title: Registration of a statistical model to intraoperative ultrasound for scaphoid screw fixation.
abstract: OBJECTIVE
  Volar percutaneous scaphoid fracture fixation is conventionally performed under fluoroscopy-based guidance, where surgeons need to mentally determine a trajectory for the insertion of the screw and its depth based on a series of 2D projection images. In addition to challenges associated with mapping 2D information to a 3D space, the process involves exposure to ionizing radiation. Three-dimensional ultrasound has been suggested as an alternative imaging tool for this procedure; however, it has not yet been integrated into clinical routine since ultrasound only provides a limited view of the scaphoid and its surrounding anatomy.
  
  
  METHODS
  We propose a registration of a statistical wrist shape + scale + pose model to a preoperative CT and intraoperative ultrasound to derive a patient-specific 3D model for guiding scaphoid fracture fixation. The registered model is then used to determine clinically important intervention parameters, including the screw length and the trajectory of screw insertion in the scaphoid bone.
  
  
  RESULTS
  Feasibility experiments are performed using 13 cadaver wrists. In 10 out of 13 cases, the trajectory of screw suggested by the registered model meets all clinically important intervention parameters. Overall, an average 94 % of maximum allowable screw length is obtained based on the measurements from gold standard CT. Also, we obtained an average 92 % successful volar accessibility, which indicates that the trajectory is not obstructed by the surrounding trapezium bone.
  
  
  CONCLUSIONS
  These promising results indicate that determining clinically important screw insertion parameters for scaphoid fracture fixation is feasible using 3D ultrasound imaging. This suggests the potential of this technology in replacing fluoroscopic guidance for this procedure in future applications.
authors.affiliation: Department of Electrical and Computer Engineering, University of British Columbia, Vancouver, BC, Canada. emrana@ece.ubc.ca.
authors.forename: Emran Mohammad Abu
authors.initials: EM
authors.lastname: Anas
authors.affiliation: Department of Electrical and Computer Engineering, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Alexander
authors.initials: A
authors.lastname: Seitel
authors.affiliation: Department of Electrical and Computer Engineering, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Abtin
authors.initials: A
authors.lastname: Rasoulian
authors.affiliation: Kingston General Hospital, Kingston, ON, Canada.
authors.forename: Paul St
authors.initials: PS
authors.lastname: John
authors.affiliation: School of Computing, Queen's University, Kingston, ON, Canada.
authors.forename: Tamas
authors.initials: T
authors.lastname: Ungi
authors.affiliation: School of Computing, Queen's University, Kingston, ON, Canada.
authors.forename: Andras
authors.initials: A
authors.lastname: Lasso
authors.affiliation: Vancouver General Hospital, Vancouver, BC, Canada.
authors.forename: Kathryn
authors.initials: K
authors.lastname: Darras
authors.affiliation: Department of Electrical and Computer Engineering, University of British Columbia, Vancouver, BC, Canada.|Department of Orthopaedics and Centre for Hip Health and Mobility, University of British Columbia, Vancouver, BC, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Wilson
authors.affiliation: BC Women's Hospital, Vancouver, BC, Canada.
authors.forename: Victoria A
authors.initials: VA
authors.lastname: Lessoway
authors.affiliation: School of Computing, Queen's University, Kingston, ON, Canada.
authors.forename: Gabor
authors.initials: G
authors.lastname: Fichtinger
authors.affiliation: Kingston General Hospital, Kingston, ON, Canada.
authors.forename: Michelle
authors.initials: M
authors.lastname: Zec
authors.affiliation: Kingston General Hospital, Kingston, ON, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Pichora
authors.affiliation: School of Computing, Queen's University, Kingston, ON, Canada.
authors.forename: Parvin
authors.initials: P
authors.lastname: Mousavi
authors.affiliation: Department of Electrical and Computer Engineering, University of British Columbia, Vancouver, BC, Canada.|Mechanical Engineering, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Robert
authors.initials: R
authors.lastname: Rohling
authors.affiliation: Department of Electrical and Computer Engineering, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Purang
authors.initials: P
authors.lastname: Abolmaesumi
mesh_terms: D001863:Bone Screws; D002102:Cadaver; D005471:Fluoroscopy; D005593:Fracture Fixation, Internal / Q000379:methods*; D050723:Fractures, Bone / Q000175:diagnosis / Q000601:surgery*; D006801:Humans; D015233:Models, Statistical; D021361:Scaphoid Bone / Q000000981:diagnostic imaging / Q000293:injuries / Q000601:surgery*; D014463:Ultrasonography / Q000379:methods*; D014954:Wrist Injuries / Q000175:diagnosis* / Q000601:surgery; D014955:Wrist Joint / Q000000981:diagnostic imaging / Q000601:surgery
keywords: Drill path; Scaphoid fracture; Screw axis; Statistical wrist model; Ultrasound guidance; Volar percutaneous approach