49. The impact of sagittal alignment on disability decreases after surgery as other factors become more influential: series of 925 patients with two-year follow-up

Abstract

<h3>BACKGROUND CONTEXT</h3> The relationship of sagittal malalignment to outcomes has been emphasized in adult spinal deformity (ASD) surgery and it is known that sagittal parameters have some correlation to HRQOL measures overall. However, the specific relationship of HRQOL to postop sagittal alignment and changes in the strength of the relationship from preop to postop for deformity surgery has not been well defined. <h3>PURPOSE</h3> To determine how postop health-related quality of life (HRQOL) correlates to sagittal alignment. <h3>STUDY DESIGN/SETTING</h3> Retrospective analysis of a large prospective multicenter ASD database. <h3>PATIENT SAMPLE</h3> This study included 925 ASD patients. <h3>OUTCOME MEASURES</h3> HRQOL: Oswestry Disability Index (ODI), Short-Form-36 (SF-36), and Scoliosis Research Society-22r (SRS-22r). Radiographic sagittal alignment thresholds for C7-S1 sagittal vertical axis (SVA), pelvic tilt (PT), mismatch between pelvic incidence and lumbar lordosis (PI-LL). <h3>METHODS</h3> Adult (=18yrs), Cobb angle=20°, SVA=5cm, PT=25°, and/or thoracic kyphosis=60°, 2-yr follow up. Pts were grouped by having met 2/3 of the sagittal alignment thresholds (SVA,PT, and/or PI-LL) at 2 years postop for either the SRS-Schwab values (+SS0) or age-adjusted values (+AGE). The age-adjusted values were calculated within +/-10 years of their actual age. The groups –SS0 and –AGE were patients who didn't meet 2/3 of the SRS-Schwab or the age-adjusted values, respectively. Baseline/2-year HRQOL were evaluated via linear regression for all groups based on 2-year correction. <h3>RESULTS</h3> Total 925 pts, mean age 60.1±14.2yrs, 602(65.1%)+SS0, 323(35.9%)-SS0, 199(21.5%)+AGE, and 283(30.6%)–AGE pts. The remaining age-adjusted pts were either overcorrected or did not have 2/3 sagittal values matched (n=443). All pts had significant improvement in all HRQOL at 2 years and for each of the subgroups (p <0.001 for all). The overall baseline R2 values for all pts for SVA, PI-LL and PT with ODI were (0.110, 0.072, 0.043, respectively) and at 2 years they were lower (0.049, 0.016, 0.008, respectively). Of the pts with pelvic fixation (n=635,68.6%), the same 2-year R2 values increased slightly but were still very weak (0.058, 0.028, 0.021, respectively). Of the pts who developed PJK, the 2-year R2 values were (PJK: 0.007, 0.024, 0.004, noPJK: 0.057, 0.017, 0.006, respectively). This same trend of low values was observed in +/-SS0 and +/-AGE pts. However, the R2 for 2-year ODI vs MCS, SRS appearance, and SRS mental, increased postop (0.19, 0.43, 0.22, respectively) compared with preop (0.17, 0.25, 0.17, respectively). <h3>CONCLUSIONS</h3> Sagittal alignment correlates weakly with preop HRQOL and postop HRQOL is improved. Preop SVA explains only 11% of preop ODI scores based on the R2 value and this decreases postop to 5%. After alignment correction, other patient factors become increasingly important such as the relationship between ODI and SRS appearance, SRS mental, and MCS. More work is necessary to better understand the postop HRQOL relationships including the possibility of a better measurement tool for surgical success. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.