Contracted Pelvis

Contracted PelvisAnatomical definition: It is a pelvis in which

one or more of its diameters is reduced below the normal by one or more centimetres.

Obstetric definition: It is a pelvis in which one or more of its diameters is reduces so that it interferes with the normal mechanism of labour.

Factors influencing the size and shape of the pelvis:Developmental factor: Hereditary or

congenitalNutritional factor: Malnutrition results in a

small pelvis.Racial factorsTrauma, diseases or tumours of the bony

pelvis, legs or spines.Sexual factors: an excessive androgen may

produce android pelvis.

Aetiology of Contracted PelvisCauses in the pelvisDevelopmental (congenital):Small gynaecoid pelvisSmall anthropoid pelvisSmall platypelloid pelvis (flat pelvis)Robert’s Pelvis: absence of both sacral alaeNaegele’s Pelvis: absence of one sacral alaHigh (6) and low (4 vertebrae) assimilated

pelvis

Aetiology of Contracted pelvisMetabolicOsteomalacia: is softening of the bones due

to a lack of vitamin D or a problem with the body's ability to break down and use this vitamin. Symptoms: Bone fractures that happen with very little injury; Muscle weakness.

Traumatic (fractures)Neoplastic (osteoma)

Causes in spine:Lumbar scoliosisCauses in lower limbs Dislocation of one/both femurs

Diagnosis of Contracted PelivcHistoryRickets: is expected if there is a h/o delayed

walking .Trauma or diseases of pelvis, spine and lower

limbs.Bad obstetric hx: Prolonged labour ended up in

difficult forceps, caesarean section or still birth.

ExaminationGait: abnormal gait suggesting abnormalities in

the pelvis, spine and lower limbs.Stature (short women)PelvimetryInternal pelvimetryIn let, cavity and outletExternal pelvimetryInlet and outlet Imaging pelvimetry ( CT ,MRI scan and x-ray)

External pelvmetry is of little values as it measures diameters of false pelvis.

Cephalometry: Ultrasonography is the safe accurate and easy method .

The biparital diameter (BPD)The occipito-frontal diameterThe circumference of the head

Cephalopelvic disproportion testsDone to detect contracted inlet if the head is

not engaged in the last 3-4wks in a primigravida.

Pinard’s methodMullerr- Kerr’s method

Degrees of Disproportion1. Minor disproportion: (the anterior surface

of the head is in line with the posterior surface of the symphysis.)

2.Moderate Disproportion: 1st degree (the anterior surface of the head is in line with the anterior surface of the symphysis. Vaginal degree may o r may not occur.

3.Marked disproportion: 2nd degree (the head overrides the anterior surface of the symphysis. Vaginal delivery can’t occur.

Minor degree: true conjugate is 9-10cm.Moderate degree: True conjugate 8-9cmSevere degree: True conjugate 6-8cmExtreme degree: True conjugate less than

6cm. NB:The true conjugate (11 cm or more), is

the distance from the upper margin of the symphysis to the sacral promontory.

The diagonal conjugate (12.5 to 13 cm) is the distance from the lower border of symphysis pubis to the promontory of the sacrum

Management of contracted PelvisDepends on the degree of disproportion .Minor degree of contracted pelvis: Vaginal

deliveryModerate degree; Trail labour, if failed

caesarean section.Severe degree; caesarean section.