[Changes of posterior osseous elements in narrowing of antero-posterior diameters of the lumbar spinal canal].

Narrowing of the antero-posterior diameters of the foramen and its influence to the posterior osseous elements were studied on 585 dry vertebral bones of 117 human lumber specimens. 1. Narrowing of the antero-posterior diameter of the foramen progresses even after reaching adult age and continues thereafter. Close correlations were found between the antero-posterior diameters and the transverse diameters and between the antero-posterior diameters and the area. 2. Narrowing of the antero-posterior diameters of the foramen was due to hypertrophy of the inside of the L3 to L5 lamina, but it is also due to shortening of the pedicle or compression of the posterior elements of L1 and L2 level. 3. Together with narrowing of the antero-posterior diameters of the foramen due to developmental stenosis and due to advanced age, the articular facets move on toward the sagittal plane keeping 90 degree angle between the laminae, and medial edges of the superior articular facets approach to the mid-line and add the depth of the lateral recesses, but the antero-posterior diameters of the lateral recesses do not correlate with narrowing of the antero-posterior diameters of the foramen. 4. Changes of the posterior osseous elements related to the narrowing of the antero-posterior diameters of the foramen are significant at the lower lumbar vertebrae of the male. It is therefore concluded that developmental inclination, muscular activity and advanced age were factors influencing the spinal canal stenosis.