[Experiences, requirements and development of cement-free hip endoprostheses]

The main problem with endoprostheses, particularly the cementless type, is the transmission of stress from the implant to the bones and vice versa. Cement is a very good solution--at least on a short-term basis. However, the major aim in using cementless endoprostheses is to improve the long-term results as compared with those obtained when using cement. To date, this has not been possible either with more modern cementing techniques (pressurization) or with cementless endoprostheses based on the principle of bony ingrowth. The differences between cementless endoprostheses and those using cement are: the design, the nature of the implant surface, and the operative technique. Experience has shown that histologically, radiologically, and clinically (although not long-term), the results with cement-fixed acetabula are better than those with cementless prostheses. Cement-free shaft endoprostheses, on the other hand, have not yet achieved the consistently good results obtained in the femur shaft by means of pressurization. Under normal circumstances, use of a cementless acetabulum and a cement-fixed shaft is the procedure of choice. In patients under 60 years of age who are still active, as well as in repeat-arthroplasties involving substantial loss of bone, the completely cementless endoprosthesis is indicated.