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.
| 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