The Clinical and Financial Implications of Incremental Increases in Operative Time Utilization Based on Procedural Clusters in Complex Adult Spinal Deformity Surgery

Background: Surgical duration is a known risk factor for postoperative complications. Its incremental role in procedural for adult spinal deformity (ASD) clusters has not been previously studied. Purpose: To investigate the association between operative duration and perioperative, radiographic, patient-reported, and financial outcomes in complex spine deformity surgery using procedural clusters. Study Design/Setting: Retrospective cohort. Materials and Methods: We included patients undergoing fusions from the thoracic spine to the pelvis for adult spinal deformity. Cohorts were substratified based on upper instrumented vertebra (UIV). Surgical duration was determined continuously, then by incremental groups: A (<3), B (3–<6), C (6–<9), D (>9 h). Postoperative realignment was determined by the sagittal age-adjusted score (SAAS). Multivariable logistic regression adjusted for age, sex, BMI, CCI, ODI, PI-LL, T1PA, SVA, levels fused, osteotomy grade (grades 4, 5, 6 separately), UIV cluster, ASA grade, revision status, and approach type. Results: In total, we included 864 patients in the analysis. Cohort breakdown was: 24.2% group A, 21.3% B, 33.8% C, and 20.7% D. In fully adjusted analyses, cases in higher operative time categories demonstrated greater odds for intraoperative adverse events (OR=1.75, 1.30–2.37), neurological deficit (OR=3.08, 1.99–4.75), and decreased odds of SAAS alignment match (OR=0.87, 0.64–1.19). When examining lower thoracic cases (T8-12 UIV, n=379 patients, mean op time 416.3±152.7 min), up to six hours, improvements in ODI and SRS-22 were significant at all time points (all P <0.001), but beyond this threshold, there were no longer any significant improvements. Similarly, beyond six hours, the risk of intraoperative complications increased by 5x (OR=5.28, 1.84–15.21, P =0.002), while the risk of postoperative neurological deficit doubled (OR=2.30, 1.22–4.33, P =0.010). The cost/quality-adjusted life year (QALY) was comparable up to six hours, beyond which each additional hour of op time translated to an additional cost per QALY of $24,719.30. When examining upper thoracic cases (T1–4 UIV, n=350, mean op time 517.3±169.3 min). The cost/QALY was comparable up to seven hours, beyond which each additional hour of operative time translated to an additional cost/QALY of $11,725.15. Conclusions: In ASD surgery, operative time functions as an integrative marker of procedural complexity. After adjustment for osteotomy type, levels fused, and deformity severity, cases exceeding cluster-specific duration thresholds demonstrate higher intraoperative complication and motor deficit rates without corresponding alignment gains. These benchmarks may inform preoperative planning and staging decisions for anticipated high-duration procedures.