Contracted Pelvis - Etiology/Causes, Diagnosis and Examination Findings in Contracted Pelvis

What is Contracted Pelvis

Anatomical definition of Contracted Pelvis:

Anatomically, a contracted pelvis is a pelvis in which one or more of its diameters is reduced below the normal by one or more centimeters.

Obstetric definition of Contracted Pelvis

In Obstetric, a contracted  pelvis in which one or more of its diameters is reduced so that it interferes with the normal mechanism of labour.

Factors that affects  the size and shape of the pelvis

1. Developmental factor
2. Racial factor.
3. Nutritional factor:
4. Hormonal factor:
5. Metabolic factor:
6. Trauma, diseases or tumours of the bony pelvis and spines.

Aetiology of Contracted Pelvis

Causes in the pelvis

A.    Developmental (congenital):

                                            i.            Small gynaecoid pelvis (generally contracted pelvis).

                                          ii.            Small android pelvis.

                                        iii.            Small anthropoid pelvis.

                                       iv.            Small platypelloid pelvis (simple flat pelvis).

                                         v.            Naegele’s pelvis: absence of one sacral ala.

                                       vi.            Robert’s pelvis: absence of both sacral alae.

                                     vii.            High assimilation pelvis: The sacrum is composed of 6 vertebrae.

                                   viii.            Low assimilation pelvis: The sacrum is composed of 4 vertebrae.

                                        ix.            Split pelvis: splitted symphysis pubis.

2. Metabolic:
• Rickets.
• Osteomalacia (triradiate pelvic brim).
3. Traumatic: as fractures.
4. Neoplastic: as osteoma.

5. Causes in the spine

1. Lumbar kyphosis.
2. Lumbar scoliosis.
3. Spondylolisthesis: The 5th lumbar vertebra with the above vertebral column is pushed forward while the promontory is pushed backwards and the tip of the sacrum is pushed forwards leading to outlet contraction.

6. Causes in the lower limbs

1. Dislocation of one or both femurs.
2. Atrophy of one or both lower limbs.

N.B. oblique or asymmetric pelvis: one oblique diameter is obviously shorter than the other. This can be found in:

• Naegele’s pelvis.
• Scoliotic pelvis.
• Diseases, fracture or tumours affecting one side.

Diagnosis of Contracted Pelvis

History

• Rickets: is expected if there is a history of delayed walking and dentition.
• Trauma or diseases: of the pelvis, spines or lower limbs.
• Bad obstetric history: e.g. prolonged labour ended by;
• difficult forceps,
• caesarean section or
• still birth.

Examination findings in Contracted Pelvis

• General examination:
• Gait: abnormal gait suggesting abnormalities in the pelvis, spines or lower limbs.
• Stature: women with less than 150 cm height usually have contracted pelvis.
• Spines and lower limbs: may have a disease or lesion.
• Manifestations of rickets as:
• square head,
• rosary beads in the costal ridges.
• pigeon chest,
• Harrison’s sulcus and bow legs.
• Dystocia dystrophia syndrome: the woman is
• short,
• stocky,
• subfertile,
• has android pelvis and
• masculine hair distribution,  
• with history of delayed menarche.
• This woman is more exposed to occipito-posterior position and dystocia.

• Abdominal examination findings in contracted pelvis
• Nonengagement of the head: in the last 3-4 weeks in primigravida.
• Pendulous abdomen: in a primigravida.
• Malpresentations: are more common.