不同长度齿突对螺钉把持力的测试

目的 评价不同长度齿突骨折螺钉内固定的生物力学效果。方法 收集20具新鲜成人枢椎标本，按齿突螺钉固定技术钻孔形成针道，模拟齿突II型骨折，测量齿突端针道长度，置入螺钉后测试旋入力矩、最大轴向拨出力和刚度测试，解剖观察钉道骨质构成。结果 钉道长度8.3mm～12.3mm，钉道长度与螺钉最大拔出力相关回归分析：相关系数r=0.28, 回归方程式：Y=156.69+67.97X (Y:：钉道长 X：拔出力)，大于10mm和小于10mm两组间旋入力矩、最大轴向拨出力和刚度t检验无统计学上差异(P>0.05)，齿尖部由皮质骨构成。结论 齿突长度和骨折端的稳定度关系不密切、与最大轴向拨出力成正比关系但并不显著，短于1cm的齿突对螺钉仍有较好的把持力。

Biomechanical evaluation of anterior screw fixation for type II fractures of the odontoid process: The influence of different lengths of the screws

Objectives To determine the influence of different lengths of the anterior odontoid screws on the fixation stability. Methods Twenty cadaveric C2 vertebrae were harvested and an osteotomy was performed to simulate a Type II fracture pattern in each vertebra. The angle of type II fracture line was 0°in 6 specimens, 17°in 8, and 25°in 6. In this way, Different lengths of fractured odontoid processes were created and then divided into 2 groups (<10mm vs >10mm). The fractures were then treated by anterior screw fixation. And insertional torque, and pull-out force and stiffness of the bone-screw was tested. Results The lengths of the screws bedded in fractured odontoid process were 8.3mm-12.3mm. The relationship between the pull-out strength (Y) and the length of the screw (X) was determined by the regression equation (Y=156.69+67.97X, r=0.28). However, No significant differences of the insertional torque, and pull-out force and stiffness of the bone-screw were found between the <10mm and >10mm groups. Conclusions Bone-screw stability is not closely related to the distal part of the fractured odontoid process. Anterior screw fixation could be used even when distal fractured part of the odontoid process less than 10mm.