These are said not only to be the most frequent of displacements, but the most frequent of pelvic disorders.

Of the backward displacements there are two: retroversion and retroflexion.

In retroversion the uterus is fixed in a position in which the fundus points upward, or backward, the cervix more or less downward or even forward or upward, the cervico-corporeal angle being unchanged or slightly extended. (Fig. 26).

Fig. 26. Retroversion.

The normal flexibility of the uterus is lost and the organ is rigid. The general condition of the uterus is very similar, but its position is the reverse of that seen in anteversion.

Fig. 27. Retroflexion.

Fig. 28. Retroposition and retroversion of the uterus, with fixation. Peritoneal adhesions bind the posterior surface of the uterus to the sacrum and rectum, holding the uterus firmly in retroversion and retroposition. (Findley, Diseases of Women.)

In retroversions the chief causes for the deviation are changes in the ligaments; in retroflexion, changes in the uterine parenchyma, together with changes in the ligaments. Retroversion easily passes into retroflexion. If the adnexa are not bound down in Douglas' pouch, they usually lie above the uterus and laterally. (Schaeffer, Atlas and Epitome of Gynecology.)

Fig. 29. Retroversion of a Fixed Uterus. The uterus is vertical and is fixed by sacro-uterine and recto-uterine adhesions—the contracted and shortened uterine ligaments. Vagina put on the stretch by the elevation of the uterus.

Fig. 30. Retroflexion of a Fixed Uterus—uterus bound down throughout its entire length to serosa of Douglas' pouch by perimetritic adhesions. Cervix forced anteriorly, anterior lip thinned, the anterior cervical wall likewise; posterior lip thickened. Vagina thrown into folds by the descensus. Pressure of the intestines upon the uterus. (Schaeffer, Atlas and Epitome of Gynecology.)

In retroflexion the uterus is fixed in a position of flexion over its posterior surface. The fundus is directed backward or downward and the cervix downward and sometimes somewhat forward. The apex of the cervico-corporeal angle is reversed and points anteriorly. The general condition of the uterus is very similar, but its position is the reverse of that seen in anteflexion (Fig. 27). In most cases of backward displacement there is some degree of both retroflexion and retroversion, the cervix pointing downward and sometimes forward.

Fig. 31. Retroposition of the Uterus. The uterus is drawn backward into retroposition by peritoneal bands of adhesions, extending from the supravaginal portion of the cervix to the sacrum (Findley, Diseases of Women.)

In practically all cases of backward displacement there is associated some downward displacement as well.

Causes

(1). Deranged Spinal Innervation. This causes relaxation of uterine tissue and ligaments and by vaso-motor disturbances causes congestion which naturally increases the weight of the organ, and if continued will lead to chronic endometritis. In every case of pronounced retro-displacement the round as well as the sacro-uterine ligaments are relaxed. Relaxation of the sacro-uterine ligaments is a necessary part of the retro-displacement of the uterus of normal size. This is especially so in cases of retroversion. Without this the cervix could not move downward and forward, allowing the fundus to move backward and upward.

(2). Inflammatory Adhesions (Figs. 28, 29, 30, 31). These may occur high up posteriorly and by their contraction draw the fundus backward. They originate from the usual causes of inflammation of the pelvic connective tissue and differ from the adhesions causing anteflexion only in that they involve an area higher on the uterus, above the cervico-corporeal angle, and by their contraction draw the body of the uterus backward. In some cases the adhesions are seemingly peritoneal in origin and secondary to the displacement. These seem to be due to the irritation caused by the opposed posterior surface of the uterus against the posterior wall of the pelvis. Often the uterus feels to bimanual palpation, as though it were glued to the posterior wall of the pelvis. No doubt the colon bacillus is an important factor in the low grade, localized peritonitis responsible for these adhesions.

(3). Developmental Errors. The relatively long cervix of the infantile uterus directed in the axis of the vagina, a correspondingly small uterine body, with a short anterior vaginal wall will sometimes cause retroversion. I have seen some of these cases in which an infantile and retroverted uterus seemed to have developed in and to have been a part of the anterior rectal wall. Senile atrophy may act in a very similar manner and cause retroversion in the aged.

(4). Posture. Following delivery it is common to have the patient remain in the dorsal position for some time. In addition to this an abdominal binder is often applied. The increased weight of the uterus of itself tends to cause a retro-displacement. The application of an abdominal binder increases this, and it needs only a distended bladder (and this is not always necessary) to cause a retro-displacement. This danger of retro-displacement continues until involution is complete. Not only must the uterus have returned to its normal size and tone, but its supporting structures as well, pelvic floor, vagina, abdominal walls, ligaments, etc. Especially must this be so of the sacro-uterine ligaments whose normal tonicity prevents the forward and downward displacement of the cervix. It requires from six to eight weeks after confinement for this normal involution to be completed.

(5). Increased Intra-abdominal Pressure. This may result from muscular efforts, violent vomiting, tumors, ascites or improper corseting. Associated with it is usually increased weight of the uterus, especially of the fundus, as may result from pregnancy (in the early months) or subinvolution. Chronic constipation, with the presence of a fecal mass in the rectum pressing the cervix forward and thus tilting the fundus backward and allowing the intra-abdominal pressure to act upon its anterior surface, is also a definite factor. Habitual over-dis tension of the bladder by forcing the fundus upward and backward is also a predisposing cause. The sudden increase of pressure resulting from a fall, especially upon the sacral region or buttocks, may cause the retro-displacement of a previously normal uterus. Rarely the fundus is prevented from occupying its usual anterior condition by the failure of the descent of an ovary.