Comparisons of lordotic cervical spine curvatures to a theoretical ideal model of the static sagittal cervical spine

Study Design. Measurements from lateral cervical radiographs of randomly selected patients are compared with two proposed ideal models. Objectives. To evaluate lordotic cervical curvatures from a large population base, to provide a geometric sagittal cervical spine model, and to test the validity of the model to predict measured angles and distances. Averages of ranges and normal values for cervical lordosis under conditions of static equilibrium are sought. Summary of Background Data. Seven angles and three distances were taken from 400 randomly selected lateral cervical radiographs of patients at a private clinic. Methods. The radiographic measurements are compared with predicted values from our geometric sagittal cervical spine model and the Delmas ideal cervical model. Results. Values were predicted successfully by the geometric model with an average error of 5% compared with the radiographic measurements. The range of lordosis, measured at the posterior of C2 and C7, was 16.5-66 degrees, with a mean of 34 degrees. The average height-to-length ratio for the cervical spine was 0.97. Conclusions. Predicted values from the geometric model were comparable with the measurements of the relative rotation angles at each vertebral interspace, absolute rotation angles from C2 to C7, and height-to-length ratios. A cervical lordosis of 34 degrees and a height-to-length ratio of 0.97 are suggested for clinical and theoretical outcomes.