Unusual facets on the acetabulum in dry adult human coxal bones: A morphological and radiological study

A smooth facet was found antero-inferior to lunate surface of 48 acetabula, in a study conducted on 315 dry adult coxal bones, 26 of which (13 pairs) were of articulated pelves. Three different shapes of the facet were oval ( 56.3%), piriform (22.9%) and elongated (20.8%). The prevalence of the oval facet was higher in both sexes. In 37.5% bones it extended to superior ramu s of pubis and in 62.5% it was limited within the acetabular margin. They w ere either discrete (58.3%) or continuous with the lunate surface (41.7%). The surface configuration was flat (29.2%), concave (43.7%) or grooved (27. 1%). One male articulated pelvis showed a bilateral presentation. Measured along the long axis the size varied between 11 to 17 mm. The radiographs sh owed notching, antero-inferior to acetabular margin in grooved facets where as concave and flat facets were seen as areas of rarefaction. It is postula ted that this facet could be a consequence of a particular posture which re sults in traction of the ligaments attached to this area. This unusual feat ure has not been reported earlier.