A hip prosthesis device including a femoral stem, the femoral stem including an elongate stem sleeve having a blind hole extending in a longitudinal direction and a hole opening at an upper frontal end of the stem sleeve； a stem core having an elongate stem shaft inserted in the blind hole and slidable in the longitudinal direction, a neck having a lower neck portion and an upper neck portion, a lower end of a lower neck portion attached to an upper end of the stem shaft, the upper neck portion attachable to a femoral head； a shock absorber mechanism operatively provided between the stem shaft and the stem sleeve to act against a downwardly directed longitudinal sliding motion of the stem shaft relative to the stem sleeve； and a closure cap positioned to close the hole opening with a through hole which the neck extends with its lower neck portion.
