title: Determination of pelvic orientation from sparse ultrasound data for THA operated in the lateral position.
abstract: BACKGROUND
  B-mode ultrasound imaging has the potential to replace conventional percutaneous digitization of bony landmarks in navigated total hip arthroplasties (THAs). For THAs operated in the lateral position, only one side of the pelvis is freely accessible. This paper presents a new ultrasound to statistical shape model (SSM) registration method for operating the pelvis in the lateral position, based on sparse ultrasound images, which does not interfere with the clinical routine in terms of redraping and repositioning the patient.
  
  
  METHODS
  It is proposed to use the mid-sagittal plane of the pelvis to symmetrically reflect data derived from sparse B-mode ultrasound images of the ipsilateral patient side to the contralateral side. A SSM of the pelvis is registered to the bilaterally available data without additional information on the pubic tubercle region.
  
  
  RESULTS
  The feasibility and robustness of the proposed method were evaluated by comprehensive in silico studies and laboratory experiments with plastic and dry cadaveric pelvises, showing a mean error of 3.48 ± 1.10° for anteversion angle and 1.26 ± 1.62° for inclination angle.
  
  
  CONCLUSIONS
  Experimental results demonstrate that the symmetry property of the pelvis could be used for registration in the lateral position without accessing the error-prone pubic tubercle landmarks.
authors.affiliation: Institute for Surgical Technology and Biomechanics, University of Bern, Stauffacherstrasse 78, CH-3014, Bern, Switzerland. steffen.schumann@ieee.org
authors.forename: Steffen
authors.initials: S
authors.lastname: Schumann
authors.forename: Lutz-P
authors.initials: LP
authors.lastname: Nolte
authors.forename: Guoyan
authors.initials: G
authors.lastname: Zheng
mesh_terms: D000465:Algorithms; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation* / Q000379:methods; D002102:Cadaver; D003198:Computer Simulation; D004867:Equipment Design; D006615:Hip / Q000000981:diagnostic imaging / Q000601:surgery; D006801:Humans; D015233:Models, Statistical; D009949:Orientation; D010388:Pelvis / Q000000981:diagnostic imaging / Q000601:surgery*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D025321:Surgery, Computer-Assisted / Q000379:methods; D014465:Ultrasonics; D014463:Ultrasonography