Thepelvis is abasin like structure which
connects the spine to lowerlimbs.
It is an important part of the skeletal system.
It transmits the weight of the trunk to the legs.
It takes the weight of the sitting body.
It allows movements of walking and
It protects the pelvicorgans.
In addition the female pelvis is adapted
for childbearing with an increased
width androunded brim.
Theilium is the flared out
part of the hip bone. It has
Iliac crest asupper border
Concaveborder is iliac fossa
Anterior superior iliac spine
Anterior inferior iliacspine
Posterior superior iliac spine
Posterior inferior iliac spine
The ischium is the thick lower part of the hip bone. It
Ischial spine: location in relation tofetal head,
i.e. above (-), below (+) or at (zerostation)
Greater sciatic Notch: extends from Sacroiliac joint
to ischial spine
LesserSciatic Notch: extends from ischial spine
to ischial tuberosity
Obturator foramen: passageof pelvic nervefibres
The two pubic bones form the anterior part
of the hip bone. It hasfollowing parts-
Inferior rami of Pubic bone(a)
Superior rami of pubic bone(b)
Symphysis pubis (a+b): It is formed at
the junction of two pubic bones.
Sub pubic angle: angle between the
inferior rami of the pubic bone.
It is awedge shaped bone made up of fivefused
It has following parts-
Sacral promontory: it is prominent upper margin
of first sacral vertebrae, projects inwards
Wings of Sacrum or Ala of Sacrum
Hollow of the Sacrum:concave
It is avestigial tail consists of four fused vertebrae
forming asmall triangular bone.
Itis articulated with the sacrum
Coccyxmoves backward during childbirth
There are four pelvicjoints:
Onepubic symphysis joint
Theseare slightly movable joints formed where
the ilium joints, first two sacral vertebrae on
Theyconnect the spine to the pelvis & are the
strongestjoints in body.
Thepelvic bones are held together with ligaments.
Sacroiliac ligament- it pass in front of and behind
each sacroiliac joint.
Pubicligament- it connect the top of pubicbones.
Sacrotuberous ligament- one ligament on each side ,
run from sacrum to the ischialtuberosity
Sacrospinous ligament- one ligament on each side of
the sacrum & the ischialspine.
Sacro coccygeal ligament-one ligament on each side
from sacrum to coccyx.
It is formed by the upper flared out portion of the
Laterally- iliac fossae,Posterior- fifth lumbar
Anteriorly – the abdominal walland inguinal
It protects the abdominal organs.
It has no obstetrical importance except that it
provides certain landmarks for externalpelvimetry.
THE PELVIC BRIMOR INLET
It is formed by the sacrum posteriorly, the iliac
bones laterally and the pubic bonesanterior.
Shape: it is almost rounded with anterio
posterior diameter being the shortest.
Its boundaries are the sacral promontory and
wings of the sacrum behind the iliac bones on
the sides and the pubic bones infront.
It is aline from the sacral promontory to the upper border of
symphysis pubis. Thisdiameter is of threetypes-
Diagonal conjugate- distance between lower border of
symphysis pubis to mid point on sacral promontory it is 12
Obstetrical conjugate- it is distance between midpoint of
sacral promontory to prominent bony projection in mid line
of symphysis pubis. it measures 10cm
Trueconjugate - it extends from the sacral promontory to the
top of the symphysis pubis. Its normal measurement is 11 cm
it is the distance between the two farthest points on
the pelvic brim over the Iliopectineallines.
it starts from the sacroiliac joint to the opposite
Thecavity extends from the brim above tothe
Shape: its shape is almost rounded.
Anterior border: Symphysispubis
Posterior border: Sacralhollow
Lateral border: Softtissues
All diameters- measure12cms.
i. Antereo-posterior (12cm) : It measures from
the mid-point on the posterior surface of the
symphysis pubis to the junction of 2nd and
3rd sacral vertebrae
ii. Transverse (12cm) : It cannot be precisely
measured as the points lie over the soft tissues
covering the sacro-sciatic notches and
THE PELVIC OUTLET
It consists of the lower border of all bonesand Sacro
It consistsof lower border ofsymphysispubis, Sacro
coccygealjoint and Sacroischial spine.
Shape:it isantero –posteriorlyoval.
This outlet has greater practical significance, because
it includes the narrow pelvic strait through which the
fetus must pass.
It is otherwise known asbonyoutlet.
Shape:it is diamond shaped.
DIAMETERS OF OUTLET:
Antero-posterior diameter (13cm): it Extend
from lower border of symphysis pubis to the tip
Oblique diameter (12): itextend from Rt. & Lt.
Sacrospinous ligament to Obturator
Transversediameter (11cm): between
the ischial spines.
It is commonly known asthe
female pelvis becausethat
type occurs most frequently
Most suitable for childbirth.
Ischial spines are blunt
Subpubic angle is 90º
2.Anthropoid pelvis: (25%)
It favors aposterior positionof
Oval in shape
Transversediameter is shorter
Seenin tall womenwith
3.Android pelvis: (20%)
It is commonly known as
male pelvis becauseit occurs
more frequently in men.
Heart shaped brim
Childbirth is difficult
4.Platypelloid (flat) pelvis:
Thistype of pelvis israre.
Kidney shaped brim
Not conductive to vaginal