CAD Assembly of Total Knee Replacement with Femur and Tibia bones for CAE Analysis

Contact mechanics determine the outcomes of a Total Knee Replacement (TKR) surgery in which the infected knee joint of a human is replaced with Total Knee Replacement components made up of bio-compatible materials. To get valuable insights into the contact mechanics of knee joint, CAD (Computer Aided Design) and CAE (Computer Aided Engineering) analysis have proved very significant. Total Knee Replacement has three components- femoral component, bearing, and tibial component. These components are fixed to Femur and Tibia with a strong cement. The assembly of TKR components with Femur and Tibia bones is presented here as CAD. This CAD assembly can be used for any finite element analysis or CAE analysis concerning the knee joint. The TKR components of a posterior-stabilized, fixed bearing total knee prosthesis, PFC (De Puy, Johnson & Johnson, Leeds, UK)(1) were modelled using reverse engineering technique that converts a point cloud data gathered after scanning an actual physical product to CAD surfaces and solids. 3D point cloud data of TKR components were obtained with ATOS compact scanner (GOM GmbH, Germany) (2) consisting of two cameras, a laser source, a software and working area. The specifications of the scanner were: camera pixels: 8 or 12 mega- pixels, measuring area: 45 x 30 to 1200 x 1000 mm², working distance: 450 to 1200 mm and sensor dimension: 340 mm x 130 mm x 230 mm. The Geometric modelling of TKR component from these point cloud data was developed using Geomagic studio 12 (Raindrop Geomagic, Research Triangle Park, NC) (3). The bones, Femur and Tibia were modelled using point cloud data from MRI images of an Indian patient collected from Apollo hospital, Bangalore. The final assembly was executed in Solidworks 2013 (Dessault Systemes, Velizy-Villacoublay, France) (4). The resection of Femur and Tibia bone was accomplished with the help of a professional TKR surgeon at Apollo hospital, Bangalore The CAD model can be meshed in a CAE software and used to perform a CAE analysis be it a simple linear implicit analysis or a complex dynamic explicit analysis. The CAD (.stp format) needs an "import" to the CAE software. All dimensions are in mm