When the smaller diameter of the pelvis is less than two and a half inches, and the child is living, the Caesarean section should be resorted to at once: no time should be lost after the first stage of labor is accomplished or nearly so. I should deem this the most opportune moment for the operation, for this is as nature would operate so far at all events. The liquor amnii should be discharged, and as the second stage cannot be accomplished as nature would require, the Caesarean section should be resorted to at once. For thus an opportunity is afforded for preserving the life of the child, and the mother has as good a chance for preserving her life as she would have in the operation of craniotomy, For in this malformed state of the pelvis, the difficulty of extracting a child piecemeal through so small an aperture would be as great hazard to the life of the mother as the Caesarean section. Should the child be dead, then, as there is but one life to consider, the extraction should be made through the natural channel.
CAUSES OF PELVIC DEFORMITIES.
We now pass to the causes and mode of production of the pelvic deformities. For a long time these, together with other deformities of the skeleton, were referred to a single cause, viz., rachitis; but modern researches have clearly proved that the pelvis may be deformed in the absence of rachitis; and from purely mechanical causes, operating at a time when on account of tender age or feebleness of constitution, they could meet but little resistance. From this view of the causes which produce changes in the form of the pelvis, we might collected formed pelves into three groups, viz.: (1) Those which are deformed from a softening of the bones, either by rachitis or mollities ossium; (2) Those deformed in consequence of a previous deformity of some other part of the skeleton, (3) Those deformed by absolute narrowness.
(1) The Pelvis deformed by Rachitis, or Malacosteon. These two diseases however differing from each other in their anatomical characteristics, yet produce the same result, viz., they soften the osseous tissue and thereby weaken its power of resistance. But the mere fact of softening the bones and their consequent weakness, is not of itself sufficient to account for the various deformities presented by the pelvis. For it is very evident that the bones, unless reduced to a gelatinous state, would maintain their general conformation unless acted on by some external force. For rachitis diminishes the solidity of the bones, but does not, of itself, produce any alteration of shape. This exterior force may be looked for in the muscular action, and still oftener in the weight of the parts which the pelvis has to support. For the pelvis, interposed between the spine which it supports and the lower extremities on which it rests, is most favorably conditioned for the action of deformity. The weight of the trunk, in its erect position, being transmitted from the lumbar vertebrae to the heads of the femurs in the direction of two lines intersecting the side of the superior strait, evidently tends to increase the curvature of the posterior part of the ilium, and to depress the osseous circle of the pelvic cavity. In this way the sacrum receives a tendency, by almost insensible degrees, to push forwards. By considering the action of the pubic bones under this pressure, we may see how it is that the superior strait is oftener affected by the contractions of the pelvis than other parts; and why at this strait the antero posterior and oblique diameters and the sacro-cotyloid intervals are more frequently contracted than the transverse ones.
When the weight acts more particularly on one side of the pelvis, the collapse is more marked in that direction, because, in this case, a change in the centre of the gravity takes place from the inclination of the spine; and there is also a very unequal pressure of the weight of the body on the two sides of the pelvis, where, on account of a difference of length in the lower extremities, one of the coxal bones is more depressed than the other. In this way the acetabulum of one side is thrown almost directly under the sacrum, and at the same time receives the weight very obliquely. The customary attitude of the individual, and the nature of her occupation, must be taken into account in considering the irregularity of figure in the pelvis.
Sometimes there is a complete fusion of the sacrum and ilium, and the sacro iliac articulation on the contracted side disappears. We simply state this fact without attempting any explanation of it.
In estimating the respective influences of mollities ossium and rachitis on the bony tissue, the distinctive characteristics of each should be carefully noted. Mollities ossium affects all parts of the skeleton indifferently, and it occurs in the adult only. The softening produced by this disease is more distinctly marked, and the most considerable retractions must be referred to it. Rachitis affects the bones of the lower extremities and ascends gradually to the upper parts: it proceeds from below, upwards; so that a deformity of any part by rachitis almost necessarily implies a deformity below. It is peculiar to infancy, and its effects on the skeleton are twofold, it softens the bones and it arrests their development. And as this arrest of development particularly affects the lower extremities, it is a necessary consequence that the ossa innominata should be much less developed in those subject to this disease than with others, and the limits of the pelvic cavity more or less contracted by
it.
It is here that we may see the difference again between rachitis and malacosteon, or rachitis adultorum, as it is sometimes called; for the first, exerting its influence at an early age of the patient, at a period when the pelvis has not yet reached its full development, permanently arrests the growth of this part of the skeleton; but the last not occurring until after puberty, at a time when the ossa innominata have reached their full development, may soften the bones, but cannot arrest their growth. Moreover, the bones of the skeleton are not only arrested absolutely by rachitis, but their growth is retarded, even after a cure has been effected, during the whole term of development.
(2) Those deformed in consequence of a previous Deformity of some other part of the Skeleton. These deformities are:
(a) Deviations of the Vertebral Column. Rachitis is not the only cause of this deformity. It is now admitted that several other diseases may produce abnormal curvatures in this column. It is thus we establish a line of distinction between those deviations which nearly always attend pelvic malformations, and those which often exist when the pelvis is well formed. The former must be referred to rachitis, the latter to some other affection. The shape and direction of the pelvis are subject to the influence of other deviations of the spine than those which depend on rickets; but it is only in subjects of an advanced age that curvatures occurring after the age of infancy exert an influence of this kind. Curvatures produced by rickets, even when not the essential cause of deformity in the pelvis, heighten the degree of contraction and affect the shape of the pelvis. The aged and the young are alike affected by the spinal deviation, but the effects are brought about more rapidly with the young than with the old. The malformation is more or less similar to that described under the name of the oblique oval pelvis.
(b) Congenital Luxations. These may cause an arrest of development, and subsequent pelvic deformity.
(c) Non congenital Luxations. A luxation remaining unreduced, and which occurred early in life, is sufficient cause for an atrophy of the iliac bone corresponding to the dislocated femur; and it is evident that the malformation of the pelvis will be proportionately great as the luxation occurred at an early age.
(d) Lesions of the Inferior Extremities. The curvatures of the lower limbs do not always diminish in length equally, and the pressure which they make on the bottom of the cotyloid cavities is not the same for both sides; the consequence of this is, that the pelvis may be affected on that side where the pressure is the greater. The lower extremities may often be curved, without injury to the pelvis, provided they maintain the same length; and where they are unequal in length there must result pelvic deformity.
The pelvis may be deformed by a shortening of one of the legs from any cause, particularly if the accident occur in early life, when the pelvis is but partially developed. Where one leg is affected with chronic disease, and the person is obliged to use crutches, bearing the whole length of the body on one leg, or where the thigh has been amputated in early childhood, the pelvis is in either case liable to deformity.
(3) Pelvis deformed by Absolute Narrowness.- The most generally accepted opinion on this topic is, “that we have no positive data concerning the causes that give rise to the general narrowing of the pelvis; and that such pelvis, as well as unusually large ones, should rather be considered as a freak of nature, belonging to the same category as a want of proportion in the head, which is not unfrequently found too large, or too small, relatively to the rest of the body.
