Lumbar spinal stenosis (LSS), a common degenerative lumbar condition characterized by low back pain, leg pain, and neurogenic claudication, significantly impairs patients' quality of life. Its prevalence continues to rise with the aging population. For patients who do not respond to conservative treatment, surgical intervention remains a key therapeutic approach, with lumbar interbody fusion (LIF) being a commonly employed procedure. The technique has evolved from posterior lumbar interbody fusion (PLIF) to transforaminal lumbar interbody fusion (TLIF) and, more recently, to minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF). Although MIS-TLIF can effectively reduce tissue trauma and complications, it still faces clinical challenges such as intraoperative visual blind spots and the potential for postoperative chronic back pain associated with reliance on conventional pedicle screws. To address these limitations, our research team independently developed a highly integrated, miniaturized (with an outer diameter of only 1.8 mm), and maneuverable L-Unitary Soft Endoscope (LUSE) minimally invasive system. Its unique design helps avoid obstruction of the surgical field and allows flexible adjustment during the procedure. Currently, there is a lack of clinical efficacy evaluations in China on the use of this LUSE system for TLIF surgery (referred to as LUSE-TLIF) in treating LSS. Therefore, this study aims to systematically compare LUSE-TLIF with the currently mainstream MIS-TLIF, evaluating its safety, efficacy, and clinical outcomes in the treatment of LSS, in order to provide spine surgeons with a novel and potentially superior minimally invasive surgical option.

Lumbar spinal stenosis (LSS) is a common degenerative condition of the lumbar spine. In its narrow definition, LSS primarily refers to central canal stenosis resulting from facet joint hypertrophy and thickening of the ligamentum flavum. Broadly, it also encompasses lateral recess stenosis and bony stenosis within the intervertebral foramen region, categories that some scholars group under lateral canal stenosis. The main symptoms of LSS include low back pain, leg pain, and neurogenic claudication, which impair patients' quality of life and severely limit function, particularly in the elderly. With the aging global population, the prevalence of LSS is rising, affecting approximately 103 million patients worldwide. Treatment options for LSS include both conservative and surgical management. Conservative treatments encompass medication, physical therapy, and lifestyle modifications. However, surgical intervention may be necessary for LSS patients who do not respond adequately to conservative therapies.

Lumbar interbody fusion (LIF) is commonly employed to treat various spinal pathologies, particularly lumbar spinal stenosis. Currently, LIF can be performed via open or minimally invasive approaches, including transforaminal, posterior, anterior, and lateral routes, each with its own advantages and disadvantages. Generally, posterior lumbar interbody fusion (PLIF) is a well-established procedure associated with good fusion rates and relatively low complication rates. However, it carries the risk of iatrogenic injury to neural structures and paraspinal muscles. Despite demonstrating favorable early outcomes, PLIF has notable limitations, including a relatively high complication rate and a challenging recovery process. In 1982, transforaminal lumbar interbody fusion (TLIF) was introduced, which offers a less traumatic and safer unilateral interbody fusion technique. TLIF addresses several shortcomings of PLIF, leading to its rapid adoption and continuous refinement within the spine surgery community. Nevertheless, traditional open TLIF faces challenges such as significant tissue trauma, potential muscle atrophy, chronic postoperative low back pain, and adjacent segment instability.

The advent of various minimally invasive techniques has helped reduce muscle injury and irritation to the posterior spinal elements. To minimize surgical trauma and facilitate rapid recovery, minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) was developed. A meta-analysis published in 2017 reported that MIS-TLIF could lower postoperative complication rates compared to conventional open procedures. Furthermore, MIS-TLIF demonstrates significant efficacy in protecting muscles (e.g., the multifidus) and ligaments. A comparative study indicated that the rates of postoperative complications and reoperations at 2-year and 3-year follow-ups were significantly lower for MIS-TLIF than for traditional TLIF. However, despite the improved visualization provided by the endoscope in MIS-TLIF, visual blind spots may still exist in certain complex anatomical areas, potentially leading to incomplete assessment of the pathological site and suboptimal placement of internal fixation devices. Additionally, MIS-TLIF relies on traditional open pedicle screw fixation, which may increase the long-term risk of postoperative chronic low back pain.

To address the aforementioned clinical challenges, our research team independently developed a L-Unitary Soft Endoscope minimally invasive system, termed LUSE (Chinese National Invention Patent: CN117017466B). It completed filing as a Class I medical device with the Guangzhou Market Supervision Administration in 2021 (Filing No.: 20210598) and is classified as a set of fundamental orthopedic surgical instruments, with its filing status remaining valid. The system features a highly integrated, all-in-one design that combines key components such as the display, camera, light source, and transmission system into a single unit, simplifying operation and maintenance. During development, particular attention was paid to controlling the size and weight of the endoscope, resulting in a compact and lightweight soft endoscope with a diameter of 1.8 mm and a length of 2-4 cm. Its volume and weight are reduced by approximately 93% compared to traditional endoscopes. This endoscope integrates multiple functions including illumination, imaging, and recording, significantly enhancing procedural convenience and patient comfort.

Compared to the traditional MIS-TLIF performed under a Quadrant expandable retractor system, the highly integrated LUSE system offers several advantages in lumbar minimally invasive fusion surgery: (1) The LUSE system supports 8K ultra-high-definition imaging, providing clear and detailed visualization of the surgical field, whereas the Quadrant retractor system only provides illumination without endoscopic magnification, limiting the ability to visualize fine anatomical structures; (2) LUSE-TLIF utilizes a percutaneous pedicle screw system, minimizing injury to the lumbar back muscles, ligaments, and blood vessels. In contrast, MIS-TLIF requires the placement of pedicle screws via a traditional open approach, which may increase the long-term incidence of chronic back pain; (3) The soft lens of the LUSE system offers 360-degree flexibility, whereas the Quadrant retractor system has inherent visual blind spots that can hinder adequate decompression and optimal implant placement. Therefore, LUSE-TLIF holds multiple advantages over MIS-TLIF. Our team has previously demonstrated the safety and efficacy of the LUSE system in anterior cervical discectomy and fusion (ACDF) and artificial disc replacement (ADR) procedures, with related studies published in leading Chinese journals such as the Chinese Journal of Orthopaedicsand the Chinese Journal of Spine and Spinal Cord. However, there is currently a lack of clinical research in China evaluating the efficacy of LUSE-TLIF for treating LSS. Consequently, this study aims to apply LUSE-TLIF for LSS treatment, observe its safety, efficacy, and clinical outcomes, and conduct a comparative analysis with MIS-TLIF, with the goal of providing spine surgeons with an additional and potentially superior surgical option.

Inclusion Criteria:

• Age ranging from 40 to 70 years, irrespective of sex.
• Presence of bilateral lower-limb pain and neurogenic claudication, with or without low back pain.
• Preoperative computed tomography or magnetic resonance imaging confirming single-level lumbar spinal stenosis accompanied by grade II or higher lumbar spondylolisthesis and/or lumbar instability.
• Persistent pain within 7 days prior to enrollment, with inadequate response to nonsurgical treatment for more than 3 months.
• Willingness to provide written informed consent and ability to comply with the study protocol and visit schedule.

Exclusion Criteria:

• Patients with evidence of vascular claudication identified by lower-limb color Doppler ultrasound.
• Patients with a history of previous lumbar spine surgery.
• Coexistence of severe lumbar disc herniation, spinal deformity, spinal tumor, infection, or inflammatory diseases.
• Pregnancy or lactation.
• Presence of severe underlying medical conditions or psychiatric disorders that preclude tolerance of the procedure.
• Known concurrent diseases considered by the investigator to preclude study entry.
• Inability to comply with study assessments or complete questionnaires for any reason.
• Patients deemed unsuitable for participation in this trial as judged by the investigator.

Study Protocol, Statistical Analysis Plan, Informed Consent Form