A bone fixation device including a retainer and an anchor. According to the detection result, the part of the area of the image data is changed to another part of the area and rotation processing of another part of the area is performed, thereby reproducing the another part of the area which was subjected to the rotation processing. An exclusive code is imprinted onto the surface of the disk and coded signals commensurate with the exclusive code are generated by a controller and mixed with the digital video signals recorded by the disk recorder to authenticate the recording of the disk outputted from the disk feeder system. The bearing element and the driven wheel define a strap path therebetween.