title: Misjudgments at the mandibular angle: freehand versus computer-assisted screw positioning.
abstract: BACKGROUND
  Distraction osteogenesis is a well known and frequently described technique in mandibular deformities. Buried intraoral devices have numerous advantages, but success hinges on precise positioning of the implants. Although computer navigation has repeatedly been described for craniofacial applications, research on navigating the mandibular region is scarce. Navigating the device placement for a mandibular distractor could become a viable method for distraction osteogenesis because of the possibility of certainty in achieving a defined device position.
  
  
  METHODS
  A clinical situation was simulated by a mandible model mounted inside a phantom head. The screws were positioned according to a virtual plan through transoral and transbuccal approaches, with and without navigation.
  
  
  RESULTS
  Without navigation, the mean deviation from the planned position was 4.9 mm (range, 0.9-10.7 mm), with a clear tendency to position the screws in the easy-to-access regions. With navigation, the mean deviation was significantly lower at 1.5 mm (range, 0.1-3.4 mm).
  
  
  CONCLUSIONS
  Computer-assisted surgery can provide a high level of accuracy in the region of the mandibular angle, where precision is crucial for buried intraoral distraction devices.
authors.affiliation: Clinic for Craniomaxillofacial and Oral Surgery, University Hospital of Zurich, CH-8091 Zurich, Switzerland. t.luebbers@gmail.com
authors.forename: Heinz-Theo
authors.initials: HT
authors.lastname: Lübbers
authors.forename: Peter
authors.initials: P
authors.lastname: Messmer
authors.forename: Klaus Wilhelm
authors.initials: KW
authors.lastname: Grätz
authors.forename: Randy E
authors.initials: RE
authors.lastname: Ellis
authors.forename: Felix
authors.initials: F
authors.lastname: Matthews
mesh_terms: D001863:Bone Screws; D006801:Humans; D008334:Mandible / Q000601:surgery*; D008348:Manikins; D008953:Models, Anatomic; D019857:Osteogenesis, Distraction / Q000295:instrumentation*; D025321:Surgery, Computer-Assisted / Q000379:methods*