Another form of unsymmetrical pelvis is described by Rokitansky, arising from a coa kscence of the base of the sacrum with the body and transverse process of the kst lum bar vertebra, on one side the median line only, and the participation of the latter in the for mation of' the sacro-iliac joint on that side. The innominate bone thus obtains a higher degree of elevation, and a greater inclination to the spine, and describes a larger and shal lower curve of the "linea innominata" than its fellow. The conjugate diameter is rendered greater, and there is a larger capacity on the abnormal side of the pelvic cavity. There is Imit slight projection of the sacral promontory, and the lumbar vertebrce are rotated, and their curve inclines to the opposite or smaller side, and may thus produce a lateral compensating curve in the thoracic region. In this latter particular, also, this form of pelvic distortion differs from that described by Naegele, in which the lumbar curve is towards the abnormal side.
I have met with two pelves presenting this abnormality. In one, that of a fenzale, which is in the collection of Dr. A. Farre (fig,121.) the kft half of the sacral base is ankylosed to the corresponding side of the body and trans verse process of the last lumbar vertebra, which are flattened and enlarged so as to as sume the form of the first sacral, leaving a hole for the transmission of the last lumbar nerve. The lumbar transverse process of the opposite side is bifurcated, the lower division being attached by ligament to the venter ilii ; and the corresponding half of' the sacro-lum bar fibro cartilage rernains unossified. The last lumbar spine and lamince are connected with the sacrum by very thin plates of bone, but preserve their own distinct outline. There is no ankylosis of the sacro-iliac or lumbo-iliac joints. The true sacral promontory projects little, but a prominent false one is formed by the last lumbar vertebra. The sacrum is short and small, but presents four distinct sacral holes, and five pieces. The lower part of the sacrum presents an abrupt forward curve, so as to leave, with the shortness of the whole bone, little room for a ketal head, which would, probably, require craniotomy in such a pelvis. There is a slight lumbar curve to the right or opposite side to the lumbar ab normality. The pubic symphysis, also, is re moved about or of an inch to the right of the median line.
The other pelvis is that of a male, in the Museum of King's College. In this pelvis, there is complete ankylosis of both the proper sacro-iliac joints, preserving behind pretty much the outline of the sacro-iliac ligaments ; and partial ankylosis of the abnormal lumbo iliac junction, which is also on 'the left side. The true sacrum is large and well formed, and the posterior crest is connected with the last lumbar spine by a thin plate of bone.
There is, apparently, no lateral spinal curve in this specimen.
Whether these pelves and those mentioned by Rokitansky are not similar to those de scribed by, Naegele as arrest of development of one side of the first sacral bone, is a question which can only be decided by ab solute cornparison of the specimens.
A greater or more advanced development of one side of the pelvis than the other is said by Knox, in a memoir " On the Statistics of Ilernia," to be frequently seen, and to pro duce a greater predisposition to hernia on that side. The author considers it as the result of a similar want of balance between the development of the lateral halves of the pelvis to that seen, in a greater degree, in the " pelvis obliqui ovata," and which is also often seen between that of the true and false pelvis.
Pelvis obstructed by e.rostosis.—Exostoses projecting from the pelvic bones most usually proceed from their internal surfaces, in which position they are also of more serious im portance in producing obstruction to parturi tion in the female. According to liamsbotham, it is a rare condition of the pelvis, he having never seen an instance. Exostoses are most frequently-found at the back part of the pelvic cavity, growing from the sacrum, near the sacro-iliac joint, or, according to Lever, at the la.st sacral piece. They are, however, by no means confined to these positions.
Many instances of this disease have been recorded, in which the diagnosis has not been verified by post-mortem exaniination ; and it is doubtful whether many of them were not projections of the sacral promontory and lumbar vertebrx, as in a case described by Nagel in the Frankfurter Zeitung (April, 1778). It has been observed in the male as well as in the female pelvis.
One of the most remarkable cases of ex ostosis of the sacrum, producing obstruction to parturition, occurred to Dr. Haber, and is recorded in Naegele's Inaugural Disser tation, published at Heidelberg in 1830. The disease was said to have followed a fall while the woman was carrying a load on her head, and which was followed by pains in the back and pelvis. On afterwards becoming pregnant, the whole of the pelvic cavity was found to be filled by a bony tumour growing from the upper part of the sacrum. The Cxsarian section was performed ; and the patient died soon afterwards. The tumour was found to be 7 inches long by 6 in. broad, reaching as high as the junction of the 3rd and 4th lumbar vertebrw and as low as from about 2,1 lines from the apex of the sacrum. Between it and the posterior surface of the pubes there was a space of 8 or 10 lines in one part, but only a line and a half in another, the mass thus filling up nearly the whole of the pelvic brim. A section of the tumour showed large cells in the interior, coinmuni eating freely with the sacral areolm.