A medical device system for implantation in a hip joint for providing at least one artificial hip joint surface for a patient, the medical device system comprising an artificial caput femur surface (45); or an artificial acetabulum surface (65) being at least partly bowl-shaped. The system has a largest cross-sectional distance being variable such that the medical device system can be inserted through a hole (18) in the pelvic bone (9), from the abdominal side of the pelvic bone, the hole having a diameter smaller than said largest cross-sectional distance. Further the artificial acetabulum surface (65) comprises at least two parts (45', 45", 46, 53a, 53b, 54b, 56, 63, 64a,) which are adapted to be interconnected to form an interconnected medical device when in use.