Pelvic teardrop
The pelvic teardrop, also known as U-figure or Köhler teardrop, is a radiographic feature seen on pelvic x-rays and results from the end-on projection of a bony ridge running along the floor of the acetabular fossa.
This was shown to be the case by demonstrating that sawing away this bony plate made the feature disappear. It has also been confirmed by Vare in 1952 by applying a thin "strip of lead foil applied to the acetabular fossa and curving round the inferior margin of this, up over the inner wall of the lesser pelvis as far as the iliopectineal eminence."
In adults, it may be used as a marker for measurement of the acetabular angle and Köhler teardrop distance (see Waldenström sign).
One of the features of Paget disease of the pelvis is disappearance of the pelvic teardrop.