Subchondral fracture of the femoral head in healthy adults.

UNLABELLED: Subchondral fracture of the femoral head has been reported to occur as an insufficiency fracture associated with poor bone quality or as a fatigue fracture in young military recruits. Transient osteoporosis of the hip has clinical and imaging findings that resemble those of a subchondral fracture, but it usually occurs in healthy middle-aged people not involved in sports or similar activities. The clinical aspects of five cases of subchondral fracture of the femoral head occurring in four healthy adults without antecedent trauma were evaluated. Of particular interest were whether subchondral fracture of the femoral head could occur without a sudden increase in daily activity and what differences could be detected from the imaging and clinical courses between subchondral fracture of the femoral head and transient osteoporosis of the hip. Three cases of subchondral fracture of the femoral head occurred without an increase in daily activity. The only difference in imaging findings between subchondral fracture of the femoral head and transient osteoporosis of the hip was the existence of a subchondral fracture line seen on magnetic resonance images of a subchondral fracture of the femoral head. The clinical courses of these disorders were similar. These findings suggest transient osteoporosis of the hip and subchondral fracture of the femoral head are subchondral bone injuries of different severity. LEVEL OF EVIDENCE: Level IV, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.