The effective analysis of percutaneous endoscopic interlaminar discectomy in the treatment of L4/5 intervertebral disc herniation

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The effective analysis of percutaneous endoscopic interlaminar discectomy in the treatment of L4/5 intervertebral disc herniation

https://doi.org/10.21203/rs.3.rs-1983641/v1

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The purpose of this study was to analyze the safety and effectiveness of percutaneous endoscopic interlaminar discectomy in the treatment of L4/5 intervertebral disc herniation. This prospective study included 36 patients diagnosed with L4/5 intervertebral disc herniation between December 2018 and July 2020 who were scheduled to undergo minimally invasive surgery: group A underwent percutaneous endoscopic transforaminal discectomy (PETD), and group B underwent percutaneous endoscopic interlaminar discectomy (PEID), after which we analyzed the effectiveness of PEID in the L4/5 segment. A total of 36 patients with an average age of 32.1±14.7 years (16 to 65 years), and an average course of disease of 24.6±10.3 months (6 to 60 months), were enrolled. There was no difference in operation time between group A and group B (P>0.05). However, the average fluoroscopy time of group B was shorter compared to group A (P<0.05). The Visual Analogue Scale (VAS) scores of patients with low back pain and lower limb pain did not significantly differ between the two groups preoperatively, and 24 hours, 72 hours, 3 months, and 1 year after the operation (P>0.05); however, they all significantly improved (P<0.05). Also, there was no significant difference in Oswestry disability index (ODI) scores between the two groups (P>0.05) preoperatively, and 3 months and 1 year after the operation; however, they all significantly improved (P<0.05). PEID is a safe and effective treatment method for L4/5 intervertebral disc herniation.

Lumbar disc herniation (LDH) is the most common clinical degenerative disease of the spine, which most frequently occurs at the L4/5 and L5/S1 segments¹. If conservative treatment is ineffective, surgical treatment is often required, where removal of diseased nucleus pulposus is of crucial importance. Percutaneous endoscopic removal of nucleus pulposus, represented by percutaneous intervertebral foramen endoscope, has been commonly used due to its advantages, such as less trauma and rapid recovery, which have been confirmed through many years of clinical practice ².

From the beginning of the birth of spinal endoscopic techniques to its subsequent popularization and application, both Yeung endoscopic spine system (YESS) and transforaminal endoscopic surgical system (TESSYS) techniques were based on the lateral transforaminal approach (percutaneous endoscopic transforaminal discectomy, PETD) ³^,⁴. Later, Ruetten et al reported that percutaneous interlaminar discectomy (percutaneous endoscopic interlaminar discectomy, PEID ⁵ should be applied to the high iliac crest and other difficult L5/S1 spaces; however, when it comes to other segments, there are few choices. Nonetheless, the posterior approach has the advantages of simple puncture, less fluoroscopy, and a relatively large intraoperative visual field, which is more in line with the practices of doctors performing spinal surgery.

In this prospective study, 36 patients with lumbar disc herniation diagnosed between December 2018 and July 2020 were randomly divided into two groups and treated with PEID and PETD methods, respectively. The effect of PEID in the L4/5 segment was analyzed, and the cases are summarized as follows.

General information. The current study was approved by the Ethics Committee of The First Affiliated Hospital of Xi'an Jiaotong University. Written informed consent was obtained from all participants or their parents/guardians. The methods were carried out in accordance with approved guidelines. A total of 36 patients, including 25 males and 11 females, with an average age of 32.1±14.7 years old (16-65 years old) and an average course of disease of 24.6±10.3 months (6-60 months) were enrolled. After various conservative treatments lasting more than 3 months, magnetic resonance imaging (MRI) showed that all responsible segments were L4/5. The lesions included: central lateral prolapse in 19 cases, prolapse in 11 cases, and free and prolapse in 6 cases. Computed tomography (CT) showed no calcifications in 28 cases and partial calcification in 8 cases. There was no obvious spinal instability on X-ray films of dynamic lumbar position. The main clinical diagnosis was intervertebral disc herniation. None of the patients had obvious radiation pain in the lower extremities and no surgical history of the diseased segments. The patients were alternately divided into two groups according to the order of admission: PETD was labeled as group A, and PEID was labeled as group B. Exclusion criteria were following: other segmental or multi-segmental disk herniation; central disc herniation, and radiation pain in both lower extremities; central lumbar spinal stenosis caused by hypertrophy of ligamentum flavum with intermittent claudication of both lower limbs; recurrent intervertebral disc herniation in L4/5 segment; extreme lateral intervertebral disc herniation.

Surgical Procedure. The surgical procedure for Group A was as follows: according to the patients' wishes, 10 in this group were treated with local anesthesia combined with intravenous enhancement, and 8 were treated with general anesthesia. The local anesthetic formula included a mixture of ropivacaine 10ml, lidocaine 10ml, and saline 20ml. A 10ml of local anesthesia was injected into the skin and subcutaneous tissue, 10ml into the fascia layer, 10ml in the intervertebral foramen, and 3ml into the epidural. For patients receiving general anesthesia, after the anesthesia was satisfactory, they were placed in the prone position, and their torso was raised to make the hip flexion as close to 90 degrees as possible, keeping the abdomen suspended in the midair. We used anteroposterior fluoroscopy to locate the L4/5 intervertebral disk, and a line was made from the tip of the upper articular process on the affected side of L5 to the intersection of the L4/5 vertebral space and the spinous process, which was the puncture route for TESS technology, about 10-12cm from the posterior midline. Also, the puncture point was determined according to the patient's body shape and the specific location of nucleus pulposus protrusion. Disinfection of shop towels was carried out regularly. The puncture was performed according to the marked puncture path. If local anesthesia was used, it was injected according to the level. The puncturing process was carried out under fluoroscopic monitoring. After the puncture needle reached the ideal position, it was expanded in sequence according to the steps, and the foramina were formed as appropriate. Also, the working channel was finally placed. The anteroposterior radiographs showed the tip of the channel between the spinous process and the pedicle, and the lateral radiographs showed the posterior upper edge of the L5. Percutaneous endoscopic was placed, the residual bone fragments during the formation were successively removed, the nucleus pulposus tissues were prominent, the intervertebral space was explored, and the nerve roots were exposed. After confirming the relaxation of the nerve roots, the bleeding was stopped, the operation was ended, and the wound was sutured. Following surgical instruments were used: German Spinedos side mirror system: endoscope working cavity inner diameter: 3.75mm, outer diameter: 6.3mm, a field of view: 80 degrees, direction of view: 30 degrees, length 181mm.

The surgical procedure for Group B was as follows: all patients were treated under general anesthesia with the same body position as group A. The L4/5 intervertebral space and the posterior midline were marked by orthotopic fluoroscopy, and the puncture point was marked by 0.5~1cm beside the intervertebral space level. Disinfecting shop towels were regularly carried out, centering on the puncture point of the incision. fascia vascular clamp appropriate expansion, channel filling into work, detect edge of L4 vertebral plate, close to edge of L4 vertebral plate and screwing in the inner core working channel, perspective to verify position after the satisfaction, into the endoscope, rf, clean up the residual muscle tissue appeared yellow ligament, basket forceps broken yellow and expand to the joint point is, Show dural sac, the microscopic dynamics or lamina rongeur to remove part of the bone, show L5 nerve root of the lateral margin, expand its shoulder space, screwing in working channel to protect nerve root, show outstanding nucleus pulposus tissue, shall be removed and probe the intervertebral disc, remove loose, nucleus pulposus probe nerve root, again confirmed that no pressure after surgery. (Figure 1) Following surgical instruments were used: Spinedos rear mirror system from Germany: endoscope working cavity inner diameter: 4.3mm, outer diameter: 7.0mm, field of view: 80 degrees, direction of view: 30 degrees, length 130mm.

Postoperative management required patients to stay in bed for 1 day, freely move both lower limbs, wear hard waistline on the ground 1 day after the operation, record the observation index, leave hospital 2-3 days after the operation, wear rigid waistline for 4 weeks, and avoid bending down to lift and carry heavy objects during 12 weeks following the operation.

Outcome Measures. The time of operation, the times of intraoperative fluoroscopy, the visual analogue score of low back pain (Visual Analogue Scale, VAS), modified Oswestry dysfunction index (Oswestry disability index, ODI), the wound healing, and intraoperative and postoperative complications were recorded. Follow-up was performed through an outpatient clinic or network information after discharge. VAS was recorded preoperatively, at 24 hours, 72 hours, 3 months, and 1 year postoperatively, while the ODI index was recorded preoperatively and at 3 and 12 months postoperatively.

Statistical Analysis. All data were analyzed with SPSS version 28.0 (SPSS, USA). All measurement data were expressed as mean ± standard deviation. An independent sample t-test was used to compare the VAS score and ODI score between the two groups before and after follow-up. Repeated analysis of variance was used to compare each follow-up before and after operation in the two groups. The α value of the test level was 0.05 on both sides. A p-value < 0.05 was considered as statistical significance.

Comparison of perioperative conditions between the two groups. The average age in group A was 39.4 ± 11.1 min, and the average course of the disease was 24.0 ± 13.2months, vs. 40.9 ± 11.5 min, and 24.3 ± 12.3months in group B, respectively. There was no significant difference in average age, course of the disease, type of protrusion, and calcification between the two groups (all P > 0.05). In group A, there was 1 case of nerve root adventitia tear during operation, which was caused by ring drilling injury during intervertebral foramen formation. There were no special changes in vital signs and no special discomfort after the operation. The other patients in the two groups successfully completed the operation with a clear field of vision and a small amount of bleeding during the operation. The postoperative pain was relieved, the puncture site healed well, and there were no obvious postoperative complications. All patients were timely discharged and followed up, and no patient needed reoperation.

In group A, the average operation time was (75.5 ± 14.9) min and the number of intraoperative fluoroscopies was (16.3 ± 14.1) vs. 75.4 ± 14.4 min and 3.5 ± 0.5 in group B, respectively. There was no significant difference in operation time between the two groups (P > 0.05). Yet, the average number of intraoperative fluoroscopy in group A was 16, while that in group B was only 3, which was significantly less than that in group A (P < 0.05) (Table 1).

Table 1

Patient Demographics and Perioperative Data.
	Group A	Group B	P
Cases number	18	18
Age(year)	39.4 ± 11.1	40.9 ± 11.5	> 0.05
Disease course (month)	24.0 ± 13.2	24.3 ± 12.3	> 0.05
Prominent type (protrude: prolapse༚free prolapse)	10:5:3	9:7:2	> 0.05
Protrusion calcification (yes/no)	3:15	5:13	> 0.05
Operation time(min)	75.5 ± 14.9	75.4 ± 14.4	> 0.05
Times of intraoperative X-ray exposure	16.3 ± 14.1	3.5 ± 0.5	< 0.05

Follow-up results of clinical efficacy of the two groups. VAS scores of patients with low back pain and lower limb pain were followed up preoperatively, 24 hours, 72 hours, 3 months, and 1 year postoperatively. Independent sample t-test showed no significant difference between the two groups (P > 0.05); however, a significant improvement was observed compared with preoperative condition (analysis of variance, P < 0.05).

The ODI scores of the patients were followed up preoperatively, and at 3 months and 1 year postoperatively. The independent-sample t-test showed no significant difference between the two groups; however, it was significantly improved compared with the preoperative condition (analysis of variance, P < 0.05) (Fig. 2).

A total of 80% of LDH can be relieved with regular conservative treatment ⁶; however, if such treatment should fail and the condition starts to interfere with patients' normal life and work, surgical intervention is needed. Regardless of the type of operation, its main purpose is to remove the diseased nucleus pulposus tissue and relieve the nerve root compression. As spinal endoscopy, represented by intervertebral foramen endoscope, has the advantages of less trauma, quick recovery, and satisfactory effect, it has become the mainstream of minimally invasive treatment for LDH. According to the different approaches, it can be divided into two techniques: PETD via lateral intervertebral foramen approach and PEID via posterior interlaminar space approach. Regardless of the initial YESS technique ³, the now popular TESS technique ⁴, the later modified BEIS technique ⁷, Jane's technique ⁸, and similar, all imply insertion through the lateral intervertebral foramen to reach the diseased tissue. Theoretically, this approach can complete the treatment of all segments of LDH; still, the learning curve is long, and most segments need intervertebral foramen plasty, especially in the L5/S1 segment, which often present problems such as high iliac crest, L5 transverse process hypertrophy, small intervertebral foramen and so on. All of these can increase the difficulty of puncture, prolong the operation time, and even prevent placing the tube to the ideal position, thus affecting the treatment effect. For L5/S1 nucleus pulposus upward free prolapse, this problem is even more intractable. Although some authors have reported that trans iliac puncture and catheterization can easily reach the focus ⁹, it undoubtedly increases the difficulty of trauma and operation. In 2005, Ruetten et al ⁵ reported the PEID of the posterior interlaminar approach, which made full use of the anatomical characteristics of L5/S1, such as wide interlaminar space and steep sacral nerve root, to solve this problem. Subsequently, Choi et al ^{10, 11} used this approach to treat L5/S1 segmental LDH and proposed their methods of puncture and breaking through the ligamentum flavum. Their results showed that the posterior approach shortened the operation time and significantly reduced the number of intraoperative fluoroscopies compared with the lateral approach. A good therapeutic effect has been achieved, which gradually popularized PEID technology. However, considering the LDH above L4/5, it is traditionally considered that as the interlaminar soft tissue window is small, this will increase the difficulty in puncture and intubation. Also, the posterior approach often requires general anesthesia, and complications such as sensory abnormalities caused by excessive nerve root traction can easily occur during the operation, so most operators still opt for PETD. Considering the choice of these two surgical approaches, the popular view is that PETD should be performed for LDH above L4/5. For L5/S1, especially for nucleus pulposus prolapse, PEID should be considered.

As 95% of LDH occur in L4/5 and L5/S1 segments, making the full use of the advantages of PEID technology, such as large operating space and shorter fluoroscopy times, as well as the safe and efficient use of PEID technology in the L4/5 segment has become the focus of many studies ^{5, 12}. Many doctors have investigated different aspects. Yanhong et al ¹³ measured the distance between the L5 nerve root and the ipsilateral dural sac in normal volunteers by using magnetic resonance neuroimaging (magnetic resonance neurography, MRN), finding it to be some 12mm, which is larger than the diameter of the usual posterior mirror channel, and can theoretically be placed in the axillary space of the nerve root to remove the nucleus pulposus. Also, it is considered that this distance would be larger with the intervertebral disc herniation, which is more conducive to the operation. Qun et al ¹⁴ measured the interlaminar space height of L4/5 in flexion position as 12.5 ~ 20.5mm, which was significantly higher than that in a prone position (9.3 ~ 18.3mm). They considered that the height of interlaminar space in flexion position could be significantly increased, the range of motion and safe operating space of percutaneous endoscopic system working channel in the spinal canal could be increased, and the bone resection of vertebral lamina reduced, which is consistent with our long-term clinical experience. When placing the patient in the position, it is necessary to raise the torso and make the hip flexion reach 90 degrees as far as possible, which is conducive to the expansion of interlaminar space, less bony removal, and operation. Also, existing literature shows that different scholars had different ways of dealing with the ligamentum flavum and unveil the herniated disc ^{15, 16}. Our experience is that under the microscope, the basket forceps can be used to bite out the ligamentum flavum from the inside out to the ipsilateral facet joint, fully exposing the lateral edge of the L5 nerve root, biting or grinding off the bone of the superior articular process tip of the L5, enlarging the shoulder space of the nerve root, and then lowering the cannula to rotate the nerve root when the space is sufficient to expose the nucleus pulposus tissue. In this way, the operative field can be clearly exposed, the anatomical structure is clear, and the injury of the dural sac and nerve root caused by blind operation can be avoided. It is also convenient to stop bleeding in the surgical field and is beneficial to the follow-up operation. Due to the expansion of the shoulder space of the nerve root, rotating the cannula can reduce the excessive inward traction of the nerve root and effectively avoid the numbness of the affected limb after the operation.

For the patients of L4/5 disc herniation according to the following conditions, we believe that the interlaminar approach is more suitable: The huge disc herniation, if the transforaminal approach is used, the disk may be left over in the armpit and dorsum of 5 nerve roots; The obvious free displacement of the nucleus pulposus, and it is difficult to reach the lesion site by conventional puncture, or a large-scale foraminoplasty is required; Those with intervertebral disc herniation and peripheral calcification, and it is difficult to treat the calcified shell through the lateral approach ; Ipsilateral recurrence after transforaminal approach. Of course, the size of the lamina space should be known through the X-ray of lumbar spine before surgery. For those patients with too narrow lamina space, the surgical method should be carefully selected.

Unlike the S1 nerve roots, most of which originate above the level of the L5/S1 intervertebral space, about 70% of the L5 nerve roots originate below the level of the L4/5 intervertebral discs ¹³. The nuclear tissue is located at the proximal end or the outer upper part of the L5 nerve root, so the excision of the nucleus pulposus along the shoulder of the nerve root is more reasonable and safe. The initial positioning point selected during the operation should be closer to the lower edge of the L4 lamina and the transition of the inferior articular process (Fig. 3), so that after biting the ligamentum flavum, the lower part of the field of view is facing the plane of the intervertebral space, and after expanding the operative field to the outside, it is the L5 nerve root placed on the shoulder, which is convenient for subsequent operations. The angle between the L5 nerve root and the dural sac is larger than that of the S1 nerve root, and its axillary space is larger, which means that part of the bone needs to be removed to reach the upper shoulder space, and the nerve exposed in the surgical field after the ligamentum flavum is cleaned is often not the L5 nerve root, but the dural sac. At this time, the ligamentum flavum and bone should be gradually removed from the lateral side, the dural sac and the outer edge of the nerve root should be distinguished, and then a section of the nerve root should be properly released and freed. The length of the L5 nerve root makes it have a certain degree of mobility. At this time, the cannula is slowly rotated to expose the nucleus pulposus and removed, otherwise the dural sac and nerve root may be easily damaged.

In conclusion, as long as the cases are selected properly and properly managed during the operation, PEID is a safe and effective treatment for L4/5 disk herniation. The approach is simple and in line with the habits of spinal surgeons. It has a short learning curve, less radiation, can be used in many types of LDH treatment, is more suitable for doctors in the field of intervertebral foramen endoscopy, and is more suitable for grass-roots promotion and popularization. However, as only a few cases were included in this study, and the observation time was relatively short, future long-term effect studies are needed for further follow-up verification.

Authors' contributions YMY designed the study. BBZ write the first draft. YMY and BBZ all participated in final writing and editing of the manuscript.

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Conflict of Interest The authors declared that they have no conflict of interest.

DATA AVAILABILITY STATEMENT

Data are available upon reasonable request to the corresponding author for purposes of results reproducibility.

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No competing interests reported.

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The effective analysis of percutaneous endoscopic interlaminar discectomy in the treatment of L4/5 intervertebral disc herniation

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