Efficacy of Modified Transforaminal Lumbar Interbody Fusion in Three-Planar Correction for Severe Adult Spinal Deformity: Radiographic and Clinical Outcomes

Background: Adult spinal deformity (ASD) significantly impacts quality of life in geriatric populations due to severe sagittal imbalance, degenerative scoliosis, and associated neurological compression that usually requires surgery when conservative treatment fails. Objective: To evaluate the clinical and radiological outcome of a modified transforaminal lumbar interbody fusion (TLIF) technique in the three-planar correction of severe adult spinal deformity (ASD). Methods: This was a single-center case series study. We recruited 72 ASD patients (mean age 64.5 years) with at least one of the following criteria met (SRS-Schwab sagittal modifier ++; Cobb angle >30°; Coronal vertical axis >3cm) operated between January 2020 and May 2025. The surgical protocol involved four modifications: (1) bilateral facetectomy and posterior column resection; (2) a concave-side approach to the disc space; (3) anterior positioning of the PEEK cage; and (4) supplemental bone grafting posterior to the cage. Clinical and radiological outcomes were evaluated at a mean follow-up of 2.3 years. Results: Significant improvements were observed in SRS-22 (2.6 to 3.7) and NCOS (43 to 74.5) scores (p < 0.05). After surgery, both PI-LL mismatch and the Cobb angle have been markedly improved (35° down to 17° and 21.5° down to 5°, respectively). The fusion rate was 90% at 1 year. Univariate analysis identified osteoporosis (OR = 13.4, p<0.05), "pear-shaped" disc morphology (OR = 14, p<0.05), and PI > 65° (OR = 13.7, p<0.05) as significant risk factors for unchanged sagittal modifier after surgery. Early complications included infection (2.7%) and pneumonia (2.7%) whereas the main mid-term adverse event was PJK (15%). Conclusion: Modified TLIF is associated with improvement of mid-term radiographic and clinical outcomes and an acceptable complication rate. Additional research involving larger cohorts and extended follow-up, preferably with a control group, is required to reach more definitive conclusions.