Clinical Impact and Predictive Value of patient specific pre-bent rods in Spinal Deformity Surgery: A Comparative Analysis of Preoperative Planned and Postoperative Outcomes

Patient-specific rods (PSRs) represent an emerging technology for spinal deformity correction, offering personalized surgical planning based on individual anatomy. How accurately do PSRs achieve planned sagittal alignment corrections, and what factors influence surgical outcomes and complications? 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. 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). 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. • Novel Assessment Metrics: Introduction of Correction Achievement Ratio (CAR) and Correction Maintenance Index (CMI) provides comprehensive evaluation of surgical accuracy and long-term stability in patient-specific rod surgery. • Learning Curve Identification: Surgical accuracy with patient-specific rods significantly improves after approximately 8 cases, with reduced variability and better target achievement thereafter. • Parameter-Specific Outcomes: PI-LL mismatch (102.8%) and TPA (91.9%) achieved closest match to planned targets, while PT and SS showed tendency to overcorrect with poor long-term stability. • Complication Risk Factors: Overcorrection of PT (CAR>120%) and PI-LL mismatch (CAR>120%) significantly increases complication risk, particularly proximal junctional kyphosis (OR=4.25, p=0.007). • Clinical Implications: While patient-specific rods improve initial sagittal alignment, maintaining long-term correction remains challenging, emphasizing the need for accurate preoperative planning to avoid overcorrection-related complications.