Minimally Invasive vs. Open L5-S1 Transforaminal Lumbar Interbody Fusion (TLIF): A Retrospective Comparison of Fusion Outcomes

Study Design: Single-center retrospective cohort study. Objective: To compare fusion and perioperative and clinical outcomes between minimally invasive (MIS) and open transforaminal lumbar interbody fusion (TLIF) at L5-S1. Summary of Background Data: MIS-TLIF reduces soft-tissue disruption, blood loss, and hospital stay compared with open TLIF, but may increase fluoroscopy use and limit visualization for endplate preparation; data isolating the biomechanically demanding L5-S1 level with rigorous fusion assessment are limited. Methods: Adults undergoing single-level L5-S1 TLIF from 2018-2023 were stratified by approach (MIS vs. open). Inclusion required 12-month postoperative CT and/or flexion-extension radiographs for fusion assessment. Perioperative variables, complications, reoperations, and patient-reported outcomes were compared using χ 2 or Fisher tests and t tests or Wilcoxon rank-sum tests. Results: Fifty-six patients met criteria (23 MIS, 33 open) with similar baseline demographics. Fusion rates were 91% with MIS and 73% with open TLIF ( P =0.168). MIS-TLIF had lower estimated blood loss (148 vs. 229 mL, P =0.075) and shorter length of stay (2.8 vs. 3.9 d, P =0.034), but higher fluoroscopy dose (36.8 vs. 34.0 mGy, P =0.006). Operative time, complication rates (13% vs. 36%, P =0.103), reoperation rates (17% vs. 15%, P =1.0), and 12-month categorical patient-reported back pain, leg pain, and quality-of-life outcomes were comparable between groups. Conclusions: At L5-S1, MIS-TLIF achieves fusion and clinical outcomes comparable to open TLIF while reducing blood loss and hospital stay at the cost of increased radiation exposure. These findings suggest that MIS-TLIF may offer perioperative advantages while demonstrating comparable observed fusion and clinical outcomes relative to open TLIF at L5-S1.