(dī-am′ĕt-ĕr )

[*dia-* + *-meter*]

The distance from any point on the periphery of a surface, body, or space to the opposite point.

anteroposterior diameter of pelvic cavity

The distance between the middle of the pubic symphysis and the upper border of the third sacral vertebra (about 5.3 in [13.5 cm] in women).

anteroposterior diameter of pelvic inlet

The distance from the posterior surface of the pubic symphysis to the promontory of the sacrum (about 4.3 in [11 cm] in women).

SYN: *SEE: conjugata vera; SEE: true conjugate diameter of pelvic inlet*

anteroposterior diameter of pelvic outlet

The distance between the tip of the coccyx and the lower edge of the pubic symphysis.

Baudelocque diameter

bigonial diameter

The distance between the two gonia. The gonion is the anthropometric point at the most inferior, posterior, and lateral points on the angle of the mandible.

biparietal diameter

ABBR: BPD The transverse distance between the parietal eminences on each side of the head (about 3.6 in [9.25 cm]).

bitemporal diameter

The distance between the temporal bones (about 3.15 in [8 cm]).

bitrochanteric diameter

The distance between the highest points of the greater trochanters.

bizygomatic diameter

The greatest transverse distance between the most prominent points of the zygomatic arches.

buccolingual diameter

The measurement of a tooth from the buccal to the lingual surface.

cervicobregmatic diameter

The distance between the anterior fontanel and the junction of the neck with the floor of the mouth.

conjugate diameter

SEE: Conjugate (2).

diagonal conjugate diameter of pelvis

The distance from the inferior border of the pubic symphysis to the sacral promontory.

external conjugate diameter

The anteroposterior diameter of the pelvic inlet measured externally; the distance from the skin over the upper part of the pubic symphysis to the skin over a point corresponding to the sacral promontory.

frontomental diameter

The distance from the top of the forehead to the point of the chin.

interspinous diameter

The distance between the two anterior superior spines of the ilia.

intertuberous diameter

The distance between the ischial tuberosities. Most commonly, this measure of the female pelvic outlet is greater than 9 cm, allowing the exit of an average-sized term fetus.

labiolingual diameter

The measurement of an anterior tooth from the labial to the lingual surface.

mentobregmatic diameter

The distance from the chin to the middle of the anterior fontanel.

mesiodistal diameter

The measurement of a tooth from the ventral or mesial surface to the distal or dorsal surface.

obstetrical diameter of pelvic inlet

The shortest distance between the sacrum and the pubic symphysis. This diameter is shorter than the true conjugate.

SYN: *SEE: obstetrical conjugate*

occipitofrontal diameter

The distance from the posterior fontanel to the root of the nose.

occipitomental diameter

The greatest distance between the most prominent portion of the occiput and the point of the chin (about 5.3 im [13.5 cm]).

diameter of pelvis

Any diameter of the pelvis found by measuring a straight line between any two points. The diameters are:*anteroposterior*, the distance between the sacrovertebral angle and the pubic symphysis; *bi-ischial*, the distance between the ischial spines; *conjugata diagonalis*, the distance between the sacrovertebral angle and the pubic symphysis; *conjugata vera*, the true conjugate between the sacrovertebral angle and the middle of the posterior aspect of the pubic symphysis (about 1.5 cm less than the diagonal conjugate); *intercristal*, the distance between the crests of the ilia; *interspinous*, the distance between the spines of the ilium; *intertrochanteric*, the distance between the greater trochanters when the hips are extended and the legs are held together; and *obstetrical conjugate*, the distance between the promontory of the sacrum and the upper edge of the pubic symphysis.*SEE: pelvis*

true conjugate diameter of pelvic inlet

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