The pelvis is a basin-shaped structure formed by bones including the sacrum, coccyx, and two innominate bones. It supports the trunk and transmits its weight to the lower limbs. The female pelvis has a wider shape adapted for childbirth. There are three parts of the true pelvis - the brim, cavity, and outlet. The brim is oval-shaped and its diameters include the anteroposterior, transverse, and oblique. The cavity extends from the brim to the outlet. The outlet is diamond-shaped with diameters including the anteroposterior. There are different pelvic types including gynaecoid, anthropoid, and android,

1. THEPELVIS

2. INTRODUCTION
 The pelvis is a basin like structure which connects the
spine to lower limbs.
 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 running.
 It protects the pelvic organs.
 In addition the female pelvis is adapted for
childbearing with an increased width and rounded
brim.

3. DEFINITION
 It is a skeletal ring formed by two innominate or hip
bones & the sacrum & the coccyx.

4. Types of pelvic bone

5. Gynecoid Pelvis

6. The female pelvis because of its characteristics, aids in
child birth. The bony pelvis in normal standing
transmits the body weight from head, trunk and the
posture
upper
extremities to the lower extremities. In female it is adapted for
child bearing. The obstetrical anatomy of a typical female
pelvis is best considered as one unit.

8. Functions of female pelvis
• The primary function of the pelvic girdle is to allow movement
of the body, especially walking and running. It permits the
person to sit and kneel. The women pelvis is adapted for child
bearing, and because of its increased width and rounded brim
women are less speedy than men.
• The pelvis transmits the weight of the trunk to the legs, acting
as a bridge between the femur. This makes it necessary for the
sacro-iliac joint to the immensely strong and virtually
immobile. The pelvis also takes the weight of the sitting body
on to the ischial tuberosities.
• The pelvis affords protection to the pelvic organs and, to a
lesser extent, to the abdominal contents. The sacrum
transmits the cauda equina and distributes the nerves to the
various parts of the pelvis.

10. TYPES OF PELVIC BONES
There are four pelvic bones that form pelvis:
 Two Hip bones (Innominate or nameless)
 One Sacrum
 One Coccyx

12. 1.TWO INNOMINATE BONES
innominate bone is made up of three bones
 Ilium
 ischium
 pubic bone

13. ILIUM
 The ilium is the flared out part of the hip bone.
It has following parts-
 Iliac crest as upper border
 Concave border is iliac fossa
 Anterior superior iliac spine
 Anterior inferior iliac spine
 Posterior superior iliac spine
 Posterior inferior iliac spine

15. Ilium
• The ilium- ilium is the larger flared out part. When the hand is
placed on the hip it rests on the iliac crest, which is the upper
border. At the front of the iliac crest can be felt a bony
prominence known as the anterior superior iliac spine .
• A short distance below it is the anterior inferior iliac spine.
There are two similar points at the other end of the iliac crest,
namely the posterior superior and the posterior inferior iliac
spines. The concave anterior surface of the ilium is the iliac
fossa.

16. ISCHIUM
 The ischium is the thick lower part of the hip bone. It
has following parts-
 Acetabulum
 Ischial tuberosity
 Ischial spine: location in relation to fetal head, i.e.
above (-), below (+) or at (zero station)
 Greater sciatic Notch: extends from Sacro iliac joint to
ischial spine
 Lesser Sciatic Notch: extends from ischial spine to
ischial tuberosity
 Obturator foramen: passage of pelvic nerve fibres

17. Ischium
• The ischium- ischium is the thick lower part. It has a large
prominence known as the ischium tuberosity, on which the
body rests when sitting. Behind and a little above the
tuberosity is an inward projection, the ischial spine. in labour
fetal head is estimated in relation to the
the station of the
ischial spines.

18. PUBIC BONE
 The two pubic bones form the anterior part of the hip bone. It
has following 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.

19. Pubic bone
The pubic bone- this bone forms the anterior part. It
has a body and two oar like projections, the superior ramus and
the inferior ramus. The two pubic bones meet at the symphysis
pubis and the two inferior rami from the pubic arch, merging into
a similar ramus and the ischium. The space enclosed by the body
of the pubic bone, the rami and the ischium is called the
obturator foramen.

20. Cont.…
• The innominate bone contains a deep cup to articulate with
the head of the femur.This is termed as Acetabulum . all
three parts of the bone contribute to the acetabulum in the
following proportions: 2/5th ilium, 2/5th ischium and 1/5th
pubic bone.
• On the lower border of the innominate bone are found two
curves. One extends from the posterior inferior iliac spine up
to the ischial spine and is called the greater sciatic notch. It is
wide and rounded. The other lies between the ischial spine
and the ischial tuberosity and is the lesser sciatic notch.

21. 2.SACRUM
 It is a wedge shaped bone made up of five fused bones.
It has following parts-
 Sacral promontory: it is prominent upper margin of first
sacral vertebrae, projects inwards
 Sacro iliac joint
 Wings of Sacrum or Ala of Sacrum
 Hollow of the Sacrum: concave

23. Cont.
Sacrum: the sacrum is a wedge shaped bone consisting of five
fused vertebrae. The upper border of the first sacral vertebra juts
forward and id known as the sacral promontory. The anterior
surface of the sacrum is concave and is referred to as the hollow
of sacrum. Laterally the sacrum extends into a wing or ala. Four
pairs of holes or foramina pierce the sacrum and through these,
pelvic
receive
nerves from the Cauda Equina emerge to supply the
organs. The posterior surface is roughened to
attachments of muscles.

24. 3.COCCYX
 It is a vestigial tail consists of four fused vertebrae forming a
small triangular bone.
 It is articulated with the sacrum
 Coccyx moves backward during childbirth

25. cont...
Coccyx: the coccyx is a vestigial tail. It consists of four fused
vertebra forming a small triangular bone. With its base
uppermost articulating with the lower end of the sacrum. During
labour it moves backward, having more space for the delivery of
the fetus this is called nodding.

26. PELVIC JOINTS
There are four pelvic joints:
 Two sacroiliac joints
 One pubic symphysis joint
 One sacrococcygeal joint

27. PELVIC JOINTS

28. Cont.…
• The symphysis pubis is formed at the junction of the
two pubic bones, which are united by a pad of
cartilage.
• The sacroiliac joints – these are the strongest joints
in the body. They join the sacrum to the ilium and
thus connect the spine to the pelvis.
• The sacro coccygeal joint – this joint is formed
where the base of the coccyx articulate with the tip
of the sacrum.

29. Cont…
⦿ In the non-pregnant state there is very little movement in
these joints, but during pregnancy endocrine activity causes
the ligaments to soften, which allows the joints to give. This
may provide more room for the fetal head as it passes through
the pelvis. The symphysis pubis may separate slightly in later
pregnancy. If it widens appreciably, the degree of movement
deflected
permitted may give rise to pain on walking.
⦿The sacro-coccygeal joint permits coccyx to the
backward during the birth of the head.

30. PELVIC LIGAMENTS
 The pelvic bones are held together with ligaments.
 Sacro iliac ligament- it pass in front of and behind
each sacroiliac joint.
 Pubic ligament- it connect the top of pubic bones.
 Sacro tuberous ligament- one ligament on each side ,
run from sacrum to the ischial tuberosity
 Sacro spinous ligament- one ligament on each side of
the sacrum & the ischial spine.
 Sacro coccygeal ligament-one ligament on each side
from sacrum to coccyx.

32. STRUCTURE OF PELVIS
FALES PELVIS
TRUE PELVIS

33. FALSE PELVIS
 It is formed by the upper flared out portion of the
ilium.
 Laterally- iliac fossae, Posterior- fifth lumbar
vertebrae, Anteriorly – the abdominal wall and
inguinal ligament
 It protects the abdominal organs. It has no obstetrical
importance except that it provides certain landmarks
for external pelvimetry.

34. TRUE PELVIS
 The true pelvis is the bony canal through which
the fetus passes during birth.
 It has three parts-
BRIM CAVITY OUTLET

35. THE PELVIC BRIM OR INLET
 It is formed by the sacrum posteriorly, the iliac bones
laterally and the pubic bones anterior.
 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 in front.

37. LANDMARKS OF THE BRIM
 Sacral promontory
 Sacral ala or sacral
wing
 Sacroiliac joint
 Iliopectineal line
 Iliopubic eminence
 Pectineal line
 Pubic tubercle
 Pubic Crest
 Symphysis pubis

38. DIAMETERS OF THE BRIM
 Anterio posterior
 Transverse
 Oblique

39. ANTERIO POSTERIOR (11CM)
 it is a line from the sacral promontory to the upper border of
symphysis pubis. This diameter is of three types-
 Diagonal conjugate- distance between lower border of
symphysis pubis to mid point on sacral promontory it is 12 cm.
 Obstetrical conjugate- it is distance between midpoint of sacral
promontory to prominent bony projection in mid line of
symphysis pubis. it measures 10 cm
 True conjugate - it extends from the sacral promontory to the
top of the symphysis pubis. Its normal measurement is 11 cm or
more.

40. Transverse (13cm) –
it is the distance between the two farthest points on
the pelvic brim over the Iliopectineal lines.
Oblique (12cm) –
it starts from the sacroiliac joint to the opposite
iliopubic eminence.

41. THE PELVIC CAVITY
 The cavity extends from the brim above to the
outlet below.
 Shape: its shape is almost rounded. It consist of
 Anterior border: Symphysis pubis
 Posterior border: Sacral hollow
 Lateral border: Soft tissues
 All diameters- measure 12cms.

42. cont.…
The pelvic cavity
This extends from the pelvic brim to the pelvic outlet. It forms
the curve of Carus, which the fetus has to navigate in order to be
born and has no specific landmarks.
The pelvic outlet
This is either an ovoid or diamond-shaped space; its perimeter is
partially comprised of ligaments. The landmarks of the pelvic
outlet are as follows:
_ Lower border of the symphysis pubis
_ Pubic arch
_ Ischial spines and ischial tuberosities
_ Sacrotuberous and sacrospinous ligaments
_ Lower aspect of the sacrum and the coccyx

43. THE PELVIC OUTLET
ANATOMICAL OUTLET:
 It consists of the lower border of all bones and
Sacro tuberous ligament.
 It consists of lower border of symphysis pubis,
Sacro coccygeal joint and Sacro ischial spine.
 Shape: it is antero – posteriorly oval.

44. OBSTETRICAL OUTLET:
 This outlet has greater practical significance, because
it includes the narrow pelvic strait through which the
fetus must pass.
 It is otherwise known as bony outlet.
 Shape: it is diamond shaped.

45. DIAMETERS OF OUTLET:
 Antero-posterior diameter (13cm): it Extend
from lower border of symphysis pubis to the tip
of coccyx.
 Oblique diameter (12): it extend from Rt. & Lt.
Sacro spinous ligament to Obturator
foramen
 Transverse diameter (11cm): between the
ischial spines.

47. TYPES OF PELVIS
GYNAECOID ANTHROPOID ANDROID
PLATYPELLOID

48. 1.Gynaecoid pelvis: (50%)
 It is commonly known as the
female pelvis because that
type occurs most frequently
in women.
 Most suitable for childbirth.
 Wider brim.
 Ischial spines are blunt
 Sub pubic angle is 90º

49. 2.Anthropoid pelvis: (25%)
 It favors a posterior position of
the fetus.
 Oval in shape
 Transverse diameter is shorter
 Seen in tall women with
narrow shoulders

50. 3.Android pelvis: (20%)
 It is commonly known as
male pelvis because it occurs
more frequently in men.
 Heart shaped brim
 Anterior posterior diameter
is shorter
 Transverse diameter is
wider
 Childbirth is difficult

51. 4.Platypelloid (flat) pelvis:
(5%)
 This type of pelvis is rare.
 Kidney shaped brim
 Anterior posterior diameter
is smaller
 Transverse diameter is
wider
 Not conductive to vaginal
delivery

52. DEFORMITIES OF PELVIS
 Contracted pelvis
 Rachitic pelvis
 Asymmetrical pelvis
 Roberts pelvis
 Nageles pelvis
 Osteomalacis / maacosteon pelvis
 Assimilation pelvis
 Others- Kyphosis, scoliosis, spondylosisthesis

53. Contracted pelvis

54. Rachitic pelvis

55. Asymmetrical pelvis

56. Roberts pelvis

57. Nageles pelvis

58. Osteomalacis / maacosteon pelvis

59. Kyphotic pelvis

60. Scoliosis pelvis

61. Spondylosisthesis