Outcomes after MI-TLIF without bone morphogenetic protein: a retrospective study.

Abstract

Objective: Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) is widely used to treat degenerative lumbar spine conditions, offering reduced tissue trauma, faster recovery, and lower complication rates compared to those with open TLIF. Recombinant human bone morphogenetic protein 2 (rhBMP-2) can enhance fusion and is often used in the interbody space in minimally invasive fusions because of the limited posterolateral surface area for arthrodesis, but it is associated with higher costs and an increased risk of complications. Authors of this study evaluated the outcomes of MI-TLIF performed without bone morphogenetic protein (BMP), focusing on fusion and complication rates.

Methods: The authors retrospectively reviewed the records of patients who underwent MI-TLIF without BMP at a single academic center between January 2012 and August 2023. Eligible patients were those with degenerative disc disease, lumbar stenosis spondylolisthesis, recurrent disc herniation, or pars defect at 1-2 lumbosacral levels that had been refractory to standard nonsurgical therapy. Demographic, surgical, and clinical data as well as perioperative, radiographic, and patient-reported outcomes were analyzed.

Results: Three hundred eight patients, 54.5% male, with a median age of 65 years were included in the study. Most procedures were single-level MI-TLIF, primarily at L4-5. The median operative time was 160.5 minutes, estimated blood loss was 50 mL, and hospital stay was 3 days. At a median follow-up of 56.2 months, the radiographic fusion rate was 91.9%. Adjacent segment disease occurred in 6.2% of patients. Patient-Reported Outcome Measurement Information System (PROMIS) short form scores demonstrated clinically meaningful early and midterm improvement across all domains. Physical Function scores increased from baseline (35.12 ± 5.92) to a peak at 12 months (43.15 ± 7.67, p < 0.001) and remained above baseline at the long-term follow-up (39.51 ± 5.41 at 60 months, p = 0.0074). Pain Intensity and Pain Interference scores showed similar substantial early improvements, peaking at 3-12 months. Although some decline occurred over 5 years, long-term scores remained comparable or slightly better than preoperative levels, consistent with expected progression of degenerative spine disease.

Conclusions: MI-TLIF without BMP demonstrates high fusion rates, durable clinical improvement, and low reoperation rates, supporting its use as a safe and cost-effective alternative to BMP-augmented fusion. Larger prospective studies are warranted to validate long-term durability and refine patient selection.