Abstract
Objective This study introduces the application of a 12° endoscope in unilateral biportal endoscopic (UBE) decompression surgery for lumbar disc herniation and discusses its advantages in UBE procedures.
Methods From December 2019 to December 2020, 75 patients (33 men and 42 women) were treated with UBE decompression using a 12° endoscope. Patient ages ranged from 26 to 78 years (mean 53.2). Pre- and postoperative visual analog scale (VAS) scores for low back and leg pain were recorded. Surgical outcomes were evaluated using MacNab criteria, with operative time and complications documented.
Results The 12° endoscope demonstrated superior maneuverability with a distortion-free visual field. Compared with 30° endoscopes, it showed better applicability within the anatomical working triangle while providing broader visualization than 0° endoscopes. This enabled effective decompression of the superior articular process medial edge, nerve root canal, and lateral recess. Low back pain VAS scores decreased from 7.3 ± 1.3 to 1.9 ± 1.2 (P < 0.001), while leg pain scores improved from 8.1 ± 1.8 to 1.6 ± 1.0 (P < 0.001). At the 12-month follow-up, MacNab criteria outcomes were excellent in 65.3%, good in 25.3%, and unsatisfactory in 9.3% of cases (χ 2 test, P = 0.002).
Conclusion The 12° endoscope demonstrates clinical value as a feasible, safe, and effective option for UBE surgery in lumbar disc herniation treatment.
Clinical Relevance Key clinical advantages of the 12° endoscope include direct visualization of key anatomical structures, minimized bone resection (particularly at the medial spinous process base), and a reduction in instrument crowding. These technical benefits contribute to effective decompression, improved patient outcomes (as measured by VAS and MacNab criteria), and potentially a shorter learning curve for surgeons adopting the UBE technique.
Level of Evidence 3.
Introduction
Lumbar disc herniation is frequently associated with nerve root canal stenosis. The L4, L5, and S1 nerve roots pass through the lateral recess before traversing the intervertebral foramen along the inferior margin of the vertebral pedicle in the lower lumbar spine. In degenerative spinal pathologies, nerve root compression in the lateral recess results from combined pathological changes, including medial migration and hyperplasia of the superior articular process, ligamentum flavum hypertrophy, vertebral body posterior margin osteophytosis, and lumbar disc herniation.1 Conventional surgical decompression is typically performed through hemilaminectomy with medial facetectomy of the superior articular process, combined with ligamentum flavum excision and herniated disc removal.2 The lateral recess represents the principal site of nerve entrapment, with contributing factors including bony stenosis, ligamentum flavum hypertrophy, and disc herniation.3
Unilateral biportal endoscopy (UBE) has been increasingly adopted for spinal decompression procedures. Endoscope selection plays a critical role in facilitating the surgical learning curve.4 Most UBE procedures utilize 0° or 30° endoscopes.5,6 While 0° endoscopes lack rotational field expansion, angled variants enable this capability. Although 30° endoscopes offer wider visualization, they present technical challenges such as directional disorientation and blind spot formation. In lateral recess decompression, 30° endoscopes frequently necessitate additional bone removal at the spinous process base for adequate ipsilateral visualization. A 12° endoscope was implemented in UBE procedures, enabling direct ipsilateral lateral recess visualization without medial spinous process resection. Compared with 0° endoscopes, the 12° variant provides an enhanced field of view while mitigating instrument crowding associated with 0° endoscope working space constraints. Endoscope rotation enhances visualization of both the ipsilateral lateral recess and ventral medial dural sac. This study demonstrates the technical advantages and clinical applicability of 12° endoscopes in UBE interventions.
Methods
Patients
Between December 2019 and December 2020, 87 patients with unilateral low back and leg pain attributed to lumbar disc herniation and lumbar nerve root compression were enrolled in the present study. Eligibility for UBE decompression surgery was determined through a comprehensive assessment of presenting symptoms, medical history, physical examinations, and imaging findings. Exclusion criteria included lumbar spondylolisthesis, vascular claudication, previous lumbar surgery, hip/knee joint pathologies, or musculoskeletal disorders. Twelve patients who met the exclusion criteria were subsequently excluded from the initial cohort. The remaining 75 patients underwent UBE unilateral decompression following informed consent.
Surgical Materials and Instruments
Lens degree refers to the tilt angle of an optical lens, defined as the angle between the lens axis and a line perpendicular to the lens surface. This parameter typically ranges from 0° to 120°, with a larger angle demonstrating greater suitability for specialized directional observation due to the deviation of the visual field from the direct line of sight. In our surgical application, the 12° lens could be rotated to expand the surgical field of view. Clinical observations revealed its particular advantages during unilateral lateral recess decompression procedures in patients with disc herniation.
The 12° lens (Eurasia, Shenyang, and Storz, Germany) had a radial angle of 12°, a field of view of 115°, and a length of 175 mm (Figure 1). A self-developed UBE surgical kit (Bomeidi, Wuhan, China) was used (Figure 1).
Twelve-degree lens and unilateral biportal endoscopic surgical kit.
Surgical Technique
All patients received preoperatively planned UBE decompression under general anesthesia. Intraoperative monitoring included continuous assessment of blood pressure, heart rate, electrocardiogram, oxygen saturation, and respiratory rate. Controlled hypotension was maintained to reduce intraoperative hemorrhage and optimize muscle relaxation for soft tissue channel preservation. Following successful anesthetic induction, patients were positioned prone with abdominal support provided by chest and iliac crest pads to mitigate bleeding secondary to elevated abdominal pressure. Prior to sterile preparation, anatomical landmarks (midline of the iliac crest and lumbar spinous processes) were identified to localize the surgical level. Aseptic draping was extended beyond standard margins to accommodate instrument maneuverability while adhering to rigorous sterile protocols. A drainage channel was established to manage irrigation fluid egress. Intraoperative localization was confirmed using a 10-gauge spinal needle under C-arm fluoroscopy, followed by positioning in reverse Trendelenburg orientation to achieve perpendicular alignment of the target intervertebral space relative to the floor.
In UBE approaches, portal placement was standardized as follows: For left-sided symptomatic cases, the endoscopic viewing portal was established 1.5 cm paramedian at the inferior pedicular border of the superior vertebra, and the working portal was positioned at the midpedicular level of the inferior vertebra (Figure 2A). For right-sided approaches, the viewing portal was placed at the inferior pedicular margin of the inferior vertebra, with the working portal located at the interpedicular midpoint between the superior vertebra’s inferior pedicle and intervertebral space superior border, maintaining a 1.5cm-lateral offset from the spinous process midline. The lateral aperture was measured at 1.5 cm from the midline of the spinous process (Figure 2B).
Unilateral biportal endoscopic spine surgery, left sided (A) and right sided (B). The dashed line indicates the medical pedicle, the red line is the viewing portal, and the blue line is the working portal.
An oblique skin incision was created with a #11 scalpel blade at the spinolaminar junction. The deep fascial incision was extended toward the endoscopic side using Metzenbaum scissors to establish an unobstructed surgical corridor. Subsequent dissection involved detachment of the multifidus muscle from the lamina using a Cobb elevator. A 12° endoscope was introduced into the surgical field and connected to a gravity-fed irrigation system maintained at approximately 70 cm above the surgical site. Subperiosteal soft tissue and osseous structures were resected with a bipolar radiofrequency device, followed by partial laminectomy using either a Kerrison rongeur or high-speed burr to access the hypertrophied ligamentum flavum, which was carefully resected to fully expose the dura mater.
The endoscope was then advanced into the spinal canal. Osseous decompression of the superior articular process was performed using a curved osteotome or endoscopic drill, with particular attention to visualization through the inferior articular window. The articular complex was removed using pituitary forceps, allowing clear identification of the traversing nerve root. Medial retraction of the nerve root exposed the herniated disc, which is subsequently excised to achieve complete decompression of the nerve. Final confirmation of adequate decompression was verified through endoscopic visualization of ventral nerve root mobility using a nerve hook. Closure was achieved with interrupted absorbable sutures in the deep fascial layer followed by subcuticular skin closure.
Postoperative Evaluation
Postoperative evaluation included lumbar spine computed tomography and magnetic resonance imaging performed 7 days postoperatively to quantify spinal canal decompression. Clinical outcomes were assessed using the visual analog scale (VAS) and MacNab criteria.7 VAS scores were obtained preoperatively and at 1-, 6-, and 12-month postoperative intervals. Patient satisfaction was specifically evaluated using MacNab criteria at the 12-month follow-up. A repeated measures analysis of variance was performed to assess the clinical manifestations prior to the operation and the outcomes of each follow-up, utilizing SPSS software to conduct t tests for result comparison.
Statistical Analysis
Statistical analysis was conducted using the software SPSS 27.0 (SPSS Corporation, USA). The measurement data (VAS for lower back pain. VAS for lower limb pain, and Oswestry Disability Index) following a normal distribution were expressed in the form of x ± s. Paired t tests were employed to assess the variance between pre- and postoperative VAS values. Enumeration data (excellent and reasonable rate according to MacNab criteria) were described as frequency (percentage) and compared using the χ 2 test. Statistical significance was set at an α value of 0.05 (2-tailed).
Results
Patients
Seventy-five patients meeting inclusion criteria underwent UBE decompression surgery. The cohort comprised 33 men (44%) and 42 women (56%) aged 26–78 years (mean, 53.2 ± 12.1 years). Symptom duration averaged 48 months (range: 6–80 months). Surgical levels included L3/L4 in 5 patients (6.7%), L4/L5 in 46 patients (61.3%), and L5/S1 in 24 patients (32.0%; Table 1).
Patients’ baseline characteristics (N = 75).
Outcomes
The mean operative time was 43.1 ± 33.2 minutes. Clinical outcomes were evaluated over a 12-month postoperative follow-up period. Low back pain VAS scores decreased significantly from 7.3 ± 1.3 preoperatively to 1.9 ± 1.2 at 12 months (mean difference: 5.4; 95% CI, 5.1–5.7; T = 24.6; P < 0.001; Figure 3A). Leg pain VAS scores showed similar improvement, declining from 8.1 ± 1.8 preoperatively to 1.6 ± 1.0 postoperatively (mean difference: 6.5; 95% CI, 6.2–6.8; T = 29.8; P < 0.001; Figure 3B). According to modified MacNab criteria, 68 patients (90.6%) reported “excellent” (65.3%, n = 49) or “good” (25.3%, n = 19) outcomes. This favorable response rate differed significantly from baseline expectations (χ 2 = 12.4, P = 0.002; Figure 3C).
Visual analog scale scores for the back (A) and leg (B) before and after the operation. (C) MacNab criteria outcome ratings.
Concerning complications and recurrence rates of the surgery, dural rips were observed in 1.3% (1/75), with recurrence rates also at 1.3% (1/75), both of which were addressed either conservatively or with a subsequent procedure.
Complications
A 5-mm dural tear was observed in 1 patient, with no associated cauda equina nerve compression. Primary dural repair was not required. The defect was covered with a gelatin sponge, and the wound was closed primarily without drainage. The patient recovered completely without neurological sequelae.
Postoperative Recurrence
Recurrent herniation occurred in a 75-year-old woman with initial L4/5 disc pathology. Intraoperative findings revealed extensive yellow-brown degenerated disc material, which was partially excised with immediate postoperative symptom resolution. On postoperative day 2, acute recurrence of lumbar and leg pain occurred during defecation, replicating preoperative symptoms. Magnetic resonance imaging confirmation demonstrated recurrent disc herniation at the operative level. After 72 hours of failed conservative management, revision surgery was performed through the existing UBE portal under local anesthesia. Transforaminal endoscopic exploration was used to identify and remove recurrent herniated disc fragments, resulting in complete symptom resolution.
Discussion
The UBE technique has gained increasing adoption in China for lumbar discectomy.8,9 While UBE is associated with marginally greater tissue trauma than transforaminal endoscopic approaches, preliminary data from our group (currently undergoing peer review) demonstrate superior clinical outcomes, particularly in foraminal decompression, postoperative satisfaction rates, and a 2-year recurrence reduction.
Prior studies have shown that transforaminal endoscopic discectomy exhibits limited efficacy in patients aged >57 years with concurrent lateral recess stenosis.1,3,10 This limitation arises from anatomical constraints of the transforaminal route, where an endoscopic working angle typically <25° is insufficient for adequate bony lateral recess decompression.11–13 The UBE’s posterior approach overcomes this through a dual-portal system, enabling 3-dimensional visualization and angled instrumentation, particularly when using 12° endoscopes.
Endoscopic techniques in spinal surgery enable UBE decompression procedures that provide a surgical field comparable to open approaches while requiring only 2 small skin incisions. This method has demonstrated significant clinical efficacy in managing lumbar degenerative disorders, as evidenced by current clinical applications.14 The UBE approach minimizes tissue trauma while maintaining procedural efficiency. Compared with single-portal endoscopic techniques, the biportal system enhances both instrument maneuverability and overall therapeutic effectiveness during decompression procedures.15 The endoscopic configuration simultaneously optimizes visualization while reducing tissue pressure.
Our utilization of a 12° angled endoscope provided superior field-of-view advantages over traditional 0° scopes by expanding visualization into normally obscured anatomical areas (Figure 4A and B). For the 30° endoscope, visual field obstruction may occur due to interference from medial bony structures, such as the sphenoidal roots. While proficient surgeons can often address this obstruction by rotating the visual field channel, complete avoidance of further bone resection is not always feasible (Figure 4C). The mentioned visual field advantage of the 12° lens compared with the 30° lens can be visualized more clearly from the intraoperative images (Figure 4D–G).
The visual field advantages of angled endoscopes. (A) The 0° endoscope provided restricted visibility of the lateral nerve root canal and lateral recess. (B) The 12° and 30° endoscopes accessed this area through rotation; however, (C) the 30° endoscope faced limitations due to the medial bone. (D and F) Twelve-degree endoscopic intraoperative view observation of decompressed traveling nerve roots (white arrow) and ipsilateral bony structures (yellow white). (E and G) Thirty-degree endoscopic intraoperative view observation of decompressed traveling nerve roots (white arrow) and ipsilateral bony structures (yellow arrow).
The 0° endoscope’s visual field is concentrically aligned with the lens axis. In UBE’s dual-channel configuration, this coaxial alignment introduces functional constraints during instrument navigation to the target area. Proximity magnification, while intended to enhance visualization clarity, further increases the risk of instrument-lens collisions due to the coaxial arrangement (Figure 5A). In contrast, the 12° and 30° endoscope’s offset visualization axis prevents trajectory overlap between instruments during target manipulation (Figure 5B and C).
The occupying effect of the endoscope: (A) the visual field of the 0° endoscope was oriented directly ahead, resulting in an occupying effect that caused instrument collisions. (B and C) The 12° and 30° endoscopes were angled to 1 side, preventing collision with the instruments.
Cauterization requirements for cavity formation were reduced when using the 12° endoscope compared with the 0° variant (Figure 6A and D). The rotational capability of the 12° endoscope allowed complete circumferential visualization of the cavity (anterior, medial, posterior, and lateral aspects), eliminating the need for additional muscle cauterization to optimize the visual field through lens repositioning. Laminar bone resection with the 12° endoscope produced less extensive removal than with the 0° scope. This technique created a conical bone aperture, enhancing the protection of the spinous process base and lateral facet joint. Following partial bone resection, the endoscope was advanced into the spinal canal to visualize and decompress the nerve root’s anterior aspect.
(A and D) The 12° endoscope facilitated observation of the nerve root canal while preserving the bone at the root of the medial spinous process of the lamina. (B and E) The medial bone limited the observation of the nerve root canal using the 30° endoscope. (C and F) The field of view of the 0° mirror is missing for the nerve root canal.
Compared with the 30° endoscope, the 12° model demonstrated superior preservation of medial spinous process base bone and subspinous ligamentum flavum during resection. To visualize the lateral recess on the approach side’s exterior, the 30° endoscope required inward angulation, necessitating the removal of obstructing medial lamina and spinous process base bone (Figure 6C and F). While some surgeons adjusted the 30° endoscope’s viewing angle to circumvent medial bone obstruction by inspecting anterior/posterior regions, this proved less ergonomic than employing the 12° endoscope for triangular working zone procedures (Figure 6B and E).
Adequate decompression is required for optimal postoperative symptom resolution. The decompression process necessitates maintaining an optimal balance between procedural efficiency and patient safety (Figure 7A–D, Figure S1). Surgical proficiency and complication rates demonstrate an inverse relationship with operator experience, as evidenced by reduced adverse events correlating with increasing case volumes.16 Unilateral lateral recess decompression performed with a 12° endoscope demonstrates enhanced operative efficiency compared with alternative approaches (Table 2). The device’s superior visualization capacity further improves procedural safety, resulting in a shortened learning curve for UBE techniques that facilitates safe and efficient ipsilateral decompression.
Preoperative (A and B) and postoperative (C and D) magnetic resonance imaging findings of a typical 12° endoscopic case showing good decompression of the lateral recess area with both facet joint preservation. (A and C) Images show good decompression of the ipsilateral side lateral recess area. (B) Preoperative compressed dural sac and herniated disc (white arrowhead). (D) Postoperative dural sac expansion areas, lateral recess angle (yellow arrowhead), and facet joint preservation volume (white arrowhead).
Comparison of 0°, 12°, and 30° endoscopes.
Conclusion
The 12° endoscope offers distinct advantages in unilateral UBE decompression procedures. This technique enables: (1) direct visualization without extensive tissue exposure; (2) minimized bone resection requirements; (3) avoidance of instrument crowding within the operative field; (4) maintenance of consistent visual clarity; and (5) enhanced procedural flexibility. These characteristics establish the 12° endoscope as the recommended standard instrumentation for unilateral decompression in UBE surgery.
Acknowledgments
This study was supported by grants from the financial support of the National Science Foundation of China (NSFC, 81974349, 82202766), 2022 In-Hospital Free Innovation Pre-Research Fund of the Scientific Research Office (F016.01003.22003.138) and Department of Science and Technology of Hubei Province General Foundation of Natural Science (2024AFB664 and 2022CFB686).
Footnotes
↵† Wenbo Wu, Yanqiu Xie, and Yinkai Xue are joint first authors.
Funding The authors received no financial support for the research, authorship, and/or publication of this article.
Declaration of Conflicting Interests The authors report no conflicts of interest in this work.
- This manuscript is generously published free of charge by ISASS, the International Society for the Advancement of Spine Surgery. Copyright © 2025 ISASS. To see more or order reprints or permissions, see http://ijssurgery.com.
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