Clinical Ecacy Evaluation of Full-endoscopic Foraminoplasty and Discectomy Under General Anesthesia in the Treatment of L5-S1 Disc Herniation

Background: Percutaneous transforaminal endoscopic discectomy (PTED) is a minimally invasive surgical method for the treatment of spinal diseases. However, the operation procedure relied on the radiative interventional technology, and was conducted under local anesthesia. Method: From June 2016 to December 2019, we performed a newly developed full-endoscopic visualized foraminoplasty and discectomy under general anesthesia in 30 patients with L5/S1 LDH. In this retrospective study, the outcomes and neurological complications of this approach were evaluated. Results: The mean visual analog scale (VAS) and Oswestry Disability Index (ODI) were signicantly improved after surgery. The postoperative MRI reexamination revealed that the degree of intervertebral disc degeneration of each subject was improved signicantly to different degrees as compared with that before surgery. The learning curve showed operative time rapidly decreased over the earlier cases, and then tapered to a steady state in the latter cases. Conclusions: Full-endoscopic foraminoplasty and discectomy under general anesthesia is ecient and safe for the treatment of the L5-S1 disc herniation.


Background
Chronic osphyalgia or osphyalgia accompanied by lower limb pain is the common symptom of spinal degenerative diseases. These manifestations are mainly caused by compression of the nerve root due to lumbar disc herniation. A variety of methods to treat the above symptoms are currently explored by clinical orthopedists. Percutaneous transforaminal endoscopic discectomy (PTED) for the treatment of chronic pain in waist and legs has been put forward and rapidly and widely adopted in clinical treatment in recent years. It has the advantages of less trauma, less bleeding, fast recovery, and less impact on spinal stability. With the advancement in the technique, PELD has realized direct decompression from outside of the disc as compared to previous indirect decompression from the inside of the disc. The most commonly used PTED in clinical practice is percutaneous lumbar discectomy (PELD), which was initially used in the treatment of lumbar disc herniation (LDH) [1][2] . The surgical e cacy of this approach is satisfactory as rated by both doctors and patients. With the improvement of surgical instruments, the methods of surgical approach have also been optimized continuously. In the case of patients with lumbar disc herniation, surgical indications and postoperative e cacies have been expanded and improved by optimizing previous indirect decompression from the inside of the disc to direct decompression from the outside of the disc. Herein, we have also optimized the treatment of many such patients based on this technology.

Patient Population
A total of 30 patients with L5-S1 LDH in our department were enrolled. Full-endoscopic visualized foraminoplasty and discectomy were performed under general anesthesia in the First A liated Hospital of Henan University of Traditional Chinese Medicine from March 2018-2019. Inclusion criteria: Single-level lumbar disc herniation at L5-S1, veri ed by magnetic resonance imaging (MRI) and computed tomography (CT); unilateral radiating leg pain with or without positive Lasegue sign; clinical symptoms and signs in accordance with imaging changes; failure of standard conservative treatment conducted for at least 12 weeks. Exclusion criteria: Vertebral infection, vertebral tumor, spinal canal stenosis, lumbar spondylolisthesis, and a history of surgery at the same level.

Observation indicators
The operation time, the visual analog scale of lower limbs (VAS-L), visual analog scale of back (VAS-B), and Oswestry disability index (ODI) [3] before surgery, 1 day, and 1 week after surgery were used for clinical evaluation.

Statistical analysis
All data were analyzed by SPSS21.0 statistical software, and relevant graphs were constructed using Microsoft Excel. The measurement data were expressed as mean ± standard deviation and the preoperative and postoperative data were analyzed by paired sample t-test, while the enumeration data were compared using the rank-sum test or X 2 test. P-value <0.05 indicates statistical signi cance.

Surgical Procedure
We have studied and applied the operation technique of Professor Yang from the Union Hospital A liated to the Huazhong University of Science and Technology [15] . The preoperative images ( Figure 1) were rstly evaluated, the operation was performed under general anesthesia, and the posterior interlaminar space approach was adopted. The patient was in the lateral position, with limb of the affected site on the top and exion of bilateral knees and hips to fully open the interlaminar space. The anteroposterior and lateral X-ray lms of the corresponding segments were obtained by C-arm uoroscopy to accurately locate the intervertebral pore. The syringe needle was inserted into the skin to locate the point where the needle entered the L5-S1 intervertebral space vertically from the back of the lumbar [16] . The anteroposterior X-ray lm indicated that the positioning needle was in the middle of the affected side of the intervertebral space, while the lateral X-ray lm indicated that the positioning needle was at the level of the posterosuperior margin of S1. The puncture target and direction were determined according to the X-ray lms to ensure the accuracy of the surgery site.
After positioning, a longitudinal incision of about 1 cm was made along the direction of the spine with the registration point as the center. After the pencil-shaped puncture rod was inserted into the interlaminar space, the working cannula and the operating endoscope were inserted slowly along the puncture rod into the interlaminar space. All subsequent operation procedures were performed under the premise of continuous irrigation and endoscopic visualization. The inferior zygapophysis of the L5 vertebral body and the lower margin of the lamina were found under the direct vision of the endoscope. If the interlaminar space was small, a part of zygapophysis at foramen intervertebral could be enlarged by grinding with an abrasion drill under the endoscope ( Figure 2). Then, the blue forceps removed a part of the ligamentum avum into the spinal canal, lamina rongeur enlarged the crevasse of the ligamentum avum to fully expose the tissues in the spinal canal, the bipolar radiofrequency scalpel separated the tissues in the spinal canal to fully expose the nerve root, dural sac, and annulus brosus, the sleeve was rotated into the spinal canal to protect the nerve root, annulus brosus fenestration was performed on the outer margin of the nerve root, the working sleeve was guided to the annulus brosus opening, and full endoscopic resection of the nucleus pulposus was performed to ensure complete decompression of the nerve root. During this process, the nerve root was clearly identi ed, and no free intervertebral disc tissue or active bleeding was observed before the end of the operation. (Figure 3) Finally, bipolar radiofrequency scalpel was adopted to control the bleeding, the external annulus plasty of the intervertebral disc was performed, and the incision was closed without additional drainage at the end.

Results
The learning curve showed operative time rapidly decreased over the earlier cases, and then tapered to a steady state in the latter cases (Fig. 4).
The mean visual analogy scale (VAS) score and Oswestry disability index (ODI) score postoperatively improved signi cantly compared with preoperative scores (P < 0.05; Table 1). *: compared to that before surgery; # : compared to that 1 day after surgery. N represents the number of patients included in the statistical analysis. Both the statistical value and the improvement value were comparative analysis results of indicators 1 week before surgery and after surgery.
The postoperative MRI reexamination revealed that the degree of intervertebral disc degeneration of each subject was improved signi cantly to different degrees as compared with that before surgery (P < 0.05; Table 2).

Discussion
Currently, there are several surgical methods for lumbar disorders [4][5][6] , and minimally invasive surgery has developed rapidly in recent years. Owing to its advantages, the methods and approaches of minimally invasive treatment under anesthesia have put forward. However, the basic application of minimally invasive technology is to remove the nucleus pulposus tissue. If the indications are to be expanded to the minimally invasive treatment, full-endoscopic technology for the treatment of lumbar spinal stenosis and partial lumbar spondylolisthesis is valuable. Then, minimally invasive fusion technology is the ultimate choice [7][8] , which requires us to expand the operation indications and reduce intraoperative uoroscopy to avoid unnecessary operation hazards due to general anesthesia. In more than three years, we have operated on about 100 cases with satisfactory results. None of the patients presented complications of intraoperative and postoperative nerve injury. However, general anesthesia also has some disadvantages, such as the requirement for solid anatomical basis and microscopic identi cation ability of the surgeon. Nonetheless, these characteristics are essential for a surgeon utilizing minimally invasive approach.
The development of PTED has gone through two stages. The rst stage was Yeung Endoscopic Spine System (YESS) technology, proposed by Yeung et al. [9] and entered through Kambin safety triangle [10] . It was characterized by disc decompression from the inside to the outside, which determined the limitations of this technology deeming it only applicable to inclusive disc herniation and disc herniation under ligaments. Thereafter, the second stage was TESSYS technique [11] , which directly decompressed and released the nerve root through the foramen intervertebral and further expanded the indications of PTED.
Thus, it could be used for intervertebral foramen stenosis, lateral recess stenosis, the stenosis of the spinal canal stenosis, intervertebral disc herniation, and nucleus pulposus into the spinal canal due to intervertebral disc herniation. Because of its direct target to remove the protruding nucleus pulposus and the con rmed postoperative decompression effect, this technique has been widely used in several types of lumbar disorders [12] . However, the traditional TESSYS technique could be performed under local anesthesia, due to which, the patients felt unbearable intraoperative pain and the operation had to be interrupted. Moreover, local anesthesia inevitably reduces indications of the operation, which could not fully meet the surgical method of nal lumbar fusion. Also, local anesthesia needs repeated puncture positioning and uoroscopy and long repeated uoroscopy is bound to bring radiation hazard to medical personnel. Therefore, we selected different body positions to remove the nucleus pulposus and other tissues under general anesthesia for patients with different segments of LDH and satisfactory results were achieved.
Different from the traditional TESSYS technology of PTED, we adopted the fully visible endoscopy technology in the operation, i.e., after positioning by uoroscopy, all operations were completed under the direct vision of endoscope after the insertion of the interforaminal lens into the operation channel. There are two main positions of PTED: prone and lateral. Both positions have their own advantages and disadvantages; either was adopted according to our needs. For patients with L5-S1 intervertebral disc herniation, due to the block of bilateral iliac spine, the access to the foramen intervertebral is relatively di cult [13] , but for this segment, the posterior intervertebral space is large. If prone position was adopted for this segment, the waist protrudes backward with nothing under the chest and abdomen to fully open the posterior intervertebral space. Due to the minimal invasiveness of PTED, the operation space is narrow, and hemostasis is di cult [14] . The needle is inserted from bilateral sites to reduce the pressure; however, the abdominal pressure is increased, the risk of abdominal viscera injury is increased, and the risk of bleeding is increased.

Conclusions
Our procedure provides a direct approach for surgeons. Overall, full-endoscopic visualized foraminoplasty and discectomy under general anesthesia is e cient and safe for the treatment of L5-S1 disc herniation. However, further prospective, randomized, controlled studies should be conducted to assess the clinical outcomes.

Consent for Publication:
Included in patient's hospital records. Patient agreed to necessary clinical information being used in this article. Patient signed a consent to publish all relevant clinical data and images provided. A copy of a written signed consent is available for review by the editors the journal.