COMPUTERISED TOMOGRAPHIC MORPHOMETRIC ANALYSIS OF ATLAS AND AXIS VERTEBRAE

Aim: To study the variations in the morphological dimensions of atlas and axis vertebrae using computerised tomographic scan in Indian population , which can be extrapolated for effective future planning and meticulous surgical technique while operating in C1- C2 region for all kind of pathologies. Materials And Methods: Fifty subjects from both sexes who took computed tomographic scan of brain or cervical spine in Coimbatore medical college for any indications without any abnormality of C1 and C2 are taken for morphological analysis. Study includes patients of adult age group of more than 20 years. Various dimensions of Atlas and Axis are measured and compared with previous studies . Results: The mean value of the various dimensions of lateral mass of atlas is 15.6 mm (AP) and 12.7 mm(TR) and lateral mass of axis is 14.5 mm(AP) and 14.2 mm(TR) respectively , the average screwable thickness in the posterior aspect of C1 lateral mass is 5.4 mm on left and right side. The safe angle for trajectory of C1 lateral mass in sagittal plane is 130 and in axial plane is 11.90 . Conclusion: Morphometric analysis of C1-C2 vertebra shows light on the ideal dimensions and screws to be used in our population. It also shows light on the safety angle and safety margin to avoid complications related to vertebral artery and spinal cord injury.