[Morpho-metrical features of the pelvis in standing posture]

The morpho-metrical features of the human pelvis differ according to gender, particularly with regard to size and shape, and bipedal standing posture appears to have been a major determinant of pelvic structure. In standing posture, the three points of the right and left superior anterior iliac spines and pubic tubercle are in contact with the vertical frontal plane. In this situation, the superior anterior iliac spine is lower than the superior posterior iliac spine. From a lateral view, the vertical line from the body's center of gravity passes through the center of the hip joint or acetabulum. The anatomical or biomechanical problem has been whether the line of gravity passes through the promontory or the center of auricular surface. To clarify this point, the three points of the acetabular center, promontory and auricular center were examined as to how they are positioned in relation to each other and the distance of each on the vertical frontal plane. Those measurements are as followed: A) distance between vertical frontal plane and promontory, B) distance between vertical frontal plane and anterior margin of auricular surface, C) distance between vertical frontal plane and mid-point of auricular surface computed from (B + D)/2, D) distance between vertical frontal plane and posterior margin of auricular surface, E) distance between vertical frontal plane and mid-point of acetabulum, F) inclination angle of the pelvis. From the results, the acetabular center and promontory are in alignment with the vertical line. The auricular center is positioned further back than the acetabular center or promontory. In this situation, the mean angle of inclination of the pelvis was found to be 63 degrees in 16 Japanese male specimens. The means of the other Japanese populations are into range of 63 degrees to 66 degrees in the males. If the auricular center coincides with the acetabular center, it is possible the angle of inclination of the pelvis would exceed 63 degrees. The frontal plane in contact with the right and left superior anterior iliac spines and pubic tubercle is not vertical. The morphological features clarified in the present study are that the promontory and acetabular center are in vertical alignment when viewed laterally and that the angle of inclination of the pelvis is 63 degrees.