Subchondral insufficiency fracture of the femoral head in young adults.

A subchondral insufficiency fracture of the femoral head (SIF) is generally observed in elderly women. In addition, SIF has been reported to occur in young military trainees, which are considered to be due to a fatigue stress fracture. This report reviewed five cases of SIF in young adults without any history of overexertion or antecedent trauma. The clinical findings, time to the initial radiograph, time to the initial magnetic resonance imaging (MRI), and follow-up period were investigated. Radiographs and MRI were obtained in both hips. Bone mineral density and bone scintigram were performed. Measurements of a bone mineral density indicated presence of osteopenia in three patients. MRI disclosed a discontinuous irregular-shaped low-intensity band surrounded by bone marrow edema in all cases. After conservative treatments, one patient's condition resolved, while four patients underwent femoral head collapse resulting in surgical treatment. In these four patients, the diagnosis of SIF was histologically confirmed. In addition, the histological findings showed thin disconnected bone trabeculae, thus indicating the presence of some degree of osteopenia. These patients were considered to demonstrate an insufficiency fracture rather than a fatigue stress fracture based on both clinical findings and histological findings. SIF needs to be considered in patients presenting with hip pain even in young cases.