The present invention provides an artificial joint which can be rapidly, securely and easily fixed while being suited to an inner surface of a bone marrow hole by a novel structure absolutely different from the conventional one. The current imbalance detection and circuit interrupter includes a housing, power supplies, a sensor for sensing a current imbalance at the line side of the electrical circuit, a logic controller and a power controller. The type of information in metadata for one type of file differs from the type of information in metadata for another type of file.