broad easy immediate surgical technique","lastPublishedDoi":"10.21203/rs.3.rs-7974947/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7974947/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eObjective\u003c/h2\u003e\u003cp\u003eTo introduce the Broad Easy Immediate Surgical (BEIS technique) technique, a novel transforaminal endoscopic approach that utilizes a natural anatomical corridor through the superior foraminal zone, and to evaluate its initial clinical outcomes.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e\u003cp\u003eThis retrospective case-series study included 392 patients. The BEIS technique is characterized by a working cannula trajectory that enters the spinal canal dorsally to the exiting nerve root via the upper foramen, requiring only minimal resection of the superior articular process (SAP) apex. With the patient in a lateral position, the puncture needle was advanced under fluoroscopy along the ventral aspect of the SAP apex (the BEIS point) to the posterior-superior edge of the vertebral body. A midline-directed channel was established using a TOMshidi needle and graduated bone drills (\u0026Oslash;4-9mm), followed by systematic endoscopic decompression.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003eThe safety of the BEIS channel was confirmed in relation to the exiting nerve root, traversing nerve root, and spinal dura. The technique demonstrated a significantly enlarged operational field and 94% patient satisfaction. Compared to conventional foraminoplasty, it achieved minimal bone resection. It also improved accessibility at the L5/S1 level in cases with a high iliac crest. Quantitative outcomes showed significant improvements in leg pain VAS (from 72.8\u0026thinsp;\u0026plusmn;\u0026thinsp;20.9 to 22.9\u0026thinsp;\u0026plusmn;\u0026thinsp;9.8) and ODI (from 38.3\u0026thinsp;\u0026plusmn;\u0026thinsp;19.2 to 11.1\u0026thinsp;\u0026plusmn;\u0026thinsp;5.2) at 1-year follow-up (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001 for both).\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e\u003cp\u003eAs an evolution of the TESSYS technique, BEIS successfully navigates the traditional \"forbidden zone\" of the upper foramen to establish a novel, safer anatomical corridor. Its advantages in bone preservation and surgical accessibility support its consideration as a valuable addition to the minimally invasive spine surgeon's armamentarium.\u003c/p\u003e","manuscriptTitle":"A Natural Anatomical Channel for Percutaneous Transforaminal Endoscopic Surgery: Concept and Initial Outcomes of the BEIS Technique","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-18 08:40:36","doi":"10.21203/rs.3.rs-7974947/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-11-11T05:15:31+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-11T02:16:02+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-10T08:52:30+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-08T13:51:35+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-08T13:22:30+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-06T17:33:04+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"219572705844914438974166837689046145108","date":"2025-11-06T14:22:03+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"207852104859470179065322042013488265248","date":"2025-11-06T10:00:33+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"307918363704678963265538195906493905498","date":"2025-11-06T09:57:16+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"246994186680615312502853498391140916689","date":"2025-11-06T09:56:06+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"105515791394586846189896726672548593485","date":"2025-11-06T09:09:32+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"228272593575138059815223833450628393893","date":"2025-11-06T08:44:45+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-06T08:28:08+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"56989670054720383415507624861920568356","date":"2025-11-06T08:10:15+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"227400217401771024402176859970320496929","date":"2025-11-06T08:07:16+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"182671949737128071823918142254853119862","date":"2025-11-06T08:00:52+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-11-06T07:47:50+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-11-06T07:45:33+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-11-05T04:15:29+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-11-04T11:44:28+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Musculoskeletal Disorders","date":"2025-11-04T11:40:37+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-musculoskeletal-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmsd","sideBox":"Learn more about [BMC Musculoskeletal Disorders](http://bmcmusculoskeletdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://author-welcome.nature.com/12891","title":"BMC Musculoskeletal Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"7cc26ca7-2150-44bc-a870-c5fdd9eed726","owner":[],"postedDate":"November 18th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-12-10T15:58:06+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-18 08:40:36","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7974947","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7974947","identity":"rs-7974947","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}