A hip prosthesis comprising a shank which is inserted into the extremity of the femur, in which the longitudinal axis of the shank follows a path substantially parallel to the external profile of the head of the femur in the top part of its cervical-trochanter area is described. The relay station comprises a control unit to generate a control signal affecting said first signal and control transmission of said control signal to said base station, and a reception processing part to receive a radio signal transmitted from said mobile station which transmits said radio signal in accordance with said first signal which is affected by said control signal. Upon the first feedback pulse after the minimum feedback pulse sampling period has passed, the current sampling period is ended, and the next sampling period is begun. A first implement is removably connected to at least one of said opposing sides of said base.