Degenerative lumbar spondylolisthesis (DLS) is a prevalent spinal condition characterized by the forward slippage of a vertebral body relative to the adjacent vertebra [1,2]. DLS predominantly affects older adults and is commonly associated with central canal stenosis, leading to debilitating symptoms, including chronic low back pain, radiculopathy, and neurogenic claudication. These symptoms significantly compromise patients’ quality of life, often requiring surgical intervention when conservative treatments fail [3].

The traditional surgical management for DLS with central canal stenosis often involves decompression with or without spinal fusion. Although these approaches effectively relieve neural compression and offer stability, they are associated with certain risks, such as adjacent segment disease (ASD), prolonged recovery time, and increased operative morbidity. Furthermore, fusion surgeries can accelerate degeneration at adjacent levels, potentially requiring additional surgical interventions, particularly in older patients with limited physiological reserve [4–6]. Therefore, the need for minimally invasive surgical alternatives that provide equivalent outcomes with reduced morbidity is increasing.

Biportal endoscopic spinal surgery (BESS) has recently emerged as an innovative minimally invasive technique that addresses these concerns. Unlike conventional open surgeries, BESS utilizes two small portals, allowing for the direct visualization of the operative field and precise decompression of neural elements [7,8]. This approach minimizes disruption to the surrounding paraspinal muscles and ligamentous structures, thereby preserving segmental stability. Unilateral laminotomy for bilateral decompression (ULBD), a key technique within the BESS framework, facilitates comprehensive neural decompression through a unilateral approach, further reducing the risk of iatrogenic instability.

Although BESS has demonstrated promising results in various spinal pathologies, limited evidence shows the efficacy and safety in treating low-grade DLS with central canal stenosis. The existing literature predominantly focuses on other minimally invasive spinal surgical techniques, and few studies have evaluated the potential advantages of the biportal approach. This study aimed to bridge this gap by providing a detailed analysis of the clinical and radiological outcomes following ULBD via BESS in patients with low-grade DLS.

In this retrospective observational study, we hypothesized that ULBD with BESS offers significant clinical improvement and maintains spinal stability, challenging the conventional paradigm that fusion is needed for managing symptomatic DLS. By analyzing patient-reported outcomes, functional scores, and radiological parameters, this study aimed to contribute to the growing body of evidence supporting minimally invasive spine surgery, thereby promoting a shift toward less invasive yet effective surgical options for spinal disorders.

BESS is a minimally invasive surgery, and this study provides evidence supporting the efficacy and safety of BESS with ULBD in treating DLS in degenerative spinal disease [15,16]. The findings demonstrate that BESS with ULBD yields significant improvements in pain relief, functional outcomes, and patient satisfaction while maintaining spinal stability, a critical factor when considering minimally invasive alternatives to traditional fusion-based approaches.

The clinical improvements corresponded with the previously reported outcomes of endoscopic spine surgery. Specifically, pain significantly reduced, as indicated by the VAS scores, where back pain decreased from 3.8±2.4 preoperatively to 1.9±2.0 postoperatively, and leg pain improved from 6.4±1.8 to 2.3±2.0. Moreover, the ODI scores reflected substantial enhancement in functional capacity, reducing from a preoperative mean of 48.9±15.7 to 23.1±17.5 postoperatively. These data highlight the potential of BESS to ameliorate pain and improve the quality of life significantly, corroborating the efficacy of minimally invasive spine techniques reported in other studies.

The advantages of BESS can be attributed to its unique approach, which minimizes the disruption to the paraspinal musculature and preserves the ligamentous and bony structures that are essential for spinal stability [17,18]. In our cohort, radiological outcomes showed stable sagittal translation from preoperative to final follow-up, with no significant difference observed (5.25±4.6 mm preoperatively versus 5.31±7.2 mm postoperatively, p=0.78). This preservation of stability is notable because it contrasts with conventional decompression methods that can potentially compromise structural integrity and necessitate additional fusion procedures. These findings indicate the ability of BESS to effectively decompress neural elements while minimizing iatrogenic instability as a primary concern in more extensive open surgeries [18]. The possibility of iatrogenic instability and residual low back pain in this study indicated that no cases of iatrogenic instability were observed during the follow-up period, as evidenced by stable sagittal translation (5.25±4.6 mm preoperatively versus 5.31±7.2 mm postoperatively, p=0.78) and sagittal angulation (4.2°±1.1° preoperatively versus 4.3°±1.3° postoperatively, p=0.81). These results could reflect the effectiveness of BESS in preserving posterior structures, such as the facet joints and ligamentum flavum, and minimizing destabilization, even in cases requiring extensive decompression. Although the progression of instability is possible in DLS because of the natural disease course, our findings suggest that BESS does not exacerbate this process. Significant improvements in low back pain were observed, with mean VAS scores decreasing from 3.8±2.4 preoperatively to 1.9±2.0 at the final follow-up (p<0.05). However, in some cases, residual low back pain could cause degenerative changes or paraspinal muscle dysfunction rather than instability because our radiological evaluations showed no significant biomechanical compromise. Further studies utilizing advanced biomechanical assessment methods and longer follow-up periods could provide deeper insights into the potential contributors to the residual symptoms and long-term stability of BESS.

The technical approach utilized in BESS, which employs two small portals for the endoscope and surgical instruments, offers several distinct benefits. In this study, the mean estimated blood loss was relatively low at 51±5.3 mL, and the mean operative time was brief, averaging 62±3.8 minutes. These parameters, coupled with the minimal tissue disruption inherent to BESS, likely contributed to the reduced postoperative recovery time, with a median hospital stay of only 10 days (range, 6–13 days). Although the median hospital stay in our cohort was 10 days, a significant outlier was observed, with one patient requiring prolonged hospitalization of 13 days because of localized wound pain. This case highlights the importance of vigilant postoperative care and early intervention in complication management, particularly in patients with comorbidities or advanced age. Future studies with larger cohorts are warranted to better understand and mitigate the factors that contribute to prolonged hospitalization in minimally invasive spine surgery. The prevalence at L3–4 compared with L5–S1 to a widely reported higher prevalence of DLS at the L5–S1 level. In this study, we observed a high number of cases at the L3–4 level. This discrepancy may reflect the unique patient demographics in our cohort, regional anatomical variations, or differences in lifestyle factors that predispose individuals to spondylolisthesis at the L3–4 level. For instance, occupations or activities of daily activities involving repetitive flexion–extension movements or axial loading may disproportionately affect the L3–4 segment. In addition, the imaging and diagnostic practices at our institution contributed to this finding. Such metrics reflect the potential for BESS to facilitate shorter operative times, reduced intraoperative blood loss, and expedited patient recovery—which are all consistent with the advantages generally ascribed to a minimally invasive surgical approach [19,20].

This study presented a low incidence of postoperative complications. No major complications, such as dural tears, infections, or permanent neurological deficits, were observed. Minor complications were limited to transient leg weakness in three patients (4.4%), which resolved without intervention. Importantly, no reoperations, readmissions, or ASD were observed during follow-up. These findings underscore the favorable safety profile of BESS, particularly when compared with open decompression and fusion, which are often associated with higher complication rates and more substantial postoperative morbidity [21,22].

This cohort had a high level of patient satisfaction, as assessed by the modified Macnab criteria, and 70.5% of the patients reported their outcomes as either “excellent” or “good.” Given that patient satisfaction is a critical indicator of surgical success, this metric indicates that BESS aligns well with patient expectations regarding pain relief and functional recovery. The combination of minimal postoperative morbidity, substantial symptom relief, and functional capacity preservation further supports the clinical utility of BESS in managing low-grade DLS with spinal stenosis [12].

The long-term stability of BESS is a notable advantage compared with traditional fusion surgeries. BESS minimizes the disruption to the paraspinal musculature, ligamentum flavum, and posterior bony structures, reducing the ASD risk, which is often associated with fusion-based approaches. Our findings demonstrate significant changes in sagittal translation (5.25±4.6 mm preoperatively versus 5.31±7.2 mm at the final follow-up, p=0.78) over a median follow-up of 1,052 days, and align with existing literature. Choi et al. [17,20] and Ahn et al. [18] have reported that preserving posterior structures through minimally invasive techniques such as BESS contributes to maintaining segmental stability while achieving adequate neural decompression. Furthermore, evidence from the studies by Eun et al. [15] and Jitpakdee et al. [7] supports the clinical utility of BESS in preventing instability, even in multilevel stenosis cases. These findings underline that BESS effectively alleviates symptoms in low-grade DLS without compromising spinal stability, making it a viable alternative to traditional fusion, particularly in older patients or those with physiologically compromised status. Further studies with larger cohorts and extended follow-ups are warranted to confirm these promising outcomes.

This study employed a retrospective study design and had a possibility of selection bias. The relatively single-center design may also limit the generalizability of our findings. Although our follow-up period was sufficiently long for medium-term outcomes, further studies with extended follow-up durations are needed to evaluate potential late-onset complications, such as delayed instability or recurrent stenosis. Finally, this study focused on patients with low-grade DLS; thus, the applicability of BESS in high-grade spondylolisthesis or multilevel stenosis warrants further investigation. BESS with ULBD is an effective, minimally invasive approach for managing low-grade DLS with central canal stenosis. The significant clinical improvements, combined with the preserved spinal stability and a low complication rate, highlight the potential of BESS as an alternative to more invasive fusion surgeries. Given the increasing interest in minimally invasive spine surgery, BESS offers a promising avenue for improving patient outcomes while minimizing the risks associated with conventional surgical interventions. Further studies, particularly prospective randomized controlled trials, are recommended to substantiate these findings and clarify the long-term role of BESS in treating degenerative lumbar pathologies.

BESS with ULBD is a promising minimally invasive alternative for the treatment of stable low-grade DLS with central canal stenosis. This technique offers significant symptom relief, improves functional outcomes, and maintains spinal stability with minimal complications. Given the increasing adoption of minimally invasive spine surgery, BESS may play a pivotal role in the surgical management of lumbar degenerative conditions, ultimately enhancing patient care and quality of life.