Table 1.

Heights of the spinal canal and cord measured on sagittal images and ratio of the height of the spinal cord to the canal.

Level	Canal (mm)	Cord (mm)	Cord-to-canal ratio
C1–C2	8.45 ± 1.06	5.48 ± 0.70	0.65 ± 0.06
C2	9.47 ± 1.50	5.72 ± 0.74	0.61 ± 0.05
C2–C3	7.00 ± 1.08	4.93 ± 0.77	0.71 ± 0.04
C3	7.38 ± 0.89	5.39 ± 0.78	0.73 ± 0.04
C3–C4	6.66 ± 0.91	4.97 ± 0.71	0.75 ± 0.03
C4	7.39 ± 0.88	5.49 ± 0.76	0.74 ± 0.02
C4–C5	7.00 ± 0.87	5.43 ± 0.71	0.78 ± 0.03
C5	7.98 ± 0.93	5.97 ± 0.81	0.75 ± 0.02
C5–C6	8.06 ± 1.00	6.18 ± 0.81	0.77 ± 0.03
C6	8.69 ± 1.00	6.48 ± 0.82	0.74 ± 0.03
C6–C7	8.24 ± 0.98	6.32 ± 0.82	0.77 ± 0.03
C7	8.02 ± 0.88	5.96 ± 0.74	0.74 ± 0.04

Data are expressed as the mean ± standard deviation.

C1, first cervical vertebra; C1–C2, first to second cervical intervertebral disk space; C2, second cervical vertebra; C2–C3, second to third cervical intervertebral disk space; C3, third cervical vertebra; C3–C4, third to fourth cervical intervertebral disk space; C4, fourth cervical vertebra; C4–C5, fourth to fifth cervical intervertebral disk space; C5, fifth cervical vertebra; C5–C6, fifth to sixth cervical intervertebral disk space; C6, sixth cervical vertebra; C6–C7, sixth to seventh cervical intervertebral disk space; C7, seventh cervical vertebra.