MODEL RELEASED. Hip replacement surgery. Image 2 of 9. Surgeon carving the head of a femur (thigh bone) that has been removed during hip replacement surgery. It will be used to strengthen and remodel the socket of the hip joint before insertion of the prosthetic joint. Joints may need to be replaced after injury, disease or deformity. This hip is being replaced because of congenital hip dysplasia, a condition where the hip joint does not fit together properly, causing it to dislocate frequently and to become worn. For a sequence showing the operation see M551/418- M551/426.