Pelvic brim

The pelvic brim is the edge of the pelvic inlet. It is an approximately butterfly-shaped line passing through the prominence of the sacrum, the arcuate and pectineal lines, and the upper margin of the pubic symphysis.

Pelvic brim
The edge of the pelvic inlet (shown in red) is the pelvic brim
Diameters of superior aperture of lesser pelvis -- female. (Pelvic brim is not labeled, but is identifiable as the central opening at the top.)
Identifiers
FMA	224780
Anatomical terms of bone [edit on Wikidata]

Structure

The pelvic brim is an approximately butterfly-shaped line passing through the prominence of the sacrum, the arcuate and pectineal lines, and the upper margin of the pubic symphysis.

The pelvic brim is obtusely pointed in front, diverging on either side, and encroached upon behind by the projection forward of the promontory of the sacrum.

The oblique plane passing approximately through the pelvic brim divides the internal part of the pelvis (pelvic cavity) into the false or greater pelvis and the true or lesser pelvis. The false pelvis, which is above that plane, is sometimes considered to be a part of the abdominal cavity, rather than a part of the pelvic cavity. In this case, the pelvic cavity coincides with the true pelvis, which is below the above-mentioned plane.

The urinary bladder lies just above the anterior pelvic brim.^[1] The sigmoid colon also passes close to the pelvic brim.^[2]

Clinical significance

The pelvic brim may be a site of compression of structures that pass through the pelvic inlet. This can include the femoral nerves, which may occur during abdominal surgery.^[3]

See also

• Linea terminalis
• Pelvis justo major
• Pelvic inlet

Additional images

• 
  Pelvis

References

This article incorporates text in the public domain from page 238 of the 20th edition of Gray's Anatomy (1918)

1. Wilson, David A., ed. (2012-01-01), "Ultrasound: Urinary Tract", Clinical Veterinary Advisor, Saint Louis: W.B. Saunders, pp. 836–838, doi:10.1016/b978-1-4160-9979-6.00269-5, ISBN 978-1-4160-9979-6, retrieved 2021-01-30
2. Jacob, S. (2008-01-01), Jacob, S. (ed.), "Chapter 4 - Abdomen", Human Anatomy, Churchill Livingstone, pp. 71–123, doi:10.1016/b978-0-443-10373-5.50007-5, ISBN 978-0-443-10373-5, retrieved 2021-01-30
3. Lalkhen, Abdul Ghaaliq (2015-01-01), Tubbs, R. Shane; Rizk, Elias; Shoja, Mohammadali M.; Loukas, Marios (eds.), "Chapter 37 - Perioperative Peripheral Nerve Injuries Associated with Surgical Positioning", Nerves and Nerve Injuries, San Diego: Academic Press, pp. 587–602, ISBN 978-0-12-802653-3, retrieved 2021-01-30