INTRODUCTION
Lumbar disc herniation (LDH) leads to compression of spinal nerve roots due to protruded disc material. Spontaneous reduction in size or complete resolution of herniated disc has been documented [1,2]. Surgical intervention becomes necessary in chronic symptomatic cases or cases with progressive or significant neurological deficits [3,4]. The conventional surgical approach for LDH is open lumbar microdiscectomy with partial laminotomy [5]. Minimally invasive spine surgery (MISS) is an advanced technique, offering benefits such as preserved bone and muscular integrity, shorter hospital stays, and smaller incisions. The earliest MISS technique to be employed was microendoscopic discectomy (MED) [6]. Percutaneous endoscopic discectomy and the unilateral biportal endoscopic (UBE) technique are the latest additions in the armamentarium of MISS spine surgeons. There are very few studies comparing the outcomes of the patient treated with MED vs. UBE [7]. This study compares the clinical outcomes of patients operated by UBE vs MED. Additionally, we explore the potential advantages of endoscopic visualization over conventional method, contributing to a deeper understanding of these evolving LDH treatment modalities.
MATERIALS AND METHODS
This study is a retrospective analysis of prospectively gathered data of clinical outcomes of patients undergoing surgery for LDH using UBE and tubular MED techniques at a tertiary hospital operated by a single surgeon. Data of total of 65 patients who underwent LDH surgery between July 2022 to October 2022 was collected in the present study. Among them, 33 patients were treated with UBE, while 32 patients received treatment with tubular MED. The inclusion criteria were LDH with pain radiating to one leg with or without axial backpain, single-level disease, symptom persistence for more than 6 weeks, failure of nonoperative treatment, and magnetic resonance images correlating with the symptoms.
The patients with motion instability exceeding > 3-mm translation or >5° angulation, revision surgery, spondylolisthesis greater than Meyerding grade II, cauda equina syndrome, comorbid tumorous or infectious conditions and traumatic disc herniation were excluded from the study. Written informed consent was obtained from all patients. We have received Institutional Review Board (IRB) approval for the study. Data collection spanned from the preoperative period until 6 months postoperative, with assessments of pain intensity, patient satisfaction, and quality of life utilizing the visual analogue scale (VAS), modified MacNab score, and Oswestry Disability Index (ODI), respectively, at 1-week, 3-month, and 6-month follow-up intervals. Clinical outcomes were evaluated using VAS scores for back and leg pain (rated on a scale of 0–10) and ODI scores (scaled from 0 to 100%). Patient satisfaction was assessed using modified MacNab criteria, which was categorized as excellent, good, fair, or poor. Perioperative data including operation time, hospital stay and complications were recorded. Time to return to work was also documented.
1. Surgical Technique
1) Unilateral biportal endoscopy
UBE is a surgical decompression procedure done with traditional arthroscopic equipment via 2 endoscopic portals.
Here is a step-by-step description of the surgical method for lumbar unilateral bilateral endoscopic discectomy:
(1) Patient positioning: The patient was placed in a prone position on a C-arm fluoro-radiolucent table under general anaesthesia.
(2) Skin marking and incision: The affected level of the lumbar spine was marked with the help of IITV (Image Intensifying Television) shoot in both the anterior-posterior (AP) and lateral views. The lateral shoot could help in the final confirmation and in cases of lumbarisation or sacralisation. An instrumented portal was generally made on centre of lower pedicle at medial pedicular line of the disc level first, and then the endoscopic portal was made 2–3 cm apart from the instrumented portal depending upon the side of the patients. Transverse skin incisions were made (Figure 1).
(3) Portal creation: Specialized dilators were used to gently separate and dilate the muscles and tissues around the spine, creating a pathway for the instruments and scope to reach the target area.
(4) Endoscope insertion: The endoscope was carefully inserted through the endoscopic portal incision.
(5) Working space preparation: Working space was created with a combination of dilators and with a radiofrequency probe. Probe is also used for haemostasis.
(6) Laminotomy and flavectomy: Laminotomy was done with the help of a arthroscopic burr or high-speed neuro burr. The laminotomy was done until the upper free margin of the ligamentum flavum was exposed. Similarly, on the lateral side, a high-speed drill was used until the lateral free margin of the ligamentum flavum was exposed. The flavum was removed using a Kerrison punch after careful dissection to release adhesion.
(7) Nerve decompression: After locating the herniated disc material, the ruptured disc fragment was removed. Additionally, discectomy was performed using pituitary forceps, ensuring root protection with a root retractor.
(8) Closure: Once the disc material had been successfully removed, the endoscope was removed, and the incision was closed with Ethilon sutures.
2) Microendoscopic discectomy
MED or tubular discectomy involves the use of a tubular retractor to create a small pathway to access and remove the herniated disc material.
Here are the steps for tubular discectomy:
(1) Patient positioning: The patient was positioned prone on the operating table under general anaesthesia.
(2) Incision: A small incision, usually around 2–2.5 cm in size, was made 1.5 cm lateral to midline on the affected side of the lower back, at the level of the herniated disc. A fasciotomy of the same length was performed.
(3) Dilator: On AP view we docked the initial dilator on the inferior portion of the superior lamina. Once the dilator was at the appropriate site, sequential dilation was performed followed by placement of the 22-mm tubular system. The tubular system was then secured to the flexible table retractor arm.
(4) Visualization: Any remaining overlying muscle and soft tissue was removed with the bipolar electro cautery to adequately visualize the underlying structure.
(5) Laminotomy and flavectomy: The inferior portion of the superior lamina, interlaminar space, and the facet joint were identified. High-speed burr was used to remove the inferior portion of the superior lamina. Laminotomy was extended until the insertion of the ligamentum flavum on both the lateral and cranial side.
The ligamentum flavum was detached and removed with a Kerrison punch and dural sac was exposed (Figure 2).
(6) Nerve retraction and removal of disc material: Specialized surgical instruments, such as pituitary forceps, were inserted through the tubular retractor to remove the protruding or herniated disc material.
(7) Confirmation of decompression was done by the retractability, mobility and visibility of the nerve root.
(8) Closure: Closure was done layer wise with the Vicryl and Ethilon.
2. Statistical Analysis
Statistical analysis was performed using the MS excel. The groups were compared using the unpaired t-test. A p-value of <0.05 was considered statistical significant (Table 1).
3. Age and Sex
The current study included a total of 30 patients in each group excluding 5 patients lost to follow-up. The average age of the MED group was 42.83 years, while the average age of the UBE group was slightly lower at 41.87 years. The table below illustrates the age-wise distribution of male and female patients in our research. Specifically, the MED group consisted of 17 males and 13 females, while the UBE group comprised 12 males and 18 females. The observation revealed that the highest number of patients undergoing discectomy fell within the age group of 30–50 years (Table 2).
4. Neurological Involvement
Among the cases, a total of 23 patients were found to have radicular pain without any neurological deficit, while 37 patients had both radicular pain and neurological deficit. Among the patients with neurological deficit, 19 patients belonged to the MED group, and 18 patients belonged to the UBE group (Table 3).
5. Disc Herniation Type
Most common type was the paracentral followed by foraminal and central type. In the UBE half of the patients were of paracentral disc herniation (Table 4).
RESULTS
1. Improvement in VAS Score
The average VAS score for radicular pain showed a significant improvement in the immediate postoperative period for the UBE group. However, after 6 months, the average VAS score had no significant difference in both groups (Table 5).
2. ODI Improvement
When comparing the preoperative ODI to the postoperative ODI, both the MED and UBE groups exhibited significant improvement. In the MED group, the preoperative ODI of 48.33% decreased to 20.93% during the 6-month follow-up period. On the other hand, the UBE group saw a decrease in the preoperative ODI from 50.33% to 20.53% during the same period (Table 6).
3. UBE Versus MED Patients Satisfaction Using Modified MacNab Criteria
At the 6-month mark, patient satisfaction was assessed using the Modified MacNab Criteria. The analysis showed that 96% of patients in the UBE group as well as MED group achieved excellent to good results. Only 1 patient from the UBE group and one patient from the MED group expressed poor satisfaction, which was attributed to complication and required second surgery after the primary operation (Table 7).
4. Perioperative Data
1) Hospital stay
In both groups, there were no significant changes in the duration of hospital stay. In the case of noncomplicated patients, both groups exhibited an average hospitalization period of 2 days.
2) Operative length
There was a significant difference in operative time between the 2 groups. The UBE group had a longer average surgical time, noted at 88 minutes (range, 64–150 minutes), compared to the MED group, which had an average time of 53 minutes (range, 34–98 minutes).
3) Complications
In the UBE group, there was a solitary case of cerebrospinal fluid leakage from the wound. Immediate surgical repair was performed on the first day after the operation to resolve the issue. Conversely, in the MED group, one adverse event and 2 complications were recorded. The adverse event defined as excessive intraoperative bleeding, leading to the prolonged surgical time of 98 minutes. Amongst the complications, 1 patient was diagnosed with dural tear intraoperative which was repaired at the same time. The other patient required reoperation after 25 days due to a recurrent disc herniation at the same level, which was subsequently addressed with a MED.
4) Return to work
There were no significant difference in the time taken to return to activities of daily living which was 13 ays for UBE and 14 days for MED (p>0.05) (Table 8).
DISCUSSION
UBE offers few advantages over conventional MED. The field of vision is nearer to the target tissue with better maneuverability of the endoscope and instruments, continuous irrigation helping to clean the debris and better illumination. Studies to compare these methods have been almost exclusively reported from the South Korean population. Hence the need for study in Indian population was needed to account for racial and demographic disease patterns.
In 1977, Caspar [8] and Yasargil [9] reported the application of microsurgical techniques to lumbar disc surgery, thus introducing the concept of microdiscectomy. By minimizing incision size and sparing paraspinal structures using a smaller, more targeted surgical exposure than traditional open discectomy, microdiscectomy served the rationale of lowering surgical approach-related morbidity, thus attempting to improve patient outcomes while retaining surgical efficacy. These principles remain the goals of all MISS. In an attempt to further these principles, MED was developed [10]. This technique made use of a small-diameter tubular retractor (14 mm) that was placed over sequential dilators that created a surgical pathway to the lumbar spine in between fascicles of the lumbar paraspinous muscles, avoiding the traditional detachment of the multifidus muscles from the spine that is common to open discectomy and microdiscectomy.
In 1983, Kambin and Gellman [11], an American-Iranian orthopedic surgeon, were among the first to investigate the application of endoscopy for lumbar discectomy. Their pioneering study, “Percutaneous lateral discectomy of the lumbar spine: a preliminary report,” established an early foundation for minimally invasive lumbar discectomy techniques.
In 1989, Schreiber et al. [12] advanced the field by employing bilateral dual-channel endoscopy for lumbar discectomy, which enhanced the procedure's efficacy and precision. Subsequently, in 1996, De Antoni et al. [13] from Argentina innovated by utilizing 2 portal endoscopic surgeries through a unilateral approach for translaminar lumbar discectomy, further minimizing surgical invasiveness.
In 2001, Dr. Abdul Gaffer from Bahrain presented his work on UBE technology at the American Academy of Orthopedic Surgeons Annual Meeting, which significantly influenced Korean surgeons. Dr. Eum from South Korea learned UBE techniques under Dr. Gaffer and subsequently introduced the method to South Korea, training several colleagues in the technology [14].
Further advancements were made by Dr. Soliman from Egypt, who in 2013 and 2015, refined UBE technology and published significant studies on lumbar discectomy and lumbar spinal stenosis, respectively [15,16]. Research conducted by De Antoni et al. [13], Soliman [15,16], Eum et al. [14], Park et al. [17], Ahn et al. [18], Kim and Choi [19], and Choi et al. [20] throughout the 2010s has collectively contributed to the current advancements in UBE technology.
In comparison to the other studies [7,21,22] (Table 9), our cohort of patients were considerably younger with a mean age group of 41.8–42.8 years. This closely resembled the cohort age of the study by Choi et al. [ 22]. The other 2 studies had patients with an average between 55–57.6 years and 63–66 years.
In the present study 29 out of 30 patients in each group underwent surgery at the L4–5 or L5–S1 levels. In the other 2 studies [7,22] this proportion ranges from 2nd/3rd to 4th/5th to 90%.
The time taken for MED versus UBE varies widely among the 3 studies done previously and probably reflects the experience of surgeon with the particular technique of surgery. The mean operation time for MED at 53 minutes is similar to that of study 2 [21] and for UBE is similar to that of study 1 [7] and 3 [22] but higher than study 2.
Pain relief was determined by the improvement in the VAS score for back and leg [23]. In the present study, VAS score improves better in UBE group as compare to MED group in early postoperative days. However, by the final follow-up, both groups exhibited comparable improvements in VAS scores. These findings concur with those of the previous studies. The UBE method has been associated with less muscle damage, as indicated by lower postoperative levels of creatine phosphokinase and C-reactive protein [22]. This could be attributed to reduced surgical trauma to the posterior musculocutaneous structures, potentially leading to decreased back pain in the early postoperative phase.
The assessment of surgical safety is significantly influenced by complications. In the present study higher complications were noted in the MED group as compared to UBE group which was in line with the previous comparative study. This may be related to limited depth perception, small visual field and limitation imposed by the fixed tubular system on instrument maneuverability [23-27]. UBE on the other hand takes vision near the target tissue and gives better instrumentation access.
Postoperative assessments were conducted at designated intervals to monitor patient recovery and surgical outcomes. In study 1, the MED group had a mean follow-up duration of 20 months, whereas the UBE group had a shorter mean follow-up of 9 months. Study 2 reported a mean follow-up time of 12.5 months, although the specific groups were not delineated. In the current study, both the MED and UBE cohorts were followed for a mean duration of 6 months postoperatively. This period was deemed sufficient to evaluate the average success rate of the surgical interventions [28]. An extended follow-up is not routinely required, provided that patients do not present with new symptoms or complaints that would warrant further evaluation.
To summarise our cohort of patients were younger, had more involvement of lower levels and had lesser complications with UBE as compared to literature cohorts.
This study is subject to certain limitations. Firstly, it is a retrospective analysis. Secondly, it lacks randomization. Thirdly, the sample size is relatively small. A well-designed randomized study with a larger sample size and with double blinded study is needed for more accurate outcomes (Table 9).
CONCLUSION
The present study demonstrates that the outcomes of UBE discectomy, including VAS back, VAS leg, ODI, and patient satisfaction by MacNab Criteria, are comparable to those of MED. While the UBE technique offers advantages over MED in terms of maneuverability, vision, and intraoperative bleeding, it also leads to lower complications. These findings highlight the potential of UBE discectomy as a promising alternative to MED for the treatment of disc-related pathologies. However, UBE has a steep learning curve associated with the skill of triangulation and use of arthroscopic techniques and instruments.
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