One Possible Cause for the Frequent Occurrence and Nonunion of Type II Odontoid Fracture 

Abstract

Background. To analyze the underlying causes of frequent occurrence and nonunion of type II odontoid fracture.Methods. CT scans along with 3D imaging software (Mimics software) were used to measure the bone density of the axis. The axis was divided into three parts, including the odontoid of the axis (the first part), the base of the odontoid (the second part) and the body of the axis (the third part). The CT value of the axis was measured and analyzed in different axial planes from top to bottom, followed by calculation and comparison of the mean CT value of the three parts of the axis.Results. The mean CT value of the odontoid (the first part), base of the odontoid (the second part) and body of the axis (the third part) was 651.35±188.32, 318.38±98.82 and 397.45±93.59, respectively. In addition, the interval variation of CT value of different axial planes was initially decreased and further increased with the change of axial planes from top to bottom.Conclusion. The mean CT value of the base of the odontoid was significantly lower than that of the odontoid or the body of the axis. Therefore, the base of the odontoid was the transition region of shape and bone density, which may be one possible cause for the frequent occurrence and nonunion in the type II odontoid fracture in axis fracture.