Figure 2

Planes of reference for measurement and pelvic XYZ coordinate system. (a) Recommended by the STC; (b) anterior pelvic plane; and (c) the sacral-base plane, recommended by the authors of this research; each picture with visualization of pelvic XYZ coordinate system. 2D, two-dimensional; 3D, three-dimensional; STC, Standardization and Terminology Committee of the International Society of Biomechanics.