Pelvic measures and methods for pelvimetry of normal and narrow pelvis. Flashcards
what is pelvimetry used for
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).
how are the measures in pelvimetry obtained ?
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
what does the bony pelvis consist of
the bony pelvis consist of the sacrum the ilium , isichum and pubis
what is michaelis -rhombus
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
why is the michaelis -rhombus an important anatomical part in pregnancy ?
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
when does the michaelis rhombus anatomically move in
by the time that the baby’s feet are born, in fact sometimes more quickly than that
what are the 4 different types of bony pelvis are described ?
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
describe the gynecoid pelvis
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
describe the anthropoid pelvis ?
> 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
describe the platypelloid pelvis?
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
describe the android pelvis
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
we have the false and the true pelvis how does this come about
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
true /lesser / lower pelvis - anything below the rim is divided into three sections and describe what encapsulates them?
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
the pelvic inlet , mid pelvis , and pelvic outlet are subdivided into 4 planes which are
*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
what are the measurements in the plane of pelvic inlet
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
for a narrow pelvis to be considered what needs to be met?
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
what is LITZMANN CLASSIFICATION ?
narrowing of the pelvic inlet based on obstetric conjugate
how many levels are there is LITZMANN CLASSIFICATION and describe them and the possibility of vaginal delivery
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
plane of greatest dimension /plane of mid cavity boundaries?
and measurements ?
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
boundaries of plane of shortest dimensions /plane of obstetrical outlet?
what is special about this plane
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
measurements in the plane of shortest dimensions /plane of obstetrical outlet ?
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
plane of anatomical pelvic outlet boundaries ?
anteriorly = pubic arch
laterally - ischiopubic rami , ischial tuberosity , sacrotuberous ligament
posterioirly = tip of coccyx
internal rotation occurs in which plane ?
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)
measurements in the plane of anatomical pelvic outlet?
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.
diagnostic physical findings in women linked to contracted pelvis ?
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
what are the typical signs of narrow pelvis during labour ?
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
what leads to functional narrow pelvis
diabetes mellitus
normal pelvis but big size fetus
Four tests for examination of narrow pelvic inlet or cephalopelvic disproportion (ONLY FOR PELVIC BRIM)?
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
the the plane of pelvic outlet can be measured if it is narrow or not through which technique
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
how does clinical internal pelvimetry go on about ?
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
what is the obstetric axis ?
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
pelvic inlet inclination
pelvic outlet inclination
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
when the pelvis becomes contracted what are the complications on the baby ?
brain injury hemotoma asphyxia fracture nerve injury intramniotic infections - due to prolonged labour
what is etiology of contracted pelvis ?
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
what is the management of contracted pelvic inlet ?
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
complications of contracted pelvis ?
during pregnancy
retroverted gravid uterus
malpresentation
during labour
PROM
cord prolapse
rupture of uterus
postpartum haemorrhage-uterine inertia
chorioamonitis
