MALFORMATION OF THE PELVIS.
Whenever the pelvis varies from the normal type to such an extent as to render labor difficult or dangerous for the mother, the child, or both, it is said to be malformed. Deviations from the normal may exist in the form, structure, and dimensions of the pelvis, or in the direction of its planes and axes. There are accordingly three principal varieties, pelves that are too large, those that are too small, and those having an abnormal inclination. The second variety is by far the most important.
These preserve their relative proportions, their only striking features being the increase in their diameters, and the thickness and solidity of their walls. They are met with in females of large stature, also in those of small or medium size. Burns has described two pelves in which each of the %liameters was increased about four-fifths of an inch; De la Tourette saw one in which the antero-posterior diameter at the brim measured nearly six inches, the transverse nearly seven inches, and the sponding diameters of the inferior strait nearly six inches. Depaul gives the following dimensions of a specimen in his collection: Antero-poste rior diameters, 5.2, 4 and 5.8 inches, transverse, 6.4, 4.8, and 5.4 inches, oblique, 6, 4.7, and 5.4 inches. In this pelvis the distance between the antero-superior iliac spines was 11.2 inches, the bis-iliac diameter was 12.8 inches, and the breadth of the symphysis, 2.4 inches. Sometimes the increase in size is confined to the upper portion (funnel-shaped pel vis), or the inferior half alone may be enlarged either on both sides or on one alone (as a result of fractures or dislocation). Such pelves give rise to certain disadvantages, viz.: The non-gravid uterus is more liable to become displaced. During pregnancy the organ remains longer within the true pelvis, and may thus cause disturbances of the bladder and rec tum; it is prone to become retroverted, and towards the end of preg nancy, the head may descend so low as to affect the other viscera. The labor may be precipitate, and we may have in consequence rupture of the perineum and post-partum hemorrhage. After delivery there is a tendency t3 displacement of the uterus, especially to prolapsus, most common in women who leave their beds too soon.
Contracted Pel•es.
Frequency. —Narrowing of the pelvis is most common in countries in which diseases that affect the shape and development of the pelvis are most frequent, especially in Flanders. Michaelis found narrowing in 72 women out of every 1000, Litzmann in 145, Schwartz in 140. Schroeder believes that the flattened, non-rachitic pelvis is quite frequent in Ger many, being found more often than any other variety of deformity. Nar rowing of the superior strait is much more common, then comes contrac tion of the inferior strait, and, finally, of the cavity, the two latter being nearly always associated. A pelvis may be diminished in all its propor tions, or it may be unequally contracted—that is to say, the normal rela tion between its diameters may be altered.
1. Generally and Regularly contracted pelvis (justo-minor) is characterized by shortening of its diameters, which, at the same time maintain their proper proportion to one another. There are two varieties. In the more common the pelvis differs only in size from the normal. (Figs. 4, 5). Its presence is not suspected before a vaginal examina Lion is made during labor. The second variety is very rare, being only met with in dwarfs; the bones present the infantile type, being fectly ossified, the sacral segments and the three portions of the os inno minatum are separated by cartilage. The relations of the diameters to one another, however, and to the pubic arch are the same as in a perfectly developed female. Figs. 10 and 11 represent a woman the antero-pos terior diameter of whose pelvis measured 2.2 inches. She was delivered with forceps of a living seventh months' child.
l's'Segel6 has described a third form in which both the bones and the pelvic diameters present an infantile character; the being due to arrested development of the genital organs, which arrest may involve the entire skeleton, and even the intellectual faculties. It possesses no interest obstetrically. Only thirteen instances have been recorded.