title: [Fluoroscopic navigation versus conventional manual positioning of the femoral component for hip resurfacing: first experimental trial].
abstract: BACKGROUND
  The most essential improvement of modern hip resurfacing arthroplasty is the metal-on-metal bearing as well as the integration of a procedure for the exact and repeatable positioning of the femoral component through a specific mechanical alignment instrument. Nevertheless, the main reasons for early implant failure are mal-positioning of the femoral component and notching of the femoral neck during femoral head preparation.
  
  
  METHODS
  In the context of an in vitro study, in each case six DUROM-Hip resurfacing prostheses were implanted in artificial femora with the prosthesis-specific mechanical alignment instrument, as well as under navigation control. The aim of the study was to evaluate the functionality and accuracy of a computer-assisted planning and navigation system on the basis of a navigation module library from Surgitaix AG (Aachen, Germany), as well as a comparison with the prosthesis-specific mechanical alignment instrument.
  
  
  RESULTS
  The main angulation error between planning and navigation of the stem-shaft angle was 0.2+/-1.2 degrees for the navigation system and 6.5+/-4.1 degrees for the mechanical alignment instrument, the main anterior offset error was 1.2+/-1.2 mm vs. -0.83+/-4.1 mm. The mean time for all five planning and navigation steps was 17+/-1.2 min vs. 14+/-0.8 min. The main distance error between planning and navigation was 1.9+/-0.6 mm for the navigation system, and 5.3+/-2.4 mm for the mechanical alignment instrument. Femoral notching was not observed for navigational or conventional positioning.
  
  
  CONCLUSIONS
  The computer-assisted fluoroscopic planning and navigation system for hip resurfacing showed, within the scope of this in vitro study, first promising experiences. The system approves a practicable planning with a high accuracy in implementation. Nevertheless, the potential benefit has to be evaluated in further clinical studies, especially from the perspective of a possible integration of this navigation system into the clinical workflow. Further studies should consider a fluoroscopy-assisted range of motion assessment under consideration of an additional cup-module to enhance the postoperative range of motion after hip resurfacing procedures.
authors.affiliation: Klinik und Poliklinik für Orthopädie und Unfallchirurgie, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Deutschland. sascha.gravius@web.de
authors.forename: Sascha
authors.initials: S
authors.lastname: Gravius
authors.forename: Peter
authors.initials: P
authors.lastname: Belei
authors.forename: Matias
authors.initials: M
authors.lastname: de la Fuente
authors.forename: Ralf
authors.initials: R
authors.lastname: Müller-Rath
authors.forename: Klaus
authors.initials: K
authors.lastname: Radermacher
authors.forename: Dieter
authors.initials: D
authors.lastname: Christian Wirtz
authors.forename: Torsten
authors.initials: T
authors.lastname: Mumme
mesh_terms: D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D005471:Fluoroscopy / Q000379:methods*; D006622:Hip Prosthesis; D006801:Humans; D010865:Pilot Projects; D025321:Surgery, Computer-Assisted / Q000379:methods*; D016896:Treatment Outcome