The analysis of imageology for screw tunnel of atlas-axis components of artificial atlanto-odontoid joint

Objective To investigate feasibility and safety for screw tunnel of atlas-axis components of artificial atlanto-odontoid joint (AAOJ) arthroplasty in bony specimens of atlanto-axial joint.Methods The thin-slice CT scannning and the three-dimension reconstruction were performed through 32 sets of artificial atlanto-odontoid joint arthroplasty in adults' bony specimens.The indicators related to AAOJ internal fixation were measured and applied to observe the safe space among screw tunnel of atlas-axis components and important anatomy structures such as transverse foramen,groove for vertebral artery,vertebral canal,etc.Results The length of screw tunnel of atlas components (L) was (21.5 ±3.7) mm,the extraversion angle of screw tunnel of atlas components (α) was ( 12.9 ± 4.8) °,the length of screw tunnel of axis components (S) was (28.6± 3.7) mm,the extraversion angle of screw tunnel of axis components (β) was (22.6 ±4.3)°,and the downslope angle of screw tunnel of axis components (θ) was ( 15.8 ±2.6) °.Conclusion There is a comparatively large safe space between screw tunnel of atlas-axis components of AAOJ arthroplasty and transverse foramen,groove for vertebral artery,vertebral canal,etc. Key words: Atlanto-odontoid joint; Artificial joint; Atlanto-axial joint; Screw; Placement