An observation of micro-structure and form of anulus fibrosus of lumbar interverbral disc L5-S1

We observed structure and form of adult anulus fibrous of lumbar intervertebral disc at fibrous layer level. Anulus fibrosus of lumbar interverbral disc was delaminated microsurgical technique. 8 testing points were taken in each layer and the angles between their fibers going and horizontal plane were measured. We got the results: Fiber going angle at each measurement point ceaselessly increased with the increasing of fibrous layer from outside to inside along radial direction in horizontal plane. The least fiber going angle was 25-30 degrees. Fiber going angle at the same layer gradually increased from front to back. The fiber going angle was 70-90 degrees at the middle of back of anulus fibrosus of lumbar interverbral disc. The fiber going was consistent with the posterior longitudinal ligament going. Through the normalized equation and normalized line, the fiber going angle at any point in any layer could be obtained conveniently. We also observe that the fibrosus were interlaced in the front, left and right of anulus fibrosus of lumbar intervertebral disc. And there were more interlaced areas in local sides of lumber intervertebral disc, but there was not interlaced areas between layers near the middle of posterior anulus fibrosus. So we got the conclusion: anulus fibrosus of lumber intervertebral disc has special micro-structure, which was in adaptation with its function. ( We have observed structure and form of lumbar interverbral disc L5-S1, this paper discussed the experiment of lumbar interverbral disc L5-S1 for the first part)