The common factor among these conditions is immobilization. No definite cause for HBF has been found. Finally, it is believed that the ossification result from transformation of primitive mesenchymal derived cells present in soft tissues into bone forming cells in response to a variety of stimuli. The clinical manifestations resemble those of inflammation which include pain, warmth, swelling, and limited range of motion. These symptoms and signs simulate thrombophlebitis, cellulitis, or osteomyelitis.
Alkaline phosphatase is the earliest to become abnormal.
Typically it is attributed to healing fractures, occult biliary disease or normal bone growth in young patients. The radiographs turn positive later in the process at 4-5 weeks following the accident. The importance of bone scanning lies at the two ends of the pathologic process. In the later stages of the process treatment consists of surgical resection of the heterotopic bone. This can be demonstrated by falling levels of alkaline phosphatase or by quantitative bone scans.