Figure 4.

Demonstration of measurement parameters (measurements made upon X‐rays for respective subject) A: L ₁ coronal bisector, drawn from T ₁₂ spinous process perpendicular to the floor (left image); B: Difference in iliac crest height, measured by using horizontal line as baseline for measurement of height differences; C: Center sacral vertical line, drawn perpendicular to the S ₁ end‐plate through the S ₁ spinous process to the coccygeal tip; D: Distance between coronal bisector and “posterior” S ₂ spinous process, measured by drawing horizontal line perpendicular to L ₁ coronal bisector (A) to the center sacral vertical line intersection with the S ₁ spinous process (C).