female bony pelvis

1. Dr Isameldin Elamin MD DOWH MBBS
Assistant professor
Obstetrics & Gynaecology Department

2.  The bony pelvis is made up of four bones:
◦ Sacrum.
◦ Coccyx.
◦ Two innominate bone.
 Innominate bone composed of:
 Ilium.
 Ischium.
 Pubis.

3.  They are held by three joints:
 Sacroiliac joints.
 Symphysis pubis.
 Sacrococcygeal joint.
 Union with the vertebral column lead to:
◦ Stabilizes the pelvis.
◦ Transmit weight to lower extremities.

4.  The sacrum:
◦ Five fused vertebrae.
 Promontory:
◦ Edge of the first sacral vertebra.
◦ Protrudes into the cavity of the pelvis.

5.  The sacrum articulates with:
◦ Ilium.
◦ Coccyx.
◦ Sacrospinous ligaments.
◦ Sacrotuberous ligaments.
 The coccyx:
◦ Three to five rudimentary vertebrae.
◦ Articulates with the sacrum.

6.  The pelvis is divided into:
 False pelvis.
◦ Bordered by:
 The lumbar vertebrae.
 Iliac fossa.
 Abdominal wall.
◦ It supports the pregnant uterus.

7.  True pelvis.
◦ Bony canal formed by:
 Sacrum
 Coccyx
ischium
 Pubis.
◦ It is the area of concern to the obstetrician.

10.  The pelvic brim or inlet bounded by:
◦ Symphysis pubis.
◦ Upper margin of the pubic bone.
◦ Ileopectineal line and the Ala of the sacrum.
◦ Promontory of the sacrum.

11.  Transverse diameter is 13.5 cm.
 Anterior–posterior (AP) diameter 11 cm.
 The angle of the inlet is normally 60º. (Inclination
angle).
 In some women it may be as much as 90º.

14.  The pelvic mid-cavity bounded by:
◦ Middle of the symphysis pubis.
◦ Pubic bone.
◦ Obturator fascia .
◦ Ischial bone and spines.
◦ The junction of the second and third sections of the sacrum.
◦ The cavity is almost round.
◦ Transverse and anterior diameters are similar at 12 cm.
 The ischial spines:
◦ Palpable vaginally.
◦ Used to assess the descent of the head. (Station).
◦ Used as landmarks to the pudendal block.

15.  The pelvic outlet is bounded by:
◦ Lower margin of the symphysis pubis.
◦ Descending ramus of the pubic bone.
◦ Ischial tuberosity.
◦ Sacrotuberous ligament.
◦ Last piece of the sacrum.
 AP diameter is 13.5 cm.
 Transverse diameter is 11 cm.

17.  Measurements related to:
◦ Maternal stature.
◦ Previous pelvic fractures.
◦ Metabolic bone disease, such as rickets.
 Pelvic ligaments become more flexible towards
labour.
 X-rays or CT scans now uncommon to be used
for predicting the outcome of labour.

18.  Caldwell and Moloy classification:
◦ Gynaecoid pelvis.
◦ Android pelvis.
◦ Anthropoid pelvis.
◦ Platypelloid pelvis.

20.  The gynaecoid pelvis:
◦ Most favourable for labour.
◦ Most common.
 An android pelvis:
◦ Deep transverse arrest.
 The anthropoid:
◦ The antero-posterior diameter is larger than the transverse
◦ Occipito-posterior (OP) position common.
 A platypelloid pelvis:
◦ Obstructed labour.

25.  Formed by the two levator-Ani muscles with
their fascia.

26.  The perineal body:
◦ Found between the vagina and the anus.
◦ It is a condensation of fibro muscular tissue.
◦ It receives attachments of:
 Bulbo-cavernous muscles.
 The superficial and deep transverse perineal muscles.
 External anal sphincter.
◦ It is involved in a second-degree perineal tear and
an episiotomy.

29.  Formed by:
◦ Bones, sutures and fontanelles.
 Fetal skull is made up of:
◦ The vault.
◦ The face and the base.
◦ The sutures are formed where the bones meet.

32.  The vault are formed by:
◦ The parietal bones.
◦ Part of occipital bones.
◦ Part of frontal bones.
◦ Part of temporal bones.
 There are four sutures:
◦ The sagittal.
◦ Frontal.
◦ Coronal.
◦ Lambdoidal sutures.

33.  Fontanelles are the junctions of the various
sutures.
 There are 2 fontanelles:
◦ The anterior fontanelle, or bregma:
◦ Diamond shaped.
◦ At the junction of:
 The sagittal suture.
 Frontal suture.
Coronal sutures.

34.  The posterior fontanelle:
◦ Triangular shaped.
◦ At the junction of:
◦ The sagittal suture.
◦ The lambdoidal sutures.
◦ Between:
 The two parietal bones.
 The occipital bone.

35.  Clinical importance sutures and fontanelles :
◦ Overlap during labour.
◦ Bones are compressible.
◦ Moulding occur easily.
◦ Severe moulding is a sign of cephalo-pelvic
disproportion. CPD.
 The ‘vertex’ is the area bounded by the two
parietal eminences and the anterior and
posterior fontanelles.

36.  The attitude is the degree of flexion and extension.
 There are different longitudinal diameters:
 Suboccipito-bregmatic diameter.
◦ Well-flexed fetal head.
◦ It measures 9.5 cm.
◦ From suboccipital region to anterior fontanelle (bregma).
 Suboccipito-frontal diameter:
◦ Less well flexed.
◦ Found in the OP position.
◦ From the suboccipital region to the prominence of the
forehead.
◦ It measures 10 cm.

38.  Occipitofrontal diameter:
◦ Further extension of the head.
◦ Measured from the root of the nose to the posterior fontanelle.
it measures 11.5 cm.
 Mento-vertical diameter:
◦ It is the greatest diameter.
◦ From chin to vertex and
◦ Measures 13 cm.
◦ Known as a brow presentation.
◦ Too large to pass through the normal pelvis.
 Submentobregmatic diameter:
◦ Measured from below the chin to the anterior fontanelle.
◦ It is 9.5 cm.
◦ It is the face presentation.

40.  The true conjugate (anatomic conjugate):
◦ From the middle of the sacral promontory to the superior
surface of the pubic symphysis.
 The obstetric conjugate:
◦ From the middle of the sacral promontory to the closest
point on the convex posterior surface of the symphysis
pubis.
◦ The shortest distance between the sacral promontory and
the symphysis pubis

41.  The diagonal conjugate:
◦ From the lower border of the pubis to the sacral
promontory .
 The obstetric conjugate is then estimated by
subtracting 1.5 to 2 cm from diagonal conjugate.
 Obstetric conjugate is adequate when:
◦ Middle finger cannot reach the sacral promontory.
◦ If the diagonal conjugate is greater than or equal to
11.5 cm.

44.  Obstetrics by ten teachers 19 editions.
 Essential of obstetrics and gynaecology.
 Hacker & Moore, fifth edition
 http://www.uptodate.com.