Three-dimensional architecture and development of lumber intervertebral discs.

The three-dimensional architecture of the collagen framework of human lumbar intervertebral discs was studied with scanning electron microscopy and polarized light microscopy concentrating on the fibrillar interconnection between the intervertebral disc and the vertebral bodies. The fibrillar framework of the annulus fibrosus and the cartilage end-plates encircled the nucleus pulposus as a closed-pack system in the adult. This closed-pack system developed in the seventh embryonic month and was completed by the tenth month. In general, fibrils composing the framework in the fetus were thinner than in the adult. There was no fibrillar interconnection between the cartilage end-plate and subchondral bone. In the inner one-third of the annulus, obliquely oriented fibrillar lamellae interconnected with the cartilage end-plate. In the outer two-thirds, the fibrillar bundles of the lamellae were firmly anchored into the vertebral bodies. This fibrillar anchoring system was already present in the full-term fetus although the vertebral rim was not ossified.