| Summary: | 博士 === 國立中央大學 === 機械工程學系 === 103 === Open wedge high tibial osteotomy has been used to treat osteoarthritis of the medial compartment of the knee with good mobility. This method relieves pain and stimulates the regeneration of the cartilage by correcting the incorrect biomechanical axis of the knee and redistributing the loading ratio of the tibial plateau. However, this makes the proximal tibia a highly unstable structure and causes plate and screws to be the potentials sources for mechanical failure. Other failures like the lack supporting ability of the implant to maintain the tibial slope, or the fracture of the lateral cortex.
To solve the above-mentioned problems, this study started with the preoperative planning. The mathematical formula between the correction angle and wedge height was built for maintaining the tibial slope while correcting the angle. For the implants, the biomechanical effects of one-leg and two-leg plate systems were compared by the biomechanical tests and computer simulations. A new plate is designed based on the results of the tests and simulations, and the suggestions of the clinical surgeon. Then the computer simulation was done to verify the design. On the purpose of simplifying the surgical procedure and enhancing the accuracy, the special surgical instruments were designed, and the surgical procedure was planned. Response to the trend of shortening the bed-ridden time, the current study combined the loading informations with the finite element analysis to investigate the biomechanics, wedge stability and the unfavorable situations for wedge healing after high tibial osteotomy in gait cycle.
The two-leg plates had better outcomes in wedge stiffness, wedge stability and supporting strength. Even in gait cycle, the undesired shear force at wedge was lower than the one-leg design. The two leg can form a force-couple mechanism to eliminate the bending moment, and avoid the zone of tension at the wedge tip. The choice of the plates involved the trade-off between surgical convenience and construct stability. Consequently, the two-leg system is suggested for the patients with heavy bodyweight or early weight bearing demands. The one-leg system with locking screws can be used for the majority of the patients with less activity and without heavy bodyweight.
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