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

Study Design: Retrospective matched-pair study. Purpose: To compare the functional and radiographic outcomes of two-level oblique lumbar interbody fusion (OLIF) and minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) in patients with degenerative lumbar disease. Overview of Literature: Comparative studies of single-level lumbar fusion have shown that OLIF results in reduced blood loss and greater radiographic correction compared with MIS-TLIF, while achieving comparable functional outcomes. However, evidence directly comparing these two techniques in multilevel disease remains limited. Methods: Among 448 eligible patients operated between 2020 and 2022 (122 OLIF and 326 MIS-TLIF), 40 patients (20 per group) were selected using propensity score matching. Functional outcomes were assessed using the Visual Analog Scale (VAS) for back and leg pain and the Oswestry Disability Index (ODI) at baseline and 1, 3, 6, and 12 months. Perioperative parameters (blood loss, operative time, and hospital stay) and radiographic measures (disc height, foraminal height and area, segmental and lumbar lordosis, cross-sectional area [CSA], and spinal canal diameter [SCD]) were compared. Results: Both groups showed significant improvements in ODI and VAS scores at all follow-ups. The MIS-TLIF group demonstrated greater leg pain reduction at 1 month (mean VAS score change -6.0 vs. -3.8, p=0.003), but no significant differences were observed thereafter. Perioperative outcomes were comparable between groups. The OLIF group exhibited significantly greater improvements in anterior and posterior disc height, foraminal height, foraminal area, segmental lordosis, and lumbar lordosis (p<0.001). No between-group differences were found in CSA or SCD. No complications were reported during the 12-month follow-up. Conclusions: OLIF and MIS-TLIF effectively improved pain, disability, and radiographic parameters in two-level lumbar degenerative disease. MIS-TLIF offered faster short-term leg pain relief, whereas OLIF achieved superior radiographic correction. Larger prospective studies are required to validate these findings and inform surgical decision-making.