bony pelvis : it is made up of four bones : the sacrum, coccyx, and two innominates (composed of the...
TRANSCRIPT
Haider Al hulialiHaider Al Ali
Normal Pelvis, types of female pelvis and fetal skull
Bony pelvis : it is made up of four bones : the sacrum ,
coccyx , and two innominates (composed of the ilium , ischium ,and pubis).
Pelvic anatomy
Joints
Pelvis is divided into the false pelvis and the true pelvis •The false pelvis is bordered by the lumbar vertebrae posteriorly , an iliac fossa bilaterally ,and the abdominal wall anteriorly .•It supports the pregnant uterus .
•The true pelvis is a bony canal and is formed by the sacrum and the coccyx posteriorly and by the ischium and pubis laterally and anteriorly .•The posterior wall is twice the length of the anterior wall.•The true pelvis is area of concern because its dimensions are sometimes not adequate to permit passage of the fetus .
The pelvic inlet The plane of greatest diameter The plane of least diameter The pelvic outlet
Pelvic planes
Lateral Posterior Anterior Pelvic Planes
iliopectinaeal line of the innominate bones.
sacral promontory
pubic crest 1- The Pelvic Inlet
upper part of the obturator foramina
junction of S2 & S3
posterior midpoint of the pubis
2- The Plane of greatest diameter
ischial spines and sacrospinous ligaments
Lower sacrum
Lower edge of pubis
3- The Plane of least diameter (Mid-pelvic Plane)
ischial tuberosity
sacrococcygeal joint
lower pubic bone
4- The Pelvic Outlet
Pelvic Diameters
The diameters of the pelvic planes represent the amount of space available at each level .
Pelvic Inlet Pelvic inlet has five important diameters :The anteroposterior diameter : described by one of
two measurements: the true conjugate (anatomic conjugate ):
from sacral promontory to superior pubis obstetric conjugate: from sacral promontory
to posterior pubis .The transverse diameter : the widest distance
between iliopectineal linesTwo oblique diameters :from sacroiliac joint to the
opposite iliopectineal eminence The posterior sagittal diameter: from AP &
transverse intersection to the middle of sacral promontory
Plane of Greatest Diameter
The anteroposterior diameter : from the midpoint of the posterior surface of pubis to the junction of S2 and S3 vertebrae .
The transverse diameter : widest distance between the lateral borders of the plane (upper part of obturator foramina )
Plane of Least diameter (midplane )
The anteroposterior diameter :extends from the lower border of the pubis to the junction of S4 and S5 .
The transverse (bispinous ) diameter : extends between the ischial spines .
The posterior sagittal diameter : from midpoint of bispinous diameter to the junction of S4 and S5
Pelvic outlet
Anatomic anteroposterior diameter :from the inferior margin of pubis to tip of coccyx
Obstetric anteroposterior diameter : from inferior margin of pubis to sacrococcygeal joint .
Transverse diameter : between the inner surface of ischial tuberosities
Posterior sagittal diameter : from middle of transverse diameter to the sacrococcygeal joint .
Pelvic Shapes
Android
30%
Gynecoid
50%
Anthropoid
18%
Platypelloid
2%
Gynecoid
Round at the inletSide walls strightIscheal spines of average
prominenceWell-rounded sacrosciatic
notchWell-curved sacrumSpacious subpubic arch, with
an angle of approximately 90 degrees
Cylindrical shape
Android
Triangular inletConvergent Side wallsShallow sacral curveLong and narrow
sacrosciatic notchNarrow subpubic archIt is the typical male type
Anthropoid
Long narrow oval inlet (AP>transverse)
Side walls that not convergeIschial spines close, owing to
overall shapeVariable, but usually posterior,
inclination of the sacrumLong sacrosciatic notchNarrow, outwardly shaped
subpubic arch
Platypelloid
Oval-shaped inlet (AP<transverse)
Straight or divergent side walls
Ischial spines close, owing to overall shape
Posterior inclination of a flat sacrum
Wide bispinous diameterA wide subpubic arch
flat shape
Clinical Pelvimetry
For assessment of obstetric capacity, most important measurements are:Obstetric conjugate of inletDistance between ischial spinesSubpubic angle & bituberous diameterPosterior sagittal of three planesCurve & length of sacrum
- It is only an estimate
- The best time is late in pregnancy when the soft tissue are distensible
Clinical Pelvimetry
palpate the SACRUMIt should be concave. Flat or convex is
abnormal
midpelvis and pelvic outlet: can’t accurately be measured clinically but it can be estimated through clinical examination.
X-ray Pelvimetry Its purpose is to aid in determining the need for C-S.
Other factors affecting need for C-S include: Fetal size, Force of contractions, & Position of fetus, & degree of molding
It is an accurate measure Indications:
No longer needed in cephalic presentation
Breech deliveryTo rule out pelvic abnormalities either
inherited or traumatic 2 films are needed
Lateral view – AP diameterInlet view – transverse diameter
Fetal Skull
General characteristicsSutures,Fontanelles and boneslandmarksDiametersCephalic pelvic disproportion
Objectives
Fetal Head: is the Largest and least compressible part
of the fetus
General characteristics
Base Cranium (Vault)
Large, ossified, firmly united and non-compressible
•Consists of occipital , parietal , frontal and temporal bones
•At birth thin, weakly ossified, easily compressible and interconnected only by membranes
Protects the vital structures within the brainstem
allows molding
General characteristicsfetal skull: 1-base
2-cranium
Definition:The membrane occupied spaces between
the cranial bones.
sutures
The membrane filled spaces located at the point where the sutures intersect.
fontanelle
fontanellesCharacteristics Closure
(ossification)
Anterior Fontanelle (bregma)
Diamond shape and found at
the intersection of sagittal , frontal and
coronal sutures2-3 cm (larger)
18 months of life
Posterior Fontanelle
Y or T-shaped and found at
the junction of the sagittal and
lambdoid sutures
6-8 weeks of life
Land Marks
Nasion
Glabella
1
2
35
6
7
(bregma)
(lambda)
(
sincipu
t
)
1- Nasion : root of the nose2- Glabella: elevated area between the orbital
ridges3-Sinciput(brow):the area between anterior
fontanelle and glabella4- anterior fontanelle(bregma)5- vertex the area between the fontanelles and
bonded laterally by the parietal eminence6- posterior fontanelle ( lambda)7- occiput the area behind and inferior to the
posterior fontanelle and lambdiod sutures
Land Marks
Antero-posterior diameters( 4 )
Transverse diameters ( 2 )
Diameters
Antero-posterior diameters
Length Definition Presentation
Suboccipitobregmatic
9.5cm Extends from occipital bone at the junction of the neck to AF .
When the head is well flexed as in occipitoanterior or occipitotransverse
Submentobregmatic
9.5cm from junction of neck and lower jaw to AF.
in the face presentation
Occipitofrontal
11cm from external occipital protuberance to glabella.
As in occipitoposterior presentation
Supraoccipitomental
13.5cm from vertex to chin.
In a brow presentation ( lead to CS )
Transverse diameters:
1. Biparietal(9.5cm): between the parietal
bones.
2. Bitemporal(8cm):between the
temporal bones
An obstetric condition where there is mismatch in size between (fetal head & the maternal pelvis), resulting in failure of the fetus to pass safely through the birth canal for mechanical reasons.
Cephalic pelvic disproportion
1- Absolute CPD: There is no possibility of a normal vaginal delivery (extremely rare).
Fetal (Temporary):macrosomia (diabetes) & Fetal
hydrocephalusMaternal (Permenant):
Congenitally abnormal pelvis.Damaged pelvis (RTA).Distorted pelvis (osteomalacia).
2- Relative CPD: the baby is large but would pass through the pelvis if the mechanisms of labor function correctly.
If, however, the head is deflexed or fails to rotate in the mid-cavity, then prolonged, abnormal labor will occur.
CPD:Can only truly be diagnosed after a trial of labour.May be suspected antenatally in women who are
≤ 1.58m height. Should be suspected in a women with a high head
at term, after excluding the other causes.
CPD
Thank You