A New Transpedicular Lag-screw For Treatment Of Hangman’s Fracture

Objective: To design a novel transpedicular lag-screw for the treatment ofHangman’s fracture.Methods: We selected20adult dried cervical vertebrae specimens, and used verniercaliper to measure the indexes of C2(①the height of pedicle,②the width of pedicle,③the distance of massa lateralis midpoint (entry point) to anterior vertebral,④theanteroposterior diameter of processus articulares superiores).We selected the X-ray film ofsix Hangman’s fracture patients after reduction, and measured the indexes of C2oncomputer (①the distance of entry point to anterior edge,②the distance of entry point tofracture line,③the distance of fracture line to anterior edge). According to the anatomicparameters of C2pedicle and the characteristics of Herbert-screw, we designed a new typeof transpedicular lag-screw, which is more suitable for the treatment of Hangman’sfracture. This screw is double-threaded. And we compared the biomechanics of newscrews with ordinary ones.Results：1. Specimen measurements: the height of pedicle:(7.40±1.04)mm; the widthof pedicle:(7.45±1.54)mm; the distance of massa lateralis midpoint to anterior vertebrae:(27.95±1.69)mm; the anteroposterior diameter of processus articulares superiors:(17.29±1.51)mm. X-ray measurements: 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)mm; the distanceof fracture line to anterior edge:(15.35±1.66)mm. Both sides of the pedicle measurementswere compared with P values, and there were no significant differences (P>0.05).2: Thenew-screw group tensile strength:(2266.47±158.82)N; the ordinary-screw group tensilestrength (1715.51±69.99)N. The data of the two groups were compared with P values, andthere were statistically significant differences (P<0.05).Conclusion：The effect of novel transpedicular lag-screws for the treatment ofHangman’s fracture is better than that of the ordinary ones.