The pelvis is split into the false or greater pelvis above, and true or lesser pelvis below. The plane of division is pelvic inlet created by the sacral promontory behind and linea terminalis at the sides and front. The linea terminalis might be followed as a continuous line from behind forwards as the arcuate line of the ilium, the iliopectineal line (pecten), and the pubic crest.
The false pelvis is actually a part of the abdominal cavity suitable. The true pelvis is involved in the process of arrival, thus named obstetric pelvis/true pelvis. So, the student must understand its size, create, and measurements in detail.
Regions of The True Pelvis
The true pelvis presents the pelvic inlet, pelvic outlet, and pelvic cavity.
Borders of The Pelvic Inlet
- Posteriorly: Sacral promontory and anterior margins of alae of the sacrum.
- Laterally: Arcuate and pectineal lines.
- In front: Upper margin of pubic symphysis and pubic crests.
Boundaries of The Pelvic Outlet
- Anteriorly: Lower margin of the pubic symphysis.
- Anterolaterally: Conjoint ischiopubic ramus on every side.
- Laterally: Ischial tuberosity on every side.
- Posterolaterally: Sacrotuberous ligament on every side.
- Posteriorly: Tip of the coccyx.
Borders of The Pelvic Cavity
- Anteriorly: Pelvic surfaces of the bodies of pubic bone, pubic rami, and pubic symphysis.
- Posteriorly: Pelvic surfaces of the sacrum and coccyx.
- Laterally: Pelvic surfaces of the ilium ischium below thearcuate line.
The pelvic brim and pelvic outlet don’t be located in the horizontal plane when the subject stands erect. The planes of pelvic inlet and pelvic outlet incline downward from behind forward. Consequently, the pla.ne of pelvic inlet creates an angle of about 55 °/ 60 ° to the horizontal plane, and the plane of pelvic outlet creates an angle of 15 ° with the horizontal plane.
Plane of best pelvic measurement: It’s an imaginary plane passing anteroposteriorly via the middle of pubic symphysis and junction between S2 and S3 vertebrae.
Plane of least pelvic measurement: Anteroposteriorly it’s an imaginary plane going through the lower margin of pubic symphysis to the tip of sacrum. Transversely, it’s an imaginary plane going through the ischial spines.