The pelvic girdle is a ring-like bony structure, situated in the lower component of the trunk. That connects the axial skeleton come the lower limbs.

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In this article, us shall look in ~ the anatomy of the pelvic girdle – its bony landmarks, functions, and its clinical relevance.


Structure of the Pelvic Girdle

The bony pelvis is composed of the 2 hip bones (also known as innominate or pelvic bones), the sacrum and also the coccyx.

There are four articulations in ~ the pelvis:

Sacroiliac joints (x2) – between the ilium that the i know well bones, and the sacrumSacrococcygeal symphysis – between the sacrum and also the coccyx.Pubic symphysis – between the pubis body of the two hip bones.

Ligaments attach the lateral border the the sacrum to assorted bony landmarks top top the bony pelvis to assist stability.


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Fig 1 – The pelvic girdle is formed by the hip bones, sacrum and also coccyx.


Functions the the Pelvis

The solid and rigid pelvis is adapted to serve a number of roles in the human body. The main functions being:

Transfer that weight native the upper axial skeleton come the reduced appendicular contents of the skeleton, especially throughout movement.Provides attachment because that a number of muscles and also ligaments used in locomotion.Contains and also protects the abdominopelvic and pelvic viscera.

The Greater and also Lesser Pelvis

The osteology the the pelvic girdle allows the pelvic an ar to be divided into two:

Greater pelvis (false pelvis) – located superiorly, it provides support the the lower abdominal viscera (such together the ileum and also sigmoid colon). That has little obstetric relevance.Lesser pelvis (true pelvis) – located inferiorly. In ~ the lesser pelvis reside the pelvic cavity and pelvic viscera.

The junction between the greater and also lesser pelvis is known as the pelvic inlet. The outer bony edge of the pelvic inlet are referred to as the pelvic brim.


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Fig 2 – The greater and lesser pelvis. The lesser pelvis is the ‘true’ pelvis and also contains the pelvic cavity.


Pelvic Inlet

The pelvic inlet marks the boundary between the greater pelvis and lesser pelvis. Its dimension is identified by that is edge, the pelvic brim.

The borders of the pelvic inlet:

Posterior – sacral promontory (the superior section of the sacrum) and also sacral wings (ala).Lateral – arcuate heat on the inner surface ar of the ilium, and also the pectineal line on the premium pubic ramus.Anterior – pubic symphysis.

The pelvic inlet determines the size and shape of the birth canal, v the significant ridges a an essential site because that attachment of muscle and ligaments.

Some different descriptive terminology deserve to be provided in explicate the pelvic inlet:

Linea terminalis – the combined pectineal line, arcuate line and also sacral promontory.Iliopectineal heat  the combined arcuate and pectineal lines. This represents the lateral border of the pelvic inlet.
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Fig 3 – Looking under onto the pelvis, the boundaries of the pelvic brim.


Pelvic Outlet

The pelvic outlet is located at the finish of the lesser pelvis, and the beginning of the pelvic wall.

Its boundaries are:

Posterior: The pointer of the coccyxLateral: The ischial tuberosities and the worse margin that the sacrotuberous ligamentAnterior: The pubic arch (the worse border of the ischiopubic rami).

The edge beneath the pubic arch is well-known as the sub-pubic angle and also is that a greater size in women.


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Fig 4 – The borders of the pelvic outlet.


Adaptation for Childbirth

The majority of women have a gynaecoid pelvis, together opposed to the male android pelvis. The slight distinctions in their frameworks creates a greater pelvic outlet, adjusted to help the process of childbirth. As soon as comparing the two, the gynaecoid pelvis has:

A wider and broader structure yet that is lighter in weightAn oval-shaped inlet contrasted with the heart-shaped android pelvis.Less prominent ischial spines, enabling for a greater bispinous diameterA better angled sub-pubic arch, more than 80-90 degrees.A sacrum which is shorter, much more curved and also with a less pronounced sacral promontory.

In addition to the bony adaptations, the sacrotuberous and sacrospinous ligaments can stretch under the influence of progesterone and increase the dimension of the outlet further.


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Fig 5 – Gynaecoid pelvis vs the android pelvis.


Clinical Relevance: evaluate of the mrs Bony Pelvis

The lesser pelvis is the bony canal v which the fetus has to pass during childbirth. It is thus of great importance to recognize the diameter that this canal and also therefore the childbearing volume of the mother.

The diameter have the right to be figured out by a pelvic examination or radiographically. There are two dimensions that are of importance:

Obstetric Conjugate

In stimulate to recognize the narrowest fixed distance the the fetus would have to negotiate, the minimum antero-posterior diameter the the pelvic inlet is measured.

This distance is between the sacral promontory and the midpoint that the pubic symphysis (where the pubic bone is thickest) and also is known as the obstetric conjugate (or true conjugate). However, this measurement cannot be assessed clinically, as result of the existence of the bladder.

Diagonal Conjugate

The diagonal conjugate is the alternative, measuring indigenous the inferior border that the pubic symphysis to the sacral promontory and also can it is in measured manually via the vagina.

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(To perform this you use the pointer of your center finger to measure the sacral promontory and also then using the other hand to note the level the the inferior margin of the pubic symphysis on the analyzing hand. Friend then usage the distance between the index finger and the pubic symphysis to measure the diagonal line conjugate, ideally 11cm or greater)

In addition to measuring the diagonal line conjugate, a mid-pelvis check is carried out. Here, the clinician is trial and error for straight side walls and measuring the bispinous diameter which is narrowest component of the pelvic canal. The broad of the subpubic angle at the pelvic outlet deserve to be determined by the distance between the ischial tuberosities.


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Fig 6 – evaluate of the mrs pelvis, via the diagonal line conjugate