Introduction

Lumbar disc herniation (LDH) is a prevalent spinal column disorder caused by the rupture of the intervertebral disc's annulus fibrosus and disk degeneration, leading to nerve root compression [1, 2]. This condition results in symptoms such as lower back pain, lower extremity numbness, and reduced mobility, significantly affecting the patient's quality of life. Surgery is the primary intervention for individuals with ineffective conservative treatment, severe disease, or neurological damage [3]. The main goal of surgical treatment is to alleviate nerve compression caused by the herniated disks, thus reducing symptoms and improving function. However, traditional open surgery requires extensive paravertebral muscle dissection, which can cause significant trauma, spinal instability, and increased complication rates. Minimally invasive techniques have emerged as viable alternatives [4]. These methods use endoscopes or microscopes inserted through small incisions to provide surgeons with a superior visual field and reduce trauma and complications [5].

A surgical approach resembling the modern unilateral biportal endoscopic (UBE) technique was first documented by De Antoni in 1996 [6]. Despite the initial lack of attention, recent studies have demonstrated the potential of the UBE technique in achieving favorable outcomes for various lumbar spinal diseases, leading to renewed interest among spinal surgeons [7]. The UBE technique distinguishes itself from other minimally invasive procedures through its dual-channel design: one channel serves as the endoscopic portal; however, the other functions as the working portal [8]. This configuration allows the UBE technique to combine the advantages of minimally invasive surgery with a larger operative workspace while maintaining surgical techniques similar to traditional open surgery [9]. Because this endoscopic procedure can successfully decompressive central and foraminal stenosis, it is currently mainly used for the treatment of lumbar spinal stenosis. In the meantime, the procedure can easily remove a migrated disk fragment, therefore, some studies have also applied it to the treatment of lumbar disk herniation. As a new technique that can treat LDH, there are no relevant guidelines to guide clinical practice. Historically, the conventional surgical approach for treating LDH has been MD [10]. This systematic review and meta-analysis aimed to compare the effectiveness of UBED and MD in treating LDH based on the most recent evidence, with the aim of providing guidance for clinicians.

Methods

Search strategy

This meta-analysis adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) 2020 statement [11] and was registered in PROSPERO with the identifier CRD42022332774 before data extraction. Two authors independently searched CNKI, Embase, PubMed, Cochrane Library, and Web of Science databases using keywords such as "biportal,” "microdiscectomy," "lumbar disk herniation," and synonyms. The search, conducted until April 2023, did not impose any language restrictions. Furthermore, the literature was assessed based on pre-established inclusion and exclusion criteria, with disagreements resolved through discussion involving a third researcher. Figure 1 shows the PRISMA flow diagram.

Fig. 1
figure 1

Study selection process. The flowchart showed the selection of included studies for meta-analysis

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Study selection

The inclusion criteria were as follows: (1) study population consisting of patients diagnosed with lumbar disk herniation; (2) interventions comparing UBED and MD, with the consistency of procedures ensured by referencing surgical procedure descriptions and images from the original literature; and (3) studies including at least two outcome indicators, such as operating time (OT), hospital stay, estimated blood loss, complications, visual analog score (VAS), Oswestry disability index (ODI), and MacNab score.

The exclusion criteria were as follows: (1) studies lacking relevant data or without accessible full text and (2) review articles, case reports, case series, or technical reports.

Quality assessment

The meta-analysis encompassed various study types, including randomized controlled trials (RCTs), case–control studies, and cohort studies, as detailed in the original literature. Quality assessment for case–control and cohort studies used the Newcastle–Ottawa Scale (NOS) [12], with higher scores indicating better quality. RCT quality was evaluated using the Cochrane Collaboration tool to assess the risk of bias [13].

Data extraction

Two investigators independently extracted data, including (1) basic characteristics: study ID (author + year), design, journal, country, surgical approach, sample size, age, follow-up time, and outcome indicators; and (2) clinical outcome indicators: operation time, hospital stay, estimated blood loss, complications, preoperative and postoperative VAS scores for back and leg pain, preoperative and postoperative ODI scores, and MacNab scores.

Statistical analysis

Statistical analyzes were performed using Review Manager software (version 5.4). Categorical variables were summarized using the Mantel–Haenszel odds ratio (OR) with 95% confidence intervals (CIs); nevertheless, continuous data were reported as mean differences (MDs) and 95% CI. The I2 test was employed to assess statistical heterogeneity, with I2 values ≥ 50% indicating significant heterogeneity and warranting a random-effects model for the meta-analysis. Otherwise, a fixed effects model was used.

Results

Search results and bias assessment

Figure 1 shows the PRISMA flow diagram outlining the study selection process. An initial search of multiple databases yielded 103 articles, and duplicates were excluded, leaving 34 articles for screening. These articles were assessed based on strict inclusion and exclusion criteria through title and abstract evaluation, which excluded non-relevant studies. A total of 16 articles underwent full-text evaluation, of which 7 were excluded because they did not meet the inclusion criteria. Finally, 9 studies were included in the meta-analysis [14,15,16,17,18,19,20,21,22]. The risk of bias was assessed using the NOS scale and the Cochrane Collaboration tool, as shown in Tables 1 and 2.

Table 1 Risk of bias of randomized controlled trials
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Table 2 Risk of bias of cohort or case–control studies (NOS evaluation)
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Characteristics of included studies

Table 3 shows the baseline characteristics of the included studies. A total of 1001 patients diagnosed with lumbar disk herniation were analyzed, with 477 patients undergoing UBED and 524 patients undergoing MD in 4 countries. Table 4 presents the meta-analysis results, and Table 5 provides a comprehensive list of the complications associated with UBED.

Table 3 Characteristics of the studies included in the meta-analysis
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Table 4 Summary of the meta-analysis
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Table 5 Complications and the number of cases in the included studies
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VAS of back pain (Preoperative/postoperative)

Six studies reported the preoperative VAS scores for back pain (262 patients in the UBED group and 319 in the MD group) (Fig. 2). A slightly lower preoperative VAS score for back pain was observed in the UBE group than in the MD (mean difference: − 0.29, 95% CI[ − 0.52,  − 0.06], P = 0.01; heterogeneity: Tau2 = 0.01, Chi2 = 5.41, df = 5, P = 0.37, I2 = 8%).

Fig. 2
figure 2

Comparison of VAS of back pain (preoperative/postoperative) between the unilateral biportal endoscopic discectomy (UBED, “experimental”) group and the microdiscectomy (MD, “control”) group. IV = inverse variance, CI = confidence interval, and df = degrees of freedom

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The same 6 studies reported 1–3 days postoperative VAS scores for back pain. Meta-analysis revealed significantly lower scores in the UBED group than in the MD group. (mean difference:  − 0.81,95% CI[ − 1.48,  − 0.14], P = 0.02; heterogeneity: Tau2 = 0.63, Chi2 = 102.65, df = 5, P < 0.00001, I2 = 95%).

Five studies reported 1–3 months postoperative VAS scores for back pain (167 patients in the UBE group and 182 in the MD group), and four studies reported 1-year postoperative VAS scores for back pain (147 patients in the UBED group and 162 in the MD group). The meta-analysis did not reveal any statistically significant differences between the groups (1–3 months postoperative VAS of back pain: mean difference:  − 0.39, 95% CI[ − 0.85, 0.07], P = 0.09; heterogeneity: Tau2 = 0.20, Chi2 = 21.17, df = 4, P = 0.0003, I2 = 81%; 1-year postoperative VAS of back pain: mean difference:  − 0.32, 95% CI[ − 0.74, 0.10], P = 0.13; heterogeneity: Tau2 = 0.10, Chi2 = 8.50, df = 3, P = 0.04, I2 = 65%).

VAS of leg pain (Preoperative/postoperative)

Seven studies reported the preoperative VAS scores for leg pain (305 patients in the UBED group and 356 in the MD group) (Fig. 3). Furthermore, 6 studies reported 1–3 days postoperative VAS scores for leg pain (262 patients in the UBED group and 319 in the MD group). In addition, 5 studies reported 1–3 months postoperative VAS scores for leg pain (167 in the UBED group and 182 in the MD group). Moreover, 4 studies reported 1-year postoperative VAS scores for leg pain (147 in the UBED group and 162 in the MD group). There were no statistically significant differences between the two groups (1. preoperative VAS of leg pain: mean difference:-0.16, 95% CI[-0.33, 0.00], P = 0.05; heterogeneity: Tau2 = 0.00, Chi2 = 1.49, df = 6, P = 0.96, I2 = 0%; 2. 1–3 days postoperative VAS of leg pain: mean difference:  − 0.19, 95% CI[ − 0.49, 0.12], P = 0.24; heterogeneity: Tau2 = 0.09, Chi2 = 15.45, df = 5, P = 0.009, I2 = 68%; 3. 1–3 months postoperative VAS of leg pain mean difference:-0.09, 95% CI[ − 0.70, 0.53], P = 0.78; heterogeneity: Tau2 = 0.37, Chi2 = 26.63, df = 4, P < 0.0001, I2 = 85%; 4. 1-year postoperative VAS of leg pain mean difference:  − 0.23, 95% CI[ − 0.81, 0.34], P = 0.43; heterogeneity: Tau2 = 0.24, Chi2 = 16.45, df = 3, P = 0.0009, I2 = 82%).

Fig. 3
figure 3

Comparison of VAS of leg pain (preoperative/postoperative) between the unilateral biportal endoscopic discectomy (UBED, “experimental”) group and the microdiscectomy (MD, “control”) group. IV = inverse variance, CI = confidence interval, and df = degrees of freedom

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ODI (Preoperative/postoperative)

Seven studies reported preoperative ODI (294 patients in the UBED group and 351 in the MD group) (Fig. 4). Furthermore, 3 studies reported the 1-week postoperative ODI (158 patients in the UBED group and 211 in the MD group). In addition, 4 studies reported 1–3 months postoperative ODI (125 patients in the UBED group and 139 in the MD group). The meta-analysis showed no statistically significant differences between the two groups in the above indicators. (1. preoperative ODI:mean difference: 0.21, 95% CI  − 1.69, 2.11], P = 0.83; heterogeneity: Tau2 = 2.78, Chi2 = 12.34, df = 6, P = 0.05, I2 = 51%; 2. 1-week postoperative ODI: mean difference:  − 1.09, 95% CI[ − 4.08, 1.90], P = 0.47; heterogeneity: Tau2 = 4.18, Chi2 = 5.01, df = 2, P = 0.08, I2 = 60%; 3. 1–3 months postoperative ODI: mean difference: − 2.15, 95% CI[ − 4.97, 0.67], P = 0.13; heterogeneity: Tau2 = 5.69, Chi2 = 16.55, df = 3, P = 0.0009, I2 = 82%). Additionally, 4 studies reported 1–year postoperative ODI (147 patients in the UBED group and 162 in the MD group), and the meta-analysis showed that the UBED group had better ODI than the MD (1-year postoperative ODI: mean difference:  − 1.40, 95% CI[ − 2.68,  − 0.11], P = 0.03; heterogeneity: Tau2 = 0.67, Chi2 = 5.10, df = 3, P = 0.16, I2 = 41%).

Fig. 4
figure 4

Comparison of ODI (preoperative/postoperative) between the unilateral biportal endoscopic discectomy (UBED, “experimental”) group and the microdiscectomy (MD, “control”) group. IV = inverse variance, CI = confidence interval, and df = degrees of freedom

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MacNab score

Five studies reported the MacNab score (254 patients in the UBED group and 294 in the MD group) (Fig. 5). The meta-analysis did not reveal any statistically significant differences between the groups. (odds ratio: 1.58, 95% CI [1.00, 2.50], P = 0.05; heterogeneity: Chi2 = 1.83, df = 4, P = 0.77, I2 = 0%).

Fig. 5
figure 5

Comparison of MacNab score between the unilateral biportal endoscopic discectomy (UBED, “experimental”) group and the microdiscectomy (MD, “control”) group. MH = Mantel–Haenszel, CI = confidence interval, and df = degrees of freedom

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Operation time

Nine studies reported the operating time in 1001 patients, with 477 in the UBED group and 524 in the MD group (Fig. 6). Specifically, the operating time was slightly longer in the MD group, with a statistically significant difference. (mean difference: 9.16 min, 95% CI[1.13, 17.20], P = 0.03; heterogeneity: Tau2 = 130.26, Chi2 = 112.00, df = 8, P < 0.00001, I2 = 93%).

Fig. 6
figure 6

Comparison of operation time between the unilateral biportal endoscopic discectomy (UBED, “experimental”) group and the microdiscectomy (MD, “control”) group. IV = inverse variance, CI = confidence interval, and df = degrees of freedom

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Estimated blood loss

Four studies reported the estimated blood loss (200 and 256 patients in the UBED and MD groups, respectively) (Fig. 7). A lower estimated blood loss was observed in the UBED group than in the MD group, with a statistically significant difference. (mean difference:  − 74.42, 95% CI[ − 114.11,  − 34.73], P = 0.0002; heterogeneity: Tau2 = 1616.29, Chi2 = 408.49, df = 3, P < 0.00001, I2 = 99%).

Fig. 7
figure 7

Comparison of estimated blood loss between the unilateral biportal endoscopic discectomy (UBED, “experimental”) group and the microdiscectomy (MD, “control”) group. IV = inverse variance, CI = confidence interval, and df = degrees of freedom

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Hospital stay

Among the 9 studies analyzed, 8 reported the hospital stays of 914 patients, with 435 in the UBED group and 479 in the MD group (Fig. 8). The results showed a statistically significant difference between the two groups, with a significantly shorter hospital stay observed in the UBED group compared to MD. (mean difference:  − 2.32 days 95% CI[ − 3.30,  − 1.35], P < 0.00001; heterogeneity: Tau2 = 1.69, Chi2 = 88.71, df = 7, P < 0.00001, I2 = 92%,).

Fig. 8
figure 8

Comparison of hospital stay between the unilateral biportal endoscopic discectomy (UBED, “experimental”) group and the microdiscectomy (MD, “control”) group. IV = inverse variance, CI = confidence interval, and df = degrees of freedom

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Complications

Seven studies reported the incidence of complications (317 and 368 patients in the UBED and MD groups, respectively) (Fig. 9). The meta-analysis revealed no statistically significant difference in the incidence of complications between the two groups (odds ratio: 1.21, 95% CI[0.63, 2.33], P = 0.56; heterogeneity: Chi2 = 1.84, df = 6, P = 0.93, I2 = 0%).

Fig. 9
figure 9

Comparison of complications between the unilateral biportal endoscopic discectomy (UBED, “experimental”) group and the microdiscectomy (MD, “control”) group. MH = Mantel–Haenszel, CI = confidence interval, and df = degrees of freedom

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Discussion

This study revealed that both UBED and MD demonstrated comparable therapeutic efficacy in treating LDH, as evidenced by analogous VAS, ODI, and MacNab scores and complication rates (minor discrepancies in the VAS score for back pain and ODI offer limited evidence for meaningful information). Additionally, the UBED group exhibited reduced hospital stays and estimated blood loss, albeit with marginally increased operative times, compared to the MD.

Efficacy of UBED

Lumbar disk herniation (LDH) is a common degenerative spinal disorder. Microdiscectomy (MD) has been the gold standard treatment for LDH for an extended period [23] and was introduced by Yasargil in 1967 using a microscope [24]. Nevertheless, the microscopic technique presents limitations, such as challenging instrument manipulation because of a single-port and the steep learning curve associated with tubular microsurgery [25]. Over the past decade, minimally invasive endoscopic spinal surgery has gained popularity for preserving normal anatomical structures, thus expediting postoperative recovery [26]. According to the North American Spine Society's (NASS) 2013 evidence-based guidelines, percutaneous endoscopic lumbar discectomy (PELD) is the primary recommended surgical approach for selected patients with LDH radiculopathy, which also indicates that the treatment concept of LDH is gradually changing to minimally invasive methods [3]. However, PELD involves a challenging learning curve [27, 28], and if not performed with the necessary skills and precision, complications such as dural and nerve root injuries can occur [29]. Due to the inevitable procedural defects of PELD, it is necessary to find another minimally invasive method to treat LDH. Recent studies have shown that the UBE technique [30], proved effective in LDH treatment [31, 32] and the findings of this study indicate that UBED exhibit therapeutic efficacy in the treatment of LDH by compared with MD, as demonstrated by similar VAS, ODI, and MacNab scores. Even more remarkable, this technique demonstrated versatility in addressing various spinal diseases, including high-grade migrated LDH, recurrent LDH, far-out syndrome, thoracic ossification of the ligamentum flavum, cervical radiculopathy, and lumbar interbody fusion [33,34,35,36,37,38,39].

Advantages and limitations of UBED

The recent orthopedic addition, the UBE technique [30], proved effective in LDH treatment [31, 32] and demonstrated versatility in addressing various spinal diseases, including high-grade migrated LDH, recurrent LDH, far-out syndrome, thoracic ossification of the ligamentum flavum, cervical radiculopathy, and lumbar interbody fusion [33,34,35,36,37,38,39]. Prior studies have documented numerous benefits of the UBE technique. Its utilization of instruments identical to those used in conventional spinal surgery presents a potential for cost reduction. Choi et al. substantiated that UBE is a more economically efficient alternative to MD, boasting a cost-effectiveness on par with other endoscopic lumbar discectomies Several benefits of the UBE technique have been previously documented. By employing instruments identical to those used in traditional spinal surgery, UBE has the potential to reduce overall costs. Choi et al. demonstrated that the UBE technique is a more cost-effective alternative to MD, with cost-effectiveness comparable to other endoscopic lumbar discectomies [16].

Many surgeons consider this technique as a superior minimally invasive approach for the following reasons. The biportal technique provides a broader visual access range than single-port endoscopes, akin to the amplified visual field achieved with a microscopeThe biportal technique offers a wider visual access range than single-port endoscopes, similar to the magnified visual field obtained using a microscope [40]. By separating the viewing and working portals, it allows unrestricted bimanual operation by surgeons, facilitating more straightforward instrument manipulation than uniportal or microscopic techniques. Additionally, the biportal technique enhances visualization of contralateral sublaminar and foraminal spaces, which can be further optimized using a 30˚ endoscopeSeparating the viewing and working portals allows unrestricted bimanual use by surgeons, enabling easier instrument manipulation than uniportal or microscopic techniques. The biportal technique also provides an enhanced visualization of the contralateral sublaminar and foraminal spaces, which can be further improved by using a 30˚ endoscope[41], fthereby promoting secure and efficient bilateral nerve decompressionacilitating secure and effective bilateral nerve decompression [42]. As a result, the biportal technique's provision of clear visual access and unrestricted instrument maneuverability is thought to lead to reduced radiation exposure.Consequently, clear visual access and unobstructed instrument maneuverability offered by the biportal technique is believed to contribute to shorter operative times and radiation exposure. This finding aligns with Merter et al.'s study, which ranked UBED above microendoscopic discectomy in terms of radiation exposure duration[43]. Subsequently, the UBE technique has gained popularity among spinal surgeons, showing faster recovery and shorter hospital stays in lumbar spinal stenosis treatment than in MD[44,45,46]. Our meta-analysis of UBED for LDH treatment supports this finding.

However, Jiang et al. identified several disadvantages of the UBE technique compared to PELD, including increased total, intraoperative, and hidden blood loss; longer operative time; and extended hospitalization periods [32]. Furthermore, meta-analyzes by Zhu et al. and Ma et al. observed no significant differences in the clinical effectiveness between UBED and PELD [47, 48]. However, PELD demonstrated superiority in operative duration, intraoperative hemorrhage, and immediate postoperative pain relief. This discrepancy may be because of the use of a double incision, the invasiveness of the procedure on the muscle tissue, and the steeper learning curve associated with this new surgical approach. Regarding potential paraspinal muscle injury, Choi et al.'s study used creatine phosphokinase (CPK) and C-reactive protein (CRP) as indicators to assess damage during surgery [14]. The PELD group showed significantly smaller cross-sectional areas of high-intensity lesions in the paraspinal muscles and lower CPK and CRP levels than the UBED group. Ahn et al. observed multifidus muscle status changes on MRI after UBE, which resolved spontaneously over time [49]. Wang et al. produced similar results, which suggested that radiological manifestations of paraspinal muscle invasiveness were comparable between UBE and percutaneous endoscopic techniques during final follow-ups of at least one year [50]. In addition, surgery duration and paraspinal muscle extent at specific levels may be considered risk factors for high blood loss in UBE surgery [51]. Consequently, reducing the surgery duration is crucial to address these issues, necessitating a focus on the learning process of the technique.

Learning curve of UBED

Choi et al. emphasized the importance of magnifying regional views through an endoscope and carefully controlling epidural bleeding to maintain a clear surgical field when learning the UBE technique [52]. Furthermore, Park et al. suggested that achieving proficiency in the UBE technique might require a significant learning duration, as demonstrated by a trainee with no prior UBE experience performing adequately in 58 cases [53]. Moreover, Xu et al.'s 2022 study identified three distinct learning curve phases for the UBE technique, requiring at least 54 cases to master the procedure, with the operation time and postoperative hospital stay decreasing as the learning curve progressed [54]. However, Chen et al. observed that mastery could be achieved with as few as 24 single-level procedures [55]. In general, there is a learning curve for this technique, so the summary of early evidence in our meta-analysis will be valuable for surgeons who are new or about to perform this technique. Notably, Sahin et al. proposed a cost-effective mobile training model to enhance biportal endoscopic skills for inexperienced practitioners [56]. This may be beneficial for shortening the learning process.

Complications and safety of UBED

The present study has identified a range of complications following UBED, such as dural tears, retinal hemorrhage, postoperative spinal epidural hematoma, recurrent intervertebral disk herniation, incomplete decompression, instability, ascites, burn injuries, infections, and neurological complicationsThe current study identified various complications after UBED, including dural tears, retinal hemorrhage, postoperative spinal epidural hematoma, recurrent intervertebral disk herniation, incomplete decompression, instability, ascites, burn injury, infection, and neurological complications [57]. Table 5 provides a summary of the complications discussed in all nine articles included in the study.

Dural tears

Table 5 summarizes the complications mentioned in all 9 included articles. Dural tears represent the most frequently occurring complication of the UBE technique, with multiple factors contributing to their incidence, including inappropriate instrument handling, inexperienced surgeons, limited visibility during the procedure, and the anatomy of the central dural fold Dural tears are the most common complication of the UBE technique, with several factors contributing to their occurrence, such as improper instrument handling, inexperienced surgeons, limited visibility during the procedure, and central dural fold anatomy [58,59,60,61]. Furthermore, Lee et al. observed that dural sac tears often occur during ligament flavum removal [58], which can be attributed to the meningovertebral ligament, a web-like anatomical interface joining the dorsal face of the dura with the lamina and ligament flavum [62]. Park et al. guided managing dural tears [59]; tears < 4 mm required no intervention; 4–12 mm tears should be treated with a fibrin sealant patch; tears > 12 mm with standard margins should undergo primary endoscopic closure using nonpenetrating titanium clips and a fibrin sealant patch; and irregular margin tears > 12 mm should be converted to direct microscopic repair. Kim et al. demonstrated that dural tears < 10 mm can be effectively treated using the fibrin seal patch technique [60]. Chun et al. reported a case of postoperative nerve root herniation caused by a dural tear in the UBE technique, suggesting an epidural blood patch as a treatment before open surgery [61].

Hematoma

Patient dissatisfaction is primarily associated with hematoma formation and incomplete decompression [63]. Kim et al. observed a higher prevalence of radiological hematoma identified through postoperative MRI than symptomatic postoperative hematoma. The risk factors for postoperative hematoma after UBED include female sex, age > 70 years, anticoagulation medication use, and intraoperative water infusion pump use [64]. Ahn et al. concluded that high e-SBP (≥ 170 mmHg) could influence postoperative spinal epidural hematoma development in UBED [65]. Furthermore, Kim et al. suggested that revision surgery may be necessary when canal encroachment by hematomas exceeds 50%, and the patient presents with related symptoms [66].

Incomplete decompression

Incomplete decompression represents a common concern across all minimally invasive procedures. This issue, particularly in UBED, often arises due to blurred vision induced by intraoperative bleedingIncomplete decompression because of intraoperative bleeding-induced blurred vision in UBED [63]. It can be effectively managed through continuous irrigation during the surgical procedure. This approach facilitates the removal of bone debris, minimizes bleeding, ensures a clear operating field, and helps in reducing intracranial pressure can be addressed through continuous irrigation during surgery to remove bone debris, minimize bleeding, maintain a clear operating space, and reduce intracranial pressure [67]. Notably, the irrigation pressure should be regulated (25–30 mmHg recommended) to avoid increased epidural hydrostatic pressure, which can delay postoperative recovery [68]. Limited depth perception during endoscopic surgery (because of 2D vision) may increase the risk of perioperative complications. However, Heo et al. introduced 3D endoscopy to improve the discrimination of anatomical structures with enhanced stereognosis and depth perception, potentially benefiting patient safety and well-being during endoscopic spinal surgery [69].

This systematic review and meta-analysis have certain limitations, such as the relatively limited number of studies comparing UBED with MD and variable findings among the reviewed studies. Furthermore, because certain studies employed distinct outcome units, they could not be incorporated into the meta-analysis. Notably, only one of the included studies was a randomized controlled trial; however, the other studies had observational designs. Therefore, to bolster the validity and reliability of this investigation, there is a pressing need for additional randomized controlled trials characterized by larger sample sizes.

Conclusion

Available evidence indicates no significant difference in efficacy between UBED and MD for lumbar disk herniation. Nonetheless, UBED has the potential to offer benefits, such as a shorter hospital stay, lower estimated blood loss, and lower complication rates. However, more robust evidence is required, and further multicenter randomized controlled trials (RCTs) are necessary to establish a definitive conclusion.