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

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

Structure the the Pelvic Girdle

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

There are four articulations within the pelvis:

Sacroiliac joints (x2) – between the ilium of the i know well bones, and also the sacrumSacrococcygeal symphysis – between the sacrum and also the coccyx.Pubic symphysis – between the pubis bodies of the 2 hip bones.

Ligaments attach the lateral border that the sacrum to assorted bony landmarks on the bony pelvis to help stability.

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

Functions that the Pelvis

The strong and rigid pelvis is adjusted to offer a variety of roles in the human being body. The main functions being:

Transfer the weight from the top axial skeleton to the reduced appendicular materials of the skeleton, especially during movement.Provides attachment for a number of muscles and also ligaments used in locomotion.Contains and protects the abdominopelvic and pelvic viscera.

The Greater and Lesser Pelvis

The osteology the the pelvic girdle enables the pelvic an ar to be split into two:

Greater pelvis (false pelvis) – situated superiorly, it gives support the the lower abdominal viscera (such together the ileum and also sigmoid colon). The has small obstetric relevance.Lesser pelvis (true pelvis) – situated inferiorly. Within the lesser pelvis reside the pelvic cavity and also pelvic viscera.

The junction between the greater and lesser pelvis is known as the pelvic inlet. The outer bony edges of the pelvic inlet are dubbed the pelvic brim.

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

Pelvic Inlet

The pelvic inlet clues the boundary between the greater pelvis and also lesser pelvis. Its dimension is characterized by that edge, the pelvic brim.

The boundaries of the pelvic inlet:

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

The pelvic inlet identify the size and also shape the the birth canal, with the significant ridges a crucial site because that attachment the muscle and ligaments.

Some alternative descriptive terminology can be provided in relenten the pelvic inlet:

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

Pelvic Outlet

The pelvic outlet is situated at the finish of the lesser pelvis, and the start of the pelvic wall.

Its borders are:

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

The edge beneath the pubic arch is known as the sub-pubic angle and also is of a higher size in women.

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Fig 4 – The boundaries of the pelvic outlet.

Adaptation for Childbirth

The majority of women have actually a gynaecoid pelvis, as opposed to the male android pelvis. The slight differences in their frameworks creates a higher pelvic outlet, adjusted to aid the procedure of childbirth. As soon as comparing the two, the gynaecoid pelvis has:

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

In enhancement to the bony adaptations, the sacrotuberous and sacrospinous ligaments deserve to stretch under the affect of progesterone and also increase the size 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 needs to pass during childbirth. The is because of this of good importance to recognize the diameter that this canal and therefore the childbearing capacity of the mother.

The diameter deserve to be determined by a pelvic examination or radiographically. There are two measurements that are of importance:

Obstetric Conjugate

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

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

Diagonal Conjugate

The diagonal conjugate is the alternative, measuring indigenous the worse border the the pubic symphysis come the sacral promontory and can it is in measured manually via the vagina.

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(To perform this you usage the tip of your center finger to measure the sacral promontory and also then utilizing the other hand to mark the level of the worse margin the the pubic symphysis ~ above the assessing hand. Friend then usage the distance in between the index finger and also the pubic symphysis to measure up the diagonal line conjugate, ideally 11cm or greater)

In enhancement to measuring the diagonal line conjugate, a mid-pelvis check is brought out. Here, the clinician is experimentation for directly side walls and measuring the bispinous diameter i beg your pardon is narrowest part of the pelvic canal. The width of the subpubic angle at the pelvic outlet have the right to be identified by the distance in between the ischial tuberosities.

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Fig 6 – assessment of the woman pelvis, via the diagonal line conjugate