title: A robust and accurate two-stage approach for automatic recovery of distal locking holes in computer-assisted intramedullary nailing of femoral shaft fractures.
abstract: It has been recognized that one of the most difficult steps in intramedullary nailing of femoral shaft fractures is the distal locking - the insertion of distal transverse interlocking screws, for which it is necessary to know the positions and orientations of the distal locking holes (DLHs) of the intramedullary nail (IMN). This paper presents a robust and accurate approach for solving this problem based on two calibrated and registered fluoroscopic images. The problem is formulated as a two-stage model-based optimal fitting process. The first stage, nail detection, automatically estimates the axis of the distal part of the IMN (DP-IMN) by iteratively fitting a cylindrical model to the images. The second stage, pose recovery, resolves the translations and the rotations of the DLHs around the estimated axis by iteratively fitting the geometrical models of the DLHs to the images. An iterative best matched projection point (IBMPP) algorithm is combined with random sample strategies to effectively and robustly solve the fitting problems in both stages. We designed and conducted comprehensive experiments to validate the robustness and the accuracy of the present approach. Our in vitro experiments show on average less than 14 s execution time on a Linux machine, a mean angular error of 0.48 degrees (std = 0.21 degrees ), and a mean translational error of 0.09 mm (std = 0.041 mm). We conclude that the present approach is fast, robust, and accurate for distal locking applications.
authors.affiliation: NEM Research Center, University of Bern, Stauffacherstrasse 78, Switzerland. guoyan.zheng@ieee.org
authors.forename: Guoyan
authors.initials: G
authors.lastname: Zheng
authors.forename: Xuan
authors.initials: X
authors.lastname: Zhang
authors.forename: Daniel
authors.initials: D
authors.lastname: Haschtmann
authors.forename: Philippe
authors.initials: P
authors.lastname: Gedet
authors.forename: Xiao
authors.initials: X
authors.lastname: Dong
authors.forename: Lutz-Peter
authors.initials: LP
authors.lastname: Nolte
mesh_terms: D000465:Algorithms; D001185:Artificial Intelligence; D001863:Bone Screws; D005264:Femoral Fractures / Q000000981:diagnostic imaging* / Q000601:surgery*; D005594:Fracture Fixation, Intramedullary / Q000295:instrumentation* / Q000379:methods*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D010363:Pattern Recognition, Automated / Q000379:methods*; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D025321:Surgery, Computer-Assisted / Q000379:methods*