Heterotopic ossification following internal fixation or arthroplasty for displaced femoral neck fractures: a prospective randomized study

One hundred hips in 99 patients of 75 years or older, with a displaced femoral neck fracture, were studied for heterotopic ossification (HO). The patients were randomized to either internal fixation or total hip arthroplasty (THA). In the THA group HO was found in 32 of 45 hips compared with 1 of 39 in the internal fixation group (P < 0.0012). The frequency of HO after THA corresponds well with findings in other studies on patients receiving THA for osteoarthrosis. In cervical fractures the surgical procedure of total hip replacement seems to be a prerequisite for HO, indicating that the procedure itself is more important than the patient's age and the diagnosis. Severe symptoms due to HO were found in only one patient. HO following THA for a femoral neck fracture is of little clinical importance and prophylaxis is unnecessary.