枕寰枢复合体后路螺钉固定技术的应变电测研究

Strain electronic measurements on craniovertebral junction fixation with posterior screw technique

目的比较4种植入方式的枕颈部螺钉在施加生理载荷时所承受的拔出应力,评价其各自在生理环境中的机械性能。方法对12具新鲜人体枕颈部标本(含Oc^C3),依次采用后路经关节螺钉固定和SUMMIT枕颈部内固定系统固定。对固定后的Oc-C1经关节螺钉(Oc-C1组)、C1,2经关节螺钉(C1,2组)、枢椎椎弓螺钉(C2IS组)和枕骨螺钉(OcScrew组)在生理载荷下三维六自由度运动时,运用电测法进行应变电阻测定4种螺钉的拔出应力,并对结果进行统计处理。结果侧屈状态下,电测法测得的所有螺钉局部应变均接近于0。在前屈、后伸、左旋和右旋运动时,随着加载载荷增大,测得的应力均逐步增大。在前屈和旋转时,螺钉均承受不同程度拉伸应力;在后伸时,螺钉所受的力均为压应力。枕骨螺钉(OcScrew组)在屈伸和旋转运动状态下,在所有3种载荷下所承受的应力均大于其它3种植钉方法,存在统计学意义(P<0.05)。结论枕骨螺钉承受的拔出应力最大,生理环境下枕骨螺钉可能更易出现内植物相关并发症,具体应用时应结合临床实际。

Objective Compare the extracting stress of four craniovertibral screws bearing biological load under the condition of three-dimensional motion in six directions and evaluation biomechanical properties in their respective biological settings. Methods Posterior transarticular fixation and SUMMIT occipitocervical fixation were performed in succession on 12 fresh craniovertebral junction specimens （containing Oc-C3 ）. Using the strain electronic measure, the extracting stress was measured of Oc-C1 transarticular screws（ Oc-C1 TA group）, C1,2 transarticular screws（ C1,2 TA group）, C2 isthmicm screws （C2 IS group） and occipital screws（Oc Screw group） that were bearing biological load under the condition of three - dimensional motion in six directions. The results were statistically analyzed. Results The strain electronic measurements showed that the local stress of all screws was near zero under lateral flexion. Stress increased with increasing load under anterior flexion, posterior flexion, left rotation and right rotation. The screws bore pulling and extending stress of varing degrees under anterior flexion and rotation, and pressure stress under posterior flexion. The occipital screws in Oc Screw group bore greater stress under flexion, extension and rotation than the other screw fixation groups; the difference was statistically significant （ P 〈 0.05）. Conclusion In vivo biomechanics studies measurement showed that the occipital screws bear the greatest extrac- ting stress of the four craniovertebral fixation screws, suggesting that the occipital screws are more likely to induce related complications under physiological conditions, and therefore use of this technique should take into account the individual clinical conditions.