Analysis of Associating Factors with C2-7 Sagittal Vertical Axis after 2-level Anterior Cervical Fusion: Comparison between Plate Augmentation and Stand-alone Cages

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 Δvalues. 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.ΔC2–7 SVA was significantly correlated with ΔT1S-CL and ΔC2–7 lordosis. ΔC2–7 lordosis was significantly correlated with ΔSA. ΔC2–7 lordosis had a significantly greater impact on ΔT1S-CL than did ΔT1 slope. The ΔSA and ΔC2–7 lordosis in the ACDF-plate were significantly higher than those in the in ACDF-cage. ΔT1S-CL and ΔC2–7 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.Level of Evidence3