Diameters of the bony spinal canal and especially its sagittal diameter belong to important factors influencing the pathogenetic situation of this space. Objective of this study were to determine the mid-sagittal diameter of the vertebral canal and the vertebral body of the 4 th and 5 th lumbar vertebrae and sagittal diameter of the lateral recessus. With use of these data the mid-sagittal canal/body ratio was determined. 206 men (mean age 51 ± 13.2 years, range 20 - 81) and 201 women (mean age 49.8 ± 13.1 years, range 21 - 83) were studied by CT and CT myelography. Patients with manifestations of secondary degenerative stenosis of the vertebral canal were excluded. The mean mid-sagittal diameter of the lumbar spinal canal was at the level of the L 4 in men 13.91 mm (SD ± 2.52) and 13.56 (SD ± 2.16) in women. The mid-saggital diameter at the L 5 was 14.3 mm (SD ± 2.81) in men and 13.8 mm (SD ± 2.47) in women. The mid-sagittal diameter of the lumbar spinal canal at the level L 4 and L 5 was 11 mm or less in 17 % of examined patients. The mean of the sagittal diameter of the lateral recess at the L 4 was 5.7 mm (SD ± 1.48) in men and 5.5 mm (SD ± 1.49) in women. At the level of L 5 the values were 5.2 mm (SD ± 1.37) in men and 5.2 mm (SD ± 1.5) in women. The sagittal diameter of the lateral recess 4 mm or less was found approximately in 30 % of examined patients. The value of the canal/body ratio 0.4-0.5 was determined for L 4 and L 5 vertebrae in 68 % of men and in 83% (L 4) and in 82 % (L 5) of women.

        Key words: lumbar spinal canal, sagittal diameters, CT