[CT analysis of developmental spinal canal stenosis].

The cervical and the lumbar vertebrae were analyzed by computed tomography in two groups. One group consisted of the patients with developmental stenosis of the cervical spine (the smallest AP diameter of the cervical spinal canal in the lateral view of X-ray was less than 12 mm) and the other was the control group (the smallest diameter was more than 14 mm). The canal to body ratio of the cross-sectional area (CBR), the modified Jones' "canal to body ratio" (JNS) and the flat index of the vertebral canal (FI) were measured at C4,C5, C6, L4 and L5. The shape of the vertebral canal of L4 and L5 was classified according to Baddeley. In the stenosis group, CBR and JNS were smaller at every measured level and FI was smaller at C4, C5 and C6 compared with the control group, Trefoil canals were found more frequently in the stenosis group. There was a clear relationship between the developmental stenosis of the cervical and the lumbar spinal canal. On treating patients with cervical spondylotic myelopathy, one should consider the possibility of pan-spinal canal stenosis.