Roentgen stereophotogrammetry is a highly accurate technique for the assessment of three-dimensional migration of prostheses.
Methodology
To achieve the high accuracy, the following steps are carried out. Small roentgen opaque markers have to be introduced in the bone and attached to the prosthesis to serve as well-defined artificial landmarks. Two synchronised roentgen foci are used to obtain a stereo image of the bone and the prosthesis. Using a calibration object that holds tantalum markers at accurately known positions, the positions of the roentgen foci are assessed. The coordinates of the bone and prosthesis markers are accurately measured with a manually operated measuring table with an accuracy of 0.02 mm. After the coordinates have been measured, the three-dimensional position of the markers is reconstructed with RSA software. Finally, the change in the position of the prosthesis markers relative to the bone markers is determined and the translation and rotations of the prosthesis can be calculated. The reported accuracy of RSA ranges between 0.05 and 0.5 mm for translations and between 0.15˚ and 1.15˚ for rotations (95% confidence interval; Kärrholm, 1989).
http://www.lumc.nl/rep/cod/redirect/2020/research/locomotorysystem/publications/2001thesisvalstar.pdf
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