Developing And Finite Element Analysis Of Atlantoaxial Interlamina Fusion Cage

OBJECTIVE:1.To complete the image anatomical measurement of atlantoaxial interlamina fusion cage and evaluate the feasibility of atlantoaxial interlamina fusion cage.2.To complete the initial design of the atlantoaxial interlamina fusion cage.3.To establish the three-dimensional finite element model of normal upper cervical spine and verify the effectiveness of the model.4.Based on the three-dimensional finite element model of normal upper cervical spine,to establish the three-dimensional finite element models of atlantoaxial instability,atlantoaxial posterior screw-rod internal fixation and atlantoaxial interlamina fusion cage plus posterior screw-rod internal fixation and analyze the mechanical properties of atlantoaxial interlamina fusion cage.METHODS:1.100 cases of normal adult atlantoaxial CT scan images were collected,including 50 males and 50 females,aging 18 to 76 years old.The PACS system workstation was used to access the image and measure the atlantoaxial relevant data.2.The use of Solidworks 2012 software initially designed atlantoaxial interlamina fusion cage.3.The three-dimensional finite element model of normal upper cervical spine was constructed by using Mimics 13.0,Geomagic Studio 2012 and Abaqus 6.14 software.Under the special constraint and loading condition,the validity of the model was verified by compared with ROM of the results in previous literature data.4.On the basis of the three-dimensional finite element model of normal upper cervical spine,the three-dimensional finite element models of atlantoaxial instability,atlantoaxial posterior screw-rod internal fixation and atlantoaxial interlamina fusion cage plus posterior screw-rod internal fixation were established,and the finite element analysis is used to calculate the activity and stress of various models under different working conditions.RESULTS:1.There was no significant difference between the data of both sides(P>0.05).After merging the data of both sides,the differences of L1,H1 and L2 between the two genders were statistically significant(P<0.05),but there was no significant difference of H2 and L between the two genders(P>0.05).Male and female L1 were 23.41mm and 22.23mm;H1 were 6.00mm and 5.28mm;L2 were 18.54mm and 17.31mm;H2 were 5.12mm and 4.98mm;L were 32.63mm and 31.39mm.2.The atlantoaxial interlamina fusion cage was designed initially.3.The three-dimensional finite element model of normal upper cervical spine was established,including 206745 cells and 72496 nodes.The effectiveness of the model was validated for follow-up study exactly.4.The three-dimensional finite element models of atlantoaxial instability,atlantoaxial posterior screw-rod internal fixation and atlantoaxial interlamina fusion cage plus posterior screw-rod internal fixation were established.The activity of the two fixation models was much less than that of the normal model and the unstable model(P<0.05)under the six working conditions of flexion,extention,left-flexion,right-flexion,left-rotation and right-rotation.(P<0.05).There was no significant difference between the activity of the two fixation models(P>0.05).The maximum stress in the atlantoaxial interlamina fusion cage was concentrated in the implanted parts of the micro-titanium nail into the bone site.The maximum stress of the screw-rod in the two fixation models is concentrated in the root of the screws and the connecting rods,and there was no significant difference between the maximal equivalent stress values of the screw-rod in the two fixation models(P>0.05).CONCLUSIONS:1.The atlantoaxial interlamina fusion cage is feasible theoretically.2.The three-dimensional finite element model of normal cervical spine is effective and can be studied in related research.3.The atlantoaxial interlamina fusion cage has stability and safety,and has no obvious effect on the fixation and stress of the posterior screw-rod.