Sex differences in the anatomy of the anterior–superior acetabular rim in relation to pincer-type femoroacetabular impingement in Koreans: a three-dimensional quantitative analysis

Abstract

Abstract Purpose The aim of this study was to compare the anatomical structures of the acetabular rim around the anterior inferior iliac spine (AIIS) ridge that indicate anterior focal coverage of acetabulum between the sexes using a three-dimensional (3D) model. Methods 3D models of 71 adults (38 men and 33 women) with normal hip joints were used. Based on the location of the inflection point (IP) of the acetabular rim around the AIIS ridge, the patients were classified into anterior and posterior types, and the ratios thereof for each sex were compared. Coordinates for the IP, the most anterior point (MAP), and the most lateral point (MLP) were obtained and compared between the sexes and between anterior and posterior types. Results Coordinates for IPs in men were located anterior and inferior to those in women. MAP coordinates for men were located inferior to those for women, and MLP coordinates for men were located lateral and inferior to those for women. Comparing AIIS ridge types, we noted that coordinates for IPs of the anterior type were located medial, anterior, and inferior to those of the posterior type. Meanwhile, MAP coordinates of the anterior type were located inferior to those of the posterior type, and MLP coordinates of the anterior type were located lateral and inferior to those of the posterior type. Conclusion Anterior focal coverage of the acetabulum appears to differ between the sexes, and this difference may affect the development of pincer-type femoroacetabular impingement (FAI). Additionally, we found that anterior focal coverage differs according to anterior or posterior positioning of the bony prominence around the AIIS ridge, which may affect development of FAI.