FIELD OF THE INVENTION

The present invention relates to hip joint endoprosthesis systems generally, and more specifically to a hip joint endoprosthesis system, comprising a medical instrument for extracting an implanted prosthesis stem of a hip joint endoprosthesis from a femur bone of a patient, which medical instrument has a coupling body with a coupling recess for accommodating a coupling cone projecting from the prosthesis stem.

BACKGROUND OF THE INVENTION

For the treatment of damaged hip joints, the latter have been replaced by hip joint endoprostheses for many years. A prosthesis stem is hereby inserted into a cavity of the femur bone prepared therefor. Prosthesis stems are known that have a projecting coupling cone which, for example, is coupleable to a neck extension or joint ball. A further component of the hip joint endoprosthesis is the joint socket which is fixed in the pelvis bone of the patient. The acetabulum may optionally accommodate a joint insert which forms a sliding pairing with the joint ball that is as wear-resistant as possible.

If, for example, in the course of an operation for implanting the hip joint endoprosthesis, a prosthesis stem that is too large or too small is inserted into the prepared bone cavity, the same must be removed. For this purpose, medical instruments are used that have a coupling body which is coupleable to the coupling cone of the prosthesis stem. One problem here is in particular that the coupling cone may be damaged when cooperating with the coupling body of the medical instrument. This is absolutely undesirable because a damaged coupling cone no longer enables a secure connection with a neck piece or a joint ball. The connection between the coupling cone and the neck piece or the joint ball hereby occur by self-locking. For this purpose, surfaces which are optimally adapted to each other are necessary. Scratches and raised portions on the coupling cone prevent a secure self-locking connection.

SUMMARY OF THE INVENTION

In a first aspect of the invention, a hip joint endoprosthesis system comprises a medical instrument for extracting an implanted prosthesis stem of a hip joint endoprosthesis from a femur bone of a patient. Said medical instrument has a coupling body with a coupling recess for accommodating a coupling cone protruding from the prosthesis stem. Said coupling body comprises a coupling base body and a coupling insert which is accommodated in a coupling insert receptacle of the coupling base body and defines the coupling recess.

