Background To prepare the femoral component during the Total knee arthroplasty (TKA), it is needed to cut off the damaged condyle to a dimension matched with one of the available implant sizes in the market. Since there is a variety of humans' knee size and shape, therefore, some parts of the distal femoral are over cut. The solution to this problem is customisation of the implants via a cohesive procedure specifically designed for medical orthopaedic implant production.
Objectives This research aims to provide a fully integrated system of digital image processing of Magnetic Resonance Imaging (MRI) data and Finite Element Method (FEM) for testing and analysing prior to manufacturing of customized medical femoral component.
Methods An automatic algorithm to segment MR images from end-of-femur condyle is developed and employed for 3D reconstruction followed by computer-aided design (CAD) system, FEM and incremental sheet forming (ISF) process. In femur segmentation, multi-resolution edge detection is applied that extracts all the edges at bone surfaces. The edge detection process followed by the selection and extraction of strong edges with enhanced active contour technique that results in separation between femur and tibia components. Morphological processing is applied to extract the femur region as the segmented outcome. Consequential of segmentation, a surfaces rendering method is applied for the 3D structure that automatically converts the model into standard tessellation language (STL) format for later CAD system and rapid prototyping preparation. Generated STL file is applied for creating a solid part and solid body. The Proper femoral component is designed using region growing technique then exported to FEM system to calculate the best metal thickness and angles, regarding the normal cartilage, to bear the maximum load with the lighter material. The process of ISF that involves machining and sheet forming parameters is using to manufacture customized medical metal femoral component but in low surface quality which increases the risk of ion release at in vivo condition. Therefore, during this technique, optimum parameters using Design of Experiment method are applied to modify and enhance the sheet stretching of final parts.
Results Applying this integrated system demonstrates a cohesive user-friendly system for creation of patients specific implants while it showed a substantial reduction in implant production time compares to the current manufacturing method. In ISF process optimum parameters are used to increase the rate of stretching together with the best sheet thickness ∼2.5 mm based on validated sheet stretching simulation. The results of this study also show that the high surface quality for femoral component up to ∼Ra 2.527 is achievable using this newly developed method.
Conclusions An integrated system that combines computational method, CAD, FEM and ISF procedure is developed that shows its potential for manufacturing of customized medical femoral component. Flexibility in size and shape make this system prominent. The best sheet thickness with respect to the cartilage thickness is calculated and obtained with the optimum process parameters for manufacturing section.
Acknowledgements The authors are thankful to the Ministry of Higher Education, Malaysia for supporting this research via FRGS/1/2014/TK01/UTP/02/8 research grant.
Disclosure of Interest None declared