One type of hip fracture, called a femoral neck fracture, involves a break in the narrow part of the femur bone where the head of the femur is joined to the main shaft. The break can be either undisplaced, which involves very little separation at the fracture site, or displaced, in which there is substantial separation. For displaced fractures, surgeons usually choose between internal fixation and hip arthroplasty, which is also known as hip replacement.