[Immobilization and bone remodeling disorder.]

Mechanical stress is essential for us to maintain bone volume and structure. Immobilization and unloading, such as motor paralysis, long-term bedrest and casting of fractured area, cause rapidly remarkable bone loss. The bone remodeling disorder following immobilization demonstrates the acceleration of bone resorption and the suppression of bone formation, and molecular mechanism of the bone remodeling disorder has been gradually revealed recently. It is very difficult for us to improve the bone loss due to disuse completely. Thus, prevention of disuse osteoporosis is important. We should choose suitable treatment after considering the pathophysiology of disuse osteoporosis, and attempt early intervention as soon as possible.