Tag: spine anatomy

– Bispinous diameter: The distance between the tips of the ischial spines is 10.5 cm.
– Pelvic planes:
– Plane of pelvic inlet: It forms an angle of 55o with the horizon and passes through the boundaries of the pelvic brim.
– Plane of mid cavity: It passes between the posterior surface of the symphysis pubis and the junction between the 2nd and 3rd sacral vertebrae. It has a diameter of 12.5 cm.
– Plane of obstetric outlet: It passes from the lower border of the symphysis pubis anteriorly to the ischial spines laterally and the tip of the sacrum posteriorly.
– Anterior sagittal diameter: It is 6-7 cm from the lower border of the symphysis pubis to the center of the bituberous diameter.
– Posterior sagittal diameter: It is 7.5-10 cm from the tip of the sacrum to the center of the bituberous diameter.
– Pelvic axes:
– Anatomical axis: It is a C-shaped line joining the center points of the planes of the inlet, cavity, and outlet.
– Obstetric axis: It is a J-shaped line representing the path taken by the head during labor.
– Caldwell-Moloy Classification of Pelvic Types: It describes four types of female pelves:
– Gynaecoid pelvis (50%): It is the normal female type with a slightly transverse oval inlet and wide sacro-sciatic notch.
– Anthropoid pelvis (25%): It has long anteroposterior diameters and short transverse diameters.
– Android pelvis (20%): It is a male type with a triangular or heart-shaped inlet and narrow sacro-sciatic notch.
– Platypelloid pelvis (5%): It is a flat female type with short anteroposterior diameters and long transverse diameters.