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

Abstract

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 that had a LIV at T1 or caudal were included. Patients were categorized into the failed outcome group if they had a cSVA of more than 4 cm within 3 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, C2-T10 SA measures corresponding to a cSVA = 4 cm.HRQL analysis was done in patients with 1-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, CI 1.10-1.35; P < 0.001). A cSVA of 4 cm correlated with a C2-T1 SA of -9.6° and C2-T10 SA of 14.7° (r > 0.38, P < 0.05). ΔDJKA was found to 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 under correction as evidenced by significantly larger postoperative in-construct angles.