Comparative Analysis of Non-Full and Full Endoscopic Spine Technique via Interlaminar Approach for the Treatment of Degenerative Lumbar Spinal Stenosis: A Retrospective,Single Institute,Propensity Score-Matched Study

Abstract

Study Design:

Retrospective study.

Objective:

To compare the clinical efficacy of posterior lumbar laminectomy decompression under full endoscopic technique (Endo-LOVE) and percutaneous endoscopic medial foraminal decompression (PE-MFD) in the treatment of degenerative lumbar spinal stenosis (DLSS).

Methods:

Between April 2017 and April 2018, 96 patients with DLSS underwent Endo-LOVE or PE-MFD, including 58 with Endo-LOVE and 38 with PE-MFD. After propensity score matching (PSM), patient characteristics, operation time, intraoperative fluoroscopy times, postoperative bedridden time, hospital stay and postoperative complications were recorded and compared. The clinical efficacy was evaluated according to Oswestry disability index (ODI), visual analogue scale (VAS), lumbar disease JOA and modified MacNab criteria.

Results:

A total of 96 patients with DLSS were included in the study. After PSM, the 2 groups were comparable in patient demographic and baseline characteristics. The operation time and intraoperative fluoroscopy times in PE-MFD group were significantly more than those in Endo-LOVE group (P < .05). The operation time in PE-MFD group was significantly less than that in Endo-LOVE group (P < .05).

The intraoperative fluoroscopy times in PE-MFD group were significantly more than that in Endo-LOVE group (P < .05). The ODI, VAS and lumbar disease JOA in the 2 groups were significantly improved comparing with those before operation (P < .05). According to the modified MacNab criteria, the excellent and good rates of the 2 groups were 93.5% in Endo-LOVE group and 87.1% in PE-MFD group (P > .05).

Conclusion:

Endo-LOVE and PE-MFD technique can both effectively treat DLSS, and the short-term follow-up results are positive. Endo-LOVE technique has the advantages of fast puncture positioning, less radiation exposure and wider indications. However, PE-MFD needs more radiation exposure and has the possibility of incomplete decompression for complex multiplanar spinal stenosis.

Keywords

degenerative lumbar spinal stenosis full endoscopic spine technique non-full endoscopic spine technique laminectomy interlaminar decompression

Introduction

Degenerative lumbar spinal stenosis (DLSS) is the most common type of lumbar spinal stenosis, which is common in people over 60 years old.¹ The pathological types of DLSS include stenosis of intraspinal (central) canal, lateral recess and neural foramen. The central canal stenosis type of DLSS is increasingly considered as a cause of disability in the aging population.^2,3 For patients with DLSS, conservative treatment is usually attempted before surgical treatment, but surgical treatment is needed to relieve symptoms and improve function when progressive neurological dysfunction or cauda equina syndrome occurs.⁴ For patients with DLSS without lumbar spondylolisthesis instability, it is reported that the traditional simple laminectomy decompression is better than lumbar fusion, because the former can reduce the incidence of postoperative complications under the condition of ensuring the curative effect.^5,6 A study from the Medicare database in the United States also confirms this conclusion.⁷ In recent years, with the rapid development of spinal minimally invasive technology represented by spinal endoscopy, more and more clinical studies have confirmed that minimally invasive surgery has the similar curative effect to traditional surgery, and has the advantages of smaller incision, less soft tissue damage, less bleeding, faster recovery, earlier ambulation.^8-21 In this situation, a variety of minimally invasive spine surgery, such as percutaneous transforaminal endoscopic discectomy (PTED), percutaneous kyphoplasty (PKP) and other technologies are rapidly popularized. However, PTED still has some outstanding problems. Due to the blockage of high iliac crest, hypertrophic transverse process and narrow intervertebral foramen, PTED may increase the radiation exposure of patients and surgeons and operation time due to the difficulty of puncture.^{14,18,19,22,23-25} At the same time, because of the wider laminar space, which provides more favorable anatomical conditions for minimally invasive interlaminar approach, and spinal surgeons are more familiar with the posterior lumbar anatomical structure, and are similar to the traditional open lumbar surgery, more surgeons are now more accustomed to percutaneous endoscopic interlaminar discectomy (PEID) for the treatment of L5-S1 lumbar disc herniation (LDH).^22,25,26 This method and technique can be applied not only to L5-S1 segment, but also to higher level LDH. Compared with PTED, PEID can more directly and minimally invasive resection of the diseased disc nucleus pulposus. However, PEID needs to reach the herniated disc target through the spinal canal, which may increase the risk of spinal canal scarring, which may be a negative consequence considered by some spinal surgeons. Therefore, on the basis of PEID, in order to reduce the excessive interference in the spinal canal, percutaneous endoscopic medial foraminal decompression (PE-MFD) was proposed as a minimally invasive surgical method instead of PEID, and has achieved satisfactory clinical effect. Since 2017, with the progress of surgical instruments and power system, PE-MFD and posterior lumbar laminectomy decompression under full endoscopic technique (Endo-LOVE) have been proposed for DLSS by our department. However, there has been no comparison between PE-MFD and Endo-LOVE. Therefore, the purpose of this study is to investigate the efficacy of PE-MFD and Endo-LOVE for the treatment of DLSS.

Methods

Characteristics of Patients and Study Design

We conducted a single center, retrospective case-control trial to compare the efficacy and safety of PE-MFD and Endo-LOVE in the treatment of DLSS. This study retrospectively analyzed 96 patients with DLSS who underwent PE-MFD or Endo-LOVE from April 2017 to April 2018, including PE-MFD group (n = 38) and Endo-LOVE group (n = 58). All operations were performed by the same surgeon who has many years of clinical experience in minimally invasive spine surgery. This study was approved by our hospital ethics committee (IRB: ECNGH-2016040), and all participants signed written informed consent. In order to make this study as close as possible to the randomized clinical trial environment, propensity score matching (PSM) was used to match the 2 groups of patients in the proportion of 1:1, so as to achieve the comparability of potential confounding variables between PE-MFD group and Endo-LOVE group. After PSM, PE-MFD (n = 31) and Endo-LOVE group (n = 31). In the study, the endoscope model is TH8700-030 L, and the manufacturer is THINK, Germany.

Inclusion/Exclusion Criteria

All patients received anterior and lateral lumbar X-ray, computed tomography (CT) and magnetic resonance imaging (MRI) examination before operation, and combined with the following inclusion and exclusion criteria, all patients were diagnosed with degenerative lumbar spinal stenosis and excluded other diseases. Inclusion criteria: (1) patients with a clear history of low back pain and lower limb neurological symptoms and signs, with the main clinical manifestations of intermittent weakness; (2) preoperative imaging examination confirmed central lumbar spinal stenosis (central sagittal diameter less than 10mm) or lateral recess stenosis (diameter less than 3mm). (3) patients who received conservative treatment for 6 months had no significant effect (except acute attack); (4) patients were followed up for at least 2 years. Exclusion criteria: (1) patients who had previous lumbar surgery history; (2) dynamic X-rays indicated that the intervertebral displacement was greater than 3mm or the angular displacement was greater than 10^o segment instability signs; (3) patients with spinal tumors or intervertebral space infection; (4) patients with incomplete follow-up information.

Surgical Methods

PE-MFD approach

Figure 1 showed PE-MFD surgical process: (1) Surgical position, anesthesia and body surface positioning: The patient lied prone on the spinal surgery bed, exposing the lower back and bending forward appropriately. The body surface insertion point of the index segment was determined and marked under X-ray fluoroscopy. One centimeter below the intervertebral space of the responsible segment and half a centimeter adjacent to the midline of the spinous process were taken as the body surface needle entry point. Local combined with basic anesthesia was performed (Local anesthesia is 0.25% lidocaine local infiltration, and basic anesthesia is continuously pumped with dexmedetomidine at the rate of 60ug/h for sedation). (2) Establishment of spinal endoscopic working channel: the needle was inserted at the body surface marker under the guidance of X-ray fluoroscopy (Figure 1A). After reaching the lateral angle of the interlaminar space, the locator was used to penetrate from the bone surface to the intervertebral space plane and the posterior upper edge of the vertebral body. During the process, the puncture direction could be adjusted according to the specific target position of protrusion and stenosis (Figure 1B). Then the skin incision of about 7mm was made. Under the guidance of the locating guide wire, the expanders were used to expand the soft tissue of the surgical path, and then step by step reamers with nerve protection blunt head was used to remove part of the laminar and articular process (Figure 1B). Finally, the working cannula was placed to complete the establishment of endoscopic working channels (Figure 1C and D). Under the guidance of X-ray fluoroscopy, the puncture needle is placed at the intersection of the medial edge of the superior articular process, the tip of the inferior articular process and the lateral angle of the interlaminar space. Under the guidance of the guide wire, the puncture needle is replaced by a TOM locator, and the TOM locator is placed into the bone surface through the above intersection point, and the TOM locator replaced with a round needle core strikes deeply safely, ensuring that the head end of the needle core reaches the plane of the intervertebral space through the medial area of the lateral recess. The direction can be adjusted appropriately according to the specific position of the protruding object. A skin incision of about 7mm was made at the point of needle entry on the body surface, a step-by-step expander was placed along the guide wire to expand the soft tissue, and a step-by-step reamer (4 to 8mm) with a blunt head with nerve protection was used to grind off part of the lamina and articular process (Figure 1C), and the working cannula was placed. X-ray fluoroscopy showed that the positive and lateral position of the tip of the working cannula was located at the medial edge of the pedicle and the posterior edge of the diseased intervertebral space respectively (Figure 1D and E). The above are the specific operations of PE-MFD technology before the application of endoscope. Connect the spinal endoscopic light source and imaging system, that is, the working channel is established. (3) Placement and debugging of the spinal endoscopic surgery system: Under the endoscope, the hyperplastic bone was further modified and abraded, the hypertrophic ligamentum flavum was excised, and the herniated disc tissues were removed (Figure 1F to K). The observation of the Dural sac and the recovery of the autonomic pulse of the nerve root was the end standard of decompression (Figure 1L).

Figure 1.

The surgical procedure of PE-MFD proceeds as follows: A working channels of PE-MFD has been established (A-E). The ligamentum flavum (LF) was removed to expose the dorsal side of the nerve root (NR) (F-H). The caudal end of the ventral NR was processed (I and J). The cranial end of the ventral NR is processed (K). The NR was beating autonomously (L).

Endo-LOVE approach

Figure 2 showed Endo-LOVE surgical process: (1) The surgical position, anesthesia and body surface positioning are the same as PE-MFD, and the surgical method referred to traditional open posterior lumbar laminectomy and decompression which was called LOVE technique. (2) Establishment of the spinal endoscopic operation channel: Under the guidance of X-ray fluoroscopy, the needle was inserted in line with the body surface marker and reached the medial edge of the inferior articular process, slightly higher and more to the mid-line than the PE-MFD positioning site at the lateral angle of lamina space (Figure 2A). Then about 7-10 mm skin incision was made. Under the guidance of positioning guide wire, expanders were used to expand the surgical path of soft tissue, without precise positioning. Working cannulation was placed and the flexibility and movement on the bone surface was maintained to establish the endoscopic operation channel (Figure 2B and C). (3) Placement and debugging of the spinal endoscope surgery system: following LOVE technique, the total spinal canal decompression operation was performed. Firstly dealing with soft tissue around the bone surface, and showing the inter-laminar space, ligamentum flavum, medial border of articular process, etc. Secondly did the fan-shaped laminectomy from inferior border of the upper laminar, articular process, superior border of lower laminar, ligamentum flavum to the base of the spinous process. Under endoscope, hyperplasia of ligamentum flavum and articular process, as well as herniated disc was removed, and the Dural sac and nerve root was revealed and autonomic pulse was restored (Figure 2D to I).

Figure 2.

The surgical procedure of Endo-LOVE proceeds as follows: A working channels of endo-LOVE has been established (A-D). The ligamentum flavum (LF) and part of articular process (AP) ware removed to expose the dorsal side of dural sac (DS) (E-G). The DS and was nerve root (NR) beating autonomously (H and I).

Outcome assessment

Background information of the patients were recorded, including demography, operation time, intraoperative fluoroscopy times, postoperative bed rest time, hospital stay and postoperative complications. And postoperative lumbar MRI or CT were observed to understand the scope of spinal canal decompression and the degree of lateral recess decompression. Follow-up data was collected by phone, e-mail, or outpatient questionnaire. The condition of the patients was evaluated before operation, 1, 3, 6, 12 months and at the last follow-up after operation (range 24 months to 35 months, 30.09 ± 2.34 months in PE-MFD group, 29.50 ± 2.71 months in Endo-LOVE group). All patients were followed up for at least 24 months. None of the above patients lost follow-up. The neurological functional outcomes were evaluated by the Oswestry Disability Index (ODI), low back and leg pain Visual Analogue Score (VAS), Japanese Orthopedic Association Scores (JOA). The degree of decompression was evaluated by performing MRI or CT before and after operation (Figures 3 and 4), and satisfaction of the patients was evaluated according to modified MacNab criteria. Referring to the related literature, minimum clinically important difference (MCID) was defined as postoperative ODI improvement > 12 and low back and leg pain VAS improvement > 3.^27,28

Figure 3.

Pre- (A-C) and postoperative (D-H) computed tomography (CT) and magnetic resonance imaging (MRI) of lumbar (71-year-old man) in Endo-LOVE group. (A) preoperative sagittal MRI finding of L4/5; (B) preoperative axial MRI finding of L4/5; (C) preoperative axial CT finding of L4/5; (D) postoperative sagittal MRI finding of L4/5; (E) postoperative axial MRI finding of L4/5; (F) postoperative axial CT finding of L4/5; (G) postoperative sagittal CT finding of L4/5; (H) postoperative coronal CT finding of L4/5.

Figure 4.

Pre- (A and B) and postoperative (C-E) computed tomography (CT) of lumbar (68-year-old man) in PE-MFD group. (A) preoperative sagittal CT finding of L4/5; (B) preoperative axial CT finding of L4/5; (C) postoperative sagittal CT finding of L4/5; (D) postoperative axial CT finding of L4/5; (E) postoperative coronal CT finding of L4/5.

Statistical Analysis

All data was analyzed with SPSS 23.0 (SPSS Inc, Chicago, IL). The statistical analysis was conducted by an independent statistician who was not directly involved in the study. For the quantitative data, t-test was selected when it conforms to normal distribution. The paired t-test, the results of which were expressed as the means ± standard deviation (SD), was used for the quantitative data with equal variance assumed between the 2 groups, and the separate variance estimation t-test was used for the quantitative data with equal variance not assumed. The Chi-square test was used to assess the qualitative data between the 2 groups. A P value < .05 was considered significant.

Results

Background Information

Between April 2017and April 2018, 96 patients with DLSS were treated with Endo-LOVE or PE-MFD, including 58 with Endo-LOVE and 38 with PE-MFD. In terms of clinical presentations, there were 58 cases of radiculopathy (including 43 cases of decreased sensation, 48 cases of myotomal weakness, 46 cases of depressed reflex, 41 cases of positive nerve root), 42 cases of intermittent claudication, 38 cases of central canal stenosis and 20 cases of stenosis of lateral recess in Endo-LOVE group, and there were 38 cases of radiculopathy (including 28 cases of decreased sensation, 31 cases of myotomal weakness, 30 cases of depressed reflex, 27 cases of positive nerve root), 31 cases of intermittent claudication, 9 cases of central canal stenosis and 29 cases of stenosis of lateral recess in PE-MFD group. After PSM, a total of 62 patients were enrolled in this study, and the details are shown in Table 1. There were no significant differences in characteristics of patients between the 2 groups (P > .05).

Table 1.

Comparison of Characteristics Before and After Propensity Score Matching in the 2 Groups.

	Total set				Matched set
Variable	Endo-LOVE (n = 58)	FE-MFD (n = 38)	Statistical volume	P	Endo-LOVE (n = 31)	FE-MFD (n = 31)	Statistical volume	P
Age at surgery (Mean ± SD)	70.14^* ± 7.24	66.37 ± 8.06	t = −2.385	.019	67.10 ± 6.83	67.65 ± 7.34	t = −0.305	.762
Male, n (%)	32 (55.2)	20 (52.6)	χ² = 0.60	.807	18 (58.1)	19 (61.3)	χ² = 0.067	.796
BMI (kg/m²) (Mean ± SD)	23.36 ± 2.48	23.76 ± 3.04	t = 0.707	.481	23.81 ± 2.09	23.65 ± 3.01	t = 0.245	.807
Follow-Up Periods (Mean ± SD)	30.09 ± 2.34	29.50 ± 2.71	t = −1.127	.263	29.26 ± 2.21	29.61 ± 2.77	t = −0.559	.579
History of previous diseases, n (%)
Number of diabetes	9 (15.5)	8 (21.1)	χ² = 0.483	.487	7 (22.6)	6 (19.4)	χ² = 0.970	.755
Number of hypertension	15 (25.9)	8 (21.1)	χ² = 0.291	.589	7 (22.6)	6 (19.4)	χ² = 0.970	.755
Number of osteoporosis	15 (25.9)	8 (21.1)	χ² = 0.291	.589	10 (32.3)	8 (25.8)	χ² = 0.313	.576
Number of smoking history	15 (25.9)	11 (28.9)	χ² = 0.012	.914	6 (19.4)	9 (29.0)	χ² = 0.791	.374
Symptoms, n (%)
Number of decreased sensation	43 (74.1)	28 (73.7)	χ² = 0.002	.960	22 (71.0)	21 (67.7)	χ² = 0.760	.783
Number of myotomal weakness	48 (82.8)	31 (81.6)	χ² = 0.220	.882	28 (90.3)	25 (80.6)	χ² = 1.170	.279
Number of depressed reflex	46 (79.3)	30 (78.9)	χ² = 0.002	.966	24 (77.4)	25 (80.6)	χ² = 0.970	.755
Number of positive nerve root tension test	41 (70.7)	27 (71.1)	χ² = 0.001	.969	20 (64.5)	20 (64.5)	χ² = 0	1
Number of intermittent claudication	42 (72.4)	31 (81.6)	χ² = 0.580	.447	28 (90.3)	26 (83.9)	0.574	.449

^* P < .01 versus FE-MFD group.

Surgical Results

There were no significant differences in postoperative bed rest time, hospital stay, Surgical segment and postoperative complications between the 2 groups (P > .05). In the PE-MFD group, the operation time was 57.19 ± 6.28 minutes and intraoperative fluoroscopy was 6.68 ± 1.38 times. In the Endo-LOVE group, the operation time was 79.10 ± 7.34 minutes and intraoperative fluoroscopy was 3.03 ± 0.48 times. The operation time (P < .05) and postoperative complications (P < .05) were significantly different in the 2 groups. The details are shown in Table 2.

Table 2.

Comparison of Operative Outcomes in the 2 Groups.

Operative outcomes	Endo-LOVE	FE-MFD	Statistical volume	P
Operation time (Mins)	79.10 ± 7.34^*	57.19 ± 6.28	t = 12.624	.000
Postoperative bedridden time	1.13 ± 0.43	1.19 ± 0.48	t = −0.560	.577
Intraoperative fluoroscopy times	3.03 ± 0.48^*	6.68 ± 1.38	t = −13.923	.000
Hospitalization time	3.45 ± 0.72	3.19 ± 0.54	t = 1.589	.118
Surgical segment (%)
L3/4 or above segment	0	0	χ² = 0.683	.409
L4/5	23 (74.2)	20 (64.5)
L5/S1	8 (25.8)	11 (35.5)
Postoperative complications
Nerve injury	0	1 (0.03)	χ² = 1.016	.313
Dural tear or spinal fluid leak	1 (0.03)	1 (0.03)	χ² = 0	1
Spinal cord hypertension	1 (0.03)	1 (0.03)	χ² = 0	1
Cardiovascular complications	0	0	–	1
Respiratory complications	0	0	–	1
Wrong level surgery	0	0	–	1
Urinary tract infection	0	0	–	1
Micturition problems	0	0	–	1
Deep vein thrombosis	0	0	–	1
Wound infection	0	0	–	1

^* P < .01 versus FE-MFD group.

Clinical Efficacy and Neurological Function Outcomes

Compared with preoperation scores, the VAS of leg and low back pain, JOA and ODI were significant improvement in both groups (P < .05), and postoperative ODI improvement > 12 and low back and leg pain VAS improvement > 3 (These results are greater than those of MCID.). SO, these results are equal to the statistical results, which are of both statistical and clinical significance. There was no significant difference in the VAS of leg and low back pain, JOA and ODI between the 2 groups either at pre- or post-operation (P > .05), and ODI score difference <12 and low back and leg pain VAS score difference <3 (These results are less than those of MCID.). SO, these results are equal to the statistical results, which are neither statistical significance nor clinical significance. According to the modified MacNab criteria, there were 18 cases of excellence, 11 cases of good, 2 cases of fair and 0 case of poor in Endo-LOVE group. And there were 14 cases of excellence, 13 cases of good, 3 cases of fair and 1 case of poor in PE-MFD group. The excellence and good rates of the 2 groups were respectively 93.5% and 87.1%. There was no significant difference in the modified MacNab criteria between the 2 groups (P > .05). The details are shown in Table 3.

Table 3.

Comparison of VAS, JOA and ODI Scores, MacNab Evaluation in the 2 Groups.

Clinical efficacy and neurological function outcomes		Endo-LOVE (n = 31)	PE-MFD (n = 31)	Statistical volume	P
VAS leg pain scores	Preop	7.19 ± 0.83	7.52 ± 1.15	t = 1.264	.211
	1 mo postop	2.10 ± 0.65^*	1.97 ± 0.48^*	t = −0.887	.379
	3 mo postop	1.97 ± 0.61^*	1.71 ± 0.53^*	t = −1.789	.079
	6 mo postop	1.97 ± 0.71^*	1.94 ± 0.57^*	t = −0.197	.844
	12 mo postop	1.32 ± 0.48^*	1.42 ± 0.50^*	t = 0.780	.439
	last	1.32 ± 0.48^*	1.26 ± 0.51^*	t = −0.513	.610
VAS low back pain scores	Preop	6.39 ± 0.84	6.32 ± 0.70	t = −0.327	.745
	1 mo postop	2.00 ± 0.68^*	1.90 ± 0.94^*	t = −0.463	.645
	3 mo postop	1.77 ± 0.92^*	2.00 ± 0.63^*	t = 1.126	.265
	6 mo postop	1.61 ± 0.76^*	1.87 ± 0.34^*	t = 1.724	.090
	12 mo postop	1.23 ± 0.43^*	1.26 ± 0.45^*	t = 0.292	.771
	last	1.19 ± 0.40^*	1.29 ± 0.64^*	t = 0.711	.480
JOA	Preop	14.55 ± 3.31	14.74 ± 2.76	t = 0.250	.803
	1 mo postop	22.10 ± 2.64^*	22.26 ± 3.72^*	t = 0.197	.844
	3 mo postop	23.06 ± 2.29^*	23.94 ± 2.67^*	t = 1.378	.173
	6 mo postop	23.42 ± 2.26^*	23.84 ± 2.46^*	t = 0.698	.488
	12 mo postop	24.03 ± 2.36^*	23.68 ± 2.34^*	t = −0.594	.555
	last	23.90 ± 2.66^*	24.00 ± 2.61^*	t = 0.145	.886
ODI (%)	Preop	53.48 ± 10.78	53.45 ± 12.57	t = −0.011	.991
	1 mo postop	27.23 ± 6.96^*	28.00 ± 6.93^*	t = 0.439	.662
	3 mo postop	23.03 ± 4.95^*	23.55 ± 4.56^*	t = 0.427	.671
	6 mo postop	22.52 ± 5.86^*	22.32 ± 6.13^*	t = −0.127	.899
	12 mo postop	22.84 ± 4.53^*	21.61 ± 4.60^*	t = −1.058	.295
	last	21.23 ± 4.67^*	20.71 ± 5.53^*	t = −0.397	.693
MacNab Evaluation	Excellence	18	14	–	–
	Good	11	13	–	–
	Fair	2	3	–	–
	Poor	0	1	–	–
	Excellence or good rate (%)	93.5	87.1	χ² = 0.738	.390

Abbreviations: VAS, Visual Analogue Score; JOA, Japanese Orthopedic Association Scores; ODI, Oswestry Disability Index; Postop, postoperative; Preop, preoperative; mo, month/months.

^*P < .05 versus preoperative.

Discussion

Traditional surgical treatments of DLSS includes open decompression with or without fusion surgery.^{9,14,26,29-32} However, the perioperative complications and long postoperative recovery time of these open surgery have emphasized the necessity of minimally invasive spine surgery (MISS).^14,33 The purpose of MISS is to minimize the damage to normal tissue while providing the same therapeutic effect.¹⁴ The emergence and development of MISS enables patients to return to normal life more quickly and improve their quality of life at the same time.^{14,15,29,34,35} With the gradual popularization of MISS in spinal surgery, especially percutaneous endoscopic (PE), the clinical application of PTED represented by YESS and TESSYS has been becoming increasingly widespread.^16,17 On the other hand, a correct understanding of spinal endoscopic technique, mastery of MISS indications and skilled operation skills is the key to achieve good clinical results.^14,19 For example, in the early stage of PTED, the main indications are LDH and lateral recess or intervertebral foramen stenosis, showing shortcomings such as longer learning curve, higher puncture techniques, easy residual compression herniation, intraoperative grinding of the superior articular process may induce symptoms of stimulation of the posterior branch of the lumbar nerve, and hypertrophy of the high iliac crest and transverse process affect the operation of the L5-S1 segment.^{14,18,19,22,25} Especially for severe complex, central DLSS, PTED appears to be “inadequate,” it is difficult to achieve total spinal canal, multiplane decompression.^18,19,22 Based on this, we draw lessons from the posterior lumbar open surgery and make it endoscopic, which is closer to the traditional spinal canal decompression. The anatomical process of the surgical approach is basically the same as the conventional open surgery familiar to spinal surgeons, and makes up for the technical blind area of PTED. PE-MFD and Endo-LOVE are both PEID. In PE-MFD technique, the tube was placed outward and upward from the lateral angle of the interlaminar space, and the working channel is located at the original site of the ligamentum flavum of the lateral articular process. The safe area between the Dural sac and the nerve root can be reasonably used to decompress the disc-flava ligament space via the medial foramen. Compared with the conventional PEID, there is less interference to the Dural sac and nerve root. PE-MFD is more advantageous for DLSS cases with lateral recess stenosis or the stenosis layer is located below the intervertebral space to the middle and upper part of the inferior vertebral body. The surgical area of the internal orifice of the intervertebral foramen is located near the line of the medial edge of the pedicle, and a very small amount of facet joints are removed, so as not to affect the stability of the spine. At the same time, a working channel is established to pass through the bone joint of the lateral recess, so part of the lateral recess is opened in the process of bone removal. Combined with endoscopic decompression can save the operation time under the curative effect. Posterior lumbar lamina laminectomy decompression was first proposed by Love in 1938.^36,37 Now the standard posterior lumbar lamina laminectomy decompression is improved on the basis of LOVE technique. The key of LOVE technique is to preserve the integrity of supraspinal ligament, interspinous ligament and facet joint, remove ligamentum flavum to the disc-flava ligament space, remove herniated intervertebral disc and release nerve root decompression.³⁷ Now modified LOVE technique is to remove facet joint less than 1/2, retain upper and lower lamina more than 1/2, and enlarge lateral recess at the same time, mainly for patients with DLSS treated with decompression of spinal canal and nerve root canal. Based on the anatomical pathway of LOVE technique, using accurate localization and full endoscopic laminectomy (FE-FE)³⁸ for reference, establishing a working channel and maintaining its relative flexibility in the medial margin of superior inferior articular process and lamina area, LOVE technique can be completed under endoscope, and named Endo-LOVE technique.

In this study, according to modified MacNab criteria, the excellence/good rates were 93.5% and 87.1% in Endo-LOVE and PE-MFD group. The postoperative VAS, JOA and ODI were significantly improved. And postoperative ODI improvement > 12 and low back and leg pain VAS improvement > 3 (These results are greater than those of MCID.). SO, these results are equal to the statistical results, which are of both statistical and clinical significance. There was no significant difference in the VAS of leg and low back pain, JOA and ODI between the 2 groups either at pre- or post-operation (P > .05), and ODI score difference <12 and low back and leg pain VAS score difference <3 (These results are less than those of MCID.). SO, these results are equal to the statistical results, which are neither statistical significance nor clinical significance. There was no significant difference in clinical efficacy between the 2 groups, which was similar to that of conventional surgery reported in the previous literature. In this study, there was no significant difference in hospitalization time and postoperative bedridden time between the 2 groups, but in the intraoperative fluoroscopy times, Endo-LOVE group was less than PE-MFD group, suggesting that Endo-LOVE has obvious advantages in radiation exposure and can avoid repeated fluoroscopy during operation. This advantage may depend on one reason: PE-MFD is non-full endoscope, which requires accurate localization, while Endo-LOVE is full endoscope, so it does not need to be too accurate, it only needs to be located in a certain range, and then further determine the location under endoscope. One reason for the short operation time of PE-MFD is that because of the non-full endoscope procedure, removing of the surgical area soft tissue has been done quickly before endoscopic operation, while Endo-LOVE is the full endoscope procedure, which needs to remove the soft tissue under endoscope leading to the relatively longer operation time. In this study, there was 1 case of Dural tear or spinal fluid leak in Endo-LOVE group and 1 case in PE-MFD group, and the condition improved after conservative treatment for 2 weeks. There was 1 case of spinal cord hypertension in PE-MFD group. After bed rest for 1 hour, the condition improved. In PE-MFD group, there was 1 case of nerve root injury, which was only nerve root adventitia injury. Fortunately, the patient had no obvious neurological symptoms.

The concept of full endoscopic technique was originally put forward by Professor Ruetten in Germany. The definition of full endoscopic technique is to place the working cannula and endoscope before the spinal canal operation, which can be beneficial to avoid the possible injury to the dural sac and nerve root. So, the full endoscopic operation is safer. While in PE-MFD, endoscopic working channel was first established going straight into the spinal canal. And then, the canal and lateral recess decompression was performed under the endoscopic vision. Therefore, PE-MFD belongs to non-full endoscopic technique. PE-MFD was developed from Professor Choi in Korea on the basis of non-full endoscopic technique, and its initial indications are various types of LDH, especially for L5–S1 LDH of high iliac crest. Compared with the posterolateral TESSYS technique, although the puncture path is different, the puncture target is almost the same, which is the disc-flava ligament space of ventral of the superior articular process, and the tip of the working cannula is naturally located in the shoulder of the traversing nerve root. When releasing the nerve root and removing the compression protrusions, it is not necessary to pull the nerve root. The trauma is less, and the operation is more convenient and safe in PE-MFD. The surgical area of the Medial foramen is located near the line of the medial border of the pedicle, and a very small amount of facet joints are removed, so as not to affect the stability of the spine. Because when the working channel is established, it passes through the lateral recess, and part of the lateral recess is opened at the same time in the process of bone removal. And Combined with endoscopic decompression and plasty can effectively treat the DLSS which is stenosis of lateral recess and which narrow layer is below the intervertebral space to the middle and upper part of the inferior vertebral body. The clinical excellent and good rate of PE-MFD in the treatment of DLSS is relatively low. The main reason is that the early indication is relatively broad. After the decompression of the lateral recess, the disc-flava ligament space and the spinal canal below the level of the intervertebral space, it is impossible to complete the enlarged decompression of the central spinal canal above the level of the intervertebral space in one stage. The PE-MFD technique uses slight different position from the other one but could reduce interference to dural sac and nerve root. However, the risk of facet violation and subsequent instability could occur, especially in cases with severe facet hypertrophy. Compared with PE-MFD, Endo-LOVE achieves multiplane and stereoscopic spinal canal decompression, which is suitable for severe and central DLSS. Based on the experience of endoscopic decompression of spinal canal stenosis of pathological changes, fine anatomy, traditional lamina laminectomy and precise positioning, the establishment of Endo-LOVE working channel and decompression are more convenient, and can complete one-stage decompression of the total spinal including the intervertebral space plane, the original site of ligamentum flavum of superior lamina, pedicle of inferior level and lateral recess. From the anatomical point of view, 4 key structures should be paid attention to in total spinal canal decompression, which includes that the hyperplasia of inferior articular process which is more likely to cause central spinal canal stenosis, the plane of intervertebral space which is the main initiating factor of spinal canal degeneration and stenosis, lateral recess and overall hypertrophy of ligamentum flavum. During the Endo-LOVE surgery, the working cannula was placed on the bone surface of the superior lamina and swung more freely. First, the inferior articular process was partial resected and the lamina was opened to the attachment part of the ligamentum flavum of the superior lamina. Then fan-shaped resection was performed along the medial edge of the facet joint to the lateral recess of the superior process. Finally, the hypertrophic ligamentum flavum was removed inward to the root of the spinous process, and the disc-flava ligament was opened, and If there was disc herniation, remove it. With the skill of Endo-LOVE surgery and the optimization of operation flow, the expanded shaping of bony spinal canal, disc-flava ligament space, nerve root canal and lateral recess was completed in a short time, and the decompression effect was more accurate and thorough, which ensured the clinical effect of DLSS with “high performance-to-price ratio.”

Although both Endo-LOVE and PE-MFD belong to posterior interlaminar endoscopic decompression operation aiming at lumbar spinal stenosis, the 2 techniques actually have some differences. PE-MFD is a non-full endoscopic technique, which requires accurate location, lamina fenestration and lateral recess decompression. Endo-LOVE belongs to full endoscopic technique, which does not need precise location, just locates at the lateral angle area of the interlaminar space. Surely, the accurate anatomic structure recognition in Endo-LOVE is needed under spinal endoscope, as well as followed by lamina fenestration, decompression of the central canal and lateral recess. However, the 2 techniques have the common points that can be comparable. Both Endo-LOVE and PE-MFD are the endoscopic interlaminar decompression techniques which have the lamina fenestration, discectomy if necessary, spinal canal and lateral recess decompression, etc. No matter the central canal or the lateral recess stenosis, the endoscopic operation for nerve root decompression is the same. In addition, DLSS has the complex pathologic changes in which multiple sites stenosis are often present simultaneously. So the indications for the 2 techniques are sometimes overlap. For example, during the decompression of central stenosis, simultaneous exploration of the lateral recess is often required. Similarly, when dealing with spinal stenosis with the lateral recess, the pressuring factors around the central dural sac also need to be addressed. However, for patients with DLSS dominated by lateral recess stenosis, more emphasis is placed on the choice of PE-MFD. For patients with DLSS who are mainly central canal stenosis or/and complicated with lateral recess stenosis, more emphasis is placed on the choice of Endo-LOVE.

Compared with traditional open surgery, spinal endoscopic surgery has certain advantages. The surgical trauma is small, and the paraspinal muscles are bluntly stripped, which can better protect the deep paraspsoas stable muscles, such as psoas major muscle, multifida muscle and semi-spinous muscle, and reduce the incidence of denervation and devascularization of paraspinal muscles, which is in line with the concept of enhanced recovery after surgery (ERAS). Better lighting conditions under endoscope, the use of endoscopic magnified images to observe the surgical field, combined with water medium washing and hydrostatic hemostasis, make the fine structure of important tissues clear and visible, and the operation is more safe and meticulous. For the patients with small interlaminar space caused by the cohesion of articular process hyperplasia, laminoplasty and arthroplasty can be performed by visual ring saw combined with intraoperative X-ray fluoroscopy, which is beneficial to the identification of anatomical structure under endoscope. PE-MFD and Endo-LOVE both retain enough facet joints, which can effectively prevent the occurrence of iatrogenic segmental instability. In addition, the surgeon can communicate with the patient in time under local anesthesia, which avoids the risk of intubation general anesthesia or epidural anesthesia and significantly reduces the complications of intraoperative nerve injury. Before surgery, combined with clinical symptoms, signs and imaging features, we can clearly judge the pathological type, responsible segment and lesion area of DLSS, reasonably choose the way of posterior interlaminar endoscopic decompression, and perform minimally invasive surgery on the target at the cost of less trauma, most of them can obtain satisfactory clinical results. However, DLSS cases generally have a long history and complex pathological changes, which has always been a difficulty in clinical treatment. Especially for elderly patients, they often come to see a doctor when intermittent claudication or neurological symptoms have significantly affected their daily life. Long-term spinal canal stenosis makes nerve roots prone to fibrosis, scar hyperplasia and even axonal degeneration. In such cases, lower limb numbness, discomfort and weakness symptoms are often not completely relieved after the release of nerve compression. In addition, severe DLSS cases are often complicated with disc degeneration and obvious facet joint hyperplasia and cohesion, so adequate nerve decompression is contradictory to maintain segmental stability. The surgeon need to make a choice between relieving neurological symptoms and avoiding postoperative unstable pain, which will often affect the postoperative effect. In young and middle-aged patients with DLSS, the course of disease is relatively short, the internal structure of nerve is basically normal, the degeneration and scar of compressed nerve are less, the threshold of neuralgia is higher, and the nerve recovery after spinal canal decompression is more ideal.

Limitations

There are some limitations in the current study. First of all, this is a single-center retrospective study, it is difficult to apply a double blind strategy in the choice of surgery, and the subjective factors from doctors are difficult to rule out, but PSM has minimized the deviation caused by retrospective study. Secondly, due to the influence of time factor, the study sample size is relatively insufficient and the follow-up time is relatively short. Although it has been followed up for at least 2 years, it is still necessary to increase the number of clinical cases and long-term follow-up in the future. There are some differences in the number of central canal stenosis and lateral recess between the 2 groups, which may cause some bias to the results, which will be avoided in future studies. In addition, due to the particularity of spinal endoscopic surgery, there was no paper to evaluate the MCID of lumbar JOA score in spinal endoscopic surgery. Therefore, we have not compared it.

Conclusions

Translaminar minimally invasive endoscopic decompression surgery is effective in the treatment of DLSS. Endo-LOVE technique has the advantages of fast puncture positioning, less radiation exposure and wider indications. However, PE-MFD needs more radiation exposure and has the possibility of incomplete decompression for complex multiplanar spinal stenosis. The key to successful operation lies in defining the pathological classification and stenosis area of DLSS, mastering fine endoscopic anatomy and minimally invasive precise operation, and reasonable selection of surgical indications.

Footnotes

Authors’ Note

The study was designed by Qiang Jiang and Yu Ding. Qiang Jiang drafted the manuscript. Qiang Jiang, Zhengcao Lu, Hongpeng Cui and Jianjun Zhang carried out and the data collection and interpretation. Bensheng Fu, Wei Du and Shiqi Cao participated in the revision of this manuscript. And finally, our manuscript was proof read by the corresponding author, Yu Ding. All authors read and approved the final manuscript. Qiang Jiang were first authors. The datasets during and/or analyzed during the current study available from the corresponding author on reasonable request. Informed consent was obtained from all patients included in the study. Published consent was obtained from the authors. Ethical approval was obtained from the ethical committee of our Hospital prior to conducting this study.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This project was funded by foundation of research and demonstration application of Capital clinical diagnosis and treatment technology of China (Grant number: Z191100006619028).

ORCID iD

Qiang Jiang, MS

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