The registration is a critical step in the computer assisted orthopaedic surgery (CAOS). The accuracy of the registration directly affects the effect of the navigation. In this paper, the influence of the fiducials configuration on the accuracy of the bi-planar method widely applied in the fluoroscopy-based navigation is investigated through theoretical analysis and computer simulation. The error distribution characteristics under the influence of the factors such as the distance between the fiducials and the number of the fiducials are obtained. The results indicate that increasing the number and spacing of the fiducials can reduce the positioning error. The configuration of the 5-point quadrangle yields a smaller error than the configurations of 4-point rectangles and 4-points triangles. This research provides a reference for the fiducials configuration selection to improve the registration accuracy in the CAOS.

configuration of fiducials  /  space registration  /  error analysis  /  computer assisted orthopaedic surgery