The success of cement-free hip endoprosthetics is largely dependent on precise surgical techniques and primary stability of the anchorage, in which favorable biomechanical conditions as well as the quality of the stabilizing bone are of considerable importance. Information gathered from more than 1500 cementless hip-joint endoprosthesis implantations is presented with biomechanical solutions and indications regarding operating techniques, and a correlation between clinical symptoms and radiological signs of complications is discussed. In close coordination with material-specific factors, design and surface characteristics are decisive in the function and quality of anchorage of the endoprosthetic replacement. In the case of the PM total hip endoprosthesis, these widely variable values were governed strictly by biomechanical considerations, with particular reference to the resulting bone reactions. Results so far, including those relating to stable integration of the implant, must be regarded as absolutely positive and confirm the design characteristics on which this model was based. Avoiding the disadvantages of bone cement, cementless hip-joint replacement, particularly in operations for the exchange of cemented prostheses after loosening, can be regarded as a step forward in hip-joint surgery.
The increasing use of orthopaedic implants makes international efforts of standardization with their objectives unification and benefit of the patient necessary and sufficient. In 1975 an ISO-Draft for "bone-screws" has been finished. To get experimental data there was a test series of breaking bone-screws of five producers by torsional stress. Comparable screws showed considerable differences. The control of conformity to standards gave partially distinct differences to the standard profile and different hardness values, what affects to the screws' security of twisting off.
Functional and anatomic characteristics of the shoulder girdle are special problems, that have to be solved in the process of using an artificial joint replacement to improve the function of a painful shoulder, which is restricted in movement. Seen from a biomechanical point of view, besides a safe fixation of the prosthesis the stability and kinematic of the artificial joint are of considerable importance for the success of the endoprosthetic treatment. The efforts of meeting these requirements by a respective prosthesis design led to a variety of prosthesis types. This study shows the possibilities for prosthetic replacement of the shoulder joint and comprises an analysis of all systems, which are available on the market, as well as of the patent applications of the past 15 years. The prostheses are listed according to their stability. Relative to the state of destruction of the joint unconstrained prosthesis types with completely free and partially restricted mobility, as well as constrained types of joints are being discussed.
Femoral stem failure in total hip replacement is becoming an increasing problem in connection with the long time of implantation. For this reason the possible facts are described mainly responsible for the failure. By 3 cases of loss the influence of material aspects are shown on failures primary due to loosening. Only by a complete and especially careful control system in production of endoprostheses it is possible in all probability to avoid "in-vivo"-cases of technical cause only.
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