A medical device for implantation in a hip joint of a patient, the medical device comprising a prosthetic replacement for the acetabulum. The prosthetic replacement for the acetabulum comprises a first part (1841) adapted to be fixated to the femoral bone of the patient； and a second part (1842) rotatably connected to the first part by means of a connecting member (1843). The first part comprises a bowl-shaped inner contacting surface portion adapted to receive a bowl-shaped outer contacting surface portion of the second part such that the second part is rotatable, relative to the first part, around a point of rotation formed by the connecting member. The second part comprises a bowl-shaped inner surface adapted to receive a ball-shaped portion of a prosthetic replacement for the caput femur, adapted to be fixated to the pelvic bone, such that the prosthetic replacement for the caput femur and the second part form a ball joint in an opposite configuration. The inner contacting surface of the second part comprises an equator line (1821, 1845) being the largest circumference of the inner contacting surface, and at least one extending portion (1823a, 1823b) extending beyond the equator line and being adapted to clasp the ball-shaped portion of the prosthetic replacement for the caput femur.
