title: A fast, accurate and closed-form method for pose recognition of an intramedullary nail using a tracked C-arm.
abstract: OBJECTIVE
  The main challenge of intramedullary nail (IM-nail) fixation surgery is to achieve the X-ray shot in which the distal holes of the IM-nail appear as circles (desired view); screw insertion is then performed. Although C-arm X-ray devices are routinely used in IM-nail fixation procedures, the surgeons or radiation technologists (rad-techs) usually utilize them in a trial-and-error manner. This increases both radiation exposure and surgery time. This study addresses the problem by presenting a C-arm-based IM-nail pose recognition method.
  
  
  METHODS
  The specific purpose of this study was to develop and validate an automated technique for identifying the current pose of the IM-nail relative to the C-arm. An accuracy assessment is performed to test the reliability of the navigation results. The algorithm starts with a sequential biplanar set of X-ray imagery (acquired from a tracked C-arm) of the distal part of an inserted IM-nail. The image-processing module then extracts features of interest, and a mathematical model incorporates them to calculate the six degree-of-freedom position and orientation parameters of the nail.
  
  
  RESULTS
  Translational accuracy was demonstrated to be better than 0.5 mm, rotational accuracy for roll and pitch to be better than 2° and for yaw to be better than 2.5° depending on the separation angle. Computation time was less than 0.5 s. .
  
  
  CONCLUSIONS
  An IM-nail distal locking navigation technique is introduced in this study that leads to more accurate and faster screw placement with a lower consumption of radiation dose and a minimum number of added steps to the operation.
authors.affiliation: Department of Geomatics Engineering, University of Calgary, 2500 University Dr. NW, Calgary, AB, T2N 1N4, Canada. Hooman.esfandiari@gmail.com.
authors.forename: H
authors.initials: H
authors.lastname: Esfandiari
authors.affiliation: Department of Orthopaedics, University of British Columbia, 3114 - 910 West 10th Avenue, Vancouver, BC, V5Z 1M9, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Amiri
authors.affiliation: Department of Geomatics Engineering, University of Calgary, 2500 University Dr. NW, Calgary, AB, T2N 1N4, Canada.
authors.forename: D D
authors.initials: DD
authors.lastname: Lichti
authors.affiliation: Department of Civil Engineering, University of Calgary, 2500 University Dr. NW, Calgary, AB, T2N 1N4, Canada.|McCaig Institute for Bone and Joint Health, University of Calgary, 2500 University Dr. NW, Calgary, AB, T2N 1N4, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Anglin
mesh_terms: D000465:Algorithms; D001863:Bone Screws; D004867:Equipment Design; D005471:Fluoroscopy / Q000379:methods*; D005594:Fracture Fixation, Intramedullary / Q000295:instrumentation*; D050723:Fractures, Bone / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D015203:Reproducibility of Results; D025321:Surgery, Computer-Assisted / Q000295:instrumentation*
keywords: C-arm; IM-nail; Pose estimation; Pose recognition; Radiation