191. Establishing a threshold of impairment to define coronal malalignment in adult spinal deformity patients

Abstract

<h3>BACKGROUND CONTEXT</h3> No radiographic alignment threshold defines preop CM in ASD patients based on disability. <h3>PURPOSE</h3> An optimal threshold exists that defines CM based on patient-reported outcomes (PROs) in ASD patients. <h3>STUDY DESIGN/SETTING</h3> Cross-sectional. <h3>PATIENT SAMPLE</h3> This study included 368 adult deformity patients. <h3>OUTCOME MEASURES</h3> Patient-reported outcomes (ODI and SRS22r) and postoperative coronal and sagittal alignment <h3>METHODS</h3> A single-institution registry was searched for all patients undergoing ASD surgery with ≥6 level fusions. Coronal vertical axis (CVA) & sagittal vertical axis (SVA) were collected. PROs were preop ODI/SRS-22r scores. First, CVA & SVA thresholds were derived to accurately differentiate patients with ODI>40 & SRS-pain+function scores<6. Second, patients were separated and compared based on 4 groups: (1) neutral alignment (NA); 2) coronal malalignment only (CM); (3) sagittal malalignment only (SM); (4) combined coronal & sagittal malalignment (CCSM). Chi-square, Kruskal-Wallis, & linear regression were performed. <h3>RESULTS</h3> A total of 368 patients underwent ASD surgery with a mean CVA of 3.1±4.1cm. Part 1: thresholds to distinguish patients with ODI>40 and SRS-pain/fx <6 were: (1) CVA=3.96cm (ODI) and 3.17cm (SRS) and (2) SVA=4.97cm (ODI) and 7.52cm (SRS). To stay conservative, the lower numbers were chosen to define each threshold: CVA=3cm; SVA=5cm. Part 2: alignment breakdown was: NA 179 (48.6%), CM 66 (17.9%), SM 65 (17.7%), & CCSM 58 (15.8%). Based on preop ODI scores, both SM (p=0.006) & CCSM (p<0.001) patients were significantly worse than NA patients. CCSM patients were significantly worse than SM alone (p=0.010). Based on preop total SRS-22r scores, only CCSM (p=0.003) patients were significantly worse than the NA group. CVA significantly correlated with 4/7 (57%) PROs (ODI/SRS-total/function/image), while SVA correlated with 5/7 (71%) PROs (ODI/SRS-total/function/image/pain). A linear relationship was seen between increasing CVA & worsening ODI (β=0.92, p=0.001). A significant yet slightly stronger relationship was seen between increasing SVA & worsening ODI (β=1.28, p<0.001). <h3>CONCLUSIONS</h3> Alignment thresholds that accurately distinguished ASD patients with severe pain and disability preoperatively were 3cm for CVA and 5cm for SVA. Preop CM was significantly associated with worse ODI, SRS-22r total/function/image scores. CCSM lead to more disability than SM alone. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.