Sex discrepancy in the canal/body ratio of the cervical spine implicating the prevalence of cervical myelopathy in men

Study Design. A radiographic analysis of the cervical spine in healthy young adults. Objectives. To investigate the size correlations among the vertebral height, the anteroposterior diameter of the vertebral body, and the anteroposterior diameter of the spinal canal and to investigate the sex discrepancy of the canal/body ratio. Summary of Background Data. Narrow spinal canal, large vertebral body, and male gender have been thought to be risk factors for cervical myelopathy. However, the association among those risk factors has been seldom analyzed. Methods. The height and the anteroposterior diameter of the vertebral body as well as the anteroposterior diameter of the spinal canal were measured on the lateral radiographs of healthy young adults (105 men and 114 women) using a distance-measuring tool of computer software. The canal/body ratio was compared between men and women. Results. The height and the anteroposterior diameter of the vertebral body were both larger in males than in females throughout C3-C7, but the anteroposterior diameter of the spinal canal was similar for both sexes. The height of the vertebral body was not correlated with the spinal canal size at any measured segment in both sexes, whereas the anteroposterior diameter of the vertebral body was significantly correlated with the size of the spinal canal in males but not in females. The canal/body ratio was significantly larger in women than in men. Conclusions. A significantly small canal/body ratio in men may implicate the male prevalence of cervical myelopathy.