Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters

BACKGROUND CONTEXT Current preoperative planning for surgical adult spinal deformity (ASD) patients takes into account patient age when establishing postoperative alignment targets for sagittal vertical axis (SVA), pelvic tilt (PT) and spino-pelvic-mismatch (PI-LL). Patient height and pelvic incidence (PI), however, have yet to be evaluated for their individual effects on achieving age-adjusted alignment targets. PURPOSE This study assesses the individual effects of patient height and PI on age-adjusted alignment outcomes of surgical ASD patients. STUDY DESIGN/SETTING Single center retrospective review. PATIENT SAMPLE A total of 205 operative ASD patients. OUTCOME MEASURES Postoperative alignment parameters (PT, SVA, PI-LL, and SS); health-related quality of life (HRQL) scores. METHODS Surgical ASD patients >18 years with full-body stereographic x-ray imaging at baseline (BL) and early postoperative follow-up ( 75th) for both BL height and PI. Correction groups were generated at postoperative follow-up for actual alignment compared to age-adjusted ideal values for PT, PI-LL, and SVA, and PI-adjusted ideal alignment values for SS, as derived from clinically relevant formulas. Chi-squared tests assessed differences in rates of matching age-adjusted alignment ideal (±10years threshold for age-adjusted targets; −7° to 5° measured minus ideal for SS target) across height and PI groups. Subanalysis of patients matching age-adjusted alignment ideal used ANOVA to compare clinical outcomes across height and PI groups. RESULTS Included: 205 ASD patients (59±16 year, 64% F, 27±6 kg/m2). Following surgery, patients showed significant improvement in PT, PI-LL and SVA (all p .05). Height groups also did not differ in age or BMI (all p>.05), although female patients comprised a greater proportion of the low (96% F vs. 4% M) and normative (75% F vs. 25% M) height groups (p 0.05). Although there were no differences across PI groups in rates of achieving ideal alignment for PI-LL, SVA or SS (all p>.05), patients with high PI reached age-adjusted ideal alignment for PT at a significantly lower rate (15%) than patients with normative (36%) or low PI (33%, p=.031). Of the 58% of patients that matched any adjusted alignment target in early follow-up, there were no significant differences in postoperative HRQL outcomes across patient height or PI groups (all p>.05). CONCLUSIONS Patients with high pelvic incidence reached ideal postoperative age-adjusted PT alignment at a significantly lower rate than patients with normative and low pelvic incidence. In contrast, patient height had no impact on postoperative age-adjusted alignment outcomes. These results suggest that current postoperative ideal alignment targets may warrant adjustment to account for the morphological factor of pelvic incidence.