Unilateral Biportal Endoscopic Discectomy versus Percutaneous Endoscopic Interlaminar Discectomy for Lumbar Disc Herniation

Introduction

Lumbar disc herniation (LDH) is a frequently encountered disease in spinal surgery, characterized by symptoms such as low back pain and sciatica.¹ When conservative treatments have failed to resolve LDH, surgical intervention is often required.² Minimally invasive spinal surgery, such as percutaneous endoscopic lumbar discectomy, has the advantages of minimal trauma and fast postoperative recovery.³ Consequently, Percutaneous Endoscopic Lumbar Discectomy (PELD) has gained widespread recognition among both surgeons and patients, which has increasingly replaced open surgery as the preferred surgical approach for LDH.⁴ Based on the different surgical approaches used, percutaneous endoscopic lumbar discectomy can be classified into two main types: percutaneous transforaminal endoscopic discectomy (PTED) and percutaneous endoscopic interlaminar discectomy (PEID).⁵ However, PEID has the drawbacks of a small surgical field, low surgical efficiency, long learning curve and difficulty in mastering.⁶ Unilateral biportal endoscopic (UBE) discectomy is a combination of open and endoscopic spinal surgery. During the procedure of UBE, one portal is for optical instruments and the saline irrigation system, and the other is for surgical instruments. This dual-port approach provides greater surgical control for decompression and wider visualization compared to traditional single-portal spine endoscopy.⁷

As the latest endoscopic spine surgery, PEID and UBE discectomy have distinct technical characteristics. The present study aims to compare the efficacy and safety of PEID and UBE discectomy for the treatment of single-segment LDH.

Methods

Study Design

A retrospective review was conducted on the medical records of 115 patients treated at the Department of Orthopedics, Shaanxi Provincial People’s Hospital between February 2019 and April 2022. The study received approval from the clinical research ethics committee of Shaanxi Provincial People’s Hospital (No. 2021–018) and adhered to the Good Clinical Practice guidelines and the principles outlined in the Helsinki Declaration. The study included 60 cases that received PEID (Group 1) and 55 cases that received UBE (Group 2).

Patients

LDH patients (aged 35 ~ 90 years old, BMI 16 ~ 38 and ASA I~III) undergoing PEID or UBE were screened in this study. The inclusion criteria were: (1) presence of single-level herniated disc at the L4/L5 or L5/S1 levels, (2) ineffective response to conservative treatment for 3 months, (3) patients experiencing low back pain and/or sciatica, and (4) confirmation of signs and symptoms through MRI and CT imaging. Exclusion criteria encompassed: (1) patients with multi-segmental disc herniation, cauda equina syndrome, lumbar spinal stenosis, spinal metastatic disease, or lumbar spondylolisthesis, (2) individuals with psychosis or uncorrectable bleeding tendencies, (3) patients lost to follow-up, and (4) those who had previously undergone lumbar surgery.

Procedures

Guided by C-arm fluoroscopy, the patient was positioned in the prone position with U-shaped pillows under the chest and both ilia so that the abdomen was suspended.

UBE

In the case of the left side, the target intervertebral space was confirmed using C-arm fluoroscopy. Two incisions were 1.5 cm in the left side to the midline and 3 cm apart from each other, which were centered on the target intervertebral space. The two guide rods were inserted through the incision and met at the junction of the upper vertebral lamina and the lower articular process, which was confirmed by fluoroscopy. Then, used a T-shaped dilator to perform blunt relaxation of the soft tissue. The cranial portal (observational channel) inserted the endoscope (Stryker, Kalamazoo, MI, USA) for view, and the caudal portal (working channel) was used for surgical instruments and radiofrequency (RF) ablation (BONSS, JiangSu, China). Used RF ablation and pituitary forceps to clean the soft tissue in the field of vision, and exposed the upper vertebral lamina and the articular process. Partial laminectomy was performed using a grinding drill (Xishan, Tianjin, China) and Kerrison punches to expose the attachment of ligamentum flavum. The ligamentum flavum was removed using Kerrison punches. Then exposed the dura mater and nerve roots in the spinal canal, the traverse nerve root was gently retracted towards the midline of spinal canal, and discectomy was performed using pituitary forceps. Finally, the absence of residual fragments was confirmed using a neural probing hook. After meticulous hemostasis, the wounds were sutured (Figure 1).

Figure 1 Male, 34 years old, L5/S1 lumbar disc herniation. (A) Preoperative sagittal MR image showed L5/S1 lumbar disc herniation; (B) Preoperative axial MR image showed herniated lumbar disc compressed nerve root and dural sac; (C) Intraoperative fluoroscopic confirmation of metal rods; (D) Postoperative sagittal MR image revealed the complete decompression of the spinal canal; (E) Postoperative axial MR image showed the complete removal of herniated disc and bony fragment; (F) Intraoperative image after complete neural decompression.

PEID

C-arm fluoroscopy was used to locate the target intervertebral segment. The guide needle was placed at the junction of the vertebral plate and the inner edge of the lower articular process, which was 1 cm beside the midline, and the target position was confirmed by fluoroscopy again. Make a 1 cm incision to the target position of the vertebral plate, and inserted the spinal endoscopic operating system. Used RF ablation clean soft tissue and used pituitary forceps to remove a portion of the ligamentum flavum. Exposed the ipsilateral recess, used a grinding drill (Xishan, Tianjin, China) and Kerrison punches to decompress the ipsilateral recess, and fully exposed the shoulder and axilla of the nerve root. Removed disc through the nerve root shoulder or axillary. The dural sac and lumbar-exiting nerve root being freely movable were observed, removed the working cannula and sutured the skin incision (Figure 2).

Figure 2 Female, 50 years old, L5/S1 lumbar disc herniation. (A) Preoperative sagittal MR image showed L5/S1 lumbar disc herniation; (B) Preoperative axial MR image showed herniated lumbar disc compressed nerve root and dural sac; (C) Intraoperative fluoroscopic confirmation of metal rods; (D) Postoperative sagittal MR image revealed the complete decompression of the spinal canal; (E) Postoperative axial MR image showed the complete removal of herniated disc and bony fragment; (F) Intraoperative image after complete neural decompression.

Postoperative treatment

All patients were instructed to wear waist protection after surgery when moving out of bed. Within one month after surgery, patients should avoid weight-bearing activities and engage in moderate lower back muscle function exercises.

Outcomes

The CTF-classification of LDH⁸ was recorded for all patients. The primary outcomes focused on assessing the visual analog scale (VAS) and the Oswestry Disability Index (ODI) scores at multiple time points: before the operation, at 1 day, 1, 3, 6, and 12 months after the operation. The secondary outcomes included several factors: operation time, hospitalization time, fluoroscopy frequency, total costs, and complication.

The VAS score was measured using a 10 cm visual analog scale. It was evaluated from 0 to 10, 0 indicates no pain, and 10 indicates the most severe pain. The ODI assesses low back pain-related disability, the higher the score means the worse the disability.

Statistical Analysis

The statistical analysis was performed with SPSS 24.0 for Windows (SPSS, Inc., IBM). Measured data were tested for normal distribution and the homogeneity of variance. Numeric variables were expressed as Mean ± SD and analyzed by Independent-Samples T-test. Repeated measures of ANOVA (with Bonferroni confidence interval adjustment) tests were conducted for VAS and ODI. Categorical data were expressed by N (%) and were analyzed with the χ2 test. The value of P < 0.05 was taken as a significant difference.

Results

General information

There were no statistically significant differences observed in terms of sex, age, body mass index (BMI), and disc herniation classification between the two groups (P > 0.05). There were no significant differences in the operation time, hospitalization time, fluoroscopy frequency and incidence of complications among the two groups. But total costs in Group 2 were significantly higher than those in Group 1 (P < 0.05).

None of the patients in any of the two groups experienced severe complications such as spinal injury or paraplegia. One case experienced nerve root injury in Group 1, while 1 case experienced dural puncture in Group 2. The complications were reversible and resolved within 3 months. The complication rate during follow-up had no significant difference between the two groups (P > 0.05) (Table 1).

Table 1 Comparison of General Data Between Group 1 and Group 2

Comparison of VAS

There was no significant difference in the VAS of the low back pain and sciatica before the operation between the two groups (P > 0.05). The VAS of the low back pain and sciatica at each observation point after the operation were significantly decreased compared with that before the operation in both groups (P < 0.05). On the first day after the operation, the VAS of lower back pain in Group 2 was higher than that in Group 1 (P < 0.05), and there was no statistical difference in the VAS of sciatica between the two groups (P > 0.05). There was no statistical difference in the VAS of the low back pain and sciatica in 1, 3, 6 and 12 months after the operation between the two groups (P > 0.05) (Table 2).

Table 2 Comparison of VAS Between Group 1 and Group 2 at Different Time

Comparison of ODI

There was no significant difference in the ODI scores before the operation between the two groups (P > 0.05). The ODI scores at each observation point after the operation were significantly decreased compared with that before the operation in both groups (P < 0.05). There was no statistical difference in the ODI at 1 day, 1, 3, 6 and 12 months after the operation between the two groups (P > 0.05) (Table 3).

Table 3 Comparison of ODI Between Group 1 and Group 2 at Different Time

Discussion

LDH is a prevalent cause of both low back pain and sciatica, significantly impacting the daily lives of patients.¹ Therefore, there is an urgent need to alleviate the pain and enhance the quality of life for these patients.² Minimally invasive surgery is often preferred by patients due to their potential for quicker postoperative recovery.³ This retrospective study demonstrated that PEID and UBE discectomy can achieve equivalent and satisfactory outcomes in the 12 months follow-up. The VAS of lower back pain on the first day after the operation and total costs in Group 2 were higher than that in Group 1.

As a minimally invasive surgery, percutaneous endoscopic lumbar discectomy is superior to conventional open surgery due to its lower bleeding volume, minimal soft tissue damage, and faster return to work.⁴ Compared to the steep learning curve of PLED, the learning curve of PEID is relatively flat.⁶ PEID aligns more closely with surgeons’ established surgical practices and exhibits a shorter learning curve.⁹ A high iliac crest, a limited disc space, and overuse of radiography examinations of the lateral transforaminal approach might all be avoided by using PEID.¹⁰ But it also has drawbacks, such as a small surgical field, low efficiency of surgical instruments, and limited decompression range.¹¹ It is difficult for the central type LDH, when to remove the intervertebral disc that deviates from the midline, it is often necessary to rotate the catheter to compress the nerves and dura sac to the opposite side, which may lead to postoperative numbness in the perineal area or weakness in dorsalis pedis extension.¹² It should be emphasized that percutaneous endoscopic requires specialized equipment, which imposes a substantial financial burden on many healthcare institutions. Therefore, not all hospitals, not all LDH patients, are suitable for PEID.

Unilateral biportal endoscopic (UBE) discectomy is a combination of open and endoscopic spinal surgery.⁷ UBE shared the same interlaminar approach with open spinal surgery. This enables the use of a wide range of conventional instruments, including curettes, Kerrison punches, osteotomes, high-speed drills, and conventional forceps. Moreover, it is worth noting that UBE utilizes an arthroscopic system, which is already owned by the majority of hospitals, so the instruments required for UBE are more readily available and comparatively less expensive. By integrating the observational and operational channels, the instrument gains a wider range of movement, enabling a superior decompression range and enhanced exploration capability compared to percutaneous endoscopic techniques.¹³ The learning curve of this technique is relatively shorter than that of percutaneous endoscopic.¹⁴ Based on the aforementioned advantages, the utilization of UBE has gained significant popularity and has been increasingly adopted for the treatment of lumbar disc herniation and lumbar spinal stenosis. Our results indicate that the VAS and ODI scores at each observation point after the operation were significantly decreased compared with that before the operation in both groups. It means both surgical methods are effective in treating intervertebral disc herniation. On the first day after the operation, the VAS of lower back pain in Group 2 was higher than that in Group 1, this may be related to UBE needs to create a cavity outside the spinal canal, it causes greater damage to the paraspinal muscles than PEID. Paraspinal muscle integrity is believed to play a critical role in low back pain (LBP) and numerous spinal deformity diseases and other pain pathologies. A number of studies have demonstrated an association between paravertebral muscle injury and worse postoperative outcomes.¹⁵

In this study, the hospitalization time in both groups was very short, which means that patients receiving PEID or UBE can achieve rapid mobilization, recovery, and prompt resumption of their daily activities. Our study revealed that patients undergoing UBE discectomy incurred higher costs compared to those treated with the PEID technique. This discrepancy in costs may be attributed to the utilization of two radiofrequency (RF) ablations during UBE surgery. Despite the utilization of open instruments with improved efficiency in UBE, the requirement of an extraspinal cavity offsets any significant difference in surgical time compared to PEID.

Among the recorded complications, 1 case experienced nerve root injury in Group 1, while 1 case experienced dural puncture in Group 2. Previous research has indicated that a dural tear is the most common complication associated with UBE.¹⁶ Several risk factors have been identified, including instrument or radiofrequency-induced damage to the dura mater, adhesion in the spinal canal, presence of giant disc fragments, and loosened dura.^17,18 Therefore, meticulous dissection of the meningo-vertebral ligament is of particular importance. PEID group showed nerve root injury is often attributed to nerve rotation and compression caused by the cannula in the spinal canal, and these symptoms typically improve within three months. Therefore, before rotating the cannula during PEID, the medial edge of the articular process should be removed to release the superior mesentery of the nerve root. Additionally, finer cannula selection and an appropriate operative route are advised to minimize nerve damage.

Our research has several limitations that should be acknowledged. Firstly, this was a retrospective study. Therefore, there may be inherent bias associated with patient selection and missing patient information. Secondly, the study was performed in only one hospital with limited patients enrolled, a larger scale clinical trial with multiple centers is needed in the future.

Conclusion

Both the UBE and PEID procedures have demonstrated comparable efficacy in alleviating pain and improving functional ability in patients with LDH. However, UBE surgery is associated with higher costs compared to PEID surgery. Clinicians should cautiously control surgical indications and choose the most effective surgical operation that is reasonable to obtain the most satisfactory clinical curative effect.