Background: Not a large number of previous studies have reported the normal sagittal balance of the cervical spine and physiological cervical lordosis (CL) has not been clearly defined yet.
Methods: This was a prospective radiological analysis of asymptomatic subjects. The following cervical sagittal parameters were measured: CL, thoracic inlet angle (TIA), T1 slope (T1S), neck tilt (NT), and C2-7 sagittal vertical axis (C2-7 SVA). The Pearson correlation test was calculated, and the stepwise multiple regression analysis was conducted by using the CL (dependent variable) and the other cervical sagittal parameters (independent variables) to determine the best sets of predictors. A paired sample t test was conducted between the predicted and measured values.
Results: The mean age of 307 participants was 24.54 + 3.07. The mean CL, TIA, T1S, NT, and C2-C7 SVA was 17.11° ± 6.31°, 67.87° ± 7.78°, 25.84° ± 5.36°, 42.53° ± 6.68°, and 14.60 ± 8.20 mm, respectively. The formula was established as follows: CL = 0.762 × T1S - 0.392 × C2-C7 SVA + 0.25 × TIA - 13.795 (R = 0.812, R2 = 0.660) (stepwise multiple regression) and CL = 0.417 × TIA - 11.193 (R = 0.514, R2 = 0.264) (simple linear regression). There was no statistical difference between the predicted CL and the measured CL (t = 0.034, P = 0.973).
Conclusions: There was a significant correlation between CL and other cervical sagittal parameters, including TIA, T1S, NT, and C2-C7 SVA in asymptomatic Chinese population. The results of this study may serve as a normal reference value for the study of asymptomatic population.
Keywords: Cervical lordosis; Cervical sagittal alignment; Predictive formula; Regression analysis; Thoracic inlet angle.