| Objective: For the purpose of analyzing the effects of lumbar internal fixation on adjacent segmental discs and exploring the mechanism of changes in lumbar discs,different experimental models of rabbits’ lumbar internal fixation were conducted.Furthermore,through this study,some basic theoretical evidence could be provided for the prevention and treatment of postoperative complications after lumbar internal fixation and the improvement of surgical methods.Methods: Sixty New Zealand white rabbits were selected and randomly divided into four groups with 15 rabbits in each group.Anterior lumbar interbody fusion was performed in group A,posterior lamina spinous process fusion was performed in group B,anterior and posterior combining fusion were performed in group C,and sham operation was performed in group D.X-ray examination,histomorphological observation and immunohistochemical examination were separately performed in 3 months,6 months and 9 months after operation.Statistical data analysis was conducted by SSPS 17.0 for Windows.Single-factor anova was used for level comparison between groups,paired t test was used for comparison between upper and lower segments within the same group,q test was used for pairwise comparison between groups,and LSD method was used for comparison between experimental groups and sham operation control group.Results:(1)X-ray examination: At 3 months,the bone healing was confirmative since there were continuous bone trabeculae in the fusion segments.There was no significant calcification in the cartilage endplate of adjacent segments in the all groups,and no significant changes in the intervertebral space.At 6 months,slight calcification was observed in the cartilage endplate of adjacent segments in each experimental group,and no significant difference was found in terms of the degree of calcification of upper and lower segments in the same group,while no calcification was observed in the cartilage endplate of adjacent segments in the control group;the adjacent vertebral space of each experimental group was slightly narrower,and there was no significant difference in terms of degree of upper and lower vertebral space of the same group,and no significant change in the vertebral space of the control group.At 9 months,obvious calcification was observed in the cartilage endplate of adjacent segments in each experimental group,and no significant difference was found in terms of the degree of calcification of upper and lower segments in the same group,slight calcification was observed in the cartilage endplate of adjacent segments in control group;the adjacent vertebral space of each experimental group was obviously narrower,and there was no significant difference in terms of degree of upper and lower vertebral space of the same group,the adjacent vertebral space of control group was slightly narrower.(2)Histomorphological observation: After 3 months,6 months and 9 months’ observation among each experimental group,HE staining observation displayed the nucleus pulposus tissues gradually atrophied and mucus degeneration.The chordate cells gradually decreased,while the chondrocytes gradually increased and the boundary between the nucleus pulposus and the annulus became blurred.Meanwhile the semi-ring concentric-circle structure of the fiber ring was gradually disordered and the fiber cells showed a decreasing trend.However,there was no significant change among the structures mentioned above in the control group.(3)Immunohistochemical examination: The positive expression of type I and type Ⅱ collagen staining was that diffuse brownish yellow particles appeared in the cytoplasm,mean number of positive reaction cells could be calculated by randomly choosing five nonrepetitive visual fields at a high magnification(10x40times).Statistics analysis could be conducted in terms of mean plus or minus standard deviation.The difference between the groups was statistically significant(P<0.05),the difference between the experimental group and the control group was not statistically significant at 3 months(P>0.05),the difference was statistically significant at 6 months and 9 months(P<0.05).The difference between 3 months and 6 months,6 months and 9 months in each experimental group was statistically significant(P<0.05),while the difference between 3 months and 6 months,6 months and 9 months in the control group was not statistically significant(P>0.05).And there was no statistically significant difference between the upper and lower nodes at in group A,group B at all three time points(3 months,6 months,9 months)and group C at 3 months(P>0.05),but there was statistically significant difference between the upper and lower nodes at 6 months and 9 months in group C(P<0.05).Conclusion:(1)Anterior lumbar interbody fusion,posterior lamina spinous process fusion as well as anterior combined posterior fusion of internal fixation can cause adjacent segmental disc to degenerate.(2)There was no significant difference in terms of the degree of degeneration between the upper and lower nodes in anterior interbody fusion and posterior lamina spinous process fusion.(3)The degree of degeneration in adjacent intervertebral discs at upper level was more severe than those at lower level in anterior and posterior combining fusion.(4)The histology of adjacent segmental intervertebral disc showed an appearance of nucleus pulposus atrophy,and a decrease in notochord cells numbers.There was also an increase in chondrocytes numbers,a disorder of annulus structure,a reduction in fibrocytes numbers.Meanwhile in terms of immunohistochemical expression,type Ⅰ collagen cells increased and type Ⅱ collagen cells decreased. |
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