Comparison of Spinopelvic Parameters of Multi-level TLIF and 360 Lumbar Fusion Adult Spinal Deformity Procedures via Medtronic Unid™ Technology

Introduction: Achieving optimal spinopelvic alignment is a crucial goal in adult spinal deformity (ASD) surgery, as it directly impacts postoperative balance, quality of life, and long-term outcomes. Patient-specific rods (PSR) have shown promise in enhancing spinopelvic alignment by allowing customized correction based on individual anatomical parameters. However, the optimal surgical approach—whether posterior-only or a combined anterior-posterior method—remains unclear. This study compares the clinical and radiographic outcomes of multilevel transforaminal lumbar interbody fusion (TLIF) and combined anterior lumbar interbody fusion with posterior spinal fusion (ALIF+PSF) using Medtronic UNiD™ PSR technology.

Methods: This retrospective single-center cohort study analyzed 14 ASD patients who underwent four or more levels of fusion with PSR technology. Sagittal spinopelvic parameters—sagittal vertical axis (SVA), pelvic tilt (PT), and pelvic incidence-lumbar lordosis mismatch (PI-LL)—were measured preoperatively, during surgical planning, and one year postoperatively using EOS imaging. Patients were divided into TLIF (n=9) and ALIF+PSF (n=5) groups, with TLIF procedures using static polyetheretherketone (PEEK) or titanium cages, and 360 fusion procedures employing expandable titanium cages. Independent two-sample T-tests were applied to assess changes between postoperative, planned, and preoperative parameters (significance level: p< 0.05).

Results: No significant difference was observed in preoperative spinopelvic alignment between the TLIF and ALIF groups. Both groups achieved high rates of ideal alignment postoperatively, with PT < 20° and PI-LL < 10° (TLIF: 89% and 78%, ALIF: 80% for both; p=0.891). The TLIF group demonstrated significantly greater postoperative lordosis correction compared to ALIF (12.89 ± 11.62 vs. 5.2 ± 3.97; p=0.049). Although the ALIF+PSF group had smaller discrepancies between postoperative and planned alignment, differences in PT, PI-LL, and SVA were not statistically significant.

Conclusion : Both TLIF and combined ALIF+PSF approaches with PSR technology effectively achieved target spinopelvic alignment in multilevel ASD surgery. While TLIF provided superior lordosis correction, overall outcomes between static and expandable cages were comparable. These findings support PSR technology in tailoring alignment but underscore the need for further studies to optimize surgical approach selection.