File:Scoliosis cobb angle measurement.png

Summary

The magnitude of a scoliosis curve is given by the Cobb angle. To measure the Cobb angle, one must first identify the “end vertebrae,” the top and bottom-most vertebral bodies in the curve. (As shown in the figure, this spine has 2 offsetting curves, denoted by green and red vertebral bodies.) Lines are then drawn along the superior endplate of the highest vertebral body (A) and the inferior endplate of the lowest vertebral body (B). These lines are then extended until they intersect; the angle between them is the Cobb angle (C). For smaller curves, the angle may be sufficiently small that the lines may not intersect on the films. In that case, the lines are extended only a short distance, but perpendicular lines are drawn from each towards the other line (as shown in D). The intersection of these perpendiculars (owing to geometry’s rule of similar triangles) likewise defines the Cobb angle. The curves shown here are approximately 40 and 90 degrees.

From https://orthopaedia.com/page/Adolescent-Idiopathic-Scoliosis

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