title: The use of a 3D navigation system in the treatment of mandibular angle fractures by minimally invasive insertion of Herbert screws for osteosynthesis.
abstract: OBJECTIVE
  We present a phantom study evaluating the use of a three-dimensional navigation system in the treatment of mandibular angle fractures with traction screw osteosynthesis. The insertion of the so-called "Herbert bone screw" was tested on phantom models of the mandible.
  
  
  METHODS
  A total of ten synthetic models of the lower jaw were prepared with navigational markers. After inducing artificial fractures in the mandibular angle region, axial CT scans of the models with 1.5-mm slice thickness were performed. The CT data was then transferred to the workstation of the navigation system (STN-Zeiss Navigation System, Aalen, Germany). The access to the fracture and the drilling depth were planned preoperatively on the computer monitor using the software. After calibration of the drill wire, the cannulated traction screws were inserted under three-dimensionally directed computer navigation.
  
  
  RESULTS
  The inferior alveolar nerve of the model was spared in all ten cases. Cortical perforation occurred twice in the ascending lower jaw branch, but secure anchorage of the screw was still possible in every case.
  
  
  CONCLUSIONS
  The navigation system is a helpful visualization tool that can prevent damage to the inferior alveolar nerve and enable secure anchoring of the traction screw centrally in the cortical bone without causing perforation. This computer guided insertion method enables stable fixation of the fracture via minimally invasive surgery. Positioning of a traction screw with additional tools belonging to the screw system (drill wire) is demonstrated.
authors.affiliation: Clinical Department of Oral and Maxillofacial Surgery, Medical University of Graz, Graz, Austria. matthias.feichtinger@meduni-graz.at
authors.forename: Matthias
authors.initials: M
authors.lastname: Feichtinger
authors.forename: Guenter
authors.initials: G
authors.lastname: Schultes
authors.forename: Hans
authors.initials: H
authors.lastname: Kärcher
mesh_terms: D001863:Bone Screws; D003198:Computer Simulation; D005593:Fracture Fixation, Internal / Q000295:instrumentation* / Q000379:methods; D050723:Fractures, Bone / Q000175:diagnosis* / Q000601:surgery; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000295:instrumentation*; D008334:Mandible / Q000473:pathology*; D008338:Mandibular Injuries / Q000175:diagnosis* / Q000601:surgery; D019060:Minimally Invasive Surgical Procedures; D008954:Models, Biological; D010865:Pilot Projects; D011300:Preoperative Care; D012984:Software