# diameter

(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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### Citation

*Taber's Medical Dictionary*, 23rd ed., F.A. Davis Company, 2017.

*Nursing Central*, nursing.unboundmedicine.com/nursingcentral/view/Tabers-Dictionary/761475/all/true_conjugate_diameter_of_pelvic_inlet.

*Taber's Medical Dictionary*. F.A. Davis Company; 2017. https://nursing.unboundmedicine.com/nursingcentral/view/Tabers-Dictionary/761475/all/true_conjugate_diameter_of_pelvic_inlet. Accessed February 29, 2020.

*Taber's Medical Dictionary*(23rd edition). F.A. Davis Company. Retrieved February 29, 2020, from https://nursing.unboundmedicine.com/nursingcentral/view/Tabers-Dictionary/761475/all/true_conjugate_diameter_of_pelvic_inlet

*Taber's Medical Dictionary*. F.A. Davis Company; 2017. [cited 2020 February 29]. Available from: https://nursing.unboundmedicine.com/nursingcentral/view/Tabers-Dictionary/761475/all/true_conjugate_diameter_of_pelvic_inlet.