FIGURE 112.17 Four contour lines of alignment with normal cervical spine lordosis: 1, anterior vertebral bodies; 2, posterior vertebral bodies (anterior spinal canal); 3, spinolaminal line (posterior spinal canal); and 4, spinous process tips (From Gerlock A, Kirchner S, Heller R, et al Advanced Exercises in Diagnostic Radiology: The Cervical Spine in Trauma Philadelphia, PA: WB Saunders; 1978:6 Reprinted with permission.)