CHAPTER XII.

DEFORMITIES OF THE PELVIS.

Importance of the Subject.-Deformities of the pelvis form one of the most important subjects of obstetric study, for from them arise some of the gravest difficulties and dangers connected with parturition. A knowledge, therefore, of their causes and effects, and of the best mode of detecting them, either during or before labor, is of paramount necessity; but the subject is far from easy, and it has been rendered more difficult than it need be from over-anxiety on the part of obstetricians to force all varieties of pelvic deformities within the limits of their favorite classification.

Difficulties of Classification.-Many attempts in this direction have been made, some of which are based on the causes on which the deformities depend, others on the particular kind of deformity produced. The changes of form, however, are so various and irregular, and similar or apparently similar causes so constantly produce different effects, that all such endeavors have been more or less unsuccessful. For example, we find that rickets (of all causes of pelvic deformity the most important) generally produces a narrowing of the conjugate diameter of the brim, while the analogous disease, osteo-malacia, occurring in adult life, generally produces contraction of the transverse diameter, with approximation of the pubic bones and relative or actual elongation of the conjugate diameter. We might, therefore, be tempted to classify the results of these two diseases under separate heads, did we not find that when rickets affects children who are running about and subject to mechanical influences similar to those acting upon patients suffering from osteo-malacia, a form of pelvis is produced hardly distinguishable from that met with in the latter disease, which by some authors is described as the pseudoosteo-malacic.

Most Simple Classification.—On the whole, therefore, the most simple as well as the most scientific classification is that which takes as its basis the particular seat and nature of the deformity. Let us first glance at the most common causes.

Causes of Pelvic Deformity.-The key to the particular shape assumed by a deformed pelvis will be found in a knowledge of the circumstances which lead to its regular development and normal shape in a state of health. The changes produced may, almost invariably, be traced to the action of the same causes which produce a normal pelvis, but which, under certain diseased conditions of the bones or articulations, induce a more or less serious alteration in form. These have been already described in discussing the normal anatomy of the pelvis; and it will be remembered that they are chiefly the weight of the body transmitted to the iliac bones through the sacro-iliac joints, and counter-pressure on these acting through the acetabula. Sometimes they act in excess on

bones which are healthy, but possibly smaller than usual, and the result may be the formation of certain abnormalities in the size of the various

pelvic diameters. At other times they operate on bones which are softened and altered in texture by disease, and which therefore yield to the pressure far more than healthy bones.

The two diseases which chiefly operate in causing deformity are rickets and osteo-malacia. Into the essential nature and symptomatology of these complaints it would be out of place to enter here: it may suffice to remind the reader that they are believed to be pathologically similar diseases, with the important practical distinction that the former occurs in early life before the bones are completely ossified, and that the latter is a disease of adults producing softening in bones that have been hardened and developed. This difference affords a ready explanation of the generally resulting varieties of pelvic deformity.

Effects of Rickets.-Rickets commences very early in life—sometimes, it is believed, even in utero. It rarely produces softening of the entire bones, and only in cases of very great severity of those parts of the bones that have been already ossified. The effects of the disease are principally apparent in the cartilaginous portions of the bones, in which osseous deposit has not yet taken place. The bones, therefore, are not subject to uniform change, and this fact has an important influence in determining their shape. Rickety children also have imperfect muscular development; they do not run about in the same way as other children ; they are often continuously in the recumbent or sitting posture, and thus the weight of the trunk is brought to bear, more than in a state of health, on the softened bones. For the same reason, counter-pressure through the acetabula is absent or comparatively slight. When, however, the disease occurs for the first time in children who are able to run about, the latter comes into operation and modifies the amount and nature of the deformity. It is to be observed that in rickety children the bones are not only altered in form from pressure, but are also imperfectly developed; and this materially modifies the deformity. When ossific matter is deposited, the bones become hard and cease to bend under external influences, and retain for ever the altered shape they have assumed.

Effects of Osteo-malacia.-In osteo-malacia, on the contrary, the already hardened bones become softened uniformly through all their textures, and thus the changes which are impressed upon them are much more regular and more easily predicated. It is, however, an infinitely less common cause of pelvic deformity than rickets, as is evidenced by the fact that in the Paris Maternity, in a period of sixteen years, 402 cases of deformity due to rickets occurred to 1 due to osteo-malacia.'

Their Varying Frequency.-The frequency of both diseases varies greatly in different countries and under different circumstances. Rickets is much more common amongst the poor of large cities, whose children are ill-fed, badly clothed, kept in a vitiated atmosphere, and subjected to unfavorable hygienic conditions. Deformities are therefore more common in them than in the more healthy children of the upper classes or of the rural population. The higher degrees of deformity, necessitating the Cæsarean section or craniotomy, are in this country of extreme rar1 Stanesco, Recherches cliniques sur les Rétrécissements du Bassin.

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ity, while in certain districts on the Continent they seem to be so frequent that these ultimate resources of the obstetric art have to be constantly employed.

Effects of Ossification of the Pelvic Articulations.In another class of cases the ordinary shape is modified by weight and counter-pressure operating on a pelvis in which one or more of the articulations is ossified. In this way we have produced the obliquely-ovate pelvis of Naegele or the still more uncommon transversely-contracted pelvis of Robert.

Other Causes of Pelvic Deformity.-A certain number of deformed pelves cannot be referred to a modification of the ordinary developmental changes of the bones. Amongst these are the deformities resulting from spondylolisthesis, or downward dislocation of the lower lumbar vertebræ; from displacements of the sacrum caused by curvatures of the spinal column, producing the kyphotic and scoliotic pelves; or from diseases of the pelvic bones themselves, such as tumors, malignant growths, and the like.

Equally Enlarged Pelvis.-The first class of deformed pelves to be considered is that in which the diameters are altered from the usual standard without any definite distortion of the bones; and such are often mere congenital variations in size for which no definite explanation can be given. Of this class is the pelvis which is equally enlarged in all its diameters (pelvis æquabiliter justo major), which is of no obstetric consequence, except inasmuch as it may lead to precipitate labor, and is not likely to be diagnosed during life.

Equally Contracted Pelvis.-The corresponding diminution of all the pelvic diameters (pelvis æquabiliter justo minor) may be met with in women who are apparently well formed in every respect and whose external conformation and previous history gave no indication of the abnormality.['] Sometimes the diminution amounts to half an inch or more, and it can readily be understood that such a lessening in the capacity of the pelvis would give rise to serious difficulty in labor. Thus, in 3 cases recorded by Naegele a fatal result followed-in 2 after difficult instrumental delivery, and in the third after rupture of the uterus. The equally lessened pelvis, however, is of great rarity. An unusually small pelvis may be met with in connection with general small size, as in dwarfs. It does not necessarily follow, because a woman is a dwarf, that the pelvis is too small for parturition. On the contrary, many such women have borne children without difficulty.

The Undeveloped Pelvis.-In some cases a pelvis retains its infantile characteristics after puberty (Fig. 129). The normal development of the pelvis has been interfered with, possibly, from premature ossification of

['It is possible for a lady to be tall, erect, weigh 180 pounds, and be conspicuous for her fine appearance, when she has a justo minor pelvis of very small interior dimensions. I examined such a patient some years ago, and not only had she the smallest vagina I have ever explored in a well-grown woman, but it has recently been found in labor that her pelvis would not admit of her being delivered of a full-grown living child. In fact, it is doubtful whether she could be delivered of one alive much later than the seventh month. Married twice and unimpregnated for years, I was surprised at her becoming at last pregnant, as an index finger filled her vagina tightly. After a labor of three days, and when the foetus was dead, it was delivered with a crushed head after long and powerful traction, and she made a good recovery. Having large hips, she was under an impression that her pelvis was of corresponding development.-ED.]

the different portions of the innominate bones or from arrest of their growth from a weakly or rachitic constitution. The measurements of these pelves are not always below the normal standard; they may continue to grow, although they have not developed. The proportionate measurements of the various diameters will then be as in the infant, and the antero-posterior diameter may be longer, or as long, as the transverse, the ischia comparatively near each other, and the pubic arch narrow. Such a form of pelvis will interfere with the mechanism of delivery, and unusual difficulty in labor will be experienced. Difficulties from a

similar cause may be expected in very young girls. Here, however, there is reason to hope that as age advances the pelvis will develop and subsequent labors be more easy.

Masculine or Funnel-shaped Pelvis.-The masculine or funnel-shaped pelvis owes its name to its approximation to the type of the male pelvis. The bones are thicker and stouter than usual, the conjugate diameter of the brim longer, and the whole cavity rendered deeper and narrower at its lower part by the nearness of the ischial tuberosities. It is generally met with in strong, muscular women following laborious occupations, and Dr. Barnes, from his experience in the Royal Maternity Charity, says that it chiefly occurs in weavers in the neighborhood of Bethnal Green, who spend most of their time in the sitting posture. "The cause of this form of pelvis seems to be an advanced condition of ossification in a pelvis which would otherwise have been infantile, brought about by the development of unusual muscularity, corresponding to the laborious employment of the individual." The difficulties in labor will naturally be met with toward the outlet, where the funnel shape of the cavity is most apparent.

Contraction of Conjugate Diameter of Brim.-Diminution of the antero-posterior diameter (flattened pelvis) is most frequently limited to the brim, and is by far the most common variety of pelvic deformity. In its slighter degrees it is not necessarily dependent on rickets, although

when more marked it almost invariably is so. When unconnected with rickets, it probably can be traced to some injurious influence before the bones have ossified, such as increased pressure of the trunk from carrying weights in early childhood and the like. By this means the sacrum is unduly depressed and projects forward, so as to slightly narrow the conjugate diameter.

Mode of Production in Rickets.-When caused by rickets, the amount of the contraction varies greatly, sometimes being very slight, sometimes sufficient to prevent the passage of the child altogether, and to necessitate craniotomy or the Cæsarean section. The sacrum, softened by the disease, is pressed vertically downward by the weight of the body, its descent being partially resisted by the already ossified portions of the bone, so that the result is a downward and forward movement of the promontory. The upper portion of the sacral cavity is thus directed more backward; but, as the apex of the bone is drawn forward by the attachment of the perineal muscles to the coccyx and by the sacro-ischiatic ligaments, a sharp curve of its lower part in a forward direction is established.

Scolio-rachitic Pelvis. (From a specimen in the Museum of St. Bartholomew's Hospital.)

Occasional Increase of Transverse Diameter.-The depression of the sacral promontory would tend to produce strong traction, through the sacro-iliac ligaments, on the posterior end of the sacro-cotyloid beams, and thus induce expansion of the iliac bones and consequent increase of the transverse diameter of the brim. So an unusual length of the transverse diameter is very often described as accompanying this deformity, but probably it is not so often apparent as might otherwise be expected, on account of the imperfect development of the bones generally accompanying rickets; and Barnes' says that in the parts of London where deformities are most rife any enlargement of the transverse diameter is exceedingly rare.