Surface metrological and computer-aided designing of a tibia bone for region-specific implants

Abstract

Load bearing joints such as knee and hip are the most-prone joints of osteoarthritis. Predominantly, Total Knee Replacement (TKR) and Total Hip Replacement (THR) are done to repair the affected knee and hip joints and reconstructed with metal implants. Proper implant fitting to the patient will avoid further revision surgeries. But, the loosening of implant is the major problem due to the unavailability of suitable implants. Implant manufacturers have designed the implants mostly with respect to the certain region-based population pool data. Most of the time, these implants don’t fit for other region’s people, creating implant loosening problem that leads to revision surgeries. Therefore, this research was aiming at designing region-specific implants with respect to regions. To retrieve the morphometric data from the regions, there is a need for efficient method to measure bones and create Computer-Aided Design (CAD) models. Tibia was taken as the subject for measurement to check for proper method to retrieve dimensions. Coordinate Measuring Machine (CMM), contact mode was used to extract the dimensional data. Since tibia bone is a complex-shaped object, reverse engineering technique was used to develop a fixture box with an aid of Three-Dimensional (3D) printer, to hold the tibia bone for measuring its complex features in eight planes (0º, 45º, 90º, 135º, 180º, 225º, 270º and 315º). The measured data of eight planes were used with the careful usage of preprocessing, registering and merging tools, to generate the master point cloud. The master point cloud was used as base with the integration of CAD tools to design 3D modelling of tibia. A comparative analysis was done between original tibia model and the 3D CAD model. Deviation analysis between the master point cloud and the 3D model was also done and the error was minimal (0.314274 mm). Thus, this work gave accurate results for using alternate scanning system other than Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) for the measurement of bone. This method can be used for retrieving bone dimensions from bone samples obtained from various regions for generating region-specific implants.