Comparison of functional and radiographic outcomes between two-level oblique lumbar interbody fusion and minimally invasive transforaminal lumbar interbody fusion in degenerative lumbar disease: a retrospective study in Thailand

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Asian Spine J. 2026;.asj.2025.0521

Publication date (electronic) : 2026 April 6

doi : https://doi.org/10.31616/asj.2025.0521

Worawat Limthongkul^1,2, Kittitouch Jirakiat^1,2, Maruay Tanayavong^1,2, Surachat Jaroenwareekul^1,2, Wicharn Yingsakmongkol^1,2, Weerasak Singhatanadgige^1,2, Vit Kotheeranurak^1,2

¹Department of Orthopaedics, King Chulalongkorn Memorial Hospital, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand

²Center of Excellence in Biomechanics and Innovative Spine Surgery, Chulalongkorn University, Bangkok, Thailand

Corresponding author: Vit Kotheeranurak, Department of Orthopaedics, King Chulalongkorn Memorial Hospital, Faculty of Medicine, Chulalongkorn University, 1873 Rama IV Road, Pathumwan, Bangkok, 10330 Thailand, Tel: +66-2-256-4230, Fax: +66-22-256-4510, E-mail: spinechula@gmail.com

Received 2025 September 2; Revised 2025 October 2; Accepted 2025 October 14.

Abstract

Introduction

Although conventional open posterior fusion techniques yield satisfactory outcomes in degenerative lumbar diseases, they are often associated with complications such as posterior tension band disruption, significant blood loss, and prolonged hospitalization [1–3]. Minimally invasive (MI) procedures have gained popularity as alternatives designed to reduce these drawbacks. MI lumbar interbody fusion has demonstrated comparable functional outcomes with fewer complications than open techniques, particularly in obese or elderly patients with multiple comorbidities [4–11].

Over the past few decades, several spinal fusion techniques employing different surgical approaches have been developed. Among these, minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) and oblique lumbar interbody fusion (OLIF) are the most widely studied. MIS-TLIF enables direct decompression of the spinal canal through a posterior approach [12,13]. In contrast, OLIF achieves indirect decompression via ligamentotaxis through vertebral body distraction, using an oblique corridor between the anterior vessels and the psoas muscle [14–16]. Both techniques are also effective in correcting deformity in the sagittal and coronal planes [17]. In single-level disease, comparative studies have shown that OLIF results in lesser blood loss and better radiographic outcomes with similar functional outcomes to MIS-TLIF [18–21].

Two-level spinal fusion is relatively common, with MIS-TLIF and OLIF together accounting for up to 20.37% of all MI spinal surgeries for lumbar degenerative disease [22]. However, technical differences in multilevel procedures may influence outcomes differently than in single-level fusion. Given the limited evidence comparing these techniques in two-level disease, this study aimed to compare the clinical and radiographic outcomes of MIS-TLIF and OLIF. We hypothesized that OLIF would provide superior radiographic correction, while both procedures would yield comparable patient-reported outcome measures.

Materials and Methods

Results

A total of 40 patients were included in the analysis, comprising 20 who underwent OLIF and 20 who underwent MIS-TLIF. The mean age was 67.75±9.95 years in the OLIF group and 68.75±7.28 years in the MIS-TLIF group. Baseline demographic characteristics, preoperative clinical variables, and radiographic parameters were comparable between the two groups (Table 1).

Table 1

Demographic data

Perioperative outcomes are summarized in Table 2. There were no significant between-group differences with respect to intraoperative blood loss (115.3±17.5 mL for OLIF vs. 113.5±15.3 mL for MIS-TLIF), operative time (165.4±33.4 minutes vs. 146.9±32.9 minutes), and length of hospital stay (3.6±0.6 days vs. 3.7±0.5 days).

Table 2

Perioperative data

Functional outcomes, detailed in Table 3, showed significant improvement from baseline in both groups across all postoperative timepoints. At 1-month postoperatively, the MIS-TLIF group exhibited a greater reduction in VAS score for leg pain (mean change: −6.0 vs. −3.8; p=0.003). However, no significant differences were observed between groups for ODI, VAS back pain, or VAS leg pain at subsequent follow-ups. No intraoperative or postoperative complications were recorded in either group during the 12-month follow-up period.

Table 3

Functional outcomes

Radiographic outcomes are presented in Table 4. Both groups demonstrated significant postoperative improvement in all measured parameters, including ADH, PDH, FH, FA, SLA, LLA, CSA, and SCD. However, the OLIF group showed significantly greater improvements in several parameters: ADH restoration (mean change: 4.52 mm vs. 1.19 mm), PDH (4.66 mm vs. 1.20 mm), FH (4.29 mm vs. 1.68 mm), FA (121.20 mm² vs. 35.62 mm²), segmental lordosis (8.55° vs. 4.65°), and lumbar lordosis (9.9° vs. 5.4°) (p<0.001 for all). No significant between-group differences were found in CSA or SCD improvement.

Table 4

Radiographic outcomes

Discussion

This study demonstrated that OLIF and MIS-TLIF significantly improved functional and radiographic outcomes in patients with two-level degenerative lumbar disease. Perioperative parameters, including blood loss, operative duration, and hospital stay, were comparable between the two groups. This finding differs from results in single-level procedures, where OLIF has been associated with lower blood loss. Zhu et al. [19] reported that OLIF resulted in significantly less blood loss than MIS-TLIF (123.1±39.8 mL vs. 232.0±83.2 mL, respectively) for single-level disease, while operative time and length of hospital stay were similar between techniques. Likewise, Yingsakmongkol et al. [20] and Hung et al. [21] observed reduced intraoperative blood loss with OLIF (90.48±19.74 mL) compared with MIS-TLIF (167.32±35.93 mL). In contrast, Passias et al. [24] noted higher average blood loss (286±320 mL) in multilevel MIS procedures. In the present study, blood loss was comparable between groups for two-level fusion. The higher blood loss reported in multilevel OLIF procedures may be attributed to increased soft-tissue dissection and retraction, as described by Zhu et al. [25]. In MIS-TLIF, hemilaminectomy and medial facetectomy performed under magnification can damage posterior bony structures and paraspinal muscles, potentially leading to increased bleeding. However, the extent of blood loss and operative time in these procedures can vary depending on the surgeon’s experience [22].

Previous studies have reported that direct and indirect decompression techniques produce comparable functional recovery. In OLIF, indirect decompression is achieved by restoring FH and disc space and by reducing the thickness of the ligamentum flavum, thereby alleviating nerve root compression [14,15]. In contrast, direct decompression via the posterior approach, allowing for direct visualization of neural structures, is a key advantage of MIS-TLIF [12]. Zhu et al. [19] found that OLIF and MIS-TLIF yielded significant improvements in VAS scores for back and leg pain, while Hung et al. [21] reported similar reductions in leg pain with the two techniques. Clinical outcomes may, however, vary with preoperative symptom severity and the degree of neural compromise.

In the present study, both approaches produced significant improvement in functional scores, with no long-term difference between groups. The transiently superior leg pain relief observed in the MIS-TLIF group at 1 month likely reflects the immediate benefit of direct decompression, whereas the effect of indirect decompression may manifest more gradually. By later follow-ups, outcomes converged, consistent with findings from previous studies.

Radiographically, OLIF demonstrated greater improvement in disc and foraminal dimensions as well as sagittal alignment (SLA and LLA), likely due to the ability to insert larger interbody cages and achieve greater disc height restoration [19,21,26]. No significant difference was found in SCD or CSA, reflecting the distinct decompression mechanisms of each technique: MIS-TLIF achieves direct canal expansion by removing posterior elements, while OLIF relies on indirect decompression through ligamentotaxis and disc height restoration. These results align with the randomized controlled trial by Isaacs et al. [27].

Some limitations of this study should be acknowledged. First, its retrospective design and the small sample size may have introduced selection bias and limited statistical power to detect subtle differences. Second, the follow-up period of 12 months may not capture long-term differences in fusion rates, adjacent segment disease, or late complications. Future multicenter studies with larger cohorts and longer follow-up durations are warranted to confirm these findings and further delineate the relative advantages of each approach in multilevel degenerative disease.

Conclusions

For two-level lumbar degenerative disease, OLIF and MIS-TLIF resulted in significant improvements in patient-reported and radiographic outcomes. Although OLIF did not demonstrate a perioperative advantage in terms of blood loss, it provided superior radiographic correction, whereas MIS-TLIF offered faster short-term relief of leg pain. These findings highlight the complementary strengths of the two approaches. Larger, multicenter prospective studies with longer follow-up are required to validate these results and to guide surgical decision-making.

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