(a) The flattening from before backwards, or shortening of the antero-posterior diameter, results from a more or less marked approximation of the anterior and posterior pelvic walls, and of this species of malformation, there are several varieties, all resulting from the extent of contraction, either in height or width. An example of this kind is presented when the superior strait alone is contracted, the excavation retaining its normal capacity. This phenomenon is due to an unusual curvature of the sacrum, which sometimes makes an obtuse angle at its middle part, so that the sacro-vertebral angle is increased to an unusual degree. Sometimes the reverse happens, and the sacrum instead of affording an anterior cavity, is quite plane, or even convex in front; and then the antero-posterior diameter of the excavation is contracted simultaneously with that of the superior strait, and the sacrum seems to lose its natural curvature, and project forward in its whole length.
Sometimes the shortening of the antero-posterior diameter of the superior strait is accompanied by an enlargement of the corresponding one at the inferior strait. This, indeed, is the arrangement most usually met with, and this is what generally happens when the sacrum, yielding to the weight of the trunk transmitted to it by the spinal column, tilts, that is, projects forward its base, while pushing backward its coccygeal extremity.
Sometimes the coccy-pubic and the sacro pubic diameters are shortened at the same time. This happens when the sacrum, instead of performing the tilting movement just mentioned, yields in such a way, that its two extremities are thrown forward; and two consequences are the result of this action, viz., the anterior curvature is greatly increased and there is an enlargement of the corresponding diameter of the excavation.
Fig 82.
The shape of the superior strait in the figure of eight pelvis.
Another case of pelvic contraction is thus described by Cazeaux: In the approximation of the antero-posterior, walls, the sacrum is nearly always the displaced bone; but although much more rare a flattening of the anterior wall is also met with; and then the symphysis pubis, instead of presenting a convexity in front, is perfectly flat, or even (as in one instance represented by Madame Boivin) presents a depression, which seems to protrude inwardly towards the prominence of the sacrum. This double inclination of the pubis and sacrum towards each other, gives to the superior strait the form of a figure-of eight; that is, its plane is divided into two rounded portions on the sides, corresponding to the iliac fossae, and is separated in the middle by a restricted part, of variable width. If the depression is considerable, the antero-posterior diameter of both straits, and of the excavation, must evidently be affected by it.
Or again, the extent of the symphysis pubis may be much greater in its vertical direction than usual, giving rise to what is termed the bar pelvis; or it may have an excessive inclination backwards at its lower end: in both these cases the pelvis is narrowed.
Sometimes the coccyx is elongated, and it takes a nearly horizontal direction. This, as well as immobility of the sacro- coccygeal articulation, may, it is alleged, contribute to the shortening of the coccy-pubic diameter.
(b) The compression of the lateral walls, by which the transverse diameter is shortened, is the rarest of all pubic malformations, that is so far as the superior strait and upper part of the excavation are concerned. As it regards the inferior strait, the approximation of the two ischial tuberosities, by which this species of deformity is produced, is quite as frequent as the shortening of the coccy-pubic diameter. The pubic arch, in this case, assumes the triangular form peculiar to the male sex. Moreover, the inward projection of the spines of the ischia may produce a sensible diminution of the lower part of the excavation in the transverse direction.
“Another variety of transverse contraction is owing to the fact of the pelvis being less developed in one of its halves than in the other, and consequently to its exhibiting a less degree of curvature in that part than upon the opposite side. In this case, the articulation of the spine with the sacrum no longer corresponds to the middle of the pelvis, and the vertebral column is found nearer to the hip of the contracted side; the transverse diameter is likewise diminished at the inferior strait by reason of the obliquity of the entering part of the coxal bone. The antagonism before alluded to, as existing between the antero-posterior diameters of the superior and the inferior straits, whereby the elongation of one most frequently coincides with a shortening of the other, rarely exists in the transverse direction; the deformity produced by a congenital displacement of the femurs is probably the only condition in which the transverse diameter of the inferior strait augments at the same time that the bis-iliac one diminishes. The enlargement in the lower part of the pelvis, in this instance, being marked by an unusual width in the pubic arch, a great obliquity of the ischio-pubic ramus, a separation of the ischial tuberosities, &c.-Cazeaux.
(c). The depression of the antero-lateral walls. The effect of this depression is the diminution of the oblique diameters. It occurs more frequently than the preceding, but not so frequently as the first variety. The essential characteristic of this deformity is the flattening or the inward projection of the coxal bone at the part corresponding to the cotyloid cavity and the junction of its three constituent pieces;- where by the curve described by the pelvic circumference is more or less diminished, even when carried to a high degree to the reversal of the curvature, its convexity being turned towards the sacrum, and the pubis pushes almost directly forwards, the coxal bones assuming the form of an italic S instead of presenting a regular arch.
We lastly, proceed to describe the oblique oval pelvis, a malformation produced by an arrest of development on the part of one lateral half of the pelvis, while the other maintains its normal condition. The effect of this, as will readily be seen, is to throw the symphysis pubis to one side of the mesial line of the body, whilst the sacrum seems to be on the other side. The consequence of this is, that the cavity of the pelvis will be oval, and will occupy one or the other lateral half.
Fig 83.
A pelvis in which the sinking in of the antero-lateral walls exists on both sides.
Fig. 84.
A figure taken from M. Naegele’s work, which exhibits the character of the oblique oval pelvis in a high degree.
The influence of these deformities on the pregnant state is rather unfavorable, from the fact that in the latter half of pregnancy the gravid uterus is not so easily and safely supported, and in the earlier. period it is often more easily displaced, or it more slowly rises above the superior strait. These and other similar circumstances have constant tendency to produce abortion, premature labor. The mode of treatment where cases of deformity occur, does not differ in the first stage from that pursued in the case of well-formed females. Where the os uteri is sufficiently dilated or dilatable, so as to permit the escape of the head, the experienced accoucheur, by a careful comparison of the presenting part with the passage will be able to decide on the possibility of a spontaneous delivery. When the vertex presents itself, sufficient time should be allowed for its engagement, descent, and final expulsion. The contractions should be supported by means of such remedies as the case may seem to require. See Labor. But should no advancement be perceptible, the forceps may be applied and an artificial expulsion effected, if possible; but if there is no reasonable hop of delivery by this means, craniotomy must be resorted to. See Forceps, a nd Craniotomy.,
When the pelvic extremity presents, the same rules apply as in natural labor; but if the deformity is too great to allow a spontaneous expulsion, the blunt-hook must be used, as hereafter to be described. When the body is in the act of being delivered, introduce as soon as possible the index finger into the mouth of the child, and force the chin down upon the sternum as much as possible, whilst traction is being made upon the shoulders. In this way the longest diameter of the head will be made to occupy the shortest possible space in the pelvis. If then it is not found possible to deliver the head, the forceps must be applied. See Forceps.
When the face presents, an effort should be made to convert it into a vertex presentation, as described on page 497; and then if necessary, apply the forceps. Desperate efforts should be made to change the face presentation to one of the vertex, as it would greatly increase the chance of the child’s life, afford relief to the mother, and contribute to our satisfaction.
When the child presents by the trunk, an effort should always be made to convert this into a presentation of the vertex; and if we discover that one part of the deformed cavity is broader than any other, the occipital diameter should be directed to that part as much as possible. If the labor has already continued so long as to make it impossible to bring the vertex into the superior strait, the foot must be seized and the mal presentation converted into one of the breech, when we may proceed as in all breech presentation.
