Comparison of clinical outcomes between biportal and uniportal full-endoscopy techniques in lumbar spinal stenosis with bilateral symptoms

Abstract

BACKGROUND

Uniportal full-endoscopy (UFE) technique has been continuously developed and applied for treating lumbar spinal stenosis. However, achieving effective decompression outcome of using the UFE technique remains technically demanding and uncertain. Previously, we have proposed the biportal full-endoscopy (BFE) technique to integrate the respective advantages of both UFE and unilateral biportal endoscopy technique. There is limited published data on the comparison of clinical outcomes between biportal and UFE techniques in lumbar spinal stenosis with bilateral symptoms.

AIM

To contrast the clinical outcomes between biportal and UFE techniques for treating lumbar spinal stenosis with bilateral symptoms.

METHODS

This study retrospectively examined 100 patients diagnosed with lumbar spinal stenosis and bilateral symptoms. Among them, 52 cases were part of group A (BFE technique group), and 48 cases belonged to group B (UFE technique group). The visual analogue scale (VAS), Oswestry Disability Index (ODI), and modified Macnab criteria were used to evaluate the clinical outcomes.

RESULTS

Group A had significantly shorter operation time than group B. Both groups experienced substantial relief in lower back and lower extremity pain on the severe side at postoperative 3 days, 3 months, and 12 months. Group A had notably lower VAS scores for mild side lower extremity pain at postoperative 3 months and 12 months compared to group B. Group A's ODI scores were significantly lower at postoperative 3 months and 12 months, whereas group B's scores did not significantly differ from preoperative values. Group A's ODI scores were significantly lower than group B's at postoperative 3 months and 12 months. Group A had a significantly higher excellent and good response rate (94.23%) compared to group B (81.25%) at postoperative 12 months based on the modified Macnab scale outcomes.

CONCLUSION

The BFE technique offers multiple benefits, including reduced trauma and quicker recovery as a minimally invasive surgery, and enhanced decompression efficiency over the UFE technique when treating lumbar spinal stenosis with bilateral symptoms.

Key Words: Biportal full-endoscopy technique; Uniportal full-endoscopy technique; Lumbar spinal stenosis; Bilateral symptoms; Clinical outcomes

Core Tip: The clinical efficacy of the uniportal full-endoscopy (UFE) technique in decompressing lumbar spinal stenosis is technically difficult and uncertain. Therefore, to overcome these limitations, we previously proposed the biportal full-endoscopy technique, which combines the advantages of both UFE and unilateral biportal endoscopy. The following is a retrospective comparison of clinical outcomes of biportal and UFE methods in the treatment of lumbar spinal stenosis with bilateral symptoms. According to the results, the biportal method has some benefits over the uniportal method such as less trauma during surgery, faster recovery time, and improved decompression efficiency of the affected regions.

INTRODUCTION

Lumbar spinal stenosis is on the rise due to the aging population, manifesting as neurogenic claudication in one or both lower limbs[1,2]. The primary factors contributing to spinal canal stenosis include ligamentum flavum hypertrophy, calcification, articular process hyperplasia, and disc herniation[3,4]. Traditional posterior laminectomy and fusion surgery has emerged as a viable approach for managing lumbar spinal stenosis[5]. Nevertheless, several issues have been highlighted in current lumbar posterior laminectomy and fusion surgery, including prolonged operation time, heightened surgical risks, and excessive workload[5]. Recent research indicates that a unilateral approach, specifically minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF), can achieve bilateral lateral recess decompression and positive clinical outcomes by restoring intervertebral space height and expanding the contralateral foramen area using interbody fusion cages[6,7]. Although unilateral MIS-TLIF effectively addresses contralateral lateral recess stenosis symptoms by enlarging the corresponding area, it necessitates resecting the unilateral articular process, potentially destabilizing the spine and requiring supplementary pedicle screw insertion, thereby increasing surgical risks and costs.

Uniportal full-endoscopy (UFE) technique has been continuously developed and applied to remove the protruding nucleus pulposus and decompress nerve roots while ensuring spine stability[8]. However, the decompression outcome of bilateral lateral recess using the UFE technique remains technically demanding and uncertain[9]. In a retrospective study, Komp et al[9] treated 72 patients with bilateral lateral recess stenosis using the UFE technique to perform unilateral laminectomy for bilateral decompression (ULBD). They found that 70.8% of patients experienced significant symptom relief on the ipsilateral (surgical) side, while improvement on the contralateral side was less pronounced during the two-year follow-up[10]. Additionally, the UFE technique also exhibits notable limitations, such as a steep learning curve and restricted indications. In recent years, the unilateral biportal endoscopy (UBE) technique has gained wide acceptance in treating lumbar spinal stenosis[11-13]. Plasma radiofrequency is utilized to treat soft tissue under UBE technique, resulting in improved treatment efficiency. Additionally, standard surgical instruments can be employed to enhance decompression efficiency[14,15]. However, UBE technique employs an arthroscope as a monitoring endoscope. The observation channel is separated from the operating channel, preventing instrument access to or from the observation channel. Consequently, the observation field of view and the operating window are not coaxial, increasing the difficulty of hand-eye coordination[16]. Moreover, because UBE technique cannot utilize endoscopic instruments and radiofrequency to control intraspinal bleeding, when such bleeding occurs, the high plasma radiofrequency energy adds challenge to precise point-to-point operations, thereby prolonging bleeding time and increasing the risk of nerve damage to some extent.

Drawing on extensive clinical experience with both surgical techniques mentioned, the author's research team has proposed the biportal full-endoscopy (BFE) technique to integrate their respective advantages. The team aims to further enhance operational efficiency and safety by using both conventional and endoscopic instruments. Therefore, we conducted this retrospective clinical study to compare and analyze the clinical outcomes of the easily mastered BFE technique and the UFE technique in treating lumbar spinal stenosis with bilateral symptoms.

MATERIALS AND METHODS

Study population and data collection

Patients who underwent the BFE technique and UFE technique for lumbar spinal stenosis with bilateral symptoms at Shanghai General Hospital between January 2022 and March 2023 were retrospectively analyzed. Magnetic resonance imaging (MRI) was performed prior to surgery in all cases to confirm lumbar spinal stenosis. The inclusion criteria included: (1) Patients experiencing lower back pain along with bilateral intermittent claudication symptoms; (2) Individuals who had undergone unsuccessful conservative treatment for three months, including physiotherapy, manual therapy, and non-morphine therapy; (3) Those showing single segmental lumbar spinal stenosis in imaging; and (4) Individuals with no prior history of spinal surgery. Exclusion criteria comprised: (1) Patients with lumbar instability; (2) Patients with lumbar spondylolisthesis; (3) Individuals with severe coagulation disorders or those taking oral anticoagulants; and (4) Subjects with contraindications for MRI, such as a history of cardiovascular or cerebrovascular stent implantation, cardiac pacemaker, or biological stimulator. This study was approved by The Ethics Committee of Shanghai General Hospital (2022SQ011), and the study was conducted in accordance with the Declaration of Helsinki. All participants provided informed consent.

Instruments and equipment

Spine endoscopy and Elliquence radiofrequency systems were purchased from SPINEDOS (Munich, Germany). The COBLATION radiofrequency system was sourced from Smith+Nephew (London, United Kingdom), and the orthopedic C-arm fluoroscope was bought from Siemens (Munich, Germany).

Sample size determination

In this study, we selected the Oswestry Disability Index (ODI) as the primary outcome, which is consistent with its widespread use in previous spinal surgery research. Many prior studies on low back pain have calculated the minimum clinically important difference for the ODI[17-20]. Therefore, we used the ODI as the primary outcome measure to estimate the sample size in this study. We set the 12-month postoperative ODI as the primary endpoint. Based on prior research and clinical experience, we expected a mean 12-month postoperative ODI of 30% in group A (SD = 15%) and 40% in group B (SD = 15%). Using a two-sided test with a significance level of α = 0.05 and power of 0.8, and accounting for a 15% loss to follow-up, the required sample size was calculated to be 43 patients per group using NCSS PASS software. In practice, we retrospectively included 52 cases in group A and 48 cases in group B.

Surgical method

BFE group (group A): The patient lay prone on the all-carbon Allen spinal operation bed, and the lesion segment to be treated was determined by C-arm fluoroscopy. Two 7 mm-length of skin incisions were performed at the upper and lower margins of the interlaminar space. The two incisions are about 1 cm apart from the midline and the upper and lower incisions are about 1.5 cm apart. The serial dilators and strippers were inserted to separate the soft tissue of the lamina, and adjust the position and angle of bilateral channels to complete the "meeting". A 30-degree spinal endoscope was inserted into the observation channel, both COBLATION and Elliquence radiofrequency were used alternately in the working channel to clean the soft tissue that attached on the lamina. Subsequently, laminotomy was carried out employing a 3.5-mm endoscopic high-speed grinding drill, endoscopic punches, and the regular trephine and Kerrison punch. The lateral boundary of decompression extended to the medial side of the ipsilateral superior articular process, while the proximal and distal boundaries were marked by the endpoints of ligamentum flavum. After the ligamentum flavum was resected using a basket punch, endoscopic punch, and Kerrison punch, the ipsilateral nerve root was exposed. Subsequently, the working channel was adjusted across the base of the spinous process to remove the medial side of the contralateral superior articular process and ligamentum flavum, thus revealing the contralateral nerve root. Following sufficient nerve decompression, a drainage tube was inserted. The BFE technique has the following four operating modes: (1) Full UBE mode (dual channels); (2) Full uniportal endoscopic mode (single channel); (3) Observation channel and working channel interchanged mode; and (4) Dual working channel mode, namely, the spinal endoscopic channel can be used as both an observation endoscopy and an operation channel to achieve simultaneous dual-channel operation (Figure 1).

Figure 1 Illustrative cases utilizing the spine biportal full-endoscopy technique for managing lumbar spinal stenosis with bilateral symptoms. A: Full uniportal endoscopic mode (single channel); B: Full unilateral biportal endoscopy mode (dual channels); C and D: Observation channel and working channel interchanged mode; E: Dual working channel mode; F: Hemostasis using spinal radiofrequency in the uniportal mode; G: Articular process resection executed with a trephine within the uniportal framework; H: Decompression performed utilizing an endoscopy punch in the uniportal mode; I: Herniated nucleus pulposus probed using radiofrequency within the uniportal mode; J: Radiofrequency-induced soft tissue ablation conducted in the biportal mode; K: Osteotome-driven decompression carried out in the biportal configuration; L: Decompression accomplished through a conventional punch in the biportal mode; M: Nerve root loosening subsequent to decompression.

UFE group (group B): The patient was positioned prone on the Allen spinal operation bed, and the location of the lesion segment was determined using C-arm fluoroscopy. An incision measuring 10 mm in length was carefully made 1.5 cm from the midline. Serial dilators and strippers were then inserted to separate the soft tissue of the lamina, creating a working channel. A 30-degree spinal endoscope was inserted, and Elliquence radiofrequency was used through the working channel to remove soft tissue, exposing the lamina and part of the facet joint. Subsequently, laminotomy was performed using a 3.5-mm endoscopic high-speed grinding drill and endoscopic punches (Figure 2).

Figure 2 Illustrative instances of bilateral symptomatic lumbar spinal stenosis managed using the uniportal full-endoscopy technique. A: Uniportal full-endoscopy technique (single channel); B: Articular process resection executed with a trephine in uniportal endoscopy; C: Radiofrequency hemostasis under uniportal endoscopy; D: Articular process resection executed with a trephine in uniportal endoscopy; E: Laminectomy by endoscopic punch; F: Osteophyte decompression by endoscopic high-speed grinding drill; G: Resection of ligamentum flavum by endoscopic punch; H: Exploring the proximal endpoint of the ligamentum flavum using a nerve hook; I: Exploring the distal endpoint of the ligamentum flavum using a nerve hook; J: Exploring the lateral endpoint of the ligamentum flavum using a nerve hook; K: Hemostasis on nerve tissue using spinal radiofrequency; L: Neural relaxation post-decompression.

Post-operative treatment

The day after surgery, patients were directed to perform rehabilitation exercises, and were primarily recommended to rest in bed for four weeks post-surgery. They were also advised to utilize a brace when not in bed. Concurrently, patients were counseled to refrain from engaging in vigorous activities, bending, and bearing weight in the immediate term.

Major observation indices

(1) Characteristics of patients; (2) Operation time, hospital stay; (3) Visual analogue scale (VAS) scores for lumbar and lower extremity radiation pain before treatment and at the 3^rd day, 3 months and 12 months after surgery; (4) ODI before surgery, and at the 3^rd day, 3 months and 12 months after surgery; (5) Excellent and good rate of modified Macnab in both groups at 12 months after surgery; and (6) Complications.

Missing data and missing data management

As this retrospective study included a relatively small number of patients, we made sure to have complete follow-up for all participants to maintain the accuracy of the analysis. As a result, there were no missing data in this study.

Statistical analysis

Statistical Package for the Social Sciences 20.0 software was utilized for statistical analysis. The measurement data were expressed as mean ± SD. The t test was employed to compare all parameters between groups. The χ² test was used to compare rates between groups. P < 0.05 was considered statistically significant.

RESULTS

Characteristics of patients

All patients successfully completed the surgery and follow-up with an average time of 16.00 months ± 1.50 months. According to the above criteria, a total of 100 patients with bilateral symptoms of lumbar spinal stenosis were included in this study, consisting of 27 men and 25 women belonging to group A, and 24 men and 24 women in group B. Group A was found to have more than 92% of stenosis at L4-5 and L5-S1 segments, while 4 cases involved L3-4 segment. The same was true for group B as its distribution of stenosis segments was similar to that of group A. The average body mass index (BMI) in both groups was more than 25. There was no significant difference in age, gender, BMI, underlying disease, smoking status, marital status surgical segment and Schizas grade between the two groups (P > 0.05) (Table 1).

Table 1 Characteristics of patients.

		Group A		Group B
Gender		Male	Female	Male	Female
		27	25	24	24
Age (years)		53.50 ± 15.20		52.80 ± 13.65
Body mass index (kg/m²)		25.6 ± 6.26		27.53 ± 5.89
Hypertension		Yes	No	Yes	No
		24	28	22	26
Diabetes		Yes	No	Yes	No
		13	39	12	36
Smoking status		Yes	No	Yes	No
		21	31	20	28
Marital status		Married	Unmarried	Married	Unmarried
		50	2	47	1
Surgical segment	L3-4	4		3
	L4-5	24		22
	L5-S1	24		23
Schizas grade	A	0		0
	B	2		1
	C	31		30
	D	19		17

Operation time and hospital stay time

The operation time in group A (90.80 minutes ± 7.25 minutes) was significantly shorter than that in group B (110.30 minutes ± 6.25 minutes) (P < 0.05). Although the average hospital stay for group A (4.25 days ± 0.65 days) was slightly longer than that for group B (3.98 days ± 1.05 days), statistical analysis revealed no significant difference between the two groups (P > 0.05).

VAS scores

The lower back pain and lower extremity pain on the severe side were notably alleviated at postoperative 3 days, 3 months, and 12 months in both groups. In group A, the VAS score for lower extremity pain on the mild side exhibited a significant decrease at postoperative 3 days, 3 months, and 12 months compared to the preoperative level. In group B, the VAS score for lower extremity pain on the mild side saw a significant decrease only at postoperative 3 days. However, in group B, the VAS scores for lower extremity pain on the mild side at postoperative 3 months and 12 months did not display a significant reduction compared to the preoperative scores. Comparing the two groups, no substantial difference was observed in the VAS scores for postoperative lower back pain and lower extremity pain on the severe side. Notably, the VAS scores for lower extremity pain on the mild side were significantly lower in group A than in group B at postoperative 3 months and 12 months (Figure 3).

Figure 3 Clinical outcomes in both groups. A: Comparison of lower back pain scores between the two groups; B: Comparison of lower extremity pain (severe side) between the two groups; C: Comparison of lower extremity pain (mild side) between the two groups; D: Comparison of quality of life Oswestry Disability Index scores between the two groups. ^aP < 0.05: Means there was significant difference before and after operation (P < 0.05); ^bP < 0.05: Means there was significant difference between groups (P < 0.05). ODI: Oswestry Disability Index; VAS: Visual analogue scale.

ODI scores

The ODI scores for both groups were notably lower at postoperative day 3 compared to preoperative levels. Additionally, for group A, the ODI scores at postoperative 3 months and 12 months were significantly reduced compared to preoperative scores. However, for group B, there was no significant difference in ODI scores at postoperative 3 months and 12 months compared to preoperative scores (P > 0.05). The comparison between the two groups revealed that the ODI scores of group A were significantly less than those of group B at postoperative 3 months and 12 months (Figure 3).

Modified Macnab excellent and good rate

The results of modified Macnab score showed that the excellent and good rate of group A (94.23%) was significantly higher than that of group B (81.25%) at postoperative 12 months.

Complications

In group A, complications included incidental durotomy (n = 1) and epidural hematoma (n = 2), while in group B, there were incidental durotomy (n = 2) and epidural hematoma (n = 1). All cases of complications were effectively managed with conservative treatment.

DISCUSSION

In this study, we propose a novel spinal endoscopy approach, namely BFE technique, which combines the benefits of the UFE technique and the UBE technique for treating lumbar spinal stenosis. We aim to compare the clinical outcomes of this approach with those of UFE. The spinal endoscopy was not only used as the monitoring endoscope but also as the operation channel in BFE technique, and a conventional surgical instrument operation channel was also constructed to achieve uniportal endoscopic operation and hands-free operation[21]. Compared with UFE, BFE approach has two working channels, and the surgery can be performed in the two channels to avoid interference between instruments. Additionally, both the observation channel and the working channel can be moved and tilted freely, thereby greatly increasing surgical flexibility is greatly increased to explore all directions of the spinal canal and achieve comprehensive decompression of the spinal canal. Additionally, all kinds of open and endoscopic instruments can be used in the operation by BFE approach to improve the efficiency of intraoperative procedures like laminectomy and separation of ligamentum flavum. In comparison to UBE technique, BFE approach employs spinal endoscopy as a monitoring channel to enable precise coaxial operation. This approach enhances accuracy and minimizes tissue damage resulting from repeated instrument insertions and withdrawals. Furthermore, BFE approach surpasses the UBE technique in achieving intraoperative hemostasis. Unlike the UBE technique, which relies on COBLATION radiofrequency for hemostasis with its broad planar working interface and substantial tissue contact area, the BFE approach ensures accurate hemostasis. This mitigates the risk of nerve injury during hemostasis within the spinal canal.

The BFE approach employs the translaminar approach, allowing for either unilateral laminectomy or ULBD of the spinal canal. Utilizing this technique, ULBD is performed to minimize damage to the posterior complex of muscles, ligaments, and laminae. With this approach, the spinal endoscope is angled to pass the root of the spinous process, reaching the ventral side of the opposite laminae. This enables resection of the contralateral ligamentum flavum to expose the dural sac and the dorsal side of the contralateral nerve root. Consequently, the VAS scores at 3 months and 12 months post-surgery for the mildly symptomatic side in group A exhibited substantial improvement compared to pre-surgery scores.

The UFE technique, compared to the spinal BFE technique, presents limitations in surgical visualization, increased challenge in instrument manipulation under the endoscope, and restricted angles of instrument use. These drawbacks reduce the efficacy of contralateral bony structure removal, making decompression of the contralateral nerve root challenging. Furthermore, the use of a single hemostasis device in the UFE technique results in an extended operating lever arm and more constrained angles for hemostasis, making it more challenging to accomplish sufficient decompression of the contralateral nerve root. As a consequence, at 3 months and 12 months after surgery, patients in the UFE group (group B) with mild symptoms did not significantly improve their VAS scores over preoperative values. Comparing the BFE group to the UFE group, patients in the former had significantly lower VAS scores for mild symptoms and lower ODI scores at 3 months and 12 months after surgery. Therefore, based on the findings of this study, the BFE technique is more effective in decompressing the contralateral nerve root compared to the UFE technique. Hu et al[22] showed that in the UFE group, the extent of facet resection on the ipsilateral side was significantly greater than that on the contralateral side, suggesting limited access and decompression on the opposite side. In contrast, the UBE group achieved a more balanced resection on both sides, enabling symmetrical decompression ranges. These findings indicated that UBE offered more comprehensive contralateral nerve root decompression compared to the UFE approach. However, whether the BFE approach surpasses the UBE approach in contralateral decompression efficacy remained unanswered in this study, warranting further exploration in future studies. In addition, both the BFE and UFE approaches effectively alleviated postoperative symptoms on the severe side compared to preoperative conditions. This is attributed to their successful decompression of the severe side, resulting in significant symptom relief without discernible differences between the two approaches. Notably, the VAS score for the mildly symptomatic side in group B on the 3^rd day post-surgery was also significantly lower than pre-surgery scores. This may be attributed to the continuous flow of water during UFE procedures, reducing the concentration of inflammatory mediators in the spinal canal and thereby mitigating inflammatory stimulation on the contralateral nerve root, leading to relief from nerve pain[23].

Despite the numerous advantages of the BFE approach, such as its effectiveness in nerve decompression, improved surgical efficiency, and reduced risk, the increased soft tissue damage associated with this technique stems from the necessity to resect more soft tissue in order to achieve a broader field of view. Consequently, this study observed a greater extent of soft tissue swelling in the BFE group compared to the UFE group, a finding akin to the results reported by Choi et al[24] in their research on the UBE technique. Choi et al[24] conducted a comparative analysis of lumbar MRI changes and inflammatory markers during the postoperative follow-up of UBE, lateral foraminal approach, and posterior interlaminar approach endoscopy techniques. Their findings revealed that the UBE technique induced more trauma than the lateral foraminal and interlaminar approaches, leading to more conspicuous postoperative MRI soft tissue swelling[24]. To mitigate the risk of intraspinal hematoma after decompression, the routine placement of drainage tubes is recommended in the BFE group. This is because the BFE technique requires a broader extent of laminectomy and ligamentum flavum dissociation, leading to more extensive nerve decompression. While the introduction of drainage tubes prolongs bed rest, this necessitates a slightly longer hospital stay in the BFE group.

Limitations

The limitations of this study are outlined as follows: (1) The study primarily encompassed single-level cases of bilateral lumbar spinal stenosis, omitting cases with multi-level involvement; (2) This research constitutes a clinical retrospective study with a relatively limited case count, lacking extensive large-scale, randomized, multicenter investigations. Moreover, since this is a retrospective study, potential selection bias and performance bias may exist; and (3) The duration of patient follow-up in this study was relatively brief, warranting extended observation over the long term to comprehensively assess clinical effectiveness, including aspects such as the impact on spinal stability following ULBD.

CONCLUSION

While the UFE technique has become popular in treating lumbar disc herniation, its deployment in lumbar spinal stenosis has been relatively limited. This has been primarily attributed to technical difficulties, inefficiency in decompression, and a high learning curve. Based on clinical experience, we introduced BFE technique to counter these shortcomings. By incorporating a secondary working canal, BFE enhances operating efficiency as well as providing more complete decompression. It also provides enhanced intraoperative bleeding control. BFE further preserves tissue integrity and allows for faster recovery as a minimally invasive procedure. Collectively, these benefits imply that BFE would be a safe, effective, and viable alternative to UFE in managing bilateral lumbar spinal stenosis.