ABSTRACT
BACKGROUND:Human femur medul ary cavity has torsional anatomic structure. If the femur medul ary cavity’s torsional structure is copied to the stem of the prosthesis, the prosthesis wil transform the force loaded to torque between femur medul ary cavity and prosthesis stem, and the torque is transmitted to the proximal femur when the prosthesis is inserted in the medul ary cavity and load force on the prosthesis. OBJECTIVE:To optimize the force transmission of the proximal femur, and to avoid the stress shielding at the proximal end of the prosthesis. METHODS:We reconstructed a three-dimensional (3D) model of the femoral canal with the CT images of specimen femur and took the 3D model as the design model for prosthesis stem. The customized stem model and the proximal model of standard prosthesis could be put together to form customized prosthesis. We took advantage of robot grinding technology to manufacture the customized prosthesis, and matched it with specimen femur canal. Finite element analysis simulation and experimental methods were used to analyze the relationship between the loading force on the prosthesis and the micromotion of proximal end of the prosthesis. RESULTS AND CONCLUSION:The simulation and experimental results showed that the torsional structure matching by femoral canal and stem could effectively transmit the force on the prosthesis to the proximal end of the prosthesis in the form of torque. The torsional fretting of the proximal end of the prosthesis was related to the movement of the handle body. However, stem micromotion can be control ed by varying the matching size between stem and medul ary cavity.
ABSTRACT
BACKGROUND:In total hip replacements, aseptic loosening of uncemented femoral hip prosthesis is the main reason for the failure of artificial hip replacement, the prerequisite of reducing aseptic loosening of prosthesis is to increase fil ing area of femoral prosthesis in femoral cavity. OBJECTIVE:To obtain the fil ing rate of customized femoral prosthesis in femoral cavity and verify the validity of the methods of CAD/CAM/Robotic integration and the robot grind. METHODIn this paper, the CT data of femur were used to reconstruct three-dimensional model of femoral cavity. According to this model, a custom uncemented femoral hip prosthesis was designed, then the model of this custom prosthesis was imported into the CAD/CAM/Robotic software to generate cut path. After the cut path was imported into the robotic control er, the custom prosthesis can be fabricated, then this custom prosthesis was inserted into the femoral cavity, and the fil ing result of the custom prosthesis in femoral cavity was analyzed. RESULTS AND CONCLUSION:The experiment results showed that the customized prosthesis in femoral cavity achieved good fil ing result, the structure of femoral cavity resisted the rotation of the customized prosthesis in femoral cavity, and the customized prosthesis obtained stable fixation in the femoral cavity.