Unilateral Biportal Endoscopic Annular Repair Using an All-Inside Meniscus Repair Device: A Technical Demonstration, Case Report, and Narrative Review
Article information
Abstract
Recurrent lumbar disc herniation remains a clinically important cause of unsatisfactory outcomes after discectomy, and annular defect size is a major risk factor. Large annular defects >6 mm have been associated with substantially higher recurrence rates after minimally invasive discectomy. This study reviews current evidence on annular repair during endoscopic lumbar discectomy and demonstrates a step-by-step surgical technique using unilateral biportal endoscopy (UBE). A narrative review was conducted to synthesize the literature on recurrent lumbar disc herniation, annular defect characteristics, and repair techniques in endoscopic spine surgery. In addition, an operative video demonstrates annular repair performed via the UBE approach in a clinical case. Annular repair during endoscopic lumbar discectomy is a feasible adjunctive technique that may reduce recurrence in appropriately selected patients.
INTRODUCTION
Lumbar disc herniation is a prevalent cause of low back pain and radiculopathy and constitutes one of the most frequent indications for spine surgery. Since the seminal description of lumbar discectomy by Mixter and Barr [1], surgical removal of herniated disc material has been established as an effective treatment for patients with persistent radicular symptoms refractory to conservative management. In recent decades, minimally invasive spine surgery techniques have advanced considerably, particularly with the development of endoscopic lumbar discectomy, which offers advantages such as reduced tissue injury, smaller incisions, decreased postoperative pain, and faster recovery compared with conventional open surgery [2].
Despite these advances, recurrent lumbar disc herniation remains a notable complication following discectomy. Previous studies have reported recurrence rates ranging from approximately 5% to 15%, often leading to persistent symptoms and the need for revision surgery [3]. Several risk factors have been implicated, including younger age, smoking, obesity, disc degeneration, preserved disc height, and mechanical factors related to the annulus fibrosus [4]. Among these, annular defect size following discectomy has been identified as a particularly important predictor of recurrent herniation. Carragee et al. [5] demonstrated that patients with large annular defects had recurrence rates as high as 27%, significantly exceeding those observed in patients with smaller defects. Additional patient-related factors, such as heavy physical workload and elevated body mass index, may further increase mechanical stress on the operated segment and predispose to reherniation [3,4].
Various strategies have been proposed to manage annular defects following discectomy. Annular repair and closure techniques aim to restore annular integrity and reduce the risk of recurrent disc herniation. Parker et al. [6] reported that annular closure may significantly reduce recurrent herniation in patients with large annular defects, and Thomé et al. [7] demonstrated that annular closure in patients with defects exceeding 6 mm resulted in lower rates of symptomatic recurrence compared with standard discectomy alone. A recent meta-analysis further corroborated these findings, reporting that the recurrence rate after conventional discectomy alone was significantly lower in patients who underwent annular repair [8].
With the increasing adoption of endoscopic spine surgery, surgeons have begun applying annular repair techniques under endoscopic visualization. Endoscopic approaches permit direct inspection of the annular defect and may facilitate precise repair while preserving surrounding structures [9]. Among these, unilateral biportal endoscopy (UBE) has gained popularity owing to its wider working space and improved instrument maneuverability compared with single-portal endoscopy. Recent evidence supports the feasibility of annular suturing during UBE discectomy; Zhou et al. [10] reported that, among 177 patients undergoing UBE discectomy, the sutured group had no recurrent disc herniation at follow-up, compared with a 3.6% recurrence rate in the nonsutured group.
However, the current evidence regarding annular repair during endoscopic lumbar discectomy remains limited and heterogeneous. Therefore, this study aims to review the existing literature on annular repair in endoscopic lumbar discectomy and to demonstrate a surgical technique for annular repair using UBE, illustrated with an operative video. A narrative literature review was performed using the PubMed/MEDLINE database to identify relevant studies related to recurrent lumbar disc herniation, annular defect size, annular repair, annular closure devices, and endoscopic discectomy techniques, including UBE. Articles published between January 2000 and December 2025 were reviewed using combinations of the keywords “annular repair,” “annular closure,” “recurrent lumbar disc herniation,” “endoscopic discectomy,” “biportal endoscopy,” and “UBE.” Priority was given to clinical studies, biomechanical investigations, systematic reviews, and studies specifically evaluating annular defect size and recurrence risk.
CASE AND OPERATIVE PROCEDURE
1. Case Presentation
A 54-year-old male presented with progressive left-sided sciatica and bilateral neurogenic claudication of 3-month duration. Symptoms had gradually worsened to the point that the patient was unable to walk more than approximately 20 steps without resting. The patient was physically active and regularly engaged in weightlifting. Neurological examination revealed sensory numbness in the L4–S1 dermatome, and the straight leg raising test was positive on the left side. Lumbar magnetic resonance imaging demonstrated a disc herniation at L4–5 with a cranially migrated fragment, along with lumbar spinal stenosis from L4 to S1 (Figure 1). Based on clinical and radiological findings, the patient was diagnosed with lumbar disc herniation with multilevel lumbar spinal stenosis. After failure of conservative treatment, the patient underwent UBE surgery, including endoscopic discectomy and unilateral laminotomy for bilateral decompression at L4–S1.
(A and B) Plain lumbosacral radiographs in anteroposterior and lateral views. (C–E) Lumbar magnetic resonance imaging demonstrates a disc herniation at L4–5 with a cranially migrated fragment and lumbar spinal stenosis from L4 to S1.
2. Operative Technique
A UBE interlaminar approach was performed at the L4–5 and L5–S1 levels. Stab incisions were created medial to the pedicle projection of L4–S1, and triangulation was directed toward the spinolaminar junction. Using a high-speed burr, laminotomy was performed until the margins of the ligamentum flavum were fully exposed. An en bloc flavectomy was then carried out to achieve unilateral laminotomy for bilateral decompression at both levels. Endoscopic discectomy and neural decompression were completed until the affected nerve root was freely mobile and no residual free fragment remained at L4–5.
Following discectomy, intraoperative assessment of the annular defect was performed according to our institutional protocol using a 6-mm L-shaped probe for measurement (Figure 2A). A large annular defect (>6 mm) was identified; therefore, endoscopic annular repair was indicated. Repair was carried out using an all-inside meniscus repair device (AccurFix, Star Sports Medicine, China; equipped with a 20° curved needle configuration and T1 [1.0 mm × 5 mm] and T2 [1.3 mm × 5 mm] implants; model M01BR; product code F08000005). The first needle was introduced approximately 3 mm below the inferior edge of the annular tear and advanced parallel to the disc space under fluoroscopic and endoscopic guidance (Figure 2B). After confirming appropriate positioning within the disc space, the implant was deployed through the annular layer. Upon exiting the needle tip intradiscally, the small anchor changed orientation (“flipped”) perpendicular to the insertion trajectory, allowing it to engage against the inner surface of the annulus fibrosus and provide resistance to pullout when tension was applied to the suture. A second needle was then inserted approximately 3 mm above the superior edge of the tear (Figure 2C) using a similar trajectory, and the second implant was deployed in the same manner to create fixation points on both sides of the annular defect. The device was subsequently withdrawn, and gradual tension was applied to approximate the annular edges. A knot pusher was then used to secure the suture (Figure 2D and E), followed by trimming the knot with a cutter. Final endoscopic inspection confirmed stable annular closure without residual disc fragments and adequate neural decompression (Figure 2F). The step-by-step operative technique is presented in Supplementary Video Clip 1. The en bloc butterfly flavectomy specimens obtained during unilateral laminotomy for bilateral decompression are shown in Figure 2G.
Intraoperative annular defect assessment using a 6-mm L-shaped probe (A), followed by placement of the inferior needle (B) and superior needle (C), suture fixation with a knot pusher and trimming (D and E), and final confirmation of stable annular closure with adequate neural decompression (F). (G) The en bloc butterfly flavectomy specimen.
Postoperatively, the patient was maintained in a lumbosacral brace for 1 month to promote annular healing. At 2 weeks postoperatively, the patient reported marked relief of sciatica and neurogenic claudication. The visual analog scale score improved from 9/10 preoperatively to 1/10 postoperatively, with sustained improvement at 6-month follow-up and no recurrence of symptoms.
DISCUSSION
Although annular repair using endoscopic techniques has been reported previously, the present study makes several additional practical contributions to the existing literature. First, beyond demonstrating the technical feasibility of annular repair under UBE visualization, this manuscript also emphasizes a clinically applicable, risk-stratified treatment strategy based on intraoperative assessment of annular defect size. The proposed concept highlights the role of direct annular defect measurement as a practical decision-making tool for selective annular repair during endoscopic lumbar discectomy. In addition, the present technical report describes several operative considerations specific to the UBE approach, including endoscopic defect localization, instrument triangulation within the biportal working corridor, and controlled suture passage under direct visualization. These technical details may help improve procedural reproducibility and assist surgeons in incorporating annular repair techniques into minimally invasive endoscopic spine surgery practice.
Recurrent lumbar disc herniation remains one of the most challenging complications following lumbar discectomy and constitutes a common cause of persistent symptoms and revision surgery [1]. Multiple risk factors have been implicated, including younger age, smoking, disc degeneration, obesity, preserved disc height, and biomechanical instability of the annulus fibrosus following removal of herniated disc material [3,4]. Among these, annular defect size has been consistently identified as one of the strongest predictors of recurrent herniation. Carragee et al. [5] demonstrated that large annular defects were associated with recurrence rates as high as 27%, and subsequent studies have confirmed that defects exceeding approximately 6 mm are associated with a substantially elevated risk [7].
Because the annulus fibrosus serves as a structural barrier preventing extrusion of nucleus pulposus material, a large residual defect may permit continued disc migration through the weakened annular ring, particularly under repetitive spinal loading [5]. To address this, annular closure devices and repair techniques have been developed to reduce recurrent herniation and reoperation rates. Parker et al. [6] reported that annular closure significantly reduced recurrence in patients with large defects, while Thomé et al. [7] demonstrated lower symptomatic recurrence rates with annular closure in defects exceeding 6 mm compared with standard discectomy alone. Pooled analyses have also indicated that annular repair may significantly reduce the risk of recurrence compared with the control group [8].
These findings support a risk-stratified treatment approach in which annular repair is selectively considered according to intraoperative annular defect size assessment (Table 1; Figure 3). The proposed threshold values are primarily derived from previous studies demonstrating a strong association between larger annular defects and recurrent lumbar disc herniation. Carragee et al. reported significantly increased recurrence rates in patients with large annular defects, while subsequent studies and annular closure trials commonly defined “large” defects as those measuring approximately 6 mm or greater in width [5,7]. Accordingly, annular defects exceeding 6 mm are considered strong candidates for annular closure because of their substantially elevated recurrence risk. In contrast, defects smaller than 4 mm are generally associated with a lower risk of recurrent herniation and may often be adequately managed with standard discectomy alone. Although a universally accepted cutoff for “small” annular defects has not been definitively established, the 4-mm threshold was selected as a practical lower-risk category based on prior literature trends and the authors’ clinical experience, recognizing that recurrence risk likely exists along a continuum rather than at a strict binary threshold. Defects measuring between 4 and 6 mm may therefore represent an intermediate-risk subgroup in which selective annular repair can be considered, depending on additional patient-related factors such as smoking status, obesity, disc degeneration, or preserved disc height. This risk-adapted strategy is particularly relevant in minimally invasive and endoscopic spine surgery, where preservation of disc tissue and annular integrity is emphasized.
Risk factors for recurrent lumbar disc herniation
Proposed clinical protocol for annular repair during endoscopic lumbar discectomy. The algorithm stratifies management according to intraoperative annular defect size and additional patient-related risk factors. UBE, unilateral biportal endoscopy; BMI, body mass index.
With the expanding utilization of endoscopic spine surgery, including percutaneous endoscopic discectomy and UBE, surgeons have begun performing annular repair under direct endoscopic visualization [9]. UBE provides a wider working space and improved instrument triangulation compared with single-portal endoscopy, rendering it well suited for advanced procedures such as annular suturing. Zhou et al. [10] reported that among 177 patients undergoing UBE discectomy, those who received annular suturing demonstrated no recurrent disc herniation during follow-up, compared with a 3.6% recurrence rate in the nonsutured group, with lower reoperation rates (2.6% vs. 5.1%). Importantly, postoperative pain and functional outcomes improved significantly in both groups with no major differences, indicating that annular suturing may provide additional protection against recurrence without compromising clinical recovery.
Several technical considerations are important to ensure the safety and reproducibility of endoscopic annular repair using the UBE approach. During needle insertion and suture passage, the risk of nerve root or dural injury can be minimized by maintaining continuous endoscopic visualization, careful trajectory control, limited penetration depth, and gentle manipulation within the working corridor. Adequate decompression and clear identification of neural structures prior to annular suturing are essential to maintain a safe operative field. However, the procedure may remain technically demanding, particularly in cases with limited working space, bleeding obscuring visualization, severe adhesions, or poor annular tissue quality that may compromise suture purchase. Excessive tension during knot tying should also be avoided to reduce the risk of tissue cut-through or neural irritation. Although no knot-related neural complication was observed in the present case, potential irritation from knot prominence or suture positioning near neural structures remains a theoretical concern, and the long-term safety profile of extracanal knot placement requires further evaluation. In addition, several contraindications should be considered, including severely collapsed disc spaces, advanced disc degeneration with insufficient residual annular tissue, extensive calcified disc herniation, or situations in which adequate endoscopic visualization cannot be safely achieved. Potential complications include incomplete closure, recurrent disc herniation despite repair, transient neural irritation, and technical failure of suture fixation. Awareness of these technical pitfalls and limitations may help improve procedural safety and optimize patient selection for endoscopic annular repair.
It should be acknowledged that, although clinical evidence supports the protective effect of annular repair in reducing recurrent disc herniation, experimental biomechanical studies suggest that direct annular repair may not fully restore the native mechanical properties of the annulus fibrosus. The inner annulus possesses limited vascularity and intrinsic healing potential, and repaired annular tissue may therefore remain biomechanically weaker than the original intact structure. As a result, annular repair should not be interpreted as complete biological restoration of disc integrity, but rather as a mechanical adjunct intended to reduce the risk of nucleus pulposus re-extrusion. This limitation has important implications for patient selection and long-term postoperative expectations. Patients with severe disc degeneration, marked disc space collapse, poor residual annular tissue quality, or significant segmental instability may derive less benefit from annular repair because the underlying disc biomechanics are already substantially compromised. Conversely, patients with preserved disc height and relatively maintained annular tissue may represent more suitable candidates for repair-based strategies. Furthermore, preservation of annular tissue during discectomy may be equally important as repair itself, and postoperative activity modification should remain part of a comprehensive recurrence-prevention strategy, as annular repair alone may not completely eliminate the risk of recurrent herniation under repetitive spinal loading conditions.
Several limitations in the current literature warrant consideration. The majority of studies evaluating annular repair are retrospective or involve relatively small patient cohorts, and heterogeneity exists in surgical techniques, patient selection criteria, and outcome measures. Furthermore, long-term comparative data specifically evaluating annular repair during endoscopic procedures remain sparse. In addition, the present study is a single-case technical demonstration and therefore inherently carries limited clinical evidence. Accordingly, the findings of this report should be interpreted primarily as a technical illustration rather than as definitive evidence of clinical superiority or efficacy in preventing recurrence. Although previously published studies have suggested that annular repair may reduce recurrent disc herniation in selected high-risk patients, the true magnitude and durability of its clinical benefit in endoscopic spine surgery remain to be fully established. Prospective randomized controlled trials with standardized protocols, larger patient cohorts, and extended follow-up are necessary to establish optimal indications and confirm the long-term outcomes of endoscopic annular repair.
CONCLUSION
Endoscopic lumbar discectomy is an effective minimally invasive treatment for lumbar disc herniation; however, recurrent disc herniation remains a clinically relevant concern, particularly in patients with large annular defects. Current evidence suggests that annular repair may reduce recurrence and reoperation rates by restoring annular integrity and preventing re-extrusion of nucleus pulposus material. Selective annular repair may therefore be considered in high-risk patients, especially those with annular defects exceeding 6 mm or moderate defects accompanied by additional risk factors. The present video demonstrates a practical UBE annular repair technique, highlighting the key steps of defect identification, measurement, and suturing. This technique may serve as a useful adjunct to endoscopic discectomy while preserving the benefits of minimally invasive surgery. Further prospective studies are warranted to validate standardized indications and long-term outcomes.
WRITTEN TRANSCRIPT
00:00 Title and Overview
Today, I am honored to present our work titled: “Unilateral Biportal Endoscopic Annular Repair Using an All-Inside Meniscus Repair Device: A Technical Demonstration, Case Report, and Narrative Review.” This study is a collaborative effort across multiple institutions. In this presentation, we will focus on 2 main aspects: first, reviewing the current evidence on annular defect management and its role in preventing recurrent lumbar disc herniation; and second, demonstrating a practical surgical technique using the unilateral biportal endoscopic approach.
00:33 Introduction
Lumbar disc herniation is a common cause of low back pain and radiculopathy, and discectomy remains the standard surgical treatment since its introduction by Mixter and Barr [1]. However, recurrence remains a significant clinical challenge, occurring in approximately 5% to 15% of cases, often leading to persistent symptoms and the need for reoperation. Previous studies have identified several key risk factors, including large annular defects, smoking, young age, disc degeneration, and obesity. Based on these findings, annular repair has been proposed to restore annular integrity and reduce the risk of recurrence, particularly in patients with large defects greater than 6 mm.
01:12 Risk Factors for Recurrent Herniated Nucleus Pulposus
A narrative review of the literature was conducted related to recurrent lumbar disc herniation, annular defect size, and annular repair techniques in endoscopic spine surgery. The most important is annular defect size, with defects greater than 6 mm strongly associated with recurrence. Patient factors such as smoking, younger age, and high body mass index (BMI) also increased risk. In addition, disc degeneration and preserved disc height reflect underlying structural vulnerability. Importantly, studies have shown that annular closure can significantly reduce recurrence, especially in large defects. Overall, recurrence is multifactorial, but large annular defects remain the key driver, supporting our strategy of selective annular repair in high-risk patients.
01:59 Protocol for Annular Repair During Endoscopic Lumbar Discectomy
In this slide, we demonstrate our systematic approach for managing annular defects during endoscopic lumbar discectomy. After completing discectomy, the next critical step is to evaluate the annular defect. The defect size is measured intraoperatively using a probe as a reference, which allows us to classify the defect based on its width. If the annular defect is less than 4 mm, we typically proceed with standard discectomy alone, as the risk of recurrence is relatively low. For defects measuring between 4 to 6 mm, we enter a gray zone; in these cases, limited annular repair may be considered, depending on additional factors such as the degree of disc degeneration and patient-specific risk factors. However, when the annular defect exceeds 6 mm, the risk of recurrence increases significantly; therefore, annular repair is recommended. Importantly, annular repair may also be strongly considered even in moderate defects when one or more high-risk factors are present. These include younger age, preserved disc height, smoking, high physical activity, and elevated BMI. This algorithm provides a practical and risk-adapted strategy to guide decision making for annular repair during endoscopic spine surgery.
03:10 Case Presentation
A 54-year-old male presented with progressive left-sided sciatica and bilateral neurogenic claudication for 3 months. His symptoms gradually worsened, to the point that he was unable to walk more than 20 steps without resting. The patient was physically active and regularly engaged in weight-lifting activities. On neurological examination, sensory numbness was noted in the L4 to S1 dermatome, and the straight leg raising test was positive on the left side.
03:36 Preoperative Imaging
Lumbar magnetic resonance imaging revealed a left-sided L4 to 5 disc herniation with cranial migration, along with multilevel lumbar spinal stenosis from L4 to S1.
03:45 Surgical Technique
A unilateral biportal endoscopic left interlaminar approach was performed at L4–5 and L5–S1. Stab incisions were made medial to the pedicle projections. An en bloc butterfly flavectomy enabled unilateral laminotomy for bilateral decompression. From the left side, the figure demonstrates a 6-mm probe, disc material from L4–5, and en bloc flavectomy specimens from the L4–5 and L5–S1 levels.
04:12 Annular Defect Assessment
Following discectomy, the annular defect was assessed intraoperatively using a 6-mm L-shaped probe according to our protocol. A large defect greater than 6 mm was identified. Therefore, endoscopic annular repair was performed using an all-inside meniscus repair device.
04:35 Annular Repair
The first needle was inserted about 3 mm below the annular tear, parallel to the disc space under fluoroscopy, and the implant was deployed with intradiscal anchoring. A second needle was placed 3 mm above the tear, and the second implant was deployed. The suture was secured with a knot pusher. The excess suture was then trimmed with a cutter. Final endoscopic inspection confirmed stable closure, no residual fragments, and adequate decompression.
06:05 Progress Note
At 2 weeks postoperatively, the patient reported marked relief of sciatica and neurogenic claudication. The pain score improved from 9 out of 10 to 1 out of 10, with sustained improvement at 6 months and no recurrence of symptoms.
06:20 Conclusion
Endoscopic lumbar discectomy is an effective treatment; however, recurrent disc herniation remains a concern, especially in patients with large annular defects. Current evidence suggests that annular repair may reduce recurrence and reoperation by restoring annular integrity and preventing re-extrusion. Therefore, selective annular repair should be considered in high-risk patients, particularly those with defects greater than 6 mm or additional risk factors. This technique serves as a useful adjunct to endoscopic discectomy, preserving the benefits of minimally invasive surgery, although further prospective studies are needed to confirm long-term outcomes.
Supplementary Material
Supplementary Video Clip 1 is available at https://doi.org/10.21182/jmisst.2026.03482.
Supplementary Video Clip 1.
Step-by-step demonstration of annular repair using unilateral biportal endoscopy after endoscopic lumbar discectomy at L4–5. The video shows annular defect assessment, needle placement, implant deployment, suture fixation, and final inspection.
Notes
Conflicts of Interest
The authors have nothing to disclose.
Funding/Support
This study received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Acknowledgments
The narration in the supplementary video was produced using the integrated text-to-speech feature provided by CapCut (ByteDance Ltd.).
Ethics Statement
Written informed consent was obtained from the patient prior to participation in this study. The study protocol was reviewed and approved by the institutional review board (IRB) of Chulabhorn Royal Academy (IRB No. 072/2569).