Morphologic features of the acetabulum

Introduction: The embryology and development of the hip joint are complex. The acetabulum is not always of the same shape, width, or depth. Minor anatomical abnormalities in the acetabular shape, joint congruences are frequent. Controversies still exist on the importance of these variations and help to prevent problems following in surgical procedures such as acetabular reconstruction and femoracetabular impingement. Material and methods: The aim of this study is to provide the location of the unusual facets, the acetabular point, and the anterior ridge of the acetabulum based on a morphological study of human pelvic bones. Morphologic features of the acetabulum, particularly determination of unusual facets, were studied in 226 human coxal bones. Results: In adult coxal bones the acetabular fossa has an irregular clover-leaf shape, the superior lobe being smaller than the anterior and the posterior lobes. Measured lunate surface area varied between 14.5 and 30.5 cm². A smooth unusual facet was found antero-inferior to the lunate surface in 62 acetabulums. Measured along the long axis, its size varied between 11 and 17 mm. Three different shapes of the unusual facet were as follows: oval (32.26%), piriform (45.16%), and elongated (22.58%). The prevalence of the piriform facet shape was higher in males. In 59.68% of the bones it extended to the superior ramus of the pubis, and in the remaining 40.32% it was limited within the acetabular margin. It is postulated that this facet could be a consequence of a particular posture, which results in traction of the ligaments attached to this area. Four distinct configurations were identified relative to the anterior acetabular ridge. The majority 98 (43.36%) were curved; 64 (28.33%) were angular; 37 (16.37%) were irregular; and 27 (11.94%) were straight. Conclusion: There have been no reports on details such as unusual facets, acetabular point, and anterior ridge of the acetabulum in a single research. These findings will be of help in planning reorientation procedures, using spikes, screws, and press-fitting for fixation.