Study and clinical significance of three-dimensional CT classification of fractures with different anatomical structures affecting the stability of single axial ring fractures

English Keywords:Axis ring fracture  Stability  Three-dimensional reconstruction of CT  MRI

English Abstract:

  【Abstract】 Objectives: To observe the imaging features of single axial ring fractures using X-ray, CT scan and MRI, three dimensional CT classification was conducted according to the characteristics of each anatomical structure fracture and its influence on stability, to explore its clinical significance. Methods: The clinical and imaging data of all patients with Hangman fracture from January 2008 to December 2018 were searched in the multi center prospective case database, and the patients with simple axis ring fracture were found(referring to Levine-Edwards type I Hangman fracture diagnosed on X-ray films, and C2/3 abnormal signal of injury of ligament complex of intervertebral disc was excluded by MRI images). The fracture of each anatomical structure of the axis ring was divided into bilateral superior articular process(SAP), bilateral inferior articular process(IAP) bilateral lamina fracture(CL), bilateral pedicle and posterior wall fractures. The fracture of axis ring was divided into anterior ring(bilateral superior articular process, bilateral posterior wall of vertebral body), middle ring(bilateral pedicle) and posterior ring(bilateral inferior articular process, bilateral lamina). The incidence of anterior, middle and posterior ring fracture was compared. According to the injury characteristics of the axial ring and the classification of the atypical Hangman fracture by the previous scholars, the simple axial ring fracture was divided into three types: A, B and C(Type A, with pedicle as the center, including bilateral C2 pedicle symmetrical or asymmetric fractures; one side pedicle fracture with opposite articular process and lamina fractures. Type B, the fracture was centered on the posterior wall of one side of the vertebral body and combined with the fracture of the contralateral pedicle, contralateral articular process and contralateral lamina. Type C, the fracture was centered on the posterior wall of both sides of the vertebral body, with the edge fracture of the axial vertebral body and the incomplete axis ring, including the symmetrical or asymmetrical fracture of the posterior wall of both sides of the vertebral body). To observe the characteristics and the incidence of the fracture of each anatomical structure in the simple axis ring fracture, and to explore the regularity and stability of the simple axis ring fracture under the condition of C2/3 intervertebral space without displacement and angulation and anterior and posterior longitudinal ligament injury. Results: According to the inclusion and exclusion criteria, data of 52 cases(34 males and 18 females) of simple fracture of the axis ring were collected. The average age was 47.9±15.7 years, ranging from 22 to 83 years old. In this group, there were 36 cases(69.2%) with 50 fractures of intervertebral joints(SAP and IAP) and 16 cases(30.8%) with 30 fractures of simple bone injury. There were 149 ring fractures: 92 anterior ring fractures(61.7%), 28 middle ring fractures(18.8%) and 29 posterior ring fractures(19.5%). The incidence of type B was the highest, type C was the second, and type A was the lowest. There was statistical difference in the incidence of complications among the three groups(P<0.05). The incidence of type A complicated with peripheral anatomical fractures was lower than that of type B and C, and there was no statistical difference between type B and C(P＞0.05). Conclusions: In the simple axis ring fracture, the incidence of the intervertebral jointfractureis high. The hyperextension compression stress mostly acts on the anterior ring and the middle ring, while the rotation stress acts on the posterior ring. Simple axis ring is a rigid closed bone ring, if there are two anatomical fracture, it is unstable; it is more unstable when there are bilateral upper articular process, bilateral lower articular process, bilateral lamina fractures. The new classification in this paper is more accurate to judge the stability of this kind of fracture.