An anthropometric-based method for the assessment of pelvis position in three-dimensional space

Determining the pelvis position remains a challenge for clinical therapists and researchers mainly due to the difficulty in assessing its potential triaxial rotations in the upright standing posture. The method described in this study aims to determine the position of the pelvis in the upright standing posture by calculating the Euler/Cardan angles of pelvic rotations based on the triaxial coordinates of the anterior superior iliac spines and the pubic symphysis. The coordinates of these bony landmarks were determined with two laser distance meters and a standard metric ruler, all mounted on a custom-made structure. The calculations of all Euler/Cardan angle rotation sequences for both the internal and external rotations of the pelvis were performed by developing an algorithm that executed via a computer program specifically designed for the purpose of this study. The validity of the algorithm was tested by comparing the actual angles of known positions at which an anatomical model of the pelvis was placed with the calculated angles. Our findings revealed <1° differences between the actual and the calculated angles of pelvis rotations regardless of the axis around which it was rotated suggesting that the proposed method can be used for clinical and research purposes. • The triaxial coordinates of pelvis bony landmarks can be measured anthropometrically using simple measuring instruments; • Pelvis posture can be determined in 3D space with great accuracy by means of the Euler/Cardan angles.