Anatomic bases for anterior spinal surgery: surgical anatomy of the cervical vertebral body and disc space.

Twenty adult cadaveric cervical spines were sectioned longitudinally through the midline to display longitudinal sections of the vertebral bodies and disc spaces from C3 to T1. Computer-assisted anatomic images were obtained for measurements of the disc spaces and vertebral bodies. Anteroposterior (AP) depth gradually increased from 16.56 +/- 2.21 mm at C3 to 19.32 +/- 2.30 mm at C7. Greater values of AP depth at the inferior endplate were found at C5 (20.75 +/- 2.87 mm) and C6 (20.56 +/- 2.31 mm) compared with the values at C3 (18.26 +/- 1.82 mm), C4 (19.27 +/- 2.88 mm) and C7 (19.21 +/- 3.22 mm). The AP depth at the superior endplate was greater than that at the inferior endplate. The height of the disc space was found to be lowest at the posterior disc space from C2-3 to C7-T1 (2.95 +/- 0.86 mm at C2-3, 2.78 +/- 0.93 mm at C3-4, 2.45 +/- 0.79 mm at C4-5, 2.92 +/- 0.64 mm at C5-6, 2.46 +/- 0.59 mm at C6-7, 2.93 +/- 1.05 mm at C7-T1), when compared to the height of the disc space at the anterior disc space from C2-3 to C7-T1 (4.07 +/- 0.85 mm at C2-3, 4.34 +/- 1.18 mm at C3-4, 3.95 +/- 1.37 mm at C4-5, 3.55 +/- 1.37 mm at C5-6, 3.55 +/- 0.76 mm at C6-7, 3.67 +/- 1.17 mm at C7-T1). The mid-axis of the disc space was situated at approximately 3 mm above the anterior midpoint of the annulus fibrosus at the level of the lower cervical spine. To reach the posterior portion of the disc space from the anterior midpoint of the annulus fibrosus, a 5 degrees cephalad angulation of the drill relative to the mid-axis of the disc space is necessary. All these original data from cadavers may be helpful during anterior approach for discectomy, vertebrectomy and anterior screw-plate placement.