Anatomy of maternal pelvis(passage)

Maternal pelvis

False pelvis:The part of pelvis which do not has active role in labour is the false pelvis. 

It supports internal visera. 

True pelvis:Maternal passage concerned with labour is the true pelvis.

Before entering in to the topic I hope that you all have basic idea about normal anatomy of pelvis.

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The true pelvis consists of the following three parts:

   

1) Pelvic brim

2) Pelvic cavity

3) Pelvic outlet

1) Pelvic Brim/inlet:

Right oblique  Right sacroiliac joint	Posterior sacral promontory	Left oblique Left sacroiliac joint
Right Lateral furthest points in the pelvic brim	Pelvic Brim/       inlet ↔	Left Lateral furthest points in the pelvic brim
Right illeo-pectineal eminence	Anterior superior margin of the pubis	Left illeo-pectineal eminence

*Obstetric Conjugate: From the centre of sacral promontory behind to the nearest point on the posterior surface of the pubic symphysis in front. It is 4-5 mm less than the true conjugate (11 cms). This is the antero posterior diameter

available for the passage of fetus at the brim.

* The Diagonal Conjugate: The diagonal conjugate extends from middle of sacralt promontory to middle of lower border of symphysis pubis. It is 12.5 cms

in length. This diameter can be measured on the patient if sacral promontory is reached. By subtracting 1.5 cms, appropriate length of obstetric conjugate can

be obtained.

*Angle of inclination:The plane of the pelvic brim is inclined at an acute angle to the horizontal and measures about 55°.

2) Pelvic Cavity:It is round in shape and its diameter is 12cms.

3) Pelvic Outlet:

	Posterior sacral tip or  Apex
Right Lateral ischeal Tuberosity	Pelvic            outlet	Left Lateral ischeal tuberosity
	Anterior. lower margin of pubic symphysis

*Pelvis DIAMETERS (in cm) 

	ANTERIO POSTERIOR	TRANSVERSE	OBLIQUE
INLET	11	13	12
CAVITY	12	12	12
OUTLET	13	11	-

Clinical anatomy:Normal Labour and Peurperium

Curve of carus or the anatomical axis of the pelvis is a line uniting centers of the plane of the brim, plane of the cavity and outlet. It is a curved line with concavity forward . it represents the true path of the foetal head through maternal pelvis. "Decrease in 1 cm or more in any of the diameters of pelvis is considered as contracted pelvis." 

Pelvis types

Classically pelvis have been described into four categories on the basis of pelvic inlet and

non-confounding characteristics. A woman’s pelvis is unlikely to be classified during life time unless she has problems during childbirth. The foetal head is the best pelvimeter.

Four types of pelvis are described:  

	Gynaecoid Typical female pelvis	Android Typical male pelvis	Anthropoid Monkey/ ape Pelvis	Platy pelloid
Brim	Rounded or Transverse oval	Heart shaped	Long oval	Kidney shaped
Sacrum	Well curved	Flat	Well curved	Flat
Fore pelvis	Generous	Narrow	Narrow	Wide
Side wall	Straight	Convergent	Straight/ Divergent	divergent
Ischeal spines	blunt	Prominent	blunt	blunt
Sacro sciatic Notch	Rounded, wide	Narrow	Wide	Wide
Sub pubic angle	90°	<_90°	>_90°	>90°
	50%	20%	25%	5%

Asking the right questions is as important as answering them

  

FAQ'S

(1)Strongest ligament in human body is? 

(2)Strongest joint in human body is? 

(3)The most common type of female pelvis is? 

(4)Station of foetal head is determined with relation to which landmark 

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