Scoliosis x-ray and demonstration of Cobb angle

(A) The patient is a 17-year-old boy with Duchenne muscular dystrophy. The x-ray shows a levoconvex scoliotic curvature of the lumbar spine with the apex of the curve at L2. Lines are drawn for calculation of the Cobb angle. The upper line is drawn parallel to the superior vertebral end plate of T12, and the lower line is drawn parallel to the inferior vertebral endplate of L4. The Cobb angle (30 degrees) is the angle formed by the intersection of these two lines. (B) An alternative method for calculating the Cobb angle also begins by drawing primary lines parallel to the superior and inferior vertebral endplates above and below the curve. Secondary lines are then drawn perpendicular to the primary lines. The Cobb angle is the angle formed by the intersection of these secondary lines. The measured Cobb angles are equivalent with the techniques in A and B. (Contributed by Dr. Daniel Bonthius.)