Image Measurement Of Craniovertebral Junction Malformation And Biomechanical Evaluation Of C2 Trans-laminar Sctew

ObjectiveCraniovertebral junction malformation are considered rare diseases,which lead to life-threatening problems because of spinal cord compression.Posterior decompression and internal fixation is the main treatment now, pedicle screw fixation is the common means of posterior atlantoaxial fixation, but to craniocervical malformation patients, the risk of pedicle screw fixation is huge. The laminar screw was first applied to the clinical by Wright,More than the normal case based on its research, is it applicable for patients with craniovertebral junction malformation? To provide the morphological and anatomical change of C2 laminar in craniovertebral junction malformation.,discuss anatomic data of posterior screw instrument in axis laminar of Craniovertebral junction malformation.,to evaluate its clinical feasibility. Through compare the pull-out strength of C2 pedicle screws and C2 trans-laminar screws to provide the biomechanical basis for clinical application of C2 trans-screw techniques.MethordFifty patients with craniovertebral junction malformation were analyzed, constructed three dimensional models after spiral CT scan, to examin the anatomical and morphological date of C2 trans-laminar screw techniques by selective display, cutting and arbitary rotation of the 3D models.The date included the thickness of the superior, median and inferior part of C2 laminar, the height of laminar, the distance between the anchor point and mid-point of C2 lateral mass, The angle between the axial of C2 laminar and sagittal plain.Seven dry specimens were used, and the c2 trans-laminar screw and pedicle screw was placed in seven fresh C2 specimens.to test and compare the pull-out strength of the screws in each specimen. The results of the two groups were analysised by SPSS software with rank sum testResultsThe thickness of superior part of C2 laminar was 4.14±0.96mm,5.78±1.42mm in media part, and 5.02±1.12mm in inferior part, the height of C2 laminar was 10.88±0.85mm, the distance from C2 laminar anchor point to medial border of vertebral artery foramen was 31.23±3.86mm, the distance from C2 laminar anchor point to mid-point of the lateral mass was 27.23±3.37mm, the angle between the axial of C2 laminar and sagittal plane was43.59±2.96°.The pull-out strength of C2 trans-laminar screw was 561.77±246.04N, the pull-out strength of C2 pedicle screw was 715.71±289.75N, higher than that of trans-laminar screw. The data were analysised by SPSS software, there is no difference between the two parameters (P> 0.05).Conclusion1 Through the image measurement of craniovertebral junction malformation, C2 trans-laminar screw could be used in 85 percent patients.2 There is malformation of C2 in different way and degree, the variation of individual discrepancy is obvious, SCT and correlative data should be performed before surgery of trans-laminar screw fixation.3 The mean pull-out strength of C2 trans-laminar screw is lower than C2 pedicle screw, but the C2 trans-screw technique possesses reliable biomechanics strength, this could be used as a supplementary method for posterior screw fixation techniques of axis.