Ossification of the sacro-sciatic ligaments is mentioned by Meckel as sometimes exist ing, and even more commonly than that of the pubic symphysis. Such a condition, if present in the female during parturition, would offer great obstruction to the passage of the head through the inferior strait, front its unyielding nature, and resistance to the extension of the coccyx. It is, however, not sufficiently common to be enumerated as one of the ordinary obstacles to parturition.
A different result of inflammatory change in the pelvic joints, is that which gives rise to the separation of the bones at their articular surfaces. This, as a pathological process, takes place most frequently by deposits of pus, as a consequence of ptierpal fever, which may entirely destroy- the joint, and separate the bones. From its more exposed position and more open structure, this change has been most frequently observed in the symphysis pubis. A case of this kind is described by Dr. W. Hunter, and many others have been observed.
A more remarkable separation of the pelvic joints is to be ascribed to a congenital origin.
It is one in which the pubic bones and with them, in a minor degree, the sacro-iliac auri cular surfaces, are separated, more or less widely, and held together by a ligamentous band. Instances in which this occurs to the extent of a third of an inch, are mentioned by Professor Otto, as being pretty frequent.t Probably one of the most extreme cases of this kind is seen in a preparation at present in the Hunterian Museum. It is the pelvis of a woman, which was presented, as I am in formed, by Mr. Mayo, of Winchester, and taken from a case which died in the infir mary of that town. The pubes are separated to the great distance of .1i inches; and con nected by a ligamentous band of about the width, in its present dried state, of front to of an inch. The pubes are more ele vated than normal, with their articular ex tremities turned outward, and the symphy sial surfaces forwards, by the action of the adductors and obturator externus. The lateral curvature of the sacrum is consider ably flattened out, and also the cotylo-sa cral rib of the ilium. The sacro-iliac joints are each opened in front, for the space of about half an inch, stretching the anterior ligaments. The great space between the pubes is evidently obtained by the flattening of tbe linea inno minata, as well as by the shortening of the innominate bones, in breadth, and their abnor mal vertical or wall-sided position. The
resulting diameters are ; — antero-posterior, from the sacral promontory to the inter-pubic ligament, 4 inches ; the inter-cotyloid, 6i inches ; and between the sciatic tuberosities, %inches. This condition, according to Meckel, is rarely met with without an analogous con genital fissure in the bladder and walls of the abdomen. Walter, however, mentions one case.
Other congenital abnormalities of the pelvic bones are mentioned by Otto and Rokitansky. In the siren formation, the coccyx and lower extremities are entirely wanting, and the lateral parts of the pelvic bones are fused together, the outlet of the pelvis being nearly completely closed, and the parts presenting the appearance of the pelvis as we have seen it in the Cetaceans and Fishes. Their deve lopment seems to have been arrested at that period of fcetal life in which this condi tion is normally, though transitorily, present. In some monstrosities, the sacrum also is wanting, or one or both the innominate bones, with the correspondig lower extremities ; or these parts may be stunfed or coalesced.
Influence of hip-joint disease upon the pelvis. — Caries and necrosis of the pelvic bones, although sometimesresulting idiopathically, or from bedsores and abscesses in the muscular sheaths or lymphatics, yet chiefly occur as the consequences of coxalgia, and have a tubercu lar origin. The formation of false acetabula and the other pathological results of this di sease or accidental malposition belong more especially to the pathology of the Hip-joint.
A preparation of one of these in the Hun terian Museum may be, however, appropriately described in this place, inasmuch as it would produce, if occurring in a parturient female, an obstruction to the fcetal head, analogous to an exostosis. The head of the femur has become displaced into the obturator foramen, and about it an osseous deposit has taken place, apparently in the obturator membrane, which forms a smooth dome-like projection into the pelvic cavity, corresponding in size to the head of the femur. The subject is a male one, and the carious and light condition of the bones and the irregular ossific projections, indicate the results of disease.