[Dynamic observation on imbalance of dynamic and static forces and degenerated cervical intervertebral disc in rats]

To study the relation between biomechanical imbalance and the degree and course of degeneration of cervical intervertebral disc in rats.

Sixty SD rats, 8 months old, were randomly divided into 6 groups, the control and model groups of 3, 5, 7 months, 10 in each group. The cervical disc dynamic and static forces imbalance of degeneration model was established to assess the degree of degeneration as well as the content some inflammatory mediators (prostaglandin E2, 6-keto-prostaglandin F1 alpha) and collagenase (MMP-1) activity.

(1) In 3 months model group and 5 months control group, fibrous ring of intervertebral disc showed some fissure and slight irregular arrangement, nucleus pulposus shrunken or became smaller, mild herniation of nucleus pulposus was seen in some disc. The nucleus pulposus of intervertebral disc in 5 months model group was fibrosed completely and the disc in 7 months model group herniated or became osteophytosis. (2) Compared with the control group of same time period, MMP-1 was increased significantly in the 5 months and 7 months model groups (P < 0.05), and prostaglandin E2 and 6-keto-prostaglandin F1 alpha elevated in the model groups (P < 0.05, P < 0.01). (3) Comparison between model groups, MMP-1 activity in 5 months and 7 months groups was higher than that in the 3 months group (P < 0.05), and 6-keto-prostaglandin F1 alpha was higher in 7 months group than that in 3 months group (P < 0.05).

Cervical intervertebral disc undergoes a progressive degenerating process. By breaking the dynamic-static balance of neck in rats could accelerate the progression of degeneration. The fact could be used to elucidate the theory of pathogenesis of cervical spondylopathy, dynamic force imbalance in priority and static force imbalance in predominance.