A bone transfixion plate for transfixing an acetabulum fragment to the os ilium, by screw means, following pelvic osteotomies with rotation of the roof of the acetabulum, particularly in a human patient. The plate comprises: a proximal region for application to the os ilium which is at least generally adapted for close application to the region to which it is applied; a distal region for application to the acetabulum fragment which is at least generally adapted for close application to the region to which it is applied, these regions being disposed at a mutual angle in the ventrodorsal/mediolateral plane in the range 10.degree.-50.degree., preferably about 30.degree. (or, in a plate for a dog, the angle in the equivalent plane is 20.degree.-70.degree. and preferably 30.degree.-60.degree.); and for forming this angle a generally wedge-shaped transition zone between the two regions, the greater width of the transition zone being preferably at the ventral edge of the plate (or, in a plate for a dog, preferably at the dorsal edge). The plate is an element of a transfixion system which may include wire loops passed over two screws in the region of the foramen ischiadicum, and additional transfixion means to the os ischium and os pubis comprising one wire loop passed over two screws, one of which is affixed to the acetabulum fragment and the other of which is affixed to the os pubis.