用于Hangman骨折治疗的椎弓根拉力螺钉的设计与生物力学测试

A new transpedicular lag-screw for treatment of Hangman＇s fracture

目的研制一种新型的专用于治疗Hangman骨折的椎弓根拉力螺钉。方法选取20具成人干燥颈椎标本，采用游标卡尺测量枢椎的椎弓根高度、椎弓根宽度、侧块中点（进钉点）至椎体前缘的距离、椎体上关节突前后径；6例Hangman骨折患者术前牵引复位后的X线片，采用计算机测量工具测量枢椎侧块中点至椎体前缘的距离、侧块中点至骨折线的距离、骨折线至椎体前缘的距离。参考Herbert螺钉的特点，根据测得的枢椎椎弓根的解剖数据设定新型螺钉各参数，研制一种专用于治疗Hangman骨折的双螺纹加压空心螺钉。用10个PVC高分子塑料制成的枢椎Hangman骨折模型，分别采用新型椎弓根拉力螺钉和普通螺钉对其进行固定，然后进行生物力学抗拉伸测试。结果标本测量：椎弓根高度平均为（7．40±1．04）mm，椎弓根宽度平均为（7．45±1．54）mm，侧块中点至椎体前缘的距离平均为（27．95±1．69）mm，上关节突前后径平均为（17．29±1．51）mm。X线片测量：侧块中点至椎体前缘的距离平均为（29．19±3．54）mm，侧块中点至骨折线的距离平均为（10．71±2．44）mm，骨折线至椎体前缘的距离平均为（15．35±1．66）mm。标本左、右侧椎弓根相关参数的差异无统计学意义。新型螺钉组抗拉伸力平均为（2266．47±158．82）N，普通螺钉组抗拉伸力平均为（1715．51±69．99）N，两组比较差异有统计学意义。结论新型螺钉经椎弓根内固定治疗Hangman骨折的生物力学性能优于普通螺钉。

Objective To design a novel transpedicular lag-screw for the treatment of Hangman＇s fracture. Methods Twenty adult dried cervical vertebrae specimens were selected and used vernier caliper to measure the indexes of C2, including the height of pedicle, the width of pedicle, the distance of massa lateralis midpoint （entry point） to anterior vertebral, and the anteroposterior diameter of processus articulares superiores. The X-ray films of six Hangman＇s fracture patients after reduction were selected, and the indexes of C2 were measured on computer, including the distance of entry point to anterior edge, the dis-tance of entry point to fracture line, and the distance of fracture line to anterior edge. According to the anatomic parameters of C2 pedicle and the characteristics of Herbert-screw, a new type of transpedicular lag-screw was designed, which is more suitable for the treatment of Hangman＇s fracture. This screw is double-threaded, and the biomechanics of which were compared with ordinary ones. Results Specimen measurements showed the height of pedicle （7.40±1.04） mm, the width of pedicle （7.45±1.54） mm, the distance of massa lateralis midpoint to anterior vertebrae （27.95±1.69） mm, and the anteroposterior diameter of processus articu-lates superiors （17.29±1.51） mm. X-ray measurements showed the distance of entry point to anterior edge （29.19±3.54） mm, the distance of entry point to fracture line （10.71±2.44） ram, and the distance of fracture line to anterior edge （15.35±1.66） ram. There were no significant differences between the two sides of the pedicle measurements. The new-screw group and the ordinary-screw group tensile strength was （2266.47±158.82） N and （1715.51±69.99） N, respectively. There were statistically significant differences between the two groups. Conclusion The effect of novel transpedicular lag-screws for the treatment of Hangman＇s fracture is better than that of the ordinary ones.