Pelvic measures and methods for pelvimetry of normal and narrow pelvis.

Question 1

what is pelvimetry used for

Answer 1

identify cephalo-pelvic disproportion, if the pelvis is inadequate to allow the fetus entry.

a woman’s pelvis loosens up before birth (with the help of hormones).

Question 2

how are the measures in pelvimetry obtained ?

Answer 2

Pelvimetry can done by

X ray - Lateral X-ray view with the patient in standing position is helpful in assessing cephalopelvic proportion in all planes of the pelvis — inlet, midpelvic and outlet

MRI ( more safe)

Low-dose 3D-rendered CT scans can be used for estimating the main pelvimetry parameters

clinical

ultrasound examination does not give information about the pelvis,
but gives information about the size of the fetus, especially the head.
biparietal diameter
ocipitofrontal diameter
head circumference

Question 3

what does the bony pelvis consist of

Answer 3

the bony pelvis consist of the sacrum the ilium , isichum and pubis

Question 4

what is michaelis -rhombus

Answer 4

kite-shaped area that includes the three lower lumber vertebrae, the sacrum and Posterior Longitudinal Ligament which reaches down from the base of the skull to the sacrum

Question 5

why is the michaelis -rhombus an important anatomical part in pregnancy ?

Answer 5

This wedge-shaped area of bone moves backwards during the beginning of second stage of labour

as it moves back it pushes the wings of the ileum out, increasing the diameters of the pelvis.

We know it’s happening when the woman’s hands reach upwards to find something to hold onto, her head goes back and her back arches

Question 6

when does the michaelis rhombus anatomically move in

Answer 6

by the time that the baby’s feet are born, in fact sometimes more quickly than that

Question 7

what are the 4 different types of bony pelvis are described ?

Answer 7

CALDWELL-MOLOY ANATOMICAL CLASSIFICATION

gynecoid - GOOD = most common

anthropoid - GOOD

PLatypelloid - NOT PREFFERED

android - NOT PREFERRED

more commonly the pelvis is a combinations of all the 4 types
except anthropoid with platypelloid

Question 8

describe the gynecoid pelvis

Answer 8

INLET

inlet shape : round
> widest transverse diametre

sacral angle : angle between the line transecting the top of the first sacral vertebra that intersects with a true horizontal line
more than 90 degrees

sacrum well curved from side to side and up to down

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PELVIC CAVITY

> sacrosciatic notch (greater sciatic notch) :
wide and shallow

> side walls should be are straight

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OUTLET

> ischial spine blunt

pubic arch more important that subpubic angle : curved
> subpubic angle about 90 degrees

> bituberous diameter : normal

= creating cylindrical shape
and the fetal head generally rotates int the ocipitoanterioir position

Question 9

describe the anthropoid pelvis ?

Answer 9

> shape of pelvic inlet : anteroposteriorly oval
it is much larger anteroposterior than transverse

> sacrum angle : more than 90 degrees

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> sacrosciatic notch :
more wide and shallow

> side walls : straight or divergent

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> ischiacal spines : not prominent

pubic arch - long and curved
subpubic angle : narrow
outwardly shape subpubic arch

bituberous diametre : normal

Question 10

describe the platypelloid pelvis?

Answer 10

pelvic inlet shape : transversely oval
short anteroposterior ,
wide transverse diameter creating an transversely oval shape

sacral angle : more than 90 degree
sacrum is short and straight

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sacrosciatic notch : slightly narrow and small

side walls : divergent

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ischial spines - not prominent
wide bispinosus diameter

short and curved pubic arch
subpubic angle : very wide more than 90 degrees

bituberous diameter : wide

Question 11

describe the android pelvis

Answer 11

male type of pelvis

triangular inlet - flat
the widest transverse diameter is closer to the sacrum

sacral angle : less than 90 degrees
sacrum is straight and inclined forwards

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sacrosciatic notch : narrow and deep

side walls : convergent

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ischial spines : prominent

long and straight pubic arch
subpubic angle : narrow

bituberous diameter - short

limited space at inlet - progressively less when moving down
fetal head forced to be in ocipitoposterioir portion
and arrest at descent is common

Question 12

we have the false and the true pelvis how does this come about

Answer 12

the pelvic brim separates the hip into two parts

false pelvis /greater / upper pelvis - everything above the brim

true /lesser / lower pelvis - anything below the rim

Question 13

true /lesser / lower pelvis - anything below the rim is divided into three sections and describe what encapsulates them?

Answer 13

the pelvic inlet - space enclosed by the pelvic brim which is the outer bony edges of the pelvic inlet

anteriorly the upper margin of symphysis pubis

laterally : arcuate line on the inner surface of the ilium, and the pectineal line on the superior pubic ramus

Posteriorly : by sacral promontory and margin of ala

what is linea terminals: pubic crest ,pectineal line , arcuate line ,sacral promontory and margin of ala

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midpelvis / pelvic cavityy - space between the pelvic inlet and the pelvic outlet

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pelvic outlet

anterior : inferior margin of pubic symphysis
inferior rami of the pubis

laterally: ischial tuberosity and sacrotuberous ligament

posterior border : tip of coccyx

Question 14

the pelvic inlet , mid pelvis , and pelvic outlet are subdivided into 4 planes which are

Answer 14

*plane of pelvic inlet

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mid pelvis

plane of mid cavity /plane of greatest dimensions (not obstetrically important)

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OUTLET

• plane of least pelvic dimensions /plane of obstetrical outlet

plane of anatomical outlet

Question 15

what are the measurements in the plane of pelvic inlet

Answer 15

1) ANTEROPOSTERIOR

obstetric conjugate
distance between mid point of inner symphysis pubic to mid point of sacral promontory
(the point bulging the most on the back of the symphysis pubis)
=11cm

^MOST IMPORTANT - MEASURED INDIRECTLY SUBSTRACTING 1.5-2CM from diagonal conjugate.

anatomical /true conjugate
distance between midpoint of sacral promontory and upper margin of symphysis pubis
=11.5 cm (MEASURED INDIRECTLY BY SUBSTRACTING 1.2CM FROM DIAGONAL CONJUGATE)

diagonal conjugate =
Measured between the sacral promontory and the lower edge of the pubic symphysis
(ONLY AP CLINICALLY MEASURED)
= 12.25cm

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2) TRANSVERSE
greatest distance between the two lines terminals

intersect the obstetrical conjugate 5cm infract of promontory

= 13cm

divides inlet into anterior and posterior segments

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3) OBLIQUES (2)

sacroiliac joint to
iliopubic eminence
=12cm

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posterior sagittal line
=4.5cm

Question 16

for a narrow pelvis to be considered what needs to be met?

Answer 16

one of the inner diameters is 1.5 to 2 cm smaller than normal

obstetric conjugate : smaller than 10 cm and

transverse diameter of the inlet of the pelvis must be smaller than 12cm.

diagonal conjugate less than 11cm

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Midpelvis is considered contracted when the sum of the interischial spinous and posterior sagittal diameters of the midpelvis (normal: 10.0 + 5 = 15.0 cm) is 13.0 cm or below

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Contracted outlet is suspected when the interischial tuberous diameter is 8 cm or less.

A contracted outlet is often associated with midpelvic contraction. Isolated outlet contraction is a rarity. Disproportion at the outlet may not give rise to severe dystocia, but may cause perineal tear

Question 17

what is LITZMANN CLASSIFICATION ?

Answer 17

narrowing of the pelvic inlet based on obstetric conjugate

Question 18

how many levels are there is LITZMANN CLASSIFICATION and describe them and the possibility of vaginal delivery

Answer 18

first level - 9.5-10cm
borderline

second level - 7.5-9cm
vaginal delivery possible if fetes is with IUGR
if less than 9cm
NO CHANCE FOR vaginal DELIVERY

third level - 5.5-7.5cm

fourth level - smaller than 5.5 cm

Question 19

plane of greatest dimension /plane of mid cavity boundaries?

and measurements ?

Answer 19

anterior : midle surface of symphysis pubis

posterior : 3/4th sacral vertebrae

lateral - ischial bones
centre os acetabulum and upper part of greater sciatic notch

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its AP , transverse average to 12.5cm

diagonal conjugate = 12.75

Question 20

boundaries of plane of shortest dimensions /plane of obstetrical outlet?

what is special about this plane

Answer 20

plane of pelvic floor

measured at level of ischial spines (ischial spine = 0 station in descend)

anteriorly = lower border of symphysis pubis

laterally - ischial spines

posteriorly - tip of sacrum

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ENGAGED if in the roof of the head reaches this plane
also a place where the pelvic axis turns forwards

Forceps is applied only when the head at this level (mid forceps) or below it (low and outlet forceps)

pudendal nerve block carried out at this level

Question 21

measurements in the plane of shortest dimensions /plane of obstetrical outlet ?

Answer 21

1) anteroposterioir

=13cm
tip of the sacrum to the lower border of symphysis pubis as the coccyx moves backwards during the second stage of labour
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2) TRANSVERSE

bispinosus (ischial spine)
=10.5cm
SMALLEST PELVIC DIAMETER

Question 22

plane of anatomical pelvic outlet boundaries ?

Answer 22

anteriorly = pubic arch

laterally - ischiopubic rami , ischial tuberosity , sacrotuberous ligament

posterioirly = tip of coccyx

Question 23

internal rotation occurs in which plane ?

Answer 23

Internal rotation of the head occurs when the biparietal diameter occupies the plane of greatest pelvic diameter

and the occiput is on the pelvic floor at the plane of the least pelvic diameters.
occiput is at the level of the ischial spine

Forceps is applied only when the head at this level (mid forceps) or below it (low and outlet forceps)

Question 24

measurements in the plane of anatomical pelvic outlet?

Answer 24

anatomical anteroposterior =11cm (9.5cm-11.5cm)
tip of the coccyx to the lower border of symphysis pubis

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TRANSVERSE diameters

bituberous (ischial) diameter = 11 cm

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the pelvic outlet which is a diamond shaped consists of two approx triangular areas

posterior and anterior triangle - having a common base which is the line between the two ischial tuberositities

Anterior sagittal diameter: 6-7 cm
from the lower border of the symphysis pubis to the centre of the bituberous diameter.

Posterior sagittal diameter: 7.5-10 cm
from the tip of the sacrum to the centre of the bituberous diameter.

Question 25

diagnostic physical findings in women linked to contracted pelvis ?

Answer 25

short < 150cm

dystocia dystrophia syndrome - short thighs and stocky built with bull neck
obese
male type hair
dysmenorrhea
subfertile
android pelvis - osteoposterioir position - deep transverse arrest
outlet dystocia

pendulous abdomen

malpresentation in primigravidae

heavy bones

short legs

claudication

michaelis rhomb - not normal quadrant shape

Question 26

what are the typical signs of narrow pelvis during labour ?

Answer 26

the head stays in high position - does not enter the true pelvis

malpresentation of the head

rupture of amnion- hand or cord can be prolapsed

secondary labour weakness or long duration of labour

oxytocin not effective

hypoxia of fetes during delivery due to worsening of uteroplacental delivery

Question 27

what leads to functional narrow pelvis

Answer 27

diabetes mellitus

normal pelvis but big size fetus

Question 28

Four tests for examination of narrow pelvic inlet or cephalopelvic disproportion (ONLY FOR PELVIC BRIM)?

Answer 28

interpretation same as muller munro kerr

abdominal method -
The head is grasped by the left hand. Two fingers (index and middle) of the right hand are placed above the symphysis pubis

note the degree of overlapping, if any, when the head is pushed downwards and backwards

• The head can be pushed down in the pelvis without overlapping of the parietal bone on the symphysis pubis — no disproportion.

 Head can be pushed down a little but there is slight overlapping of the parietal bone — moderate disproportion.

 Head cannot be pushed down and instead the parietal bone overhangs the symphysis pubis displacing the fingers — severe disproportion

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Zangemeister ,

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pinard
placed in semi-sitting position to bring the foetal axis perpendicular to the brim.
The left hand pushes the head downwards and backwards into the pelvis while the fingers of the right hand are put on the symphysis to detect disproportion.

beginning of labour between contractions

Mueller-Hillis test

fingers were inserted into the vagina and the ischial spines and fetal head were identified. Pressure was then applied transabdominally to the fundus with the opposite hand . The descent of the head with reference to the interspinous line was evaluated.

. A positive Mueller-Hillis maneuver was defined as descent of the fetal head of at least one centimeter.

Any lesser degree of descent was defined as a negative result.

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before labour
muller-munro kerr

best

finger tips placed at the level of ischial spines and thumb is placed over the symphysis pubis. The head is grasped by the left hand and is pushed in a downward and backward direction into the pelvis

(1) The head can be pushed down up to the level of ischial spines and there is no overlapping of the parietal bone over the symphysis pubis — no disproportion

(2) The head can be pushed down a little but not up to the level of ischial spines and there is slight overlapping of the parietal bone — slight or moderate disproportion;
vaginal delivery may or may not happen

(3) The head cannot be pushed down and instead the parietal bone overhangs the symphysis pubis displacing the thumb — severe disproportion

Question 29

the the plane of pelvic outlet can be measured if it is narrow or not through which technique

Answer 29

interteuberous siamtere may be measured by plcing a normal sized closed fist against the perineum at the level of the tuberoities

THOM’s rule :
if the sum of bituberous diametre which has to be more than 8cm (transverse ) + posterioir sagittal (X ray pelvimetry ) = more than 15cm vaginal delivery allowed with epstiotomy
less than that caesarian

arch of the pubis

angle of less than 90 degrees lead to obstructed labour - and prognosis of vaginal delivery depends on the posterior sagittal diameter

Question 30

how does clinical internal pelvimetry go on about ?

Answer 30

two fingers inserted in the vaginal and reach the promontory of the sacrum, and the point which the sphysisis pubis touches the metacarpal bones of the hand which in the vagina - the distance distance measured with pelvimetere= measure greater than 11.5cm is adequate

IN VERTEX PRESENTATIOn done after 37th week but best at beginning of labour due to sofenin for issues

and two fingers inserted

-sacrum smooth short and well curved , sacral promontory usually not reached

INLET
iliopectineal lines - no breakage suggesting of android pelvis

by the diagonal conjugate

the distance from the sacral promontory to the inner inferior surface of the pubis, which is measured

MEDPELVIS - pelvic cavity

• ischial spines smooth and difficult to palpated
  if both ischial spines can be touched simaltenous by the two examining fingers it is of adequate size more than 9.5cm

side walls - straight
to determine - start from pelvic brim dow to the base of the ischial spines

relation between the index and middle finger at the base of ischial spines to the thumb on the other hand at the ischial tuberosity

if the thumb is medial - side wall convergent
lateral - divergent

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Lower pelvis
- greater sciatic notch large enough for two fingers to be easily placed on the sacrospinous ligament covering the notch

sacrococcygeal joint mobility testes
by pressing firmly on the coccyx while an external send determines its mobility

The width of the subpubic angle is determined by the distance between the abducted thumb and index finger between the right and the left ischial tuberosities

Anteroposterior diameter of the outlet—The distance between the inferior margin of the symphysis pubis and the skin over the sacrococcygeal joint can be measured either with the method employed for diagonal conjugate or by external calipers

Question 31

what is the obstetric axis ?

Answer 31

imaginary line represents the way passed by the head during labour
J shaped

passes downwards and backwards along in the inlet till the ischial spines

plane of obstetric outlet where it becomes more passing downwards and forwards along the the pelvic outlet

Question 32

pelvic inlet inclination

pelvic outlet inclination

Answer 32

when standing erect

pelvic inclination is the angle between the horizontal plate and the plane of pelvic inlet = 55 degrees
more than this the descend is difficult

pelvic outlet = 15 degrees with horizontal

Question 33

when the pelvis becomes contracted what are the complications on the baby ?

Answer 33

brain injury 
hemotoma
asphyxia 
fracture 
nerve injury 
intramniotic infections - due to prolonged labour

Question 34

what is etiology of contracted pelvis ?

Answer 34

nutritional and environmental defects

major variation -both rare
1) rachitic
> promontory pushed downwards and forwards >shortening of AP
> transverse diameter stays the same and sometimes increased
>sacrum flat and tilted back
> outet transverse dimatere increased , and pubic arch angle increased

2) and osteomalacic
>promontory pushed downwards and forwards
anterior wall forms a beak
shape of inlet triadiate

kyphosis - tuberculosis or rickets caused

scoliosis (obliquely contracted)

paralysis of the lower limbs

arthritis

spondylolisthesis -
5th lumbar vertebrae pushed forward
promontory pushed back
tip of sacrum pushed forward - outlet contraction

poliomyelitis

fractures

developmental defects - naegele pelvis - (arrest in development of one ala of the sacrum)

robert pelvis - ala of both sides are absent
sacrum fused with the bones

high assimilation pelvis - sacrum composed of 6 vertebrae

low assimilation pelvis - sacrum composed of 4 vertebrae

Question 35

what is the management of contracted pelvic inlet ?

Answer 35

minor -
induction of labour (2-3 weeks before due date
not favoured nowadays

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moderate degree :
trial labour
contra : Associated midpelvic and outlet contraction; Presence of complicating factors like elderly primigravida, malpresentation, postmaturity
and c section not available

ideally labour should be spontaneous in onset , progress of labour carefully observes
and no oral feeding

if failure to progress amniotomy / oxytocin infusion
but never before cervix 3cm dilated

termination of trial in unfavourable conditions
abnormal uterine contraction;
Cervical dilatation less than 1 cm per hour in the active phase ;
Descent of fetal head less than 1 cm per hour in protracted active phase
inspite of regular uterine contractions;
Arrest of cervical dilatation and nondescent of fetal head in spite of oxytocin therapy;
FETAL DISTRESS

with spontaneous delivery
forceps and venous
c section

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major degree and moderate degree
c section

Question 36

complications of contracted pelvis ?

Answer 36

during pregnancy
retroverted gravid uterus
malpresentation

during labour
PROM
cord prolapse
rupture of uterus

postpartum haemorrhage-uterine inertia
chorioamonitis