Pelvic Cavity - Measurements

Measurements

The pelvis can be classified into four main types by measuring the pelvic diameters and conjugates at the pelvic inlet and outlet and as oblique diameters.

Pelvic measurements
Measurement From To Length
Transverse diameter
(of inlet)
Between extreme lateral points of pelvic inlet 13.5-14 cm
Oblique diameter I Right sacroiliac joint Left iliopubic eminence 12-12.5 cm
Oblique diameter II Left sacroiliac joint Right iliopubic eminence 11.5-12 cm
Anatomical conjugate
(true conjugate)
Pubic symphysis Promontory ~12 cm
obsteric conjugate Retropubic eminence
(posterior surface
of symphysis)
Promontory >10 cm
Diagonal conjugate* Inferior pubic ligament Promontory 11.5-12 cm
Straight conjugate Lower border of symphysis Tip of coccyx 9.5-10 cm
Median conjugate Lower border of symphysis Lower border of sacrum 11.5 cm
Transverse diameter
(of outlet)
Between ischial tuberosities 10-11 cm
Interspinous distance Between anterior superior iliac spines 26 cm
(female)
Intercristal distance Between furthest lateral points of iliac crest 29 cm
(female)
External conjugate Spinous process of fifth lumbar vertebra Upper edge of symphysis ~20 cm
Intertrochanteric distance Between femurs 31 cm
*Because the true conjugate can not be measured directly it is derived from the diagonal conjugate which is measured through the vagina.

Read more about this topic:  Pelvic Cavity