Fig. 7From: Three-dimensional reduction method with a modified C2 isthmus screw in irreducible atlantoaxial dislocation: a technical noteMeasurement of the O-C2A, CCA and CMA. a O-C2A: Angle between McGregor line (A line) and the line (B line) tangential to the inferior aspect of the axis. b CCA: Angle of the line of inferior 1/3 clivus (line C) and the line extending from the posterior border of the dens to the posteriorinferior border of the axis body (line D). c CMA: Angle of the line extending the anterior border of the ventral medulla (line E) and the line extending the anterior border of the ventral upper cervical spinal cord (line F) in midline sagittal T2 MRI. O-C2A, Occipitoaxial angle; CCA, clivus-canal angle; CMA, cervicomedullary angleBack to article page