A new model-based RSA method validated using CAD models and models from reversed engineering

• Published in: Journal of biomechanics Vol. 36; no. 6; pp. 873 - 882
• Main Authors: Kaptein, B.L., Valstar, E.R., Stoel, B.C., Rozing, P.M., Reiber, J.H.C.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 01.06.2003; Elsevier Limited
• Subjects: Algorithms; Arthroplasty, Replacement, Knee - adverse effects; Computer Simulation; Computer-Aided Design; Equipment Failure Analysis - methods; Humans; Imaging, Three-Dimensional - instrumentation; Imaging, Three-Dimensional - methods; Joint Instability - diagnosis; Joint Instability - diagnostic imaging; Joint Instability - etiology; Joint Instability - physiopathology; Knee Joint - diagnostic imaging; Knee Joint - physiopathology; Knee Joint - surgery; Model-based; Models, Biological; Motion; Phantoms, Imaging; Photogrammetry - methods; Pose estimation; Prosthesis Failure; Radiographic Image Enhancement - methods; Radiographic Image Interpretation, Computer-Assisted - methods; Reproducibility of Results; Roentgen stereophotogrammetry; Rotation; RSA; Sensitivity and Specificity; Roentgen stereophotogrammetry; RSA; Pose estimation; Model-based
• DOI: 10.1016/S0021-9290(03)00002-2
• ISSN: 0021-9290

Roentgen stereophotogrammetric analysis (RSA) was developed to measure micromotion of an orthopaedic implant with respect to its surrounding bone. A disadvantage of conventional RSA is that it requires the implant to be marked with tantalum beads. This disadvantage can potentially be resolved with model-based RSA, whereby a 3D model of the implant is used for matching with the actual images and the assessment of position and rotation of the implant. In this study, a model-based RSA algorithm is presented and validated in phantom experiments. To investigate the influence of the accuracy of the implant models that were used for model-based RSA, we studied both computer aided design (CAD) models as well as models obtained by means of reversed engineering (RE) of the actual implant. The results demonstrate that the RE models provide more accurate results than the CAD models. If these RE models are derived from the very same implant, it is possible to achieve a maximum standard deviation of the error in the migration calculation of 0.06 mm for translations in x- and y-direction and 0.14 mm for the out of plane z-direction, respectively. For rotations about the y-axis, the standard deviation was about 0.1° and for rotations about the x- and z-axis 0.05°. Studies with clinical RSA-radiographs must prove that these results can also be reached in a clinical setting, making model-based RSA a possible alternative for marker-based RSA.