Introduction
Lumbar degenerative disease (LDD) is a common condition in adults, primarily arising from age-related changes in the lumbar spine. This condition can manifest clinically as lumbar disc herniation (LDH) and lumbar spinal stenosis (LSS). With the global population aging, the incidence of LDD continues to rise. Radiographic studies indicate that more than 90% of individuals over the age of 60 years exhibit imaging evidence of LDD [1]. Typical symptoms include lower back pain, numbness, and neurogenic claudication. When conservative treatments fail, surgical interventions such as lumbar decompression through discectomy or laminectomy are often required [2,3].
Since Kambin pioneered endoscopic decompression in the 1970s, uniportal endoscopic spine surgery has become an increasingly popular minimally invasive technique [4–6]. This approach aims to minimize soft-tissue damage, with particular emphasis on preserving the integrity of the paraspinal muscles and posterior ligamentous structures [7,8]. Compared with traditional open surgery, uniportal endoscopy is associated with fewer complications, faster recovery, and reduced postoperative pain [9,10]. However, it has notable limitations, including a restricted field of view and a steep learning curve [11]. The most recent advancement in minimally invasive surgery, biportal endoscopy, has garnered considerable interest due to its relatively shorter learning curve, broader visualization, and greater instrument maneuverability, especially for effective spinal canal decompression [12–14]. In this technique, two portals are created: one for the endoscope (observation portal) and another for instruments (operation portal) [15,16]. This approach effectively integrates the advantages of uniportal endoscopy with those of traditional open surgery.
Despite recent advancements, there is a lack of conclusive evidence on whether uniportal or biportal endoscopy yields superior outcomes for patients with LDD. Previous systematic reviews have mainly compared these approaches in discectomy alone, a focus that may reduce heterogeneity but limits the generalizability of their findings [17,18]. Moreover, many of these reviews included relatively few studies and patients, further constraining their scope. To address this gap, we conducted a comprehensive, large-scale meta-analysis comparing uniportal and biportal approaches for LDD, systematically evaluating clinical outcomes of discectomy and laminectomy/laminotomy to provide the most up-to-date and inclusive evidence on these decompressive procedures for LDD management.
Methods
Ethical approval and informed consent were not required for this study as it did not involve human or animal subjects.
Search strategy
A comprehensive search of PubMed (MEDLINE), Embase, and Scopus databases was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and Cochrane Handbook recommendations to identify all related articles published before December 13, 2023. The search strategy combined keywords, synonyms, and variations of “endoscopic spine surgery,” “lumbar,” “discectomy,” “laminectomy,” and “laminotomy” using Boolean operators. Reference lists of included studies were also screened to ensure completeness.
Selection criteria
Eligible studies were comparative investigations of patients with LDD undergoing biportal endoscopic spine surgery versus uniportal endoscopic spine surgery. Studies were required to report at least one of the following outcomes: Visual Analog Scale (VAS) scores for back and leg pain, Oswestry Disability Index (ODI), complication rate, operative time, or length of hospital stay. The exclusion criteria were as follows: (1) patients with fractures, tumors, infections, or scoliosis; (2) noncomparative studies, case reports, reviews, conference abstracts, or letters; (3) studies lacking adequate outcomes data, specifically missing mean and standard deviation values. Only articles published in peer-reviewed journals in English were included.
Study screening and data extraction
Two reviewers independently screened titles, abstracts, and full texts according to the inclusion and exclusion criteria. Discrepancies were resolved by discussion with a third reviewer, and reasons for ineligibility or exclusion were documented. The senior author (S.K.C.) confirmed the final study selection.
Data extraction was independently performed by the reviewers using standardized forms, collecting study characteristics (authors, year of publication, design, surgical corridor, sample size, age, and sex ratio) and outcomes (VAS scores for back and leg pain, ODI, operative time, length of hospital stay, and complication rate).
Risk of bias assessment
Methodological quality of nonrandomized studies was assessed independently by two reviewers using the Newcastle-Ottawa Scale (NOS) [19]. This scale evaluates selection, comparability, and outcome, with a maximum score of 9. Studies scoring between 5 and 9 were considered to have a lower risk of bias; scores below 5 indicated a higher risk. Any disagreements between the two reviewers were resolved by a third reviewer.
Statistical analysis
Clinical outcomes, including operative time, length of stay (LOS), VAS score, and ODI, were compared between uniportal and biportal cohorts. Subgroup analyses were conducted for discectomy and laminectomy subgroups. Mean values were pooled following Cochrane’s Handbook for Systematic Reviews of Interventions. Differences between uniportal (control) and biportal (treatment) cohorts were calculated using Cohen’s d effect size under a random-effects model to account for between-study variability and improve generalizability. Outcomes were categorized as immediate postoperative (≤3 days), short-term (1–3 months), and long-term (≥1 year) to align with previous literature and reduce temporal heterogeneity. Heterogeneity was assessed using Cochran’s Q-test and I2 statistics. Statistical significance was set at p<0.05. All analyses were performed using IBM SPSS Statistics ver. 29.0 (IBM Corp., Armonk, NY, USA).
Results
Search results
The initial database search yielded 634 records after removing duplicates. Following title and abstract screening, 357 records were excluded. The remaining 277 full-text articles were assessed for eligibility, of which 11 studies met the inclusion criteria and were included in the final analysis. Nine studies were retrospective, and two were prospective. A PRISMA flowchart summarizing the screening process and literature search is presented in Fig. 1.
From 2018 to 2023, 11 comparative studies evaluating lumbar uniportal versus biportal endoscopic spine surgery were analyzed [20–30]. In total, 374 patients underwent uniportal procedures and 368 underwent biportal procedures. The uniportal cohort had a mean age of 50.37±15.06 years and included 193 (51.6%) men. The biportal cohort had a mean age of 52.17±15.45 years and included 185 (50.3%) men. Baseline characteristics and risk-of-bias assessments for the included studies are summarized in Table 1.
Overall outcomes
Cohen’s d effect size revealed significantly lower ODI scores in the biportal cohort compared with the uniportal cohort at 1–3 months postoperatively (d=−0.28 [−0.45 to −0.11], p=0.001) and at final follow-up (d=−0.22 [−0.38 to −0.07], p=0.005) (Fig. 2). At 1–3 months, the mean ODI was 15.37±9.14 in the biportal cohort versus 16.97±10.18 in the uniportal cohort; at final follow-up >1 year, the means were 10.97±8.72 versus 11.36±9.31, respectively. LOS was significantly greater in the biportal cohort (d=1.06 [0.09 to 2.04], p=0.03) (Fig. 3), with a mean LOS of 4.69±2.80 days compared with 3.64±3.23 days in the uniportal cohort. There were no significant between-group differences in complication rate, operative time, VAS scores for back and leg pain, or ODI at the remaining time points. Mean values and p-values for all outcomes across the 11 studies are presented in Table 2. Heterogeneity analyses demonstrated significant between-study variability for operative time (I2=0.97, Q=248.89, p<0.001), LOS (I2=0.97, Q=157.85, p<0.001), and VAS score for back pain at 3 days (I2=0.88, Q=49.70, p<0.001). No significant heterogeneity was observed for the remaining variables.
Biportal vs. uniportal discectomy
Seven studies specifically addressed endoscopic discectomy, including 250 uniportal and 229 biportal patients. The uniportal cohort had a mean age of 44.50±13.48 years (140 men, 56.0%), and the biportal cohort had a mean age of 45.05±13.33 years (118 men, 51.5%). Cohen’s d indicated significantly lower ODI scores in the biportal group compared to the uniportal group at 1–3 months (d=−0.24 [−0.46 to −0.02], p=0.03) and at final follow-up (d=−0.22 [−0.42 to −0.01], p=0.04). Mean ODI at 1–3 months was 14.58±8.30 in the biportal group versus 16.02±9.99 in the uniportal group; at final follow-up, means were 7.16±6.03 versus 8.00±7.56, respectively. Operative time (d=1.33 [0.60 to 2.06], p<0.001) and LOS (d=1.59 [0.36 to 2.83], p=0.01) were significantly greater in the biportal group (Fig. 4). The mean operative time was 98.63±36.61 minutes for biportal versus 73.11±24.42 minutes for uniportal patients; mean LOS was 5.08±2.44 days versus 3.52±3.18 days, respectively, demonstrating a significant difference. Outcomes for the discectomy subgroup are summarized in Table 2. Significant heterogeneity was noted for operative time (I2=0.92, Q=61.85, p<0.001), LOS (I2=0.97, Q=125.13, p<0.001), and VAS score for back pain at 3 days (I2=0.91, Q=48.50, p<0.001), with no significant heterogeneity for the remaining variables.
Biportal vs. uniportal laminectomy/laminotomy
An additional subgroup analysis was conducted for the three studies of endoscopic laminectomy and one study of laminotomy, encompassing 124 uniportal and 139 biportal patients. Patients undergoing uniportal endoscopic laminectomy/laminotomy had a mean age of 62.19±10.44 years (53 men, 42.7%), and the biportal cohort had a mean age of 63.89±10.89 years (67 men, 48.2%). At the final follow-up, the biportal cohort demonstrated significantly lower ODI scores compared with the uniportal cohort (d=−0.35 [−0.63 to −0.07], p=0.02), with a mean ODI of 16.59±10.23 versus 18.68±10.37, respectively. ODI differences at other time points were nonsignificant. There were no significant between-group differences in operative time, LOS, complication rates, or VAS scores for leg and back pain at any time point. Clinical outcomes for the laminectomy subgroup are summarized in Table 2. Heterogeneity analysis revealed significant variation between studies regarding operative time (I2=0.97, Q=84.55, p<0.001), ODI at 3 days (I2=0.63, Q=8.13, p=0.04), and VAS score for leg pain at >1 year (I2=0.65, Q=8.47, p=0.04). No significant heterogeneity was observed for the remaining variables.
Discussion
Over the last decade, minimally invasive spine surgery has advanced rapidly, with endoscopic spine surgery, performed via uniportal or biportal approaches, representing a major development [15,31]. Both techniques aim to minimize muscle and soft-tissue injury, reduce bony resection, and thereby decrease postoperative instability, pain, and disability [31]. Despite growing interest, there is a lack of comprehensive comparative meta-analyses evaluating perioperative characteristics, postoperative outcomes, and the respective advantages and disadvantages of these approaches. The present study provides an updated comparison of uniportal versus biportal endoscopic spine decompression, specifically examining two major procedural categories: discectomy and laminectomy/laminotomy. Our analysis of 11 studies (seven discectomy studies and four laminectomy/laminotomy studies) encompassing 374 uniportal and 368 biportal patients found similar demographic profiles, with mean ages approximating 50 years and an almost equal sex distribution.
Overall, analysis of perioperative characteristics demonstrated no significant differences in operative time or complication rates between uniportal and biportal approaches. However, the uniportal technique was associated with an approximately 1-day (approximately 22%) shorter hospital stays than the biportal technique. These findings are consistent with a previous meta-analysis by Xu et al. [17], who found no significant differences in operative time or complication rate between 198 uniportal and 185 biportal patients across seven studies. Unlike Xu et al. [17], we observed a significant difference in LOS, likely due to our larger pooled sample. Subgroup analysis showed that this difference in LOS was primarily driven by discectomy cases, where the uniportal technique also exhibited shorter operative time. Differences in operative time between uniportal and biportal discectomy are likely due to the surgical access rather than the endoscopic approach itself. For example, in Hao et al. [20], uniportal percutaneous discectomy was performed via a transforaminal approach that provided direct access to the herniated disc, while biportal discectomy employed a posterior interlaminar approach requiring laminotomy before disc removal [20]. The uniportal discectomy technique may also produce less muscle and bone tissue damage, potentially facilitating earlier hospital discharge. Nevertheless, these perioperative differences should be interpreted cautiously. Although statistically significant, the differences in LOS (approximately 1 day) and operative time (approximately 10 minutes) are modest, may lack clinical relevance, and could reflect variability in discharge protocols, patient selection, or institutional workflow rather than meaningful improvements in recovery or resource use.
With respect to postoperative outcomes, no significant differences were observed between approaches with respect to VAS scores for back pain or leg pain. Although the biportal approach was associated with significantly lower ODI at 1–3 months and ≥1 year postoperatively, no individual study reported a significant ODI difference at any time point. These results likely stem from the larger composite sample size of our meta-analysis rather than a true clinical effect [32], and do not meet the minimal clinically important difference (MCID) of 12.8 for ODI defined by Copay et al. [33]. Further research employing additional or more sensitive outcome measures may be required to elucidate subtle differences in recovery between uniportal and biportal techniques.
An important factor not captured in our meta-analysis is the learning curve associated with each approach. Mastery of minimally invasive spine surgery correlates with reductions in operative time, LOS, and complication rates, thereby improving costs and patient recovery [34–38]. Biportal endoscopic spine surgery appears to have a relatively short learning curve of 40–60 cases. One study reported near-constant operative time after the 14th case of biportal endoscopy for LDH [37]. While our findings show similar operative time and complication rates overall, future research should determine whether proficiency (and associated perioperative improvements) is achieved more quickly with the biportal or the uniportal approach for lumbar decompression.
It should be emphasized that each approach poses unique challenges. Biportal surgery may be complicated by increased bleeding (“red screen”) and the presence of multiple instruments in a confined space, which can hinder targeting and contralateral foramen access. Conversely, the uniportal approach may be more technically demanding due to its single working channel, narrow visual field requiring endoscope rotation, and reduced maneuverability [39]. All included studies in our meta-analysis examined single-level procedures, except for Wu et al. [28], which included 14 patients with multilevel decompression (seven uniportal and seven biportal). Therefore, LOS differences are likely not attributable to the number of levels operated on. Future studies should evaluate the comparative effectiveness of uniportal versus biportal approaches in multilevel pathology.
Recent developments in uniportal endoscopic spine surgery, including the adoption of 7–10 mm working channels [40,41], allow the use of more robust instruments, improved visualization, and more complex procedures (e.g., decompressions and interbody fusions), while preserving the minimally invasive benefits. This evolution from smaller channels (typically 4–6 mm) to 7–10 mm has expanded indications for uniportal surgery, enabling safe and effective management of a broader range of spinal pathologies, including migrated disc herniations and spinal stenosis, with reduced soft-tissue disruption and faster recovery relative to open or conventional minimally invasive approaches [42]. Although our meta-analysis found no significant differences in complication rates or pain scores between uniportal and biportal approaches, such uniportal advancements may further shorten operative time and reduce intraoperative challenges for experienced surgeons. Future studies should investigate whether these design modifications translate into tangible improvements in outcomes and perioperative metrics.
From a workflow standpoint, uniportal endoscopy generally requires fewer instruments and a simpler setup, streamlining operating room processes and reducing turnover time [15]. By contrast, the biportal technique, while offering enhanced visualization and instrument flexibility, often necessitates more extensive fluid management, a larger instrument set, and longer setup times, which may prolong operative time and LOS in elderly or comorbid patients [43,44]. Nevertheless, evidence suggests that both approaches support early mobilization and short hospital stays, and differences in operative time are not always clinically significant [28,45].
Economically, cost structures also differ. The uniportal platform requires a dedicated high-definition endoscope and specialized instruments that are not interchangeable with standard MIS trays, incurring substantial upfront and maintenance costs. The biportal approach can leverage existing arthroscopy towers and conventional spinal instruments, potentially lowering initial investment, but it may also require more elaborate fluid management systems and dual monitors, increasing infrastructure and setup expenses. Comparative cost analyses between uniportal and biportal systems remain limited, and further research is necessary to establish their relative cost-effectiveness in diverse healthcare settings [42,46–48].
Strengths and limitations
This meta-analysis has several limitations, primarily reflecting the quality of the available literature. Most included studies were retrospective, and no randomized controlled trials were identified, limiting the strength of causal inference. Variability in the definitions and techniques of uniportal and biportal endoscopic surgery, as well as inconsistent follow-up schedules, may have affected comparability. Outcomes such as operative time and blood loss could also have been influenced by surgeon experience and surgical corridor (e.g., transforaminal vs. interlaminar), which were not stratified in our analysis [49–52]. The severity of disc herniation or stenosis was likewise not explored; as detailed data were inconsistently reported. Additionally, restricting inclusion to English-language publications may have led to the omission of relevant non-English studies.
Although the Newcastle-Ottawa Scale was used to assess methodological quality, publication bias was not formally evaluated. The limited number of eligible studies precluded meaningful funnel-plot or statistical testing, but the potential for publication bias remains and may have favored studies with positive or significant findings.
Heterogeneity among the included studies was anticipated, given differences in design, surgical technique, and patient populations. This is a common challenge in meta-analyses of observational or nonrandomized data. We formally assessed heterogeneity using Cochran’s Q-test and I2 statistics, which confirmed heterogeneity in outcomes. Such heterogeneity likely reflects institutional differences in clinical protocols, surgeon expertise, and patient selection criteria. Nonetheless, each included study employed a comparative design, analyzing biportal and uniportal procedures within the same cohort, which likely minimized within-study confounding by balancing baseline characteristics such as age, sex, and disease severity. A random-effects model was therefore used to incorporate both within-study error and between-study variation, strengthening the robustness and generalizability of our pooled estimates.
Another limitation was the concentration of data sources: eight of the 11 studies were conducted in the same country. Differences in discharge protocols, hospital resources, and surgeon training models across healthcare systems may influence perioperative outcomes such as operative time and LOS, thereby limiting external validity. Future multicenter and multinational comparative studies are needed to enhance generalizability.
Corridor equivalence was also inconsistent across studies. In some discectomy studies, the uniportal approach was transforaminal while the biportal approach was interlaminar, which may partly explain differences in operative time and LOS. Only a subset of studies compared both techniques via the same interlaminar corridor, and none directly compared transforaminal uniportal with biportal approaches. Future research directly comparing uniportal and biportal procedures performed through identical corridors is necessary to isolate the effect of portal number independent of surgical approach.
Despite these limitations, the study has notable strengths. Although randomized controlled trials were unavailable, the included studies achieved high NOS scores and demonstrated consistent findings. Potential bias was minimized through rigorous inclusion and exclusion criteria, an extensive literature search, and independent data extraction. To our knowledge, this is the first comprehensive systematic review and meta-analysis comparing uniportal versus biportal discectomy and laminectomy. Large, multicenter randomized controlled trials are needed to validate these findings and inform evidence-based clinical recommendations.
Conclusions
This meta-analysis provides a comprehensive comparison of biportal and uniportal endoscopic decompression for LDD. Both approaches achieved comparable postoperative outcomes in terms of VAS scores for back and leg pain. Although the biportal technique was associated with significantly lower ODI at 1–3 months and at final follow-up, this difference did not exceed the MCID, and its clinical relevance remains uncertain. On subgroup analysis, uniportal discectomy showed an association with a significantly shorter LOS and reduced operative time compared to biportal discectomy, suggesting potential benefits in terms of recovery time and surgical efficiency; however, the clinical significance of these modest differences remains uncertain. Large multicenter randomized controlled trials directly comparing uniportal and biportal endoscopic spine surgery in the context of LDD can provide more definitive evidence.
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