In a femoral head cap implant having a cup-shaped cap component and a pin fixed to its concave inner surface, a pick-up coil is arranged in the latter, each respective terminal of the same being connected to a tissue electrode. One tissue electrode comprises a cap component, the other an electrode provided insulated on the pin or on at least one part of the pin which is electrically insulated from the cap component. By inducing a low-frequency alternating current in the pick-up coil by means of an external coil, this low-frequency alternating current flows from the two tissue electrodes through the femoral head bone provided with the implant, thereby promoting the maintenance of its vitality.