Efficacy of the Unilateral Uniportal Endoscopic Approach in Management of Monosegmental Lumbar Canal Stenosis

Background Data: Multiple surgical techniques have been used to treat spinal canal stenosis, including open, microscopic, and endoscopic decompression and fusion surgery. Purpose: This article investigates the safety and the efficacy of unilateral endoscopic decompression for patients with monosegmental degenerative lumbar spinal canal stenosis (LCS). Study Design: Prospective clinical case series. Patients and Methods: Thirty consecutive patients with degenerative LCS were treated with endoscopic laminotomy with medial facetectomy. Patients were treated with the EasyGO! 2nd Generation system (Karl Storz, Tuttlingen, Germany) at our institutions between March 2018 and September 2020. Primary outcomes parameters included the Numerical Pain Rating Scale (NPRS) and Oswestry Disability Index (ODI) to quantify pain and disability, respectively. The length of the incision, the duration of surgery, the operative blood loss, and the duration of hospital stay were calculated. The mean follow-up period for patients was 10.5 ± 2.3 (range, 6–12) months. Results: The mean age was 56.5 ± 5.7 years. All thirty patients had neurogenic claudication. 63% of the patients had bilateral leg pain, 37% had unilateral leg pain, and 66% had low back pain. Seven patients (23%) had motor weakness preoperatively. The spinal segments affected were as follows: L4-L5 in 22 cases; L3-L4 in 6 cases; L2-L3, one case; L5-S1, one case. There was a statistically significant reduction in the mean values of NPRS for both leg and back pain in the follow-up period (P < 0.001). Moreover, the ODI mean value was statistically significantly reduced in the follow-up period (P < 0.001). the mean operative blood loss was 147.2 ± 68.3 ml, the mean operative time was 134.7 ± 28.34 minutes, and the mean hospital stay was 1.4 ± 0.8 days. We had four patients with intraoperative dural tears (13%) with no postoperative CSF leak, three patients (10%) had superficial wound infection, no patients had deep wound infection or discitis, and no reoperation was reported in the follow-up period. Conclusion: The unilateral uniportal endoscopic approach is a safe and effective technique in patients with degenerative lumbar canal stenosis. It allows for adequate decompression of the neural elements and preserves spinal stability. (2021ESJ236)


INTRODUCTION
The main symptom of lumbar canal stenosis (LCS) is neurogenic claudication and affects mainly the old age group. 34 It has three main types: central, lateral recess, and foraminal. 11,34 The main causes are hypertrophy of the superior articular facet, ligamentum flavum, and disc herniation. The radiological extent of stenosis does not usually go hand in hand with the clinical picture; many cases are radiologically positive for stenosis but clinically asymptomatic. 28, 33,35 Multiple surgical techniques have been advocated for managing LCS, including microscopic and endoscopic decompression and fusion surgery. 3 With the evolution of endoscopic techniques for decompression of the lumbar spine, various treatment options with minimal tissue injury, lower costs comparative to fusion, and similar or better results have been developed. 13, 23, 27, 32 A targeted and pathology-oriented approach is the key to success to guarantee the therapeutic effect. 19 The most important full-endoscopic techniques are the transforaminal and interlaminar approaches. 27, 36,43 Transforaminal endoscopic techniques have been reported to be successful in disc surgery and unilateral foraminal stenosis, but there are anatomic limitations for symptomatic bilateral lateral recess stenosis. This is more evident at the L5-S1 level, where a high iliac crest, prominent transverse process of the fifth lumbar vertebra, and a large facet joint are prevalent. 15 As regards the orientation and familiarity, the interlaminar endoscopic approach resembles the tubular microscopic surgical technique and are close to each other. 17 All procedures of the conventional approaches can be completely substituted and fully managed endoscopically by the interlaminar surgical technique. 9 With advances in endoscopic techniques and instruments, earlier contraindications have become indications for full-endoscopic spinal decompression in treating lumbar degenerative diseases. Advantages of the technique are reduced iatrogenic injury of the neural elements and preservation of the posterior vertebral column while reaching the surgical target as regard canal decompression. 40 This study aimed to assess the safety and efficacy of the unilateral uniportal endoscopic approach in managing monosegmental LCS.

PATIENTS AND METHODS
This is a prospective clinical case series that included thirty patients with LCS. All patients underwent an operation in Alexandria Main University Hospital and Kafr El-Sheikh University Hospital during the period from March 2018 to September 2020. Inclusion criteria were as follows: patients who had neurogenic claudication (unilateral or bilateral) with or without low back pain (LBP) that is consistent with a radiologically demonstrated monosegmental LCS, either bony or ligamentous, central or lateral recess of different degrees, and who failed conservative treatment for at least eight weeks. Exclusion criteria were multilevel canal stenosis, degenerative spondylolisthesis more than Meyerding Grade I, degenerative scoliosis, and prior surgery in the same segment. All patients were submitted to clinical evaluation where the pain was assessed preoperatively using the Numerical Pain Rating Scale (NPRS) for both leg and back pain (if present), and disability was assessed using Oswestry Disability Index (ODI). All patients were assessed with preoperative MRI and dynamic standing X-ray; however, a CT scan was requested when there was a suspicion of pars defect in selected patients. All patients underwent operation using EasyGO! ® 2nd Generation endoscopic system (Karl Storz, Tuttlingen, Germany). The incision length, duration of surgery, mean operative blood loss, and duration of hospital stay were calculated. The study was approved by our institutional review board. All patients gave written informed consent before the surgery. The study was conducted according to the WMA Declaration of Helsinki-Ethical Principles for Medical Research Involving Human Subjects. Surgical Technique Following general anesthesia, patients were placed in the prone position. After skin sterilization, a 23 mm (which is the diameter of the trocar) vertical skin incision is made nearly one and half cm off the midline, on the more symptomatic side. Under fluoroscopy, the Kirschner wire is inserted to the target point of the desired level (upper limit of the caudal lamina medial to the facet joint); the fascia is incised; then, serial dilators are docked, splitting the paraspinal muscles towards the interlaminar space. Finally, the operating sheath (trocar) is inserted, angled medially, and attached to the holder; then, the endoscopic system is inserted (Figure 1).
Using a high-speed drill with a diamond bur, laminotomy and partial medial facetectomy to decompress the ipsilateral traversing root in the foramen were performed using Kerrison rongeur. Then, the base of the spine process is drilled to gain access to the contralateral side. After completing bony decompression, the ligamentum flavum is removed with Kerrison rongeur and hook to expose the dural sheath centrally. The lateral expansion of the yellow ligament is removed to decompress the ipsilateral nerve root. After sufficient decompression has been achieved ipsilaterally, two cottonwoods are inserted under the base of the spinous process in both cranial and caudal directions to protect the dural sac. Moreover, a working space is made between the dural theca and contralateral lamina by the dissector exposing the contralateral canal clearly under endoscopic vision. Then, the contralateral laminotomy, in the same manner, is done. Any compressing disc material is removed ( Figure 2). Epidural bleeding is controlled by gelatin sponge, oxidized cellulose, and bipolar coagulation. The incision was closed in layers with Vicryl. To prevent dural injuries, the ligamentum should be kept intact until completion of bony work and cottonoids should be inserted between the dura and the contralateral lamina during laminotomy. If this happened, postoperative bed rest in the Trendelenburg position was recommended for three days.

Postoperative Care
All patients had intramuscular NSAIDs for pain control upon recovery from anesthesia. Then, they were given oral NSAIDs only when needed. Intravenous third-generation cephalosporins were given at the time of anesthesia induction and continued for another two days during the hospital stay. Then, patients were given oral quinolone for five days. Patients were encouraged to increase their activities one week after the operation. Follow-up: Patients were followed up routinely at our outpatient clinic at 2 weeks, 3 months, 6 months, and 12 months. The mean follow-up was The EGYPTIAN SPINE Journal 10.5 ± 2.3 months (range, [6][7][8][9][10][11][12]. The assessment included clinical evaluation using NPRS and ODI. Data were obtained from outpatient clinic follow-up visits by two independent physicians, while dynamic X-rays, CT, and/or MRI were only done when clinically indicated.

RESULTS
This report included 30 patients with LCS, 20 females (67%) and 10 males (33%), with a mean age of 56.53 ± 5.78 years (range, 45-65 years). All patients had neurogenic claudication: bilateral in 19 patients (63%) and unilateral in 11 patients (37%). Twenty patients (67%) had LBP. Only seven patients (33%) had motor weakness preoperatively. The most affected level was L4-L5 (73%), followed by L3-L4 (20%), and L2-L3, and L5-S1 (3%) for each level. Preoperative NPRS for back pain was 7.45 ± 1.19; there was a statistically significant reduction to 2.0 ± 0.79 at the last follow-up (P < 0.001). The mean NPRS was 2.0 ± 0.79 at 2 weeks, 1.75 ±0.44 at 3 months, 1.25 ± 0.44 at 6 months, and 2.0 ± 0.79 at 1-year follow-up (Table 1). Preoperative the mean NPRS leg pain was 8.43 ± 1.14, and there was a statistically significant reduction 2.0 ± 0.83 at the last follow-up (P < 0.001). The mean NPRS was 2.0 ± 0.83 at 2 weeks, 1.50 ± 0.51 at 3 months, 1.50 ± 0.51 at 6 months, and 2.0 ± 0.83 at 1-year follow-up (Table 2). Preoperative ODI mean value was 66.67 ± 7.37, which significantly improved statistically postoperatively (P < 0.001). The mean value was 19.13 ± 4.62 at 2 weeks, 19 ± 4.39 at 3 months, 15 ± 4.39 at 6 months, and 13.4 ± 3.89 at 1-year follow-up ( Table 3). The mean operative blood loss was 147.2 ± 68.3 (range, 60-280) ml. All patients were followed up for at least 6 months. The mean operative time was 134.7 ± 28.34 (range, 80-180) minutes. The mean duration of hospital stay was 1.40 ± 0.77 (range, 1-3) days. Reported complications in this study were as follows: four patients (13%) had dural tears managed operatively with no postoperative CSF leak reported and three patients (10%) had superficial wound infection managed conservatively. No patients had deep wound infection or discitis, and none encountered postoperative instability in the follow-up period. In some patients, a multislice CT scan of the lubra spine has been requested to evaluate the adequacy of segmental decompression (AP diameter ≥11.5 mm) (Figure 3).   , 23-165). The lower mean time might be attributed to the higher number of levels operated (753) and the more experience of the surgeon. Our relatively long time may be due to the time needed to prepare the access system and EDL intrinsic technical difficulties that include 2D visualization issues, resulting in handeye coordination difficulty and limited working space, which needs a steep learning curve. As we became familiar (after 20 cases) with the lumbar anatomy on endoscopy, the basic usage of the endoscopic instruments, drills, and punches and total operation times were much shortened. 6,29 Our outcome parameters are parallel with those of Lee et al. 16 18 , which may be due to careful hemostasis. In line with Ikuta et al. 10 and Pao et al., 24 postoperative neural complications in the form of transient dysesthesia due to manipulation were observed in 6% of patients; however, dysesthesia was mild and resolved gradually. Thus, minimal, delicate manipulation and earlier dissection of adhesion of neural structures are essential for minimizing these complications and the usage of highintensity bipolar cautery should be avoided around neural structures. Postoperative radiological investigations were not routinely used in our study. As we mentioned before, there is no significant relationship between the extent of radiological decompression and clinical outcomes, so we mainly depended on clinical symptoms and signs as the main outcome measure. 7,8 One of the shortcomings of our study is the relatively small number of patients as a large number of patients will strengthen the outcome parameters. Another shortcoming is that not all patients had postoperative CT scans as we did not like to expose our patients to the effect of extra radiation and due to the noncompliance of patients.

CONCLUSION
Endoscopic surgery for bilateral decompression through a unilateral approach is a useful and effective procedure for treating patients with LCS with encouraging results.