P104. Crossing the bridge from degeneration to deformity: when good outcomes necessitate sagittal correction in adult spinal deformity surgery

BACKGROUND CONTEXT Patients with less severe adult spinal deformity undergo surgical correction and often achieve good clinical outcomes. However, it is not well understood how much clinical improvement is due to sagittal correction. PURPOSE Derive baseline thresholds in radiographic parameters that, when exceeded, result in dramatic clinical improvement from surgical correction. STUDY DESIGN/SETTING Retrospective. PATIENT SAMPLE A total of 689 ASD patients. OUTCOME MEASURES Radiographic alignment, clinical outcomes (ODI SCB). METHODS ASD patients with BL and 2-year (2Y) data included. Parameters assessed: SVA, PI-LL, PT, T1PA, L4-S1 Lordosis, C2-C7 SVA (cSVA), C2-T3 and C2 Slope (C2S). Outcomes: Good Outcome (GO): [Meeting either: 1) SCB for ODI by 2Y (change greater than 18.8), or 2) ODI 4.5 by 2Y. Binary logistic regression assessed each parameter to determine if correction was more likely needed to achieve GO. Conditional inference tree (CIT) run machine learning analysis generated baseline thresholds for each parameter, above which, correction was necessary to achieve GO. RESULTS Included: 447 ASD patients. There were 223 (50%) patients achieving GO by 2 years. Binary logistic regression analysis demonstrated correction of all 5 thoracolumbar parameters (SVA, T1PA, PI-LL, PT, L4-S1) were more often needed to achieve GO (all p.001). Of patients with baseline T1PA above 20°, 95% required correction to meet Good Outcome (95% vs 54%, p.001). CIT-generated thresholds were significant for each parameter, with a baseline C2 slope above 15° necessitating correction more often to obtain clinical success (OR: 8.1, [4.1-16.2]; p.001). CONCLUSIONS Our study highlights there is a tipping-point beyond which sagittal correction has an exponential influence on clinical improvement, reflecting the line where deformity becomes a significant contributor to disability. These new thresholds delineate patients suitable for sagittal correction, as opposed to conventional treatment of degenerative disc processes. Adherence to these benchmarks may improve the utility gained from surgical intervention for degenerative conditions and deformity. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs. Patients with less severe adult spinal deformity undergo surgical correction and often achieve good clinical outcomes. However, it is not well understood how much clinical improvement is due to sagittal correction. Derive baseline thresholds in radiographic parameters that, when exceeded, result in dramatic clinical improvement from surgical correction. Retrospective. A total of 689 ASD patients. Radiographic alignment, clinical outcomes (ODI SCB). ASD patients with BL and 2-year (2Y) data included. Parameters assessed: SVA, PI-LL, PT, T1PA, L4-S1 Lordosis, C2-C7 SVA (cSVA), C2-T3 and C2 Slope (C2S). Outcomes: Good Outcome (GO): [Meeting either: 1) SCB for ODI by 2Y (change greater than 18.8), or 2) ODI 4.5 by 2Y. Binary logistic regression assessed each parameter to determine if correction was more likely needed to achieve GO. Conditional inference tree (CIT) run machine learning analysis generated baseline thresholds for each parameter, above which, correction was necessary to achieve GO. Included: 447 ASD patients. There were 223 (50%) patients achieving GO by 2 years. Binary logistic regression analysis demonstrated correction of all 5 thoracolumbar parameters (SVA, T1PA, PI-LL, PT, L4-S1) were more often needed to achieve GO (all p.001). Of patients with baseline T1PA above 20°, 95% required correction to meet Good Outcome (95% vs 54%, p.001). CIT-generated thresholds were significant for each parameter, with a baseline C2 slope above 15° necessitating correction more often to obtain clinical success (OR: 8.1, [4.1-16.2]; p.001). Our study highlights there is a tipping-point beyond which sagittal correction has an exponential influence on clinical improvement, reflecting the line where deformity becomes a significant contributor to disability. These new thresholds delineate patients suitable for sagittal correction, as opposed to conventional treatment of degenerative disc processes. Adherence to these benchmarks may improve the utility gained from surgical intervention for degenerative conditions and deformity.