DISPLACEMENTS
Minor variations in position of the uterus occur constantly with changes in posture, with straining or with changes in the volume of bladder content. Only when the uterus becomes fixed or rests habitually in a position beyond the limits of normal variation should a diagnosis of displacement be made and it should be considered pathologic only when such a position results in symptoms.
In the erect position, the cervix bends approximately at right angles to
the axis of the vagina. The corpus curves slightly forward, and the uterus thus
rests in an almost horizontal position on top of the bladder. It is maintained
in this position by intraabdominal pressure exerted by the intestines against
the posterior surface of the corpus while standing or sitting; the intrinsic
tone of the uterine musculature and the specific fibro-muscular bands or
ligaments in the pelvis, namely, the round ligaments, the cardinal ligaments,
and the utero-sacral ligaments; and the fasciae and muscles of the perineum.
Three ligaments suspend the uterus: (1) the round ligaments, (2) the
cardinal ligaments, and (3) the utero-sacral ligaments, with the cardinal
ligaments being the most significant. The round ligaments tend to pull the
fundus to its anterior position, provided the cervix is held backward by the
uterosacral ligaments. These and the round ligaments contribute to the correct
position of the uterus in relation to the vagina, whereas the cardinal
ligaments provide the cervix with lateral and axial stability.
Retrodisplacement most frequently occurs after parturition when the
stretched ligamentous supports are no longer able to counteract the
intraabdominal pressures and when the uterus, during involution, may be lacking
in normal myometrial tone. The fundus is thus forced backward toward the
sacrum.
Less frequently, retroposition of the uterus results from adhesions
caused by endometriosis, tumors, or infections, such as pelvic inflammatory
disease, that hold the uterine corpus in a fixed posterior position.
Occasionally, in aged women, backward displacement results from postmenopausal
atrophy and loss of muscular tone of the uterine body and the suspensory
structures.
Retroversion signifies a turning backward of the whole uterus without a
change in the relationship of the corpus to the cervix. This is in contrast to
retroflexion where the relationship between cervix and uterus is altered. Retroflexion
signifies a bending backward of the corpus on the cervix at the level of the
internal os. In most cases, the cervix will have lost its normal right-angle
relationship with the vaginal apex, and therefore some retroversion will be
present as well.
First-degree retroversion includes all deviations from the anterior
position in which the cervix-corpus axis
points anterior to the axis of the vagina. This is common and of no clinical
significance. When the cervix and corpus point directly along the axis of the
vagina, the retroversion is designated as second degree or mid-plane. Any
deviations beyond this point are termed third degree, or
true, retroversion. Clinically, the first-degree changes are of little
consequence, are often transient and no doubt occur physiologically. Second-degree
displacements are very common, without refer-able symptoms.
In obese patients, this diagnosis often must be made by demonstrating
that the endocervix extends straight back, whereas the fundus can be felt
neither anteriorly over the symphysis nor posteriorly in the cul-de-sac of Douglas. In third-degree retroversion, the examining finger comes upon the
corpus lying directly back on the anterior surface of the rectum.
The term retrocession describes a slumping backward of the cervix and vaginal apex toward the coccyx, with the uterine relationships otherwise normal. It is generally associated with anteflexion, a forward bend of the corpus at the isthmus, which brings the fundus under the symphysis.
