膝関節シミュレーターを用いた人工膝関節置換後の応力解析 : 歪みゲージ法による

Abstract

In artificial joints, prosthesis loosening is influenced by its design and fixation technique with the bone. There are many designs of total knee prosthesis, including the hinged and nonhinged condylar type, in use today. In many recent clinical reports, sinking and loosening have been cited as a significant complication. For the purpose of making clear the relation between the loosening and the prosthesis design, a machine simulating the knee joint was manufactured and the relative deflections on the surface of the bone and between the component and the bone were measured by means of the strain gauge method utilizing the dynamic loading test. For the tests, GUEPAR prosthesis, Kinematic Rotating Hinge prosthesis, Total Condylar prosthesis and KOM Ceramic prosthesis were prepared. Fourteen different tibial components were also prepared including one compartmental, two anteriorly joined, eleven one-piece components with one, two, or three fixation pegs, all-plastic components or those with metal trays or with ceramic trays, for purpose of comparision. These prosthesis were fixed in femurs and tibia of cadaver bones with cementing. Strain gauges were glued to the surface of the around knee prosthesis, using cyanoacrylate instant cement. Maximum load was 100kg. In the GUEPAR prosthesis representative of the hinged type, the deflection was much larger at some distance from the knee joint, especially around the tip of the femoral stem, than in the periphery. In the Kinematic Rotating Hinge prosthesis, the hinged type admitted rotational movement, and the load was transmitted to the posterior cortical bone of the femur and tibia and compressive deflection occurred on these parts. The deflections were decreased around the tip of the stem. In the femoral component of the non-hinged type, KOM Ceramic prosthesis and Total Condylar prosthesis, the deflection around the periphery of the joint was not abnormally larger than the physiological state. In the tibial component, on the other hand, the compartmental component and anteriorly joined and one-piece components with short pegs deflected the most on the periphery of the anterior of tibia where the subchondral bones and trabeculate were weak and the cortical bones were thin. The least deflections occurred with the components with one or three strong pegs transmitting the load to the thick cortical bones. In fixing the tibial component, if it is designed to be loaded on the rigid cortical bone and is fixed so as to be supported by the rigid subchondral bone and cancellous bone of the plateau as well as by the rigid cortical bone on the medial and lateral sides or posterior slant surface and then loads are transmitted, it is considered that abnormal stress concentration can be decreased. The metal tray and ceramic tray prevent the deformation of the plastics and the stress concentration on the bone and cement.