Figure 2

Cobb Angle Calculation in the Sagittal Spine. α represents the Cobb Angle. The curved segment has B as its top vertebra and C as its bottom vertebra. Vertebra B’s superior surface tilts to the side of the concavity of the curve, while vertebra A’s inferior surface tilts to the convexity side. The intervertebral space between vertebrae A and B on the side of the concavity is wider than the side of convexity. Vertebra C’s inferior surface tilts to the side of the concavity of the curve, while vertebra D starts to tilt to the convexity side; the intervertebral space between vertebrae C and D on the side of concavity is wider than the side of convexity. Line 1 is parallel to the superior surface of the top vertebra in the segmental curve (here vertebra B), while line 2 is parallel to the inferior surface of the bottom vertebra in the curve (here vertebra C). The angle formed by the intersection of lines 1 and 2 is the Cobb Angle, which is the “angle of the curve”.