189. A data-driven approach to assessment of sagittal alignment: defining the spinopelvic ratio's impact on clinical outcomes in adult spinal deformity patients

Abstract

BACKGROUND CONTEXT Analysis of interactions spinal alignment metrics may uncover novel and powerful alignment parameters, similar to pelvic incidence minus lumbar lordosis (PI-LL). PURPOSE This study utilized a data driven approach to hypothesis generation by testing all possible division interactions between a set of spinal alignment parameters. TPA divided by PI (TPA/PI) was identified and subsequently characterized. STUDY DESIGN/SETTING Retrospective analysis of a multicenter, prospectively-defined, consecutive cohort of ASD patients. PATIENT SAMPLE A total of 1,439 patients with baseline ODI were included for hypothesis generation; 666 patients had 2-year postoperative follow-up and were included for validation. OUTCOME MEASURES The primary outcome measure was Oswestry Disability Index (ODI). METHODS All possible combinations of division interactions between baseline metrics were assessed with linear regression against baseline ODI. Further analyses also utilized linear regression. RESULTS From 247 raw alignment metrics, 32,398 division interactions were considered in hypothesis generation. Low-cervical and high-thoracic pelvic angles divided by pelvic incidence accounted for 7 of the top 10 most significant interactions. Conceptually, the TPA/PI is a measure of the relative alignment of the line connecting T1 to the femoral head and the line perpendicular to the sacral end plate. Among the validation cohort, the mean TPA/PI was 0.41 (SD 0.24) at baseline and 0.30 at 2 years postoperatively (SD 0.18). Higher TPA/PI was linearly associated with worse ODI at baseline (β 28.7 for TPA/PI 1 vs 0, p CONCLUSIONS This study utilized a data-driven approach for hypothesis generation and identified TPA/PI, the spinopelvic ratio (SPR), as a promising measure of sagittal spinal alignment among ASD patients. This value is strongly associated with the Schwab modifier classification system. Patients with SPR ≥0.21 exhibited inferior HRQOL. The SPR classification accounted for a directionally greater proportion of variance in ODI as compared to the three Schwab modifiers. These results highlight the interaction between global sagittal alignment and adequate pelvic structural support. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.