189. Evaluation of coronal alignment from the skull using the novel orbital-coronal vertical axis line

Abstract

<h3>BACKGROUND CONTEXT</h3> Conventional adult spinal deformity (ASD) measurements evaluate coronal alignment from C7-sacrum. Little is known about coronal alignment from the skull. <h3>PURPOSE</h3> Assess coronal alignment evaluated from the skull and correlations with preoperative/postoperative measurements and function. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort. <h3>PATIENT SAMPLE</h3> Adult spinal deformity patients from a multi-surgeon single-institution database. <h3>OUTCOME MEASURES</h3> Patient-reported outcomes and postoperative radiographic parameters. <h3>METHODS</h3> A single-institution, ASD database was searched for adult spinal deformity patients with at least six or more levels fused. Traditional C7-coronal vertical axis (C7-CVA) measurements were obtained, as was the orbital-CVA (ORB-CVA): the distance between the sacral plumb line and a vertical line from the mid-point between medial orbital walls. The ORB-CVA was correlated with traditional coronal measurements, including C7-CVA, maximum coronal cobb angle, pelvic obliquity (PO), & leg length discrepancy (LLD). Coronal malalignment (CM) was defined as C7-CVA >3cm. Measures of clinical improvement were: (1) group PRO means, (2) minimum clinically important difference (MCID) and (3) minimal symptom scale (MSS) (ODI<20 or SRS-pain+fx>8). <h3>RESULTS</h3> A total of 243 patients underwent ASD surgery, and 175 had 2-year follow-up. Ninety (37%) patients had preop CM while mean (range) ORB-CVA at each time point was: preoperative 2.9±3.1 (-14.2-25.6), 1-year postoperative 2.0±1.6 (-12.4-6.7), 2-year postoperative 1.8±1.7 (-6.0, 11.1) (p<0.001 from preoperative to 1-year and 2-year). Preoperative ORB-CVA correlated best with CVA (r=0.842, p<0.001), max coronal Cobb (r=0.166, p=0.010), PO (r=0.293, p<0.001), and LLD (r=0.158, p=0.006). Postoperative, ORB-CVA correlated only with CVA (r=0.627, p<0.001) & LLD (r=0.160, p=0.013). Of the total, 155 (63.2%) patients had an ORB-CVA that was ≥5mm different than C7-CVA. Women were more likely than men to have an ORB-CVA closer to midline than C7-CVA (69% vs 45%, p=0.004). ORB-CVA correlated as well and sometimes better than C7-CVA in SRS-22r subdomains. The ORB-CVA slightly outperformed C7-CVA in its ability to capture patients achieving MCID for SRS-appearance (AUC=0.664 vs 0.513) and with MSS (AUC 0.609 vs AUC 0.542). <h3>CONCLUSIONS</h3> The ORB-CVA correlated well with known coronal measurements and PROs. Sixty-three percent of patients had an ORB-CVA >5mm different than the C7-CVA, and women were more likely than men to have an ORB-CVA closer to midline than the C7-CVA, indicating a potential compensatory ability. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.