Hip joint device and method

A method for implantation of a medical device in a hip joint of a human patient, a natural hip joint having a ball shaped caput femur integrated with a collum femur having a collum and caput center axis, extending longitudinally along the collum and caput femur, in the center thereof, as the proximal part of a femoral bone with a convex hip joint surface towards the center of the hip joint and a bowl shaped acetabulum as part of a pelvic bone with a concave hip joint surface towards the center of the hip joint, the medical device comprising;

• an artificial convex caput femur comprising a convex surface towards the center of the hip joint, an elongated portion connected to a prosthetic spherical portion of said artificial convex caput femur and adapted to be fixated to the pelvic bone of the patient, wherein the artificial convex caput femur has a center point, being the radius center of the prosthetic spherical portion, and wherein said method comprises the steps:
• a. fixating the artificial convex caput femur to the pelvic bone of the human patient through said elongated portion fixation to the pelvic bone,
• b. movably connecting the artificial convex caput femur with a prosthetic artificial acetabulum surface,
• c. fixating the prosthetic artificial acetabulum surface to the femoral bone of the patient, the prosthetic artificial acetabulum surface comprising at least one extending portion clasping said prosthetic spherical portion, and wherein said elongated portion comprises a restricting portion formed at a distal portion of said elongated portion abutting the prosthetic spherical portion,
• d. restricting a motion range of said prosthetic artificial acetabulum surface in relation to said artificial convex caput femur with said restricting portion,
• wherein the distal portion of said elongated portion is rotationally asymmetric with respect to a central axis extending along a longitudinal extension of the elongated portion, due to a form of the restricting portion, wherein said restricting portion is formed such that the restricting portion enables a motion range of said prosthetic artificial acetabulum surface which is larger in some movements and smaller in some movements in relation to said artificial convex caput femur, and
• e. placing a major portion of said restricting portion of said elongated portion, when implanted, dorsal to a vertical acetabulum plane (PX′Y′) coinciding with the collum and caput center axis, to enable an advantageous motion range in relation to said prosthetic artificial acetabulum surface.