[Ultrastructure of intervertebral disk in the corresponding area after internal fixation of spinal column].

Objective: To observe ultrastructural changes of the intervertebral disk in the corresponding area after internal fixation of spinal column.
Methods: Twenty-four Japanese big ear rabbits were divided into internal fixation of spinal column group (n=12) and control group (n=12). The internal fixation model was made as follows: The spinous processes and erector spinal muscle were exposed and the T10-L3 spinous processes and the relevant two-side articular processes under the periosteum were isolated. With the help of L-shaped Kirschner wires, the steel wire was threaded through the articular of T11, T12, LI and L2, and were connected with L-shaped Kirschner wires. After 6 months of operation, the following intervertebral disk tissues were observed with transmission electron microscope: nucleus pulposus, internal anulus fibrosus and external anulus fibrosus of L1 intervertebral disk. The T12 and L2 intervertebral disk surface structure was observed horizontally and longitudinally with scanning electron microscope, respectively.
Results: After internal fixation of spinal column, the structural changes of cells in nucleus pulposus and internal annulus fibrosus occurred earlier than that in the external annulus fibrosus. Proteoglycan and special structure were found in nucleus pulposus and matrix of annulus fibrosus. However, the forms of special structure in nucleus pulposus and internal layer of annulus fibrosus were different. In the degeneration matrix of intervertebral disc, the proteoglycan particles and special structure were obviously decreased.
Conclusion: Abnormal stress environment can result in the degeneration of intervertebral disk. There is a regular distribution of the special structure in nucleus pulposus and matrix of annulus fibrosus, which is related to biology behaviour of proteoglycan particles in the degeneration of intervertebral disk.