Bony pelvis: Anatomy & Measurements

Bony pelvis. Anatomy & MeasurementsKey facts about the anatomy of the bony pelvis. Pelvic measurements.
~ 3 min

For a comprehensive understanding of the anatomy of the pelvic girdle, we must examine the bony pelvis.

Pelvis
Pelvis

Its consists of:

  • hip bone (os coxae), 2x

Hip bone (os coxae)
Hip bone (os coxae)
  • sacrum (os sacrum)

    Sacrum (os sacrum)
    Sacrum (os sacrum)
  • coccyx (os coccygis)

    Coccyx (os coccygis)
    Coccyx (os coccygis)

    There are the greater pelvis (pelvis major)

    Greater pelvis (pelvis major)
    Greater pelvis (pelvis major)
    Lesser pelvis (pelvis minor)
    Lesser pelvis (pelvis minor)

    and the lesser pelvis (pelvis minor).

  • The walls of the greater pelvis are formed by the following structures:

    • anterior wall is formed by the muscles of the anterior wall of the abdomen

    • posterior wall is formed by the fifth lumbar vertebra, the base of the sacrum, the iliolumbar ligament

    lateral walls are formed by the wings of the ilia

    The walls of the lesser pelvis are formed by the following structures:

    • anterior wall is formed by the pubic bones and pubic symphysis

    • posterior wall is formed by the sacrum and the coccyx

    • lateral walls are formed by the ischia, the obturator membrane, the sacrotuberous and the sacrospinous ligaments

    • The pelvis also has two apertures (inlet/outlet):

      • pelvic inlet (apertura pelvis superior), which is bounded by the linea terminalis (linea terminalis). In turn, the linea terminalis extends through the following formations: pubic symphysis → pecten pubis → arcuate line → promontory

      • pelvic outlet (apertura pelvis inferior) is bounded by the following formations: pubic symphysis → inferior pubic ligament → inferior pubic ramus → ramus of ischium → ischial tuberosity → sacrotuberous ligament → coccyx

      • Pelvic inlet (apertura pelvis superior); linea terminalis (linea terminalis)
        Pelvic inlet (apertura pelvis superior); linea terminalis (linea terminalis)

        One must also understand the differences between the sexes in the pelvis:

        Pelvic outlet (apertura pelvis inferior)
        Pelvic outlet (apertura pelvis inferior)
      • Male pelvis is narrower, taller, the wings of the ilia are upright, the pelvic inlet is rounded, and the pubic bones form a pubic angle

      • Female pelvis is wider, the wings of the ilia are horizontal, the pelvic inlet is heart-shaped, and the pubic bones form the pubic arch

      In obstetrics, the study of the pelvis is critical because the structure and size of the pelvis are crucial to the course and outcome of the birth. The presence of a normal pelvis is one of the main conditions for the correct course of childbirth. In this regard, it is essential to know the measurements of the female pelvis.

      Male pelvis
      Male pelvis
      Female pelvis
      Female pelvis

      The following dimensions of the pelvis are distinguished:

      Greater pelvis (false pelvis) diameters
      Distantia spinarum
      (distantia spinarum)
      Distance between the superior anterior iliac spines 25-26 cm
      Distantia cristarum
      (distantia cristarum)
      Distance between the most distant points of the iliac crests 28-29 cm
      Distantia trochanterica
      (distantia trochanterica)
      Distance between the greater trochanters of the femurs 31-32 cm
      External conjugate
      (conjugata externa)
      Distance between the spinous process of the 5th lumbar vertebra and the most prominent point of the external surface of the pubic symphysis 20-21 cm
      Pelvic inlet diameters
      Anatomical conjugate
      (diameter recta / conjugata anatomica)
      Distance between the superior border of the pubic symphysis and the most prominent point of the sacral promontory 11.5 cm
      True conjugate
      (diameter vera / conjugata gynecologica)
      Distance between the most prominent point of the posterior surface of the pubic symphysis to the most prominent point of the sacral promontory 10.5-11.0 cm
      Diagonal conjugate
      (conjugata diagonalis)
      Distance between the bottom of the pubic symphysis and the most prominent point of the sacral promontory 12.5-13.0 cm
      Transverse diameter
      (diameter transversa)
      Distance between the distant points of the arcuate line 13.5 cm
      Oblique diameter
      (diameter obliqua)
      Distance between the iliopubic eminence on one side and the sacroiliac joint on the other side 12-12.5 cm
      Pelvic cavity (true pelvis) diameters
      Anteroposterior diameter
      (diameter recta)
      Distance between the middle of the pubic symphysis and the place of articulation of II and III sacral vertebrae 12.5 cm
      Transverse diameter
      (diameter transversa)
      Distance between the centers of the acetabula 12.5 cm
      Pelvic outlet diameters
      Anteroposterior diameter
      (diameter recta)
      Distance between the apex of the coccyx and the inferior border of the pubic symphysis In women, it is 9 cm, and due to the mobility of the coccyx during childbirth it increases to 11 cm.
      Transverse diameter
      (diameter transversa)
      Distance between the tubercles of the ischia 11 cm

      The line connecting the centers of all anatomical conjugates of the pelvis is called the pelvic axis. It is along this line that the fetus passes through the birth canal.

      Dictionary

      Bony pelvis

      pelvis
      pelvis
      hip bone
      os coxae
      sacrum
      os sacrum
      coccyx
      os coccygis
      greater pelvis
      pelvis major
      lesser pelvis
      pelvis minor
      pelvin inlet
      apertura pelvis superior
      pelvin outlet
      apertura pelvis inferior
      distantia spinarum
      distantia spinarum
      distantia cristarum
      distantia cristarum
      distantia trochanterica
      distantia trochanterica
      external conjugate
      conjugata externa
      anatomical conjugate
      diameter recta/conjugata anatomica
      true conjugate
      diameter vera/conjugata gynecologica
      diagonal conjugate
      conjugata diagonalis
      transverse diameter
      diameter transversa
      oblique diameter
      diameter obliqua
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