Is It Possible To Evaluate the Ideal Cervical Alignment for Each Patient Needing Surgery? An Easy Rule To Determine the Appropriate Cervical Lordosis in Preoperative Planning

Background Cervical sagittal alignment parameters are essential to plan stages of surgery. The aims of this study were to evaluate the relationship between cervical sagittal alignment parameters and surgical outcomes after anterior cervical arthrodesis; to identify parameters linked to a better outcome; to determine the role of the T1 slope, C7 slope, cervical lordosis, and C2-C7 plumb line; and to describe an innovative method to calculate cervical lordosis. A cohort of 70 patients without cervical kyphosis was included in our retrospective study. We analyzed C7 slope, T1 slope, cervical lordosis, and the C2-C7 sagittal vertical axis (SVA). Clinical postoperative outcomes were evaluated with the Neck Disability Index (NDI) and Visual Analog Scale (VAS) score. Results Significant correlation was found between the C2-C7 SVA, C7 slope, T1 slope and the CL/C7 slope. Statistically significant differences were found between group 1 (NDI = 0; VAS = 0) and group 3 (NDI > 17; VAS > 5) regarding C2-C7 SVA ( P  = 0.0026), C7 slope ( P  = 0.0014), T1 slope ( P  = 0.0095) and CL/C7slope ( P  = 0.0012). A value less than 25 mm found in the C2-C7 SVA correlate with positive outcomes. C7 slope correlated with NDI and VAS ( P  = 0.0014). CL/C7 slope ratio is significantly correlated to NDI and VAS scores (ratio: −0.52; P  = 0.0012). Patients with CL/C7 slope greater than 0.7 had better clinical outcomes. Conclusions Sagittal parameters are directly correlated with clinical outcome. If C7 slope increases, higher cervical lordosis is necessary to obtain a good outcome. CL/C7 slope (0.7) multiplied by C7 slope can determine the ideal lordosis.