RSA calibration accuracy of a fluoroscopy-based system using nonorthogonal images for measuring functional kinematics.

When performing radiostereometric analysis (RSA) in a clinical setting it may be desirable to orient the two imaging devices nonorthogonally to obtain the best views of an anatomical structure. In this study, a calibration frame was constructed that allowed the relative angles of fiducial and control planes to be adjusted. Precision and accuracy were quantified across multiple trials and orientations. The 90 degrees frame was always of equivalent or greater accuracy than a calibration frame with the fiducial and control planes aligned parallel to the image intensifiers. This study also showed that RSA may be performed with imaging devices at relative angles other than 90 degrees without compromising accuracy. This allows researchers greater freedom in positioning equipment.