Surface replacement of the femoral head (resurfacing head) and/or the acetabular cup (surface replacement cup). The "resurfacing head” is used to describe a femoral component that is designed only to cover the patient’s own femoral head. There may be an anchoring device which is integral to the component and which extends into the femoral neck. It is used with a corresponding “surface replacement cup” which is made of one piece of material (monobloc).