Background The medical implants are an essential methodology in medical science community especially for knee joint. Due to the number of patients with different shapes and sizes of knees, the lack of customized implants for total knee arthroplasty is authorized.
Objectives This research aims to provide an integrated system consisting digital image analysis of Magnetic Resonance Imaging (MRI) data and Computer-aided-design (CAD) system for modelling and designing of customized implants for human knees.
Methods The process of Incremental Sheet Forming (ISF) that involves machining and sheet forming parameters are used to manufacture customized metal implants suitable for individual patient's knee joints. In this research, an automatic algorithm to segment femoral bone from knee MRI images is developed and used for 3D reconstruction followed by the ISF process. For the feasibility study, MR data with the following parameters: TR=37ms, TE=20 ms, flip angle=8°, image resolution =0.47x0.51x1.5mm, is used. For femur segmentation, multi-resolution edge detection is applied that extracts all the edges at bone surfaces. This is followed by the selection and extracton of strong edges with enhanced active contour method that results in extraction of femur and tibia bones. Further morphological processing is applied to extract the femur region as segmented outcome. Resultant of segmentation are further processed and a surfaces rendering method “Marching Cubes” is applied for the 3D reconstruction that are converted into Standard Tessellation Language (STL) format for later design and manufacture procedure. Generated STL file are hilled, jointed and changed to a solid part then exported to CAM system for ISF programming procedure. During the ISF process, optimum parameters are applied to increase the surface quality of final parts.
Results Applying this integrated system shows a substantial reduction in production time compare to current manufacturing method. The total time required for 3D modeling of femur is ∼2 minutes. The time taken for prototyping is ∼3.5 hours while the time of production for permanent mold casting, forging and machining process are 4, 1 and 7 hours respectively. Preparation time for every of methods is also considered which are, 0.5, 0.1 and 0.2 hour for current manufacturing method and 0.2 hour for ISF. Besides that the roughness of the surface is measured in all methods before polishing procedure which are Ra 5.713 um for ISF and 12.268 um, 9.459 um, 6.142 um, for other method correspondingly.
Conclusions In this research, an integrated method that combines computational method and prototyping procedure is developed that shows its applicability for the customized knee implants. Flexibility in size and shape together using all biocompatible sheet metals with variety of thicknesses make this method more practical than other current methods of metal implants production.
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Acknowledgements The authors all thankful to Ministry of Education Malaysia for kindly providing us the grant (Ref: FRGS/1/2014/TK01/UTP/02/8) to conduct this research.
Disclosure of Interest None declared