Analysis of Success Versus Poor Realignment in Patients With Cervical Deformity : In-Construct Angles Provide Novel Targets for Correction

Multicenter prospective study. The present study investigates in-construct measurements of sagittal angles (SA) within the fusion from C2 to various thoracic vertebrae, which can be used as targets for CD correction. Correcting cervical deformity (CD) has the potential to significantly improve patient function. However, previously described radiographic parameters cannot be measured intraoperatively. Patients with CD who had a lower instrumented vertebrae (LIV) at T1 or caudal were included. Patients were categorized into the failed outcome group if they had a cervical sagittal vertical axis (cSVA) of more than 40&#xa0;mm within three months postoperatively. The in-construct measurements were based on patients' LIV. All patients had a C2-T1 SA. C2-T4 SA were compared between groups with LIV below T4, and C2-T10 SA between groups with LIV below T10. Change in C2-LIV SA described the correction within the fusion for each patient. Linear regression analysis was used to determine the C2-T1, C2-T4, and C2-T10 measures corresponding to a cSVA equaling 40 mm. Health-related quality of life (HRQL) analysis was done in patients with a one-year follow-up. Among 143 patients (mean age 63, 60% female), 51% had radiographic failure. Multivariate regression showed that postoperative C2-T1 SA independently predicted failed alignment (OR: 1.22, 95% CI: 1.10-1.35; P < 0.001). A cSVA of 40 mm correlated with a C2-T1 SA of -9.6&#xb0; and C2-T10 SA of 14.7&#xb0; ( r > 0.38, P < 0.05). Change in the distal junctional kypohotic angle (&#x394;DJKA) was found to be significantly correlated with the C2-T10 SA ( r > 0.57, P = 0.02). Though HRQL outcomes did not differ significantly between groups, greater C2-LIV SA correction was associated with improved neck pain ( r > 0.42, P = 0.036). Failure to restore cSVA and development of DJK was independently associated with undercorrection as evidenced by significantly larger postoperative in-construct angles.