A centring device for orthopaedic surgery, usable in operations that envisage intramedullary nailing, applied to a semi-circular "C" shaped metal frame (10) provided with a brilliance amplifier (12) facing an X-ray tube (14), comprising at least one fixed bar (18) fixed to the same semi-circular "C" shaped frame (10) and whereon mobile means is slidingly moved cooperating with the incident beam of the bundle of X rays emitted by the X-ray tube (14).
