Analysis of Success Versus Poor Realignment in Patients With Cervical Deformity

STUDY DESIGN: Multicenter prospective study. OBJECTIVE: 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. SUMMARY OF BACKGROUND DATA: Correcting cervical deformity (CD) has the potential to significantly improve patient function. However, previously described radiographic parameters cannot be measured intraoperatively. MATERIALS AND METHODS: 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 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. RESULTS: 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° and C2-T10 SA of 14.7° ( r > 0.38, P < 0.05). Change in the distal junctional kypohotic angle (ΔDJKA) 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). CONCLUSION: Failure to restore cSVA and development of DJK was independently associated with undercorrection as evidenced by significantly larger postoperative in-construct angles.