Clinical impact and predictive value of patient specific pre-bent rods in spinal deformity surgery: A comparative analysis of preoperative planned and postoperative outcomes.

Introduction: Patient-specific rods (PSRs) represent an emerging technology for spinal deformity correction, offering personalized surgical planning based on individual anatomy. Research question: How accurately do PSRs achieve planned sagittal alignment corrections, and what factors influence surgical outcomes and complications? Material and methods: Twenty-two consecutive patients underwent spinal deformity correction using UNiD™ PSRs. Two novel metrics were developed: Correction Achievement Ratio (CAR) and Correction Maintenance Index (CMI). Radiographic parameters were measured preoperatively, postoperatively, and at one-year follow-up. Results: Twenty patients (91%) completed follow-up. PI-LL mismatch (CAR = 102.8%) and TPA (CAR = 91.9%) achieved near-perfect correction. PT (CAR = 149.2%) and SS (CAR = 123.5%) showed overcorrection. Learning curve analysis revealed improved accuracy after case 8. Overcorrection significantly increased complication risk (PT>120%: OR = 3.41, p = 0.025; PI-LL>120%: OR = 4.25, p = 0.007). Discussion and conclusion: PSRs effectively achieve planned sagittal corrections with high initial accuracy. However, maintaining correction remains challenging, and overcorrection increases complication risk. Surgical precision improves with experience. While promising for reducing mechanical complications, the technology requires further refinement for optimal outcomes.