Kummer B
Z Orthop Ihre Grenzgeb. 1986 Mar-Apr;124(2):179-87. doi: 10.1055/s-2008-1044544.
Graphical analysis of forces, acting on the hip joint and the study of x-ray pictures show clearly, that there exist no shifting components, pushing the femoral head out of the acetabulum as described by Bombelli in several publications. Therefore, shifting forces cannot have any causal effect on the development of primary arthrosis.