Analysis of Associating Factors with C2-7 Sagittal Vertical Axis after Two-level Anterior Cervical Fusion

Study Design. A retrospective review. Objective. We investigated the longitudinal change of cervical alignment parameters including C2-7 lordosis, C2-7 sagittal vertical axis (SVA), T1 slope, and segmental angle (SA) after two-level anterior cervical discectomy and fusion (ACDF). Summary of Background Data. Cervical alignment may influence postoperative clinical outcomes. Several studies have suggested that cervical alignment may serve as a parameter for assessing cervical deformities similar to those used to assess thoracolumbar spine deformities. However, to our knowledge, no studies have investigated the effect of ACDF on cervical sagittal alignment. Methods. We enrolled patients whom had ACDF, 23 patients with stand-Alone cages and 22 with plate augmentation. Radiologic parameters including C2-7 lordosis, C2-7 SVA, T1 slope, and SA at the operated level were evaluated preoperatively and at 1 week and 6 months postoperatively. The differences between preoperative and 6-month postoperative parameter values were designated as Dvalues. T1S-CL was calculated as the T1 slope minus C2-7 lordosis. Clinical outcome were obtained by the Visual Analog Scale (VAS) and the Neck Disability Index (NDI). Results. DC2-7 SVA was significantly correlated with DT1S-CL and DC2-7 lordosis. DC2-7 lordosis was significantly correlated with DSA. DC2-7 lordosis had a significantly greater impact on DT1S-CL than did DT1 slope. The DSA and DC2-7 lordosis in the ACDF-plate were significantly higher than those in the in ACDF-cage. DT1S-CL and DC2-7 SVA in the ACDF-plate were significantly lower than those in the ACDF-cage. Conclusion. C2-7 SVA after two-level ACDF was affected more significantly by the SA and C2-7 angle than by the T1 slope. Two-level ACDF with plate restored more cervical lordosis by obtaining more segmental lordosis at the operated level and was more effective in terms of cervical alignment compared with ACDF using stand-Alone cages.