Morphological Changes of the Fetal Hip Joint and Their Effect on the Stability of the Joint During Its Intrauterine Development

Background: Hip joint dislocation and dysplasia are frequent congenital malformations with a multifactorial etiology with a major role played by intrauterine mechanical forces during development. Our aim was to define the surface of the femur and acetabulum, and to study the changes in geometrical parameters and the relationships between them during development.
Material and method: In this study we dissected the hip joints of 10 post-mortem fetuses. Fetal age was determined using crown-rump length (CRL) (min. 8.5 cm, max. 30 cm). Then we performed morphological and geometrical measurements on the articular components. We calculated the area of the articular surfaces, then determined the femoral head coverage and compared the antetorsion (AT) of the femur with the AT of the acetabulum.
Results: in the 3 months fetus the surface areas of the femur and acetabulum are almost identical, the femoral head coverage is maximal, and later with age progression the head coverage decreases, as its growth is more intense than that of the acetabulum. During development the increase of femoral AT determines the increase of the acetabular AT.
Conclusions: The decrease in femoral head coverage during development results in a decrease in articular stability. The femoral head’s position and compression plays an important role in the development of the acetabulum.