Endoscopic Discectomy and Annulus Suture in Recurrent Lumbar Herniation: A Retrospective Analysis

Introduction

Lumbar disc herniation (LDH) is a condition in which damage to a lumbar spine disc leads to leakage of the inner core through a tear in the outer layer of the disc. Often termed a slipped or ruptured disc, LDH symptoms vary from none to severe, including radiating pain, sensory disturbances (tingling or numbness), and motor weakness in the legs and feet [1,2]. The various etiologic factors for LDH include disc degeneration with age and axial overloading on a large biomechanical force on the healthy disc, which means that surgery may not address all issues arising from lumbar disc protrusion [3]. Treatments of LDH range from conservative methods (rest, physical therapy, medication) to more invasive procedures, like injections or surgery, which may involve removing the protruding disc material or vertebral fusion [3]. Advances in spinal endoscopic technology over the past decade have allowed more patients to benefit from percutaneous endoscopic lumbar discectomy (PELD), which is safe, effective, and minimally invasive [4,5]. However, the annular defects remaining after nucleus pulposus removal (NPR) raises the risk of postoperative recurrence [6,7]. The estimated risk of recurrent LDH post-PELD is 5–20% [8–10].

The concern for potential recurrence, persistent pain, and uncertain outcomes exerts significant mental and physical stress on individuals with recurrent LDH, frequently resulting in a preference for secondary surgeries that tend towards fixation fusion [3–7]. In addition, recurrent LDH brings a heavy burden to patients and society, such as healthcare costs, quality of life, or economic burden [3–7]. The primary surgical intervention for lumbar disc protrusion, which utilizes endoscopic NPR with lumbar annulus fibrosus suture (LAFS), termed NPR-LAFS, has been demonstrated in clinical settings to avert re-herniation of the nucleus pulposus and preserve the biomechanical integrity of the affected spinal segment [11]. This approach effectively reduces the risk of further herniation while also addressing symptoms of nerve compression [11]. Unilateral biportal endoscopic discectomy (UBE) is a minimally invasive surgical technique used for the treatment of LDH [12]. UBE involves creating 2 small incisions to form viewing and working channels, allowing surgeons to remove herniated disc material and decompress the affected nerve root [12,13].

However, clinical studies focusing on similar methods for patients with recurrent lumbar disc protrusion are limited. Therefore, this retrospective study from a single center included 21 patients with recurrent LDH and aimed to evaluate outcomes from treatment with UBE and NPR-LAFS.

Material and Methods

ETHICS APPROVAL:

Ethics approval for the study was granted by the hospital Ethics Committee (No. 2021-05). The requirement for written informed consent was waived for this study due to its retrospective nature.

PATIENTS:

The study was conducted from May 2020 to July 2022 at Mianyang Orthopedic Hospital and involved 21 patients (15 males and 6 females; age range, 17–62 years; mean age, 45.14±15.26 years) with recurrent LDH. These patients underwent NPR-LAFS by UBE. The initial surgery was performed at the host hospital for 3 patients and at other institutions for 18 patients. Recurrence was noted in the following segments and types with 4 extrusion types and 17 protrusion-type herniations: L3/4 (n=1); L4/5 (n=9); L5/S1 (n=11). The average time-to-recurrence after the initial surgery was 30.76±23.02 months. All participants underwent a suture procedure using a disposable suture device. The same team of surgeons performed all of the operations and was responsible for data collection and analysis, as detailed in Table 1.

CRITERIA FOR PATIENT SELECTION:

The inclusion criteria were: 1) patients needing surgical treatment for recurrent LDH; 2) clinical symptoms, signs, and imaging results consistent with LDH; 3) soft protrusion (extrusion) without significant calcification or ossification of the annulus fibrosus; and 4) treatment with UBE and annulus fibrosus suture and a relatively intact annulus fibrosus post-NPR. The exclusion criteria were: 1) patients declining further minimally invasive surgery; 2) recurrence in segments with lumbar instability, intervertebral space collapse, or severe disc degeneration; and 3) inability to comply with follow-up evaluations.

SURGICAL METHOD:

Written informed consent was obtained from all patients for the treatment approach. The surgical procedure for the 21 patients in this group, all performed by the same team of physicians, used the left L5/S1 approach. The procedures were as follow. First, after general anesthesia had been administered, the patient was positioned in the prone position with the abdomen suspended on a silicone pad. Using C-arm fluoroscopy in the lateral position, the surgical bed was adjusted so that the intervertebral space of the target segment was as vertical to the floor as possible, stretching the interspinous space and straightening the lumbar back. The surface projection points of the left L5/S1 interspinous space and pedicle had been marked with a positioning board in the anteroposterior view. Second, routine disinfection and draping was performed, and 2 Kirschner wires were placed at the junction of the left spinous process and lamina as markers, making a proximal viewing channel incision of approximately 0.4 cm and a distal working channel incision of 1 cm. The incision was deepened to the fascia, and soft tissue was dilated step-by-step to the bone surface, stripping the dorsal soft tissue of the lamina and ligamentum flavum. Third, radiofrequency ablation under endoscopic guidance was used to reveal the soft tissue down to the ligamentum flavum, exposing the bone surfaces of the lower edge of the L5 lamina and the upper edge of the S1 lamina. The lower part of the left L5 lamina, part of the medial aspect of the inferior articular process, and part of the S1 superior articular process and lamina were removed to enlarge the bony spinal canal, lateral recess, and S1 nerve root canal using a power drill, osteotome, and rongeur. The outer edge of the ligamentum flavum was removed to expose the dura mater and nerve root. Fourth, adhesions were dissected and released, and the S1 nerve root was retracted with hooks to expose the annular fissure (for herniated types, a 0.5-cm longitudinal incision was made with a disc annulotomy tool to facilitate suturing), and degenerated herniated nucleus pulposus tissue was removed with a nucleus forceps. After thorough exposure of the nerve root under the microscope, the nucleus pulposus and annulus fibrosus was shaped with a radiofrequency knife head and the annular fissure had been filled with gelatin sponge. Fifth, a disposable annulus fibrosus suture device was used to repair the annular fissure. For a longitudinal fissure, the first needle of the suture device was inserted into the annulus fibrosus approximately 3 mm from the inner edge of the fissure near the nerve root and the handle wheel of the suture device had been slid back and forth 3 times to push out an I-shaped rod, which was then lightly pulled to test if the I-shaped rod was tight; and the tail of the thread was then threaded through the loop of the second needle of the suture device and the annulus fibrosus was pierced approximately 3 mm from the outer edge of the fissure away from the nerve root, pushing out an I-shaped rod with the inner core guide wire, and again lightly pulling the rod to test if it was tight. The suture was slowly tightened to close and lock the fissure, then 2–3 surgical knots had been tied with the pusher, alternately pulling the threads of the first and second needles with slow and gentle movements to prevent the suture from being cut. The thread was cut after suturing was completed. Sixth, hemostasis was achieved, the decompression area was irrigated with 160 000 units of gentamicin sulfate injection and 5 mg of dexamethasone phosphate sodium injection, a 14# drainage tube was placed, and the incision was closed layer-by-layer (see Figure 1 for microscopic procedures; see Figure 2 for incision marking and suturing schematic). Finally, gradual decompression was generally performed from the beginning and end of the ligamentum flavum to release the scar adhesion when treating recurrent patients with UBE, especially when the initial operation was the interlaminar approach. The position and severity of scar adhesion was clearly observed under a microscope. Our team generally uses a neurostripper hook knife, a small round knife, or a small radiofrequency cutter head for nibbling and peeling. It was not necessary to separate the nerve root if the dural adhesion was severe but only to decompress the nerve root and strip the scar. If the recurrent intervertebral disc was herniated, there were generally no severe adhesions. In the case of a prominent recurrence, partial tension is provided where the posterior longitudinal ligament adheres to the nerve root through a nerve retractor, then separated with a nerve stripper hook, a small round knife, or a small radiofrequency cutter head. In the case of a small dural rupture only drainage and incision are required; no sutures or other treatments are necessary. In the case of a large dural tear, the sutures and tamponade are evaluated after laminectomy and window opening.

POSTOPERATIVE MANAGEMENT:

Upon awakening from anesthesia, motor strength of the responsible nerve roots was assessed; cardiac activity was monitored for 8 h; measures were implemented to prevent infection, reduce swelling, manage pain, and nourish nerves; treatment was initiated to prevent constipation; pneumatic compression therapy was applied to both lower limbs; and ankle pump exercises were performed. On the second postoperative day, the drainage tube was removed, and bed exercises for turning were taught, and straight-leg raising and side-lying position exercises were begun. Beginning on the third postoperative day, a waist protector was worn for 6–8 weeks. Six weeks after surgery, gradual functional training of the lumbar and back muscles was begun, such as glute bridges and ‘bird-dogs.’

EVALUATION CRITERIA:

The surgical time, blood loss, and complications were recorded to assess surgical efficiency, trauma, and safety. Pain levels were documented using the visual analog scale (VAS), and functional disability was assessed using the Oswestry Disability Index (ODI) at various stages to evaluate lumbar and leg pain, as well as lumbar spine functional status. On the third postoperative day, a lumbar spine CT scan was performed, and from the third to sixth months postoperatively MRI and lumbar spine dynamic X-rays were performed to assess disc removal, nerve decompression, and lumbar spine stability. Evaluations using the MacNab criteria 3 months postoperatively were performed to assess treatment effectiveness during the follow-up period.

VAS and ODI scores and the MacNab criteria were carefully explained to the patients by the same experienced physician. Then, the patients completed the VAS, ODI, and MacNab criteria according to instructions by the same physician, who was blinded to this retrospective study. For the VAS, the marked side was turned away from the patient and the patient was asked to mark the corresponding position on the ruler that represented the degree of the pain. The physician rated the patient based on the marked position. The clinical assessment was as follows: 0–2 indicated excellent, 3–5 indicated good, 6–8 indicated acceptable, and >8 indicated poor. The ODI assessment scale contains 10 entries, including pain, independent living ability, walking, sleep, sex, social activities, and travel. Each item is scored 0–5 points. Patient scores reflected the actual situation; the higher the score, the more severe the degree of functional impairment. The MacNab criteria is a scoring system used to assess outcomes after lumbar spine surgery, mainly to evaluate the recovery of patients after lumbar spine surgery. The standard divides postoperative outcomes into 4 grades: excellent indicates the patient has no pain, has limited movement, and is able to participate in normal work and activities; good indicates occasional non-neuropathic pain, major symptoms are relieved, and able to take part in accommodated work; fair indicates some degree of functional improvement but still disabled and/or unemployed; and poor indicates persistent manifestations of nerve root damage were detected, postoperative symptoms recurred, and surgery was necessary.

STATISTICAL METHODS:

The statistical data graphs were created using GraphPad Prism 9 software. Statistical analysis was performed using SPSS 25.0 software. The measurement data, including perioperative parameters (operative time, blood loss, and the follow-up VAS and ODI scores), were subjected to a normality test and conformed to have normal distribution. The data are presented as the mean±standard deviation (SD). The excellent-to-good rate was expressed as a percentage (%). The t test was used for comparisons between 2 groups and the paired-sample t test was used for pre- and post-operative comparisons. A P value <0.05 was considered statistically significant.

Results

PERIOPERATIVE INFORMATION:

In the first procedure, the surgery for 17 patients was performed using a lateral approach, and 4 underwent surgery using an interlaminar approach. Surgical treatment of all 21 patients with recurrent LDH was successful. The operative times ranged from 82 to 146 min, with an average of 106.71±17.9 min. Blood loss was 34–107 ml, with an average of 72.62±21.32 ml. Notably, 3 patients presented with significant ventral adhesions of the nerve roots. During and after surgery, there were no serious complications such as nerve damage, cauda equina syndrome, dural tear with cerebrospinal fluid leakage, or infection. Four patients had mild-to-moderate radicular pain between the 3^rd and 5^th postoperative days, which was attributed to hematomas or inflammatory edema, which resolved after receiving anti-inflammatory and edema-relieving treatment.

FOLLOW-UP RESULTS:

All patients had a lumbar CT scan on the 3rd day postoperatively, which confirmed effective decompression of the spinal canal and intervertebral disc. The patients were discharged 5–7 days postoperatively. Follow-up evaluations ranged from 4 to 17 months, with an average duration of 15.76±5.17 months. During this period, no LDH recurrences occurred. There was significant improvement in postoperative VAS scores for back and leg pain and the ODI score (P<0.05). According to the MacNab criteria, the outcomes were rated as excellent in 16 cases, good in 3, and fair in 2, yielding an excellent-to-good rate of 90.47% (Table 2).

Table 2 and Figure 3 present a comprehensive analysis of patient outcomes measured by the VAS scores for back and leg pain, as well as the ODI score that compared preoperative data and the last follow-up data. Before surgery, the average back pain VAS score was 5.9±1.09, the leg pain VAS score was 6.1±0.77, and the ODI score was 57.08±9.72%. At the last follow-up evaluation, these values significantly decreased to 1.38±0.81 for back pain, 1.29±0.46 for leg pain, and 11.29±1.86% for the ODI score. The t values (16.588 for back pain, 25.25 for leg pain, and 20.954 for the ODI score) and P values (all 0.000) indicate highly significant statistical improvements. This analysis demonstrates the effectiveness of the surgical intervention in reducing pain and disability among patients.

Figure 4 depicts a 51-year-old man with recurrent L5-S1 disc herniation 8 years after surgery. Initial scans in 2015 revealed herniation, followed by successful decompression after PELD. In 2023 recurrence was evident and subsequent revision surgery showed effective decompression. MRI scans 3 months later indicated annulus fibrosus repair with stable positioning shown on dynamic X-rays at L5-S1.

Discussion

LIMITATIONS:

The first limitation of this study was the relatively small number of PELD recurrence cases from a single center. Second, the absence of long-term clinical follow-up data only demonstrated the primary efficacy of the NPR-LAFS under UBE for recurrent LDH. Third, a control group without the use of an annulus fibrosus suture device in the patients with recurrences was not set up, which made it difficult to demonstrate the advantages of the annulus fibrosus suture device in surgical outcomes. Therefore, the long-term therapeutic effect of NPR-LAFS under UBE for recurrent LDH still requires further understanding through extensive clinical sample statistics, collaborative research across multiple hospitals, and long-term follow-up studies.

Conclusions

The findings of the current study indicate no recurrence and complications, substantiated by postoperative improvements in VAS for back and leg pain, and the ODI scores for the recurrent LDH patients under treatment with NPR-LAFS and UBE during a 1-year follow-up. These results suggest that UBE-NPR-LAFS is safe in clinical applications. However, corollary studies with large samples from multiple centers and long-term follow-up are needed.