Abstract
Arthroplasty possibly is one of the three most important inventions in last few decades, and just behind antibiotics for its contributions. In various types of arthroplasties, total knee arthroplasty (TKA) is the most established and reliable procedure. The survivorship can last for up to 20 years. In 2009-2011, there were about twenty thousand TKA performed in Taiwan. Along with progressively lengthen life expectancy, Number of revision of TKR increases annually and there are almost one thousand cases per year. Application of bone cement (PMMA) achieves a faster and better bone implant interface in TKA especially in tibial component. In the other hand, this secured fixed implant caused troublesome in removal of bone implant during revision TKA surgery. Orthopedic surgeons always find difficulties in removing bone cement between bone and implant. It also found that massive trabecular and cortical bone are sacrificed. In this study, for decreasing the degree of difficulty in separation of implant from bony component, a new locking mechanism and implant structure are designed to avoid unnecessary bone loss. The locking mechanism based on plug-in surface in the rim of tibial cutting surface and sit on the peripheral strong cortical bone. The multiple plug-in locations showed provide enough combination forces and should be comparable with present stability design. In our experiment, we use Solidwork and ANSYS to analysis the position of stress concentration. The result shows that stress concentrates on cortical bone rather than cancellous bone. We design a new total knee arthroplasty and made several tensile test. Testing models about tensile forces of the Instron device were obtained in mechanical testing. In this research, we set four pig-knee models which are placed on new type artificial knee joint and have tensile test. Results showed that the maximum fracture force for three of all models happened on the interface between rim of the cortical bone and bone cement. The magnitudes are 278.6694 (N), 245.2942 (N) and 193.9125 (N). The last set had support by trapezoid-shape structure, so its magnitude is 564.5499(N). In terms of the model which doesn’t fit between rim of the cortical bone and bone cement, the force between trapezoid-shape fillister and bone cement is about 810(N). Those data could show the importance of the trapezoid-shape structure. For TKA revision, new design arthroplasty take advantage of the weakness of the bone cement which hardly bearing the shear force to remove arthroplasty rapidly. It also improved the convenience of Revision and achieved the purpose of this research.