Kaan Yücel M.D., Ph.D. anteroposterior (AP) diameter of the lesser pelvis True (obstetrical) conjugate ... When the pelvis is compressed laterally, the acetabula and

Kaan Yücel M.D., Ph.D. 14.January.2014 Tuesday

Sexual differences are related mainly

1. Heavier build and larger muscles of most men

2. Adaptation of the pelvis (particularly the lesser pelvis)

in women for parturition (childbearing).

The difference

between the male

and female pelvis

Difference

Between Male

& Female

Pelvis

41% of women

male or funnel-shaped pelvis with a

contracted outlet

long, narrow, and oval shaped

wide pelvis 2% of women

In forensic medicine (the application of medical and anatomical

knowledge for the purposes of law), identification of human

skeletal remains usually involves the diagnosis of sex.

A prime focus of attention is the pelvic girdle because sexual

differences usually are clearly visible.

Even fragments of the pelvic girdle are useful in determining

sex.

Feature Male pelvis Female pelvis

General Structure

Thick & Heavy Thin & Light

Greater pelvis

Deep Shallow

Lesser pelvis

Narrow and deep, tapering

Wide and shallow, cylindirical

Pelvic inlet Heart-shaped, narrow Oval and rounded, wide

Pelvic outlet Comparatively small Comparatively large

Ischial spines

Project further medially into the pelvic cavity

Do not project as far medially into the pelvic cavity & smooth

Feature Male pelvis Female pelvis

Obturator foramen

Round Oval

Acetabulum Large Small

Greater schiatic notch

Narrow, inverted V (approximately 70

degrees)

Almost 90 degrees

Subpubic angle

Smaller (50-60 degrees)

Larger (80-85 degrees)

Sacral promontory

Prominent Not prominent

Size of the lesser pelvis important in obstetrics

Because it is the bony canal through which the fetus passes

during a vaginal birth.

To determine the capacity of the female pelvis for childbearing,

diameters of the lesser pelvis are noted radiographically or

manually during a pelvic examination.

PELVIC DIAMETERS (CONJUGATES)

PELVIC DIAMETERS (CONJUGATES)

Anatomical antero-posterior diameter 11cm from tip of the coccyx to lower border of symphysis pubis

Obstetric antero-posterior diameter 13 cm from tip of the sacrum to lower border of symphysis pubis

as the coccyx moves backwards during the second stage of labour.

Diameters of pelvic outlet Antero - posterior diameters

Bituberous diameter 11 cm between inner aspects of ischial tuberosities

Bispinous diameter 10.5 cm between tips of ischial spines

Diameters of pelvic outlet Transverse diameters

Anatomical antero-posterior diameter True conjugate 11cm

from tip of sacral promontory to upper border of symphysis pubis

Diameters of pelvic inlet Antero - posterior diameters

Obstetric conjugate 10.5 cm from tip of sacral promontory to the most bulging point on back of symphysis pubis ,about 1 cm below its upper border.

shortest antero-posterior diameter

Diameters of pelvic inlet Antero - posterior diameters

Diagonal conjugate 12.5 cm 1.5 cm longer than the true conjugate From tip of sacral promontory to lower border of symphysis pubis

Diameters of pelvic inlet Antero - posterior diameters

Minimum anteroposterior (AP) diameter of the lesser pelvis

True (obstetrical) conjugate

Narrowest distance through which the baby's head

must pass in a vaginal delivery. This distance, however, cannot be measured directly during a pelvic

examination because of the presence of the bladder.

Diagonal conjugate (from inferior pubic lig. to promontory)

Measured by palpating sacral promontory with the tip of the middle finger, using the other hand to mark the level of the inferior margin of the pubic symphysis on the examining hand.

After the examining hand is withdrawn, the distance between the tip of the

index finger (1.5 cm shorter than the middle finger) and the marked level of the

pubic symphysis is measured to estimate the true conjugate, which should be

11.0 cm or greater.

Transverse diameter is the greatest distance between the linea

terminalis on either side of the pelvis.

Anteroposterior compression of the pelvis occurs during

crush accidents (as when a heavy object falls on the pelvis).

This type of trauma commonly produces fractures of the

pubic rami.

When the pelvis is compressed laterally, the acetabula and

ilia are squeezed toward each other and may be broken.

Fractures of the bony pelvic ring are almost always multiple

fractures or a fracture combined with a joint dislocation.

Pelvic fractures can result from direct trauma to the pelvic

bones, such as occurs during an automobile accident, or be

caused by forces transmitted to these bones from the lower

limbs during falls on the feet.

Weak areas of the pelvis, where fractures often occur:

Pubic rami

Acetabula

Region of the sacroiliac joints

Alae of the ilium

25 Year Old Male with displaced fracture of the sacrum and symphysis pubis. The most severe pelvic fractures separate the two sides of the pelvis from each other.

Pelvic fractures may cause injury to pelvic soft tissues, blood

vessels, nerves, and organs.

Fractures in the pubo-obturator area are relatively common and

are often complicated because of their relationship to the urinary

bladder and urethra, which may be ruptured or torn.

Sacroiliac joint dysfunction

Degenerative arthritis (osteoarthritis) Pregnancy Gout Rheumatoid arthritis Psoriasis Ankylosing spondylitis

X-ray of the sacroiliac joints showing joint space narrowing, erosive change and indistinct margins, due to sacroiliitis