Lateral Roentgenometry of the Pelvis—A Newly Modified Technic *

The purpose of the present communication is to emphasize again the value in obstetric procedures of lateral roentgenograms of the pelvis and to describe a newly modified technic which appears to be a definite improvement on that hitherto used in this clinic. Eight years ago, one of us published a communication' on this subject and pointed out that roentgenograms of the pelvis taken laterally possessed certain unique advantages not to be found in the use of antero-posterior roentgenometric methods. These advantages and others may be summarized: 1. All of the antero-posterior diameters of the bony pelvic canal may be measured accurately in centimeters, induding such important diameters as those of the superior strait, the mid-pelvis, and the inferior strait. 2. The size and contour of the anterior surface of the sacrum may be studied. This is of importance in the recognition of sacral abnormalities, especially those resulting from the influence of rickets. 3. If lateral roentgenograms are made at term or early in labor the relation of the position of the presenting part to the superior strait may be studied. Such information is of especial value in instances where disproportion is suspected and non-descent or engagement of the fetal head is present. 4. In most cases of vertex presentation at term the all-important biparietal diameter of the fetal head may be determined with reasonable accuracy. 5. In certain instances of doubtful diagnosis respecting the presence of multiple pregnancy or fetal abnormalities such as hydrocephalus, anencephaly, etc., lateral roentgenograms may give more information than is obtained by the usual antero-posterior technic. 6. The inclination of the pelvis and the lateral relationships of the lower vertebrae may be studied.