From the many specimens which had come under his observation in so short a time, and with but few opportunities of seeing them, Naegele was led to coaclude that this de formity occurred pretty frequently.
Its influence upon parturition will present an obstacle, not only to the forward progress of the foetal head, but also to its proper rota tion, which will vary with the general extent of the pelvic diameters. If the pelvis be of large size, this deformity, though great, will have less influence than in a smaller pelvis, with a less degree of distortion. The foetal head may enter the brim with its long diameter in the long oblique diameter of the distorted pelvis ; but when in the pelvic cavity it will not be able to make the requisite turn into the antero-posterior diameter of the outlet, and will generally, in the opinion of Naegele, re quire the use of the forceps to extract it.
The obstruction occurs in the first labours, and its importance may be considered as equal to those resulting from rickets and malacos teon, when it is considered, that in all the cases of labour hitherto published, where this deformity has been present, both mother and child have been lost, although in the hands of the most experienced accoucheurs.
The diagnosis of the oblique distortion by the usual measurements is very difficult. It is rendered still more difficult by the absence of any history or peculiar appearance of the patient, indicative of the condition of the pel vis ; persons affected with it being usually, in other respects, well built and healthy. The diagnosis, moreover, is usually called for in first labours. The promontory of the sacrum is not to be felt by the finger, an usual indication of plenty of room at the brim ; and yet there may be sufficient contraction in the oblique or sacro-cotyloid diameters, to require the Csarian section. The antero-posterior diameter, which would show, if a section were made in the centres of the sacral-promontory and pubic symphysis, a clear space of 31 to 4 inches, may appear, in the living subject, to be contracted to NI- inches. The contraction of this distortion is as totally unrecognisable by the use of Baudelocque's calipers, which may lead to gross error.
The amount, in the well-formed female, of the measurements instituted by Naegele for the purpose of ascertaining the presence of this deformity upon the living subject, have been given in a former section of this article. The results of the measurements of eight female pelves obliquely deformed, in five of which the ankylosed joint was that of the left side, gave the following differences in measure ment between the two sides.
In these measurements it is to be remarked, that thefirst presents the most marked dif ferences on the two sides. This results fi.om
the fact that the sciatic tuberosity of the an kylosed side is placed more posteriorly than the :opposite one, while the posterior supe rior iliac spine is lower on the side free from ankylosis. Hence it results that the anhylasis is always found on that side of which the sciatic tuberosity is nearer to the opposite posterior su perior iliac spine. These two points on a lean subject are easily to be distinguished. On the fat subject, there is, in the position of the iliac spine, a depression caused by the firmer attach ment of the integuments to the bone at that place.
Another test of the presence of the ob lique deformity practised by Naegele was, to place the patient upright with the back against an even wall, so that the shoulders and nates should equally touch it, and then drop ping two plumb-lines, one from the spine of the first sacral or last lumbar vertebra, and the other from the centre of the lower border of the pubic symphysis. In the well-formed pel vis, the plane in which these two lines fall, forms two right angles with the plane of the wall, but in the pelvis obliquely deformed, it is an obtuse angle on the ankylosed side, and fin acute angle on the side opposite ; the dif ference between these two angles marking the degree of distortion.
Cause of the obliquely deformed pelvis. — Dr. Naegele was inclined to the opinion that the cause of this peculiar condition of the pelvis was, an arrest of development of one side of the sacrum and the corresponding in nominate bone ; with ossification of the joint instead of its normal development. The following reasons led him to this conclusion. The intimate and complete fusion of the bones into one piece ; and the absence of any mark or cicatrix indicating a former separa tion, except a sca-cely perceptible line on the upper aspect of the place of junction ; a section of the ankylosis exhibiting an uniform areolar texture in the internal structure. The defective development, in its whole length, of the ankylosed side and lateral mass of the sacrum, as well as of the innominate bone in breadth, as particularly exhibited in the narrowing of the sciatic notch ; and the analogy herein drawn, from the defective de velopment and fusion of other bones, especi ally those of the cranium. The great re semblance between the several pelves affected by this disease, which argues identity of cause ; original deficiency of development being more likely to produce similarity of results than the accidental and subsequent inflammation. And lastly, the presence of the distortion froni the earliest period, together with the youth of the individuals affected, and the total absence of any symptoms whatever, indicating an ex ternal cause for the distortion, in the whole course of their history.