Modified Transfacet Full-Endoscopic Lumbar Interbody Fusion: 1-Year Clinical and Radiological Outcomes

Article information

J Minim Invasive Spine Surg Tech. 2026;11(Suppl 2):S262-S272

Publication date (electronic) : 2026 July 31

doi : https://doi.org/10.21182/jmisst.2025.03027

Abhirat Suebsing¹, Siravich Suvithayasiri^2,3, Akarawit Asawasaksakul⁴, Khananut Jaruwanneechai^,1

¹Department of Orthopedics, Warinchamrab Hospital, Ubon Ratchathani, Thailand

²Bone and Joint Excellence Center, Thonburi Hospital, Bangkok, Thailand

³Department of Orthopedics, Chulabhorn Hospital, Chulabhorn Royal Academy, Bangkok, Thailand

⁴Spine Clinic, Department of Orthopedics, Ramkhamhaeng Hospital, Bangkok, Thailand

Corresponding Author: Khananut Jaruwanneechai Department of Orthopedics, Warinchamrab Hospital, 46 M6 Srisaket Road. Kamnamsab, Warinchamrab, Ubon Ratchathani, Thailand, 34190 Email: j.khananut@gmail.com

Received 2025 November 30; Revised 2026 March 18; Accepted 2026 March 22.

Abstract

INTRODUCTION

Lumbar degenerative disc disease, spinal stenosis, and spondylolisthesis are leading causes of chronic low back and leg pain, contributing to substantial disability, reduced quality of life, and high socioeconomic burden due to healthcare utilization and loss of productivity [1,2]. When conservative management fails, lumbar interbody fusion is a well-established surgical option to restore segmental stability, correct deformity, and decompress neural elements [3,4]. Over the past 2 decades, surgical trends have shifted toward tissue-sparing approaches that aim to reduce iatrogenic muscle damage. In this context, endoscopic spine surgery has evolved from simple decompression procedures to more complex techniques, including full-endoscopic lumbar interbody fusion (FE-LIF), which seeks to combine adequate neural decompression and spinal stabilization with minimal soft tissue trauma [5,6].

Minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) using tubular retractors or percutaneous instrumentation has been widely adopted and associated with reduced blood loss, shorter hospital stays, and faster recovery compared to open techniques, while providing comparable fusion and clinical outcomes [7,8]. However, MIS-TLIF still requires retraction of the paraspinal musculature, which may lead to persistent muscle ischemia, denervation, postoperative pain, and limited visualization of the contralateral canal and foraminal regions. FE-LIF techniques have been introduced to further minimize approach-related morbidity [9,10]. Early reports suggest that FE-LIF can achieve satisfactory decompression and fusion with smaller incisions, less postoperative pain, and shorter hospital stays [11,12]. Nevertheless, FE-LIF remains technically demanding, with challenges including a limited working space, complex instrumentation, a steep learning curve, and concerns regarding optimal cage placement and endplate preparation [13,14]. Therefore, the full-endoscopic modified transfacet approach has been proposed to access the disc space through partial removal of the facet joint, providing more direct route to the intervertebral disc while preserving much of the posterior ligamentous complex [15]. This approach aims to combine direct decompression, discectomy, and cage insertion through a focused bony window, potentially improving visualization and working angles compared with classical transforaminal approaches via Kambin triangle.

This study aims to report of 1-year clinical and radiological outcomes of a modified transfacet FE-LIF technique in patients with single-level degenerative lumbar pathology treated by a single surgeon. By providing early data on pain relief, functional outcome improvement, fusion rates, and complications, this study seeks to clarify the potential role of the modified transfacet FE-LIF technique within the spectrum of minimally invasive lumbar fusion options and to inform the design of future comparative or prospective studies.

MATERIALS AND METHODS

This retrospective cohort study included 41 patients who underwent single-level modified transfacet full-endoscopic lumbar interbody fusion (FE-LIF) between January 2023 and June 2024. All procedures were performed in a single tertiary hospital by a single spine surgeon. The study protocol was approved by the institutional review board of Ubon Ratchathani Provincial Health Office (SSJ.UB 04.038).

Patients were identified from the institutional operative database. Eligible patients met the following inclusion criteria: (1) age ≥ 18 years, (2) symptomatic degenerative lumbar pathology treated with a single-level modified transfacet FE-LIF approach, (3) radiographic grades I–II spondylolisthesis according to the Meyerding classification, and (4) availability of a minimum of 1-year clinical and radiological follow-up. Exclusion criteria were prior lumbar fusion surgery, active spinal infection, and primary or secondary spinal tumor. Baseline demographic and clinical variables, including age, sex, body mass index, comorbidities, index operated level, and preoperative radiographic parameters, were collected from medical records.

1. Surgical Technique

All procedures were performed under general anesthesia with the patient in the prone position on a radiolucent table. The modified transfacet FE-LIF technique followed the method previously described by Asawasaksakul et al. [15], with minor adjustments to the trajectory and working corridor tailored to the patient’s anatomy (Figure 1). Under fluoroscopic guidance, a Jamshidi needle was introduced to the middle of the facet joint line on the symptomatic side, followed by guidewire placement, serial dilation, and docking of a circular working sleeve on the dorsal surface of the facet joint.

Figure 1.

Intraoperative sequence of the modified transfacet full-endoscopic lumbar interbody fusion procedure. (A) Anteroposterior (AP) view showing the initial placement of Jamshidi needles in the pedicles. (B and C) Lateral and AP views demonstrating docking of the circular working sleeve onto the target facet joint. Note the simultaneous placement of contralateral percutaneous pedicle screws. (D) Lateral fluoroscopic view obtained during the endoscopic phase, showing instruments used for keyhole facetectomy, discectomy, and endplate preparation through the working cannula. (E) Preparation of the bone graft mixture, consisting of autologous bone and demineralized bone matrix, loaded into delivery syringes. (F) Lateral view showing insertion of a polyetheretherketone cage using a cage glider system. (G and H) Final postoperative lateral and AP fluoroscopic views confirming optimal positioning of the interbody cage and bilateral percutaneous pedicle screw fixation.

A keyhole facetectomy was performed along the facet trajectory using endoscopic burrs and osteotome to collect autologous bone graft, while preserving the lateral and medial facet walls to protect the exiting and traversing nerve roots (Figure 2). After entering the disc space, endoscopic discectomy and endplate preparation were performed using pituitary rongeur, curette, radiofrequency probe, and a high-speed burr. Cartilaginous endplate was removed carefully while preserving subchondral bone to reduce the risk of cage subsidence. A polyetheretherketone cage filled with a mixture of local autograft bone obtained from the facetectomy and demineralized bone matrix was introduced through the working sleeve and positioned in the intervertebral space under endoscopic visualization and biplanar fluoroscopy. The use of the cage glider system has several benefits, including the smooth cage insertion into the position, protection of the endplates during insertion of the cage, and allowance of serial dilation to restore the intervertebral disc height without the need for contralateral facet release (Figure 3). Additional decompression, such as removal of hypertrophic ligamentum flavum or undercutting of the lamina, was carried out as needed to achieve sufficient neural decompression. Following cage placement, bilateral percutaneous pedicle screws were inserted under fluoroscopic guidance, and reduction maneuvers were performed when appropriate in patients with spondylolisthesis.

Figure 2.

Endoscopic view demonstrating keyhole facetectomy performed using the modified transfacet approach. Partial resection of the inferior articular process and superior articular process is performed while preserving a thin bony shell of the facet joint. The preserved medial bony shell functions as a protective barrier for the dural sac, whereas the lateral cortical shell shields the exiting nerve root. This keyhole corridor provides a controlled working channel to the intervertebral disc space, allowing safe discectomy, endplate preparation, and subsequent interbody cage insertion along the same trajectory.

Figure 3.

Intraoperative fluoroscopic sequence demonstrating the transition from the endoscopic working channel to the cage glider system for endplate protection and interbody cage insertion. The endoscope is first exchanged for the cage glider to protect the vertebral endplates. Sequential disc space preparation is then performed using serial disc shavers for gradual dilation and disc removal. Finally, a polyetheretherketone interbody cage is advanced through the cage glider and positioned within the disc space to restore disc height and provide interbody support.

RESULTS

The study cohort comprised 41 patients undergoing single-level modified transfacet FE-LIF, with a mean age of 61.9±6.3 years and a predominance of female patients (82.9%). The pathology was primarily degenerative spondylolisthesis (grade I in 78.0% of cases), most frequently affecting the L4–5 level (65.9%). Perioperative metrics reflected the minimally invasive nature of the procedure; the mean operative time was 143.9±12.0 minutes with minimal estimated blood loss (91.3±22.6 mL) and negligible postoperative drain output. Consequently, recovery was rapid, allowing for a mean hospital length of stay only 3.1±0.8 days (Table 1).

Table 1.

Patient demographics and operative data (N=41)

Regarding clinical pain outcomes, patients experienced immediate and sustained symptomatic relief. VAS scores for both back and leg pain demonstrated statistically significant improvements since the first postoperative day (p<0.001). This favorable trajectory continued throughout the study period; by the 12-month follow-up, the mean VAS back score had decreased to 1.05±0.55 (an 86.5% reduction), and the mean VAS leg score had decreased to 0.85±0.53 (an 89.2% reduction) compared to preoperative baselines (Table 2).

Table 2.

Visual analogue score (VAS) results for pain in the back and leg

Functional recovery, assessed via the ODI, paralleled to the improvements of pain scores. The mean ODI improved substantially from a severe disability level of 67.61%±2.87% preoperatively to 10.29%±2.08% at the final follow-up. This represented an overall 84.8% reduction in disability burden. Statistically significant improvements were confirmed at every postoperative time point (p<0.001), indicating a consistent and progressive return to daily activities for the cohort (Table 3).

Table 3.

Oswestry Disability Index (ODI) results

Radiological assessment at 1 year confirmed successful spinal stabilization, with a solid fusion rate (Bridwell grade I or II) achieved in 95.1% of patients. Specifically, complete fusion with trabecular remodeling (grade I) was observed in 23 cases (56.1%). Incomplete fusion (grade III) was noted in only 2 patients (4.9%), both of whom presented with significant systemic comorbidities (end-stage renal disease and thalassemia), yet neither exhibited graft collapse. The procedure demonstrated a high safety profile, with no major perioperative complications, infections, or implant failures record during the follow-up period (Table 4). Illustrative cases demonstrating clinical and radiographic outcomes at the 1-year follow-up are presented in Figures 4–6.

Table 4.

Fusion status stratified by the Bridwell classification at the 12-month follow-up

Figure 4.

Illustrative case of a 67-year-old male patient treated using the modified transfacet full-endoscopic lumbar interbody fusion technique. (A) Preoperative lateral radiograph demonstrating Meyerding grade I degenerative spondylolisthesis at L4–5. (B) Postoperative day 1 lateral radiograph showing successful reduction of the spondylolisthesis and restoration of spinal alignment. (C) Lateral radiograph at the 1-year follow-up demonstrating maintenance of reduction and construct stability. (D) Midsagittal computed tomography (CT) reconstruction at 1 year confirming solid interbody fusion with trabecular bone bridging through the cage. (E) Coronal CT reconstruction further confirming the fusion mass and implant integration.

Figure 5.

Illustrative case of a 72-year-old male patient with single-level degenerative pathology. (A) Preoperative lateral radiograph demonstrating Meyerding grade I spondylolisthesis at L4–5. (B) Postoperative lateral radiograph obtained on day 1, showing successful reduction of the spondylolisthesis and appropriate instrumentation placement. (C) Lateral radiograph at the 1-year follow-up confirming maintained spinal alignment and construct stability. (D) Midsagittal computed tomography (CT) reconstruction at 1 year demonstrating solid interbody fusion with continuous trabecular bone bridging through the cage. (E) Coronal CT reconstruction further confirms a successful fusion mass between the vertebral bodies.

Figure 6.

Illustrative case of a 59-year-old male patient presenting with high-grade pathology. (A) Preoperative lateral radiograph demonstrating Meyerding grade II degenerative spondylolisthesis at L4–5. (B) Postoperative lateral radiograph obtained on day 1, demonstrating significant reduction of the slip and restoration of sagittal alignment. (C) Lateral radiograph at the 1-year follow-up showing maintained reduction and stable instrumentation. (D) Midsagittal computed tomography (CT) reconstruction at 1 year confirming solid interbody fusion with robust trabecular bone bridging. (E) Coronal CT reconstruction confirming integration of the fusion mass between the vertebral bodies.

DISCUSSION

The present study substantiates the clinical efficacy and safety of FE-LIF utilizing a modified transfacet approach for the treatment of single-level degenerative lumbar pathology. Our findings demonstrate that this technique yields rapid and sustained symptomatic relief, with significant reductions in ODI and pain VAS scores observable as early as the first postoperative day. At the 1-year follow-up, patients exhibited a marked functional recovery, evidenced by an 84.8% reduction in disability burden and near-complete resolution of back and leg pain. Furthermore, the procedure was associated with a favorable safety profile, characterized by minimal blood loss, short hospitalization, and the absence of major perioperative complications. These results corroborate the growing body of evidence suggesting that endoscopic fusion can effectively restore segmental stability while minimizing iatrogenic soft tissue trauma associated with conventional approaches. Notably, the preponderance of female patients (82.9%) in this cohort reflects the established epidemiological pattern of degenerative spondylolisthesis, which was the primary pathology treated in 78.0% of our cases. This demographic distribution is consistent with clinical literature reporting that degenerative spondylolisthesis is 4 to 6 times more prevalent in women than in men, likely due to differences in pelvic morphology and hormonal factors [17]. Consequently, the gender ratio in our series represents a reflection of the natural disease incidence rather than a specific selection bias.

Our clinical outcomes compare favorably with established benchmarks in the FE-LIF literature, with some metrics demonstrating superior results. Previous studies on endoscopic fusion typically reported operative times of 120 to 200 minutes and estimated blood loss of 50 to 200 mL [18]. Our cohort’s mean operative time of 143.9 minutes and blood loss of 91.3 mL fall well within these efficient ranges, suggesting that the modified transfacet approach does not add unnecessary surgical complexity. Moreover, while contemporary MIS-TLIF series generally report 60%–80% improvements in pain scores [19], our series achieved an 86.5% reduction in back pain and an 89.2% reduction in leg pain. This magnitude of improvement supports the premise that the ultraminimally invasive nature of full-endoscopic surgery may enhance early recovery trajectories without compromising midterm efficacy.

Radiologically, the achievement of a solid fusion is the paramount goal of interbody fusion surgery. We observed a fusion rate of 95.1% (Bridwell grade I–II) at 12 months, which lied at the upper end of the 85%–95% range reported in comparable FE-LIF and biportal endoscopic series [14]. We hypothesize that the modified transfacet approach contributes to this high union rate by facilitating the consistent harvest of local autogenous bone graft from the partial facetectomy, which typically yields 2–3 mL of graft material and biological profile superior to synthetic substitutes alone. Notably, the only 2 cases of incomplete fusion (Bridwell grade III) in this cohort occurred in patients with severe systemic comorbidities: end-stage renal disease on hemodialysis and thalassemia. These conditions are well-documented risk factors for impaired bone metabolism and delayed healing [20]. The occurrence of nonunion in these medically complex patients underscores the importance of rigorous patient selection and metabolic optimization, even when employing tissue-sparing endoscopic techniques.

In the evolving landscape of endoscopic spine surgery, it is crucial to position FE-LIF relative to the biportal endoscopic lumbar interbody fusion procedure (BE-LIF/unilateral biportal endoscopic lumbar interbody fusion [UBE-LIF]). While recent systematic reviews indicate that biportal techniques achieve excellent fusion rates and clinical outcomes comparable to our findings [21], the uniportal FE-LIF approach offers distinct advantages in terms of reduced invasiveness, requiring only a single small incision and potentially lower fluid infusion pressures. However, UBE is often cited as having a flatter learning curve due to the separation of optical and working channels [22]. Our results suggest that the modified transfacet FE-LIF technique can bridge this gap. By achieving clinical outcomes numerically comparable to those reported in published UBE series, this technique demonstrates that a single-port approach can be just as practical when the surgical corridor is optimized.

From a technical perspective, the steep learning curve remains a primary barrier to the widespread adoption of FE-LIF. While traditional trans-Kambin or posterolateral approaches are effective, they often involve a steep learning curve and risks of exiting nerve root irritation within the narrow working triangle [23,24]. In contrast, the modified transfacet FE-LIF utilizes familiar posterior bony landmarks to provide a more intuitive and reproducible trajectory. By docking on the facet joint plane, the surgeon can create a working corridor that protects the neural structures within a bony shell, potentially facilitating a safer transition for surgeons accustomed to tubular or open procedures. The absence of major complications and the consistency of operative times in our series suggest that this approach offers a stable platform for surgeons to master endoscopic fusion with a reasonable safety margin. Despite these advantages, the technique has specific drawbacks. The focused nature of the keyhole facetectomy may limit the volume of harvested local autograft compared to more extensive resections. Consequently, in patients requiring significant graft material, surgeons may need to perform additional lamina undercutting or rely more heavily on bone graft substitutes to ensure adequate biological scaffolding for fusion. Nevertheless, a comparison table between the conventional trans-Kambin and the modified transfacet approach is demonstrated in Table 5.

Table 5.

Comparison between the conventional trans-Kambin and the modified transfacet approach for full-endoscopic lumbar interbody fusion

This study is not without limitations. First, the retrospective design and relatively small sample size (N=41) from a single center may limit the generalizability of the findings. Second, the absence of a direct control group, such as MIS-TLIF or UBE-LIF, precludes head-to-head statistical comparisons, although our data compares favorably with historical controls. Third, the 1-year follow-up period, while sufficient for assessing fusion and early clinical success, limits our ability to evaluate long-term outcomes such as adjacent segment disease. Fourth, the radiological assessment in this study was primarily centered on evaluating interbody fusion status via the Bridwell criteria. Consequently, other comprehensive radiological parameters, such as disc height restoration, segmental lordosis, cage subsidence, and specific slip reduction metrics, were not routinely collected or analyzed in this retrospective dataset. While these factors are vital for understanding the impact of the modified transfacet FE-LIF on sagittal alignment and biomechanical stability, they were beyond the primary scope of this study, which focused on the feasibility, safety, and clinical effectiveness of the technique. Future prospective studies incorporating these detailed radiographic parameters are warranted to more fully define the long-term structural benefits and potential limitations of this modified approach. Fifth, the retrospective design of this study precluded a systematic quantitative analysis of sagittal alignment parameters, such as segmental lordosis, interscrew angle changes, and specific measurements of cage subsidence. While our illustrative cases demonstrate successful stabilization and solid interbody fusion, the absence of cohort-wide quantitative data limits our ability to definitively assess the procedure’s impact on long-term sagittal spinopelvic balance or construct stability. Future prospective research incorporating standardized radiographic protocols to investigate these critical biomechanical outcomes is necessary to more fully define the clinical role of this technique. Despite these limitations, this study provides valuable midterm data confirming that the modified transfacet FE-LIF is a safe, effective, and reproducible technique. Future research should focus on prospective, multicenter randomized controlled trials to definitively establish the superiority or noninferiority of this approach compared to other minimally invasive fusion strategies.

CONCLUSION

The modified transfacet FE-LIF technique represents a safe and effective evolution in the minimally invasive management of single-level degenerative lumbar pathology. Our 1-year outcomes confirm that this approach reliably achieves the dual goals of neural decompression and spinal stabilization, delivering substantial symptomatic relief and functional recovery that parallel established minimally invasive benchmarks. By utilizing a facet-based working corridor, this technique addresses the technical challenges traditionally associated with endoscopic fusion, offering a reproducible anatomical trajectory that may facilitate the learning curve for surgeons transitioning from tubular or open procedures. Furthermore, the high rate of solid fusion observed in this cohort validates the biological efficacy of the procedure when accompanied by meticulous endplate preparation and autologous grafting. However, given the retrospective design without a control cohort and the single-surgeon nature of this series, these findings should be interpreted as early observational outcomes rather than definitive comparative evidence. As such, our results emphasize the technique's feasibility and safety while establishing a clinical foundation for future prospective, controlled trials. Long-term, randomized comparative studies are warranted to fully define its position relative to other fusion strategies. The modified transfacet FE-LIF stands as a promising, ultraminimally invasive alternative surgery that minimizes surgical morbidity without compromising clinical or radiological success. Furthermore, we recognize that long-term success requires a balance between reducing surgical invasiveness and achieving robust biomechanical reconstruction; therefore, the impact of this technique on segmental lordosis and adjacent segment health warrants further investigation in high-quality prospective trials.

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