1. Sacral index: (Width x 100) / Straight Length
2. Curvature index: (Straight Length x 100) / Mid -ventral curved length
3. Index of body of Ist Sacral vertebra: (AP daimeter of body of S 1 x 100) / Transeverse dia of body of S 1
4. Corporo-basal index: (Transverse diameter of body of S1 x 100) / Width of sacrum
5. Alar index: (Length of ala x 100) / Transverse diameter of body of S1
6. Auricular index: (Length of auricular surface x 100) / Width of sacrum
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1. Maximum length of sacrum (Wilder's mid- ventral Straight length) -measured along the mid-line of sacrum with the sliding caliper from middle of antero-superior margin of promontory to middle of antero-inferior margin of the last sacral vertebra.
2. Maximum breadth of sacrum -measured with the sliding caliper by taking two points at the upper part of auricular surface anteriorly (or lateral most part of alae of sacrum), thus maximum breadth is measured on anterior aspect of sacrum.
3. Curved length of sacrum (Mid-ventral curved length)- measured along the mid line of the anterior surface of the sacrum (from middle of antero-superior margin of promontory to middle of antero-inferior margin of the last sacral vertebra) by the flexible steel tape.
4. Antero-posterior diameter of the body of Ist sacral vertebra - It is the maximum possible diameter of Ist sacral vertebra measured with the sliding caliper by taking one point on antero-superior border and another point on the postero-superior border of Ist sacral vertebral body.
5. Transverse diameter of the body of Ist sacral vertebra- It is the maximum transverse diameter of Ist sacral vertebra measured with the sliding caliper by taking one point on each side of the lateral most point on the superior surface of body of Ist sacral vertebra.
6. Length of alae -It is measured on both sides with the sliding caliper by taking one point on lateral most point of superior surface of body of Ist sacral vertebra and another point on lateral most part of alae. The mean of the length of the two sides is taken as length of alae.
7. Maximum length of auricular surface-It is the straight auricular length measured on lateral aspect of sacrum by means of a sliding caliper by taking one point on the upper most part of auricular surface and another point on the lower most part of auricular surface of sacrum.
