3D-CT Observation Of The Effects Of Simple Fracture Structures Of The Axis Ring

Objective: To observe the imaging characteristics of simple fracture of the axis ring by X-ray,CT scan,three-dimensional reconstruction and MRI images,and to explore the stability of simple fracture of the axis ring.Methods: The clinical and imaging data of all patients with Hangman fracture from January2008 to December 2018 were searched in the prospective case database of our department.In patients with cervical spine X-ray,CT plain scan,threedimensional reconstruction and MRI images,patients with simple axis ring fracture were searched(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 observation objects of peripheral anatomical structure fracture associated with axis ring fracture were divided into bilateral superior articular process(SAP),bilateral inferior articular process(IAP)and bilateral lamina fracture(CL).The incidence of simple axis ring fracture combined with peripheral anatomical structure fracture was observed.Axis ring fracture was divided into anterior ring(bilateral superior articular process,bilateral posterior wall of vertebral body),middle ring(bilateral pedicle of vertebral arch)and posterior ring(bilateral inferior articular process,bilateral lamina)fractures.The incidence of anterior,middle and posterior ring fracture was counted and compared.According to the injury characteristics of the axis ring and the classification of atypical Hangman fracture by previous scholars,the simple axis ring fracture is classified as type A: The fracture takes pedicle as the axis,including symmetrical or asymmetrical fractures of the bilateral C2 pedicle(POC),and one side pedicle fracture combined with contralateral inferior articular process and lamina fracture.Type B: Posterior wall of the Axis body(PWA)as the axisof the fracture with contralateral pedicle fracture,or one side of the posterior wall of the vertebral body as the axis with contralateral inferior articular process and contralateral lamina fracture;Type C: fracture with bilateral posterior wall or superior articular process as the axis,posterolateral edge fracture of the axis,incomplete axis ring,including bilateral posterior wall symmetry or asymmetrical axis ring.To observe the characteristics of each type of axial ring fracture with bilateral superior articular process,bilateral inferior articular process and bilateral lamina fractures,and to explore the occurrence and stability of simple axial ring fracture without displacement of C2/3intervertebral space into angle and injury of anterior and posterior longitudinal ligaments.Results: According to the inclusion and exclusion criteria,52 cases of simple fracture of the axis ring were collected,34 males and 18 females.The youngest age was 22 years old and the oldest was 83 years old,with an average age of(47.88 + 15.73)years.Causes of injury: 23 cases of high fall injury,15 cases of traffic accident injury,5 cases of heavy crush injury,4 cases of life injury,5 cases of other causes.Among this group,there were 37 cases with peripheral anatomical structure fractures and 57 fractures accounted for 71.2%(37/52).24 cases(11 cases on the left side,9 cases on the right side and 4 cases on the bilateral superior articular process)were complicated with fractures of the superior articular process,accounting for 46.1% of the simple fracture of the axis ring,22 cases(3 cases on the left side,19 cases on the right side,0cases on both sides)with fractures of the inferior articular process,accounting for 42.3% and 7 cases(3 cases on the left side and 4 cases on the right side)with fractures of the lamina,accounting for 13.5%.Fifteen cases(28.8%)were not complicated with peripheral anatomical fracture.There were 149 anterior,middle and posterior ring fractures,92 anterior ring fractures(61.7%),28 middle ring fractures(18.8%)and 29 posterior ring fractures(19.5%).Type A fractures accounted for 19.2%(10/52),bilateral pedicle fractures accounted for70%,left pedicle fractures combined with contralateral inferior facet fracturesaccounted for 20%,left pedicle fractures combined with contralateral lamina fractures accounted for 10%,and no bilateral superior facet fractures were found.Type B fractures accounted for 59.6%(31/52),15 cases(9 left,6 right,0bilateral)with superior articular process fractures accounted for 48.4%,16 cases without superior articular process fractures accounted for 51.6%;20 cases(3 left,17 right,0 bilateral)with inferior articular process fractures accounted for 64.5%,11 cases without inferior articular process fractures accounted for35.5%;12 cases with pedicle fractures(7 left,5 right),accounted for 51.6%.38.7%,19 cases were combined with pedicle fracture(61.3%),6 cases with lamina fracture(2 cases on the left side and 4 cases on the right side)accounted for 19.4%,25 cases without lamina fracture(80.6%).In addition,there are five types of fracture combinations in type B fracture: unilateral superior articular process fracture in 2 cases(left 1 case,right 1 case);unilateral inferior articular process fracture in 10 cases(all right side);simultaneous fracture of superior and inferior articular process in 10 cases(simultaneous fracture of left superior and right inferior articular process in 7 cases,simultaneous fracture of right superior and left inferior articular process in 3 cases);simultaneous fracture of articular process and pedicle in 12 cases;There were 6 cases of simultaneous fracture of articular process and lamina.11 cases of type C fracture accounted for 21.2%(11/52),9 cases of upper facet fracture(2 cases of left superior facet fracture,3 cases of right superior facet fracture,4 cases of double superior facet fracture)13 cases accounted for 81.8%,and 2 cases of no upper facet fracture accounted for 18.2%.There were 0 cases of inferior articular process fracture,0cases of pedicle fracture and 0 cases of lamina fracture.The incidence of type B was the highest,type C was the second,and type A was the lowest.There were statistical differences in the incidence of complications among the three groups(P < 0.05)(Table 3): 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.Type A overextension compressionstress mainly acts on the middle ring of bilateral pedicle,while rotation stress mainly acts on the posterior ring opposite to the pedicle fracture;Type B overextension compression stress mainly acts on the unilateral anterior ring of the axis ring,accompanied by rotation stress leads to the fracture of the contralateral middle and posterior ring.If the rotation stress is not too large,the fracture of the contralateral pedicle(middle ring)will occur,and if the direction stress is moderate.Contralateral inferior articular process(posterior ring)fractures occur,and contralateral lamina(posterior ring)fractures occur when direction and stress are large enough.Overextension compression stress of type C fractures mainly acts on the anterior ring of the axis ring,without rotational stress leading to posterior ring fractures.The rotation stress of the central annulus of type B fracture is greater than that of type A fracture.Conclusion: 1.The incidence of simple axis ring fracture combined with intervertebral joint injury was 69.2%,and that of lamina fracture was 13.4%.2.For simple fracture of the axis ring,the overextension compression stress mostly acts on the front and middle rings,and the rotation stress acts on the back rings..Simple fracture of the axis ring itself is a rigid closed double fracture,which is unstable fracture;it is more unstable when combined with fracture of bilateral upper articular process,bilateral inferior articular process,bilateral lamina and other surrounding anatomical structures;4.In the absence of combined C2/3 disc ligament complex injury,the fracture of the axis ring is damaged according to the condition.Traumatic characteristics can be divided into three types: pedicle fracture,posterior wall fracture of one side and posterior wall fracture of both sides.These three types include all types of fracture of the axis ring.Especially when combined with the fracture of the surrounding anatomical structure observed in this study,the epidemiological characteristics of the classification of spinal injury are accorded with.