后路枕颈部4种螺钉技术的应变电测研究

Strain electronic measurements of posterior screws inserted to craniovertebral junction

目的比较枕颈部后路4种不同植入方式的螺钉在施加生理载荷时所承受的应力,评价各自在生理环境中的机械性能。方法对16例新鲜人体枕颈部标本(含O_c^C_3),采用后路枕寰枢复合体经关节螺钉固定和SUMMIT系统枕颈固定。对固定后的经寰枕关节螺钉(O_c^C_1组)、经寰枢关节螺钉(C_1~C_2组)、枢椎椎弓螺钉(C_2PS组)和枕骨螺钉(O_c Screw组)在生理载荷下三维六自由度运动时,运用应变电阻测定法测定4种螺钉的应力,数据进行统计学处理。结果在侧屈状态下,电测法测得的4种螺钉局部应变均接近于O_o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不同程度承受拔出应力,在后伸时,螺钉所受的为压应力。枕骨螺钉(O_c Screw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,差异有统计学意义(P<0.05)。结论生理环境下,枕骨螺钉承受的拔出应力最大,其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 To compare the extracting stress of four kinds of craniovertibral screws by strain electronic mea-surements. Methods Posterior craniovertebral transarticular screw fixation and SUMMIT occipitocervical fixation were performed in succession on 16 fresh craniovertebral junction specimens（containing Oc- C3）. Using the strain electronic measurement, the ex-tracting stress was measured on Oc- C1 transarticular screws （Oc- C1 TA group）, C1- C2 transarticular screws （C1- C2 TA group）, C2 pedicle screws （C2 PS group） and occipital screws （Oc Screw group）, when these screws were bearing biological load under the condition of three- dimensional motion in six directions. Results The strain electronic measurements showed that the local stress of al 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 pul ing and extending stress of varying degrees under anterior flexion and rotation, and pressure stress under posterior flexion. The Oc Screw group bore greater stress under flexion, extension and rotation than the other screw fixation groups （P〈0.05）. Conclusion In vivo biomechanics studies show that the occipital screws bear the greatest extracting stress among 4 kinds of craniovertebral fixation screws, suggesting that the occipital screws are more likely to induce related complications under physiological conditions, and therefore individual clinical conditions should be taken into account when this technique is used.