Anatomical Variations in the Female Pelvis: Their Classification and Obstetrical Significance

Six years ago one of us [W.E. C.] instituted, at the Sloane Hospital for Women, an investigation of the influence of pelvic size and shape upon the mechanism of labour.From clinical experience it seemed apparent that certain pelvic abnormalities not adequately described in obstetrical texts played an important part in the cause of dystocia and increased the difficulty in operative delivery.We believed that if the obstetrician could appreciate the size and shape of the pelvis, it would be possible to predict the type of difficulty which might occur in labour, or to terminate the labour with less trauma to the mother and child by the use of mechanical procedures applicable to the individual case.The results of this investigation, which are briefly reviewed in this report, have proved the correctness of our original contention [1-8].During the early months our study was directed to the large collection of skeletal material at the American Museum of Natural History, New York; the U.S. National Museum, Washington; the Hanna Museum of Western Reserve University, Cleveland; and the Department of Anatomy, College of Physicians and Surgeons, New York.It soon became apparent that the accepted obstetrical classification of pelves failed to give a true concept of the marked variation in pelvic shape which existed in skeletal miiaterial.This suggested the need for roentgenologic study of the pelvic form in living women.Hitherto no use had been made of roentgen methods of examination at the Sloane Hospital so far as pelvic shape or size was concerned.A review of the literature pointed to the use of a frame method which would outline the superior straight by the use of the semi-sitting position.This method was used in two trial cases, but the results were not satisfactory, as distortion and the lack of bone detail in the lower pelvis prevented the adequate visualization of pelvic shape which the study of skeletal material had shown to be desired.Dr. Ross Golden and Dr. Paul C.Swenson, of the Roentgen-ray Department of the Presbyterian Hospital, were consulted, and acquainted with our difficulties and our objectives.The use of stereoroentgenograms was advised, and we were thereby gratified with the three- dimensional visualization of the pelvic cavity from the inlet to the outlet.Thus, by mieans of a roentgenological examination, it became possible to study in conjunction with skeletal material the variations in pelvic shape in living women.Patients who had encountered major difficulty during labour were asked to report from the post-partum clinic for roentgenologic examination, and in a short time all the various types of extreme variation in pelvic shape observed in skeletal material were found in living women.Since complete details of the difficulties encountered in the operative delivery of these patients were available, it was possible to correlate these difficulties with the size and shape of each pelvis and to demonstrate that, in certain instances, the operator had attempted an obstetrical manceuvre which was NOV.-OBSTET.1