[Examination of the extension of the osseous facies lunata. A functional study (author's transl)].

In 30 human acetabula the osseous facies lunata was examined and measured. It was found that the acetabular notch is inclined ventrally against the vertical line for an amount of 18,3 degrees (mean value). It was further found that the widest region of the facies lunata is not situated in the acetabular roof (which is usually visible in X-ray photographs), but about 15 degrees in front of it. The outer margin of the osseous acetabulum corresponds to a parallel of latitude of 11,5 degrees, that means that it is situated distinctly above the equator. The cornu anterius is always narrower than the cornu posterius; the similarity between the sockets examined was so great, that a division into different types did not seem to be necessary and an "average acetabulum" was calculated. The width of the facies lunata is interpreted as an equivalent for the amount of stress brought upon; now and then existing indentations of subdivisions of the joint surface are correspondingly understood as places of reduced stress.