Arthroscopic-assisted uni-portal spinal surgery combined with modified unilateral laminotomy with bilateral decompression for the treatment of lumber epidural lipomatosis: Case report and new therapeutic method

Abstract

Background

Lumbar spinal epidural lipomatosis (SEL) is a rare condition characterized by the pathological proliferation of adipose tissue in the epidural space of the spinal canal. This study presents the case of a 59-year-old male with lumbar SEL treated effectively in the short term through arthroscopic-assisted uniportal spinal surgery (AUSS) combined with a modified circle-drawing unilateral laminotomy with bilateral decompression (ULBD) technique.

Methods

A modified circle-drawing ULBD procedure was executed via AUSS for a patient with SEL. The procedure involved the excision of diseased adipose tissue from the spinal canal, enlargement and decompression of the spinal canal, liberation of nerves, and post-operative evaluation of imaging results and clinical outcomes.

Results

The patient exhibited improvements in the dural sac cross-sectional area, low back pain Visual Analogue Score (VAS, leg pain VAS, lumbar spine Japanese Orthopaedic Association (JOA), and EQ-5D post-surgery.

Conclusions

AUSS offers comprehensive visualization, straightforward positioning, facilitating a broad field of view and precise lesion management. The modified circle-drawing ULBD technique characterized by its simplicity, operational freedom, and extensive decompression range, contributes to symptom alleviation and patient recovery.

1. Introduction

In recent years, with the improvement of minimally invasive surgical concepts and spinal endoscopic techniques and instrumentation, endoscopic treatment of the lumbar degenerative spine has been widely used.1, 2, 3, 4 Arthroscopy-assisted uniportal spinal surgery (AUSS),alternative name is uni-poral non-coaxial spinal endoscopic surgery(UNSES), enables visualization throughout the entire procedure, with less fluoroscopy and more freedom of operation. Lumbar spinal epidural lipomatosis (SEL) is a rare disease in which the pathologic proliferation of normal fatty tissue in the epidural space within the spinal canal compresses the spinal cord and nerves, causing symptoms. When conservative treatment fails, surgical treatment is required. Surgical treatment is usually small-incision laminectomy and decompression or microscope-assisted laminectomy and decompression,^5,6 etc. There are few reports in the literature on treating SEL using endoscopy. Kang et al.⁷ used the Unilateral biportal endoscopy (UBE) technique to treat patients with SEL and the short-term efficacy was satisfactory, Yu et al.⁸ used percutaneous uniaxial spinal endoscopy to treat SEL in the short term and also achieved some efficacy. In this technical report, we performed a modified circle-drawing ULBD procedure by AUSS. This surgical approach combines modern arthroscopic and spinal surgical techniques and may provide an advanced and effective method for treating SEL.

2. Materials and methods

This study was permitted by the Institutional Ethics Review Committee of the Second People's Hospital of Qujing City (NO.2023-010-01) approved this study.

2.1. Medical history and imaging data

A male patient with 59 years old with recurrent symptoms of numbness and weakness in both lower limbs lasting for one year, which gradually worsened in the last month; felt soreness, numbness, and weakness in both lower limbs after walking about 100 m. The symptoms were relieved after resting, which was more pronounced, especially on the left side. The dorsal extensor strength of the lesser toes was grade V. Rheumatoid arthritis was diagnosed 20 years ago, and methotrexate and leflunomide had been taken for a long time. The BMI was 26.45/m2, the VAS score of lumbar pain was 3, the VAS score of leg pain was 7, the lumbar spine JOA score was 8, and the EQ-5D score was −0.002. The lumbar spine was unstable in the power position of the X-ray, and the dural sac of the L4/5 on the Magnetic resonance imaging (MRI) was severely compressed in the shape of a “polygonal shape"(Fig.1ABCD). “Polygonal shape”, and the cross-sectional area of the dural sac measured by computed tomography (CT)⁹ was approximately 55.8 mm2. The diagnosis was 1) secondary lumbar epidural lipoatrophy, Borré II, ¹⁰Manjila type II,¹¹ and 2) rheumatoid arthritis.

2.2. Equipment and instruments

4 mm diameter 30° arthroscope and sheath (Shenyang Shenda Endoscopy Co., Ltd. Shenyang, China), imaging system (Jiangsu Yikoda Electronic Technology Co., Ltd. Jiangsu, China), Zirui power system, 3 mm diamond grinding head with protective sheath, and 4 mm diamond grinding head (Guizhou Zirui Science and Technology Co., Ltd. Guizhou, China) for bone abrasion, and Bekbang spinal canal decompression Ltd. Anhui, China), radiofrequency plasma surgical electrodes (Shanghai Machinery Note Quasi 20172010683 Shanghai Langmai Medical Devices Technology Co. Ltd. Shanghai, China) are used for intra-vertebral canal hemostasis, soft tissue stripping; bipolar radiofrequency ablation electrodes (Guomao Note Quasi 20183010162 Shanghai Langmai Medical Devices Technology Co. Soft tissue stripping, hemostasis, etc.

2.3. Surgical method

General anesthesia, take the prone position, fluoroscopy to locate the responsible segment, make a longitudinal incision of about 15 mm in the line of the midline of the spinous process to the left side of the spinous process for about 3 cm, and incise the skin, subcutaneous tissues, and lumbar dorsal fascia sequentially. Using T-shaped bone peeling to contact the junction area of the L4 spinous process root and L4 inferior lamina, and L5 spinous process and L5 superior lamina, the soft tissue was expanded, and fluoroscopy was accomplished again to check the excellent position, connecting the arthroscope and the mirror sheath, the light source wire, the magic drill, the radiofrequency, and the rinsing saline (see Fig. 1).

Fig. 1.

Preoperative MRI images revealed an accumulation of fat within the lumbar spinal canal and severe stenosis at the L4/5 level. A)sagittal T1 images; (B)The images of Short TI Inversion Recovery(STIR); (C, D)Axial images showed L4/5 spinal canal stenosis, increased epidural fat, and polydactyly, pressing on the dural sac.

2.3.1. Exposure

The natural fissure stop of the ligamentum flavum at the root of the spinous process of the L4 vertebrae (Fig. 2A and D), the tip of the supraspinous articular process of the ipsilateral L5 vertebrae (Fig. 2B), the natural fissure stop of the ligamentum flavum at the root of the spinous process of the L5 vertebrae (Fig. 2C and E), and the tip of the contralateral supraspinous articular process of the L5 vertebrae (Fig. 2F) are exposed in turn, using a bipolar radiofrequency ablation electrode and a 4-mm emery tip, either clockwise or counter-clockwise.

Fig. 2.

Microscopic anatomical view of AUSS combined with a modified circle-drawing ULBD technique for lumbar epidural lipoatrophy(L4-5level). (A, D)The natural fissure stop of the ligamentum flavum at the root of the spinous process of the L4 vertebrae(; (B)Ipsilateral L5 superior articular eminence tip; (C, E)The natural fissure stop of the ligamentum flavum at the root of the spinous process of the L5 vertebrae; (F)Contralateral L5 superior articular eminence tip.

LF: ligamentum flavum; epidural adipose tissue; meniscus ligamentum; dural sac.

2.3.2. Spinal canal decompression

Use radiofrequency plasma surgical electrodes to separate the ligamentum flavum along the natural fissure of the ligamentum flavum bilateral, exploration, hemostasis, and separation. 2 mm and 3 mm 130° vertebral plates were used alternatively to cut off the interspinous ligamentous junction, resect the yellow ligamentum flavum of the contralateral side and the ipsilateral side, and adequately expose the epidural fatty tissues (Fig. 2F), stopping the hemorrhage and separating the fatty tissues, paying attention to differentiate the membranous vertebral ligamentum flavum (Fig. 2G) and the dural sac folds (Fig. 2H) to avoid dural sac tear.

2.3.3. Nerve root canal decompression

Firstly, the radiofrequency plasma surgical electrode revealed the contralateral intervertebral disc, loosened the contralateral walking root, and enlarged the osseous root canal to the medial wall of the contralateral L5 pedicle with 3 mm adamantine with a protective sheath; then the radiofrequency plasma surgical electrode was used to reveal the contralateral intervertebral disc, loosened the same side of the walking root, and enlarged the osseous root canal to the medial wall of the ipsilateral L5 pedicle with 3 mm adamantine with a protective sheath, and the dura mater was well pulsed under the direct vision, and the nerve root relaxation was observed. A drain was left, and the incision was sutured to end the operation.

3. Results

Postoperative pathology revealed an abundance of mature adipocytes within the spinal canal (Fig. 3A). Repeat CT scans demonstrated an expanded dural sac, with its cross-sectional area measuring approximately 168.5 mm² (Fig. 3B–D). The patient's postoperative outcomes included evaluations of low back pain VAS, leg pain VAS, lumbar JOA score, and EQ-5D (Fig. 4). A comparative analysis of preoperative and postoperative data indicated a significant reduction in the patient's leg pain VAS. Furthermore, there were improvements in the lumbar JOA score and EQ-5D, along with an increase in the dural sac's cross-sectional area. The therapeutic outcomes were deemed satisfactory, with no instances of complications such as cerebrospinal fluid leakage or nerve damage reported.

Fig. 3.

Postoperative pathology findings and preoperative and postoperative CT images of the patient. (A) Pathological findings; (B) Postoperative L4-5 CT 3-D reconstruction; (C) Preoperative L4-5 axial image; (D) Postoperative L4-5 axial image.

Fig. 4.

Postoperative follow-up results for the patient's low back pain VAS score, leg pain VAS score, lumbar JOA score, and EQ-5D.

4. Discussion

In the physiological state, the intradural adipose tissue can serve as a buffer structure for the dura mater and nerves. Still, when the adipose tissue is pathologically increased, it may lead to spinal cord or nerve compression and clinical symptoms, known as the syndrome of increased intradural adiposity, the prevalence of which ranges from about 2.5 % to 25 %.¹² It occurs in the middle-aged and elderly populations, with a more significant number of males than females. The lumbar spine is most frequently affected, followed by the thoracic spine, while the cervical spine is rare. Possible pathogenesis includes long-term steroid hormone therapy, obesity, Cushing's syndrome, metabolic syndrome, or idiopathic factors. Symptoms may comprise low back pain, intermittent claudication, radiating pain in the lower extremities, fatigue, and a polygonal, star-shaped, or Y-shaped shape of the dural sac on imaging. According to reports in the literature,^13,14 the diagnosis was confirmed by axial MRI, showing a thickness of epidural fat greater than 7 mm in the diseased segment and a ratio of epidural fat thickness to canal diameter greater than 50 %, exclusion disc herniation, and intradural tumors. Borre et al.¹⁰ categorized epidural fat into four grades based on the ratio of epidural fat to the diameter of the spinal canal; however, in patients with severe epidural fat increase, this grading system presents difficulties in calculating cross-sectional area. Therefore, Manjila et al.¹¹ proposed a novel and simple classification system that allows for a more visual and accurate assessment of the degree of dural sac compression. The classification system uses a 3x3 grid manually outlined or labeled on axial spine imaging while helping to select the appropriate surgical approach.

The patient, a patient with rheumatoid arthritis for many years and on long-term hormone use, was diagnosed with secondary lumbar epidural lipodystrophy, Manjila type II. Due to the poor results of conservative treatment, the patient underwent a modified unilateral approach bilateral. Prof En Song first proposed decompression surgery with AUSS in 2021,¹⁵ combining the advantages of uniaxial endoscopy and biaxial endoscopy,^1,3,8 and has the following features: i) the use of aqueous media, the complete process of visualization; ii) compared with UBE,^4,7 the dual orifices are combined into an uni-portal orifice; iii) it is compared with uni-portal-axis endoscopy, where the endoscope is separated from the operating instruments; iv) The endoscope and instruments are operated in an uni-portal orifice, running in the same plane, accessible and flexible, which has the characteristics of endoscopicization of routine surgery; v) similar to dual-channel spinal endoscopy,^3,4 the technique has a wide range of indications for the use of the trans-thoracolumbar spine.

In 1988, Young et al.¹⁶ first proposed ULBD, in which decompression is achieved bilaterally via unilateral access laminectomy, followed by subliminal decompression of the contralateral side via the base of the spinous process on that side, preserving the integrity of the contralateral muscles. In 2002, Cuiot et al.¹⁷ verified the feasibility of ULBD on human cadaveric specimens. The effectiveness of decompression depended on the ability to visualize pedicles and outlet roots, while for the first time the same time, the microscopic endoscopy combined with the ULBD technique was firstly applied to the clinic and had the same decompression efficacy when compared with open laminectomy decompression. With the continuous development of microscopic and endoscopic techniques, combined microscopic and endoscopic techniques for ULBD have become a new surgical approach.18, 19, 20 Prof. En. Song improved ULBD by combining the characteristics of other endoscopic techniques (modified circle-drawing ULBD technique). In this modified technique, the natural fissure stop of the ligamentum flavum at the root of the cephalad spinous processes of the vertebral body(Fig. 5i–A), the tip of the superior articular process of the ipsilateral inferior vertebral body(Fig. 5ii-B), the natural fissure stop of the ligamentum flavum at the root of the caudal spinous processes(Fig. 5iii-C), and the tip of the superior articular process of the contralateral inferior vertebral body(Fig. 5iv-D) are used as anatomical landmarks by exposing them and drawing a circle either clockwise or counterclockwise. This technique is easy to understand, flexible in operation, has a large surgical space, adequate decompression, safe and reliable. This modified ULBD technique, which synthesizes the features of several endoscopic techniques, demonstrates many advantages and is expected to be widely used in spinal surgery.

Fig. 5.

The schematics of modified circle-drawing ULBD technique; AUSS endoscopy, instrumentation, incisions, and modified circle-drawing ULBD technique anatomy.(i-A)Natural fissure stop of the ligamentum flavum at the root of the spinous process of the cephalad vertebrae; (ii-B)Ipsilateral inferior supra-articular process tip of the vertebral body; (iii-C)Natural fissure stop of the ligamentum flavum at the root of the caudal lateral spinous process; (iv-D)Tip of the superior articular process of the contralateral inferior vertebral body.

However, the technique has some limitations. First, qualified surgeons and assistants should perform this technique, as the operation requires high technical requirements and proficiency. Second, to assess the clinical outcomes of this new technique more fully, multicenter, large-sample studies are needed to determine its feasibility and effectiveness in clinical practice.

5. Conclusion

Overall, our use of AUSS combined with the modified ULBD technique for the treatment of SEL has the following advantages: simple positioning and less fluoroscopy; operation and observation channels in one incision, reducing trauma; use of a 30° arthroscopy with a wide field of view, flexible operation, and a sizeable surgical space; and conforming to the concept of minimally invasive open surgery, resulting in less trauma and quicker recovery. This combined surgical approach synthesizes the advantages of arthroscopic and endoscopic techniques, providing an advanced, effective, and safe option for treating SEL. The use of this technique was expected to improve surgical outcomes, reduce patient symptoms, and promote recovery.

Ethical statement

Informed consent from individuals was obtained and it was written in this article to ensure that there is no breach of privacy or confidentiality in the usage of potentially identifiable images or data.

Funding statement

This study was supported by Yunnan Province Clinical Center for Bone and joint Diseases Programme(ZX2019-03-04)

Guardian patients consent

This study was permitted by the Institutional Ethics Review Committee of the Second People's Hospital of Qujing City (NO.2023-010-01) approved this study. Patient's consent was not required.

Credit Author Statement

All the researchers had read and ratified the final revised version before submission. The following is the researcher’s involvement: YL and ES proposed the study’s design, obtaining data, analysis, and interpretation, FQ measured and analyzed radiological outcomes and FS delivered a schematic diagram. YL drafted the manuscript that ES revised critically. All researchers agreed to the manuscript and gave their approval to the final version.

Declaration of competing interest

All statements presented in this article only reflect the researcher's thoughts and do not stand for the position of their organizations, publishers, editors, and reviewers. The publisher's role is neither endorsing nor guaranteeing any product that may be reviewed in this article, nor any claim that may be made by its manufacturer.

List of Abbreviations

(SEL)

Lumbar spinal epidural lipomatosis

(AUSS)

Arthroscopic-assisted uni-portal spinal surgery

(ULBD)

Unilateral laminotomy with bilateral decompression

(VAS)

Visual Analogue Score

(JOA)

Japanese Orthopedic Association

(UBE)

Unilateral biportal endoscopy

(MRI)

Magnetic resonance imaging

(CT)

Computed tomography