Bekkenrand

Bekkenrand, or pelvic brim, is the edge of the pelvic inlet that marks the boundary between the false pelvis (upper part of the pelvis) and the true pelvis (lower part). It is roughly circular to oval and serves as a defining boundary of the pelvic inlet, which forms the ceiling of the true pelvis.

The brim is formed by several bony landmarks: anteriorly the pubic crest and pectineal line; laterally the arcuate line of the ilium; and posteriorly the sacral promontory. Together these points align to form the linea terminalis, the continuous line that delineates the pelvic inlet.

Function and clinical relevance: The bekkenrand defines the opening through which the pelvis communicates with the abdomen and, in obstetrics, represents the upper boundary of the birth canal. The size and shape of the pelvic inlet influence obstetric considerations, with female pelves typically having a wider and more oval brim to facilitate childbirth. In clinical practice, the brim serves as a key anatomical landmark in imaging, surgical planning, and the assessment of pelvic dimensions (alongside measurements such as the diagonal conjugate).

Variations and terminology: The term bekkenrand is commonly equated with the pelvic brim, and in anatomy the brim is sometimes described as part of the linea terminalis. While the general concept is consistent across humans, its exact shape and dimensions can vary between individuals and between sexes.