PELVIC ASSESSMENTCLINICAL PELVIMETRY

SIGNIFICANCE

• A process used to assess the size of the birth canal by means of systematic vaginal palpation of specific bony landmarks in the pelvis.

• By doing pelvimetry obstetrician can measure various diameters of the true pelvis in order to determine if the head can easily negotiate the dimensions during parturition & to conduct delievery vaginally or do caesarean section.

BONY PELVIS

PELVIS• Anatomically pelvis is divided into two parts- True pelvis False pelvis Boundary line being the brim of the pelvis. Bony land marks on the brim of pelvis from anterior to

posterior on each side are Upper border of pubic symphysis,Pubic crest , Pubic tubercle, Pectineal line ,Iliopubic

eminence,Iliopectineal line,Sacro iliac articulation,Anterior border of ala of sacrum and Sacral promontary.

FALSE PELVIS

• Formed by iliac portion of innominate bonesand limited above by the iliac crest.

• Little obstetric significance.• Predicts the size and configuration of true

pelvis.• Posteriorly-lumbar vertebrae.• Laterally- Iliac fossa• Anteriorly-Anterior abdominal wall.

TRUE PELVIS

• Chief concern of the obstetrician.• Shallow in front formed by symphysis pubis

and measures 4 cm. It is deep posteriorly formed by sacrum and coccyx and measures 11.5 cm.

• For descriptive purposes divided into• Inlet, Cavity, Outlet.

INLET

DIAMETERS OF INLET• What are the conjugates related to pelvic diameter?• Anatomical conjugate

– anteroposterior conjugate diameter -11.5 CM– extends from the upper margin of the pubic symphysis to the middle

of the sacral promontory• Obstetrical conjugate-10 CM

– shortest diameter through which foetal head must pass in it’s course throught the inlet

– measured from middle of back of pubic symphysis to the sacral promontory

• Diagonal conjugate-12CM.– anteroposterior diameter of inlet as measured par vaginum– inability to palpate the sacral promontory suggests that the conjugate

diameter of the inlet is adequate for parturition• palpated means contracted pelvis

– distance between the lower margin of pubic symphysis & sacral promontory

– Subtraction of diagonal conjugate by 1.5cm gives approximate measurement of anatomical conjugate

DIAMETERS OF INLET

• Tranverse diameters-Two farthest point on the pelvic brim over the iliopectineal line.-13 cm.

• Oblique diameters- There are two right, left Measures from sacro iliac joint to opposite

iliopubic eminence.-12cm Right or left denotes the sacroiliac joint.

CAVITYCavity is bounded above by the inlet and below by plane of

least pelvic dimensions.It starts from the lower border of the symphysis pubis to the tip of ischial spines.and posteriorly to meet the tip of the 5 sacral vertebra.

Diameters-• Antero posterior diameter-From mid point on the posterior

surface of the pubic symphysis to the junction of 2 & 3 sacral vertebrae. 12cm

• Transverse diameter- canot be precisely measured as soft tissues cover the sacroiliac notches and obturator foramina.

OUTLET• It is the segment of the pelvis bounded by the

plane of least pelvic dimension and below by the anatomical outlet.

• Anterior wall is deficient at the pubic arch.• Lateral walls formed by ischial bones• Posterior –whole of coccyx.• Diameters- Tranverse-Bispinous-10.5 cm Antero posterior-11cm Posterior saggital 5cm

MID PELVIS• Segment of the pelvis bounded above by the

plane of greatest pelvic dimensions and below by the mid pelvic plane.

• Midpelvic plain-starts from lower margin of the pubic symphysis through the level of ischial spines to meet either junction of s4 5 s5or tip of the sacrum depending upon the configuration of sacrum.

DIAMETERS OF MID PELVIS

• Transverse diameter-bispinous diameter10.5• Antero posterior- extends from lower border of pubic symphysis to the point on the sacrum

at which the midpelvic plain meets. 11.5 cm Posterior saggital diameter-extends from the

midpoint of the bispinous diameter to the point on the sacrum at which the mid pelvic plain meets. 4.5 cm

ASSESSMENT METHODS

• 1 Bimanual examination.• 2 Imaging studies 1 Radio pelvimetry• 2Computed tomography.• 3 Magnetic resonance imaging.

CLINICAL PELVIMETRY• Done manually.• Time – In vertex presentation a-beyond 37 wks b-beginning of labour.• Suspicion of pelvic contraction a-Malpresentations in primi b-Head not engaged. c- previous premature delievery d- previous caesarian section

PROCEEDURE• Empty the bladder.• Patient is lying in the dorsal position.• Examination should be• gentle,thorough,methodical,purposeful.• Sterilised gloved fingers once taksten out should not be reintroduced.• Presence of lady attendent if male gynaecologist is examining.• Verbal consent of the patient.• Following features should be noted simultaneously.— state of the

cervix.• Station of the presenting part in relation to• ischial spines.• To test for CPD in non engaging head.• To note the resiliance and elasticity of the • perineal muscle.• .• • •

LEVEL OF ASSESSMENTBRIM MID PELVIS OUTLETDIAGONAL CONJUGATE-

SACRUM SIDE WALLS

POSTERIOR SURFACE OF THE PUBIC SYMPHYSIS-

ISCHIAL SPINES SACRO COCCYGEAL JOINT

ILIO PECTINEAL LINE-

SACRO SCIATIC NOTCH

SUB PUBIC ARCH

SACRO SCIATIC NOTCH-

SIDE WALLS SUB PUBIC ANGLE

TRANSVERSE DIAMETER OF OUTLET

STEPS

• SACRUM- smooth.• well curved.• inaccessible beyond lower 3 pieces.• The length breadth and its curvature• from above down and side to side • are to be noted.

STEPS

• SACRO-SCIATIC NOTCH • Notch is sufficiently wide so that

2 fingers can be easily placed over the sacro spinous ligament covering the notch.

• Configuration of the notch denotes the capacity of the posterior segment of the pelvis and side walls of the lower pelvis.

STEPS

• ISCHIAL SPINE• Spines are usually smooth

everted and difficult to palpate.• May be prominent and encroach

to the cavity diminishing the available space in the mid pelvis.

STEPS

• Ilio pectineal lines-• if beaking suggests fore

pelvis contraction.

• Side walls- normally not palpable by sweeping fingers unless convergent.

STEPS

• Posterior surface of the symphysis pubis• - normally forms smooth curve.• presence of beaking or angulation• suggests abnormality.• SACRO-COCCYGEAL JOINT-• Mobility and presence of hooked • coccyx.

STEPS

• Pubic arch – normally rounded and • accomodates palmer aspect of two• fingers.

• Diagonal conjugate- It is the distance between the lower border of pubic symphysis

to midpoint of sacral promontory. 12 cm.• Obstetric conjugate is obtained by substracting

1.5-2cm from the diaognal conjugate.

DIAOGNAL CONJUGATE

STEPS

• If the middle finger fails to reach the sacral promontary or touches it with great difficulty

• it is likely that the conjugate is adequate for average size head to pass through.

Pubic angle- In normal pelvis angle corresponds

to fully abducted thumb and index finger. In narrow corresponds to fully abducted middle and index finger.

INTER TUBEROUS DIAMETER

STEPS

• Transverse diameter of the outlet- Measured by placing the knuckles of the first interphalangeal joints or knuckles of the clinched fist betweeen the ischial tuberosities.

• Antero-posterior diameter of the outlet – the distance between the inferior margin of the symphysis pubis and the skin over the sacro-coccygeal joint.

DISPRORTION• Disparity between the head and the pelvis.• INLET CONTRACTION-• Obstetric conjugate <10 cm• Greatest tranverse dia <12 cm• Diaognal conjugate <11cm• MIDPELVIS CONTRACTION-• Sum of inter ischial spinous diameter• and posterior saggital diameter is 13cm or below.

• OUTLET CONTRACTION- inter ischial tuberous diameter• 8cm or less•

• Fetal head is the best pelvimeter.• Satisfactory progress of labour is the best indicator

of pelvic adequacy.• Isolated outlet contraction without midcavity is a

rarity.• A thorough assessment of the pelvis and the

identification of the presence and degree of CPD are to be noted while evaluating a case of contracted pelvis.

DIAGNOSIS OF CPD AT THE LEVEL OF BRIM

• CLINICAL- Abdominal method Abdomino vaginal Muller munro

kerr.

IMAGING PELVIMETRY- CEPHALOMETRY-

IMAGING METHODS

• X-Ray pelvimetry-• Poor predictor of pelvic adequacy.• useful in cases of fractured pelvis and

for the important diameters not assessed by clinical examination.

IMAGING METHODS

• Computed tomography-involves less radiations and easier to perform .

• Accuracy greater than x-ray.

IMAGING METHODS

• MRI • Most accurate to assess the bony pelvis.• Can also assess the fetal size and maternal

soft tissue which are involved in dysocia.• Has no radiation risk.