[The motility of hip joint endoprostheses (author's transl)].

The motility of a healthy hip joint normally seems to be better than the motility of an endoprosthesis. The movement of all models of endoprostheses must fulfill minimum requirements as well in total motility as in each way. The arithmetical investigation of the motility of commercial total endoprostheses shows good locomotion for most cases. Decisive is the relation between prosthesis head- and prosthesis neck diameter. Insufficient motility of endoprosthetic models results if especial--redundant--constructive details of the socket are selected. It seems to be more problematical to produce double cup endoprostheses which reveal sufficient function. Normally the motility of double cup prostheses must be essentially less than that of total endoprostheses or of a healthy hip joint. A special implant technique and various constructive assumptions are necessary to reach a sufficient functional result.