Introduction: Increased C2-T3 angle has been identified as a risk factor for sagittal malalignment following thoracolumbar surgery. No ideal cervicothoracic alignment thresholds exist in the literature. As several studies have demonstrated a relationship between the normal aging spine and sagittal alignment, such ideal-alignment thresholds should also account for patient age.
Methods: Patients >18yrs with cSVA<4cm, available full-body stereographic x-ray imaging, and NDI data at baseline were included. Patients were stratified by age: <35, 35-45, 45-55, 55-64, 65-74. Linear regression modeling allowed for identification of NDI values corresponding to ODI US-norms, as previously published. Linear regression analysis established correlations between C2-T3 angle, age, and NDI. Normative NDI values were then used to establish age specific targets.
Results: Overall, 223 patients (50±20yrs, 65% F) met inclusion criteria, presenting with a mean sagittal vertical axis (SVA) of 17.8±47.7mm, cervical SVA 19.8±11.2mm, T1 Slope-C2-C7 lordosis 24.7°±16.2°, and C2-T3 of 2.1°±16.5°. At baseline, increased C2-T3 angle was significantly correlated with both NDI score (r=0.266, p<0.001) and patient age (r=0.458, p<0.001). Baseline NDI showed a significant correlation with ODI (r=0.751, p<0.001), permitting extrapolation of US-normative NDI scores. US-normative NDI scores increased with age: <35yr: 10.1, 35-45yr: 11.8, 45-55yr: 14.7, 55-64yr: 18.8, 65-74yr: 21.7, >75yr: 27.8. Liner regression analysis showed a significant relationship between NDI score, age, and baseline cervicothoracic alignment, as assessed by C2-T3 angle (r=0.497, p<0.001). Using US-normative NDI scores and mean age within each patient age group, this regression equation yielded age-specific ideal alignment targets for C2-T3, all of which increased with age: <35yr: -11.6°, 35-45yr: -4.7°, 45-55yr: -1.4°, 55-64yr: 1.8°, 65-74yr: 4.7°, >75yr: 6.7°.
Conclusions: Significant relationships exist between age, neck disability, and cervicothoracic alignment, suggesting broad measurements across the cervicothoracic junction may be clinically relevant in predicting postoperative outcomes of surgical spine deformity patients. This study offers a set of ideal age-adjusted alignment targets for C2-T3.
Patient Care: By proposing a set of normative, age-specific cervicothoracic alignment targets, this study better facilitates individual optimization of surgical planning.
Learning Objectives: To develop age-specific cervicothoracic alignment targets using previously published age-specific normative Neck Disability Index (NDI) values.