Comparison of the model-based and marker-based roentgen stereophotogrammetry methods in a typical clinical setting.

Roentgen stereophotogrammetric analysis (RSA) is an established method for the precise measurement of implant migration. Model-based RSA (MBRSA) alleviates the need to attach tantalum markers to the prosthesis, which has prevented wider application of RSA. The goal of this study was to investigate the equivalence of both methods for the clinical measurement of implant migration. Tibial component migration was measured in 24 patients using both methods from the same set of radiographs. The maximum agreement interval, mean (+/-2 standard deviations), of the difference between both methods was modest, at 0.002 mm (0.144 mm) and -0.078 degrees (0.782 degrees ). The results suggest that MBRSA can be used interchangeably with the marker-based method and that the advantages of MBRSA do not come at the cost of a loss in accuracy.