An upgraded optical coordinate measurement machine for the dimensional analysis of complex geometric devices

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Artificial joints that alleviate pain and restore function have become a reality due to advances in the natural sciences and engineering. Unfortunately, early failures and patient dissatisfaction with outcomes after joint replacement surgery are on the order of 5-20%. A major limitation is wear and corrosion of implant components generating metal and plastic wear particles. These tribological and chemical phenomena can cause biological reactions including bone resorption, implant loosening, and soft tissue damage, reducing the longevity of the device and necessitating a revision surgery to replace the failed implant. Wear and corrosion can be affected by implant design, surgical technique, and patient factors, such as weight and certain diseases. Understanding and/or optimizing these factors to support greater device longevity requires accurate measurement of dimensional changes due to wear and corrosion, thereby quantifying implant performance. Dimensional changes due to material loss on the order of tens of microns may be sufficient to generate metal hypersensitivity and failure in patients, therefore highly sensitive equipment is required. We have Canada's first optical coordinate measuring machine optimized for performing these types of dimensional measurements on spherical hip implant components, such as the head-neck taper junction or acetabular cup, two components commonly associated with wear and corrosion. However, growing evidence suggests wear and corrosion is occurring in other types of implants including the knee, shoulder, and spine causing early failures. To be able to analyze these other kinds of components that lack rotational symmetry, we require an upgrade to our optical coordinate measuring machine by adding an additional sensor so that we can scan more complex, asymmetrical geometries. Such an upgrade will allow us to immediately start analyzing all the >5,500 hip, knee, and shoulder implants collected at our institution that have failed and been removed from patients. An additional benefit is that the upgraded system will better enable scanning of non-orthopaedic components, allowing us to share the system with other users with a need to reconstruct complex surface geometries. Measuring the dimensional changes to the retrieved implant components in our research projects will allow us to objectively determine which factors are associated with greater wear or corrosion. We can use this new knowledge to help design better, longer lasting implants, to inform clinicians about the best choices across different devices on the market, and to develop tests for corrosion and metal hypersensitivity reactions.