title: The influence of various registration procedures upon surgical accuracy during navigated controlled petrous bone surgery.
abstract: OBJECTIVE
  The goal of this study was to investigate the dependence of surgical accuracy with a navigated controlled (NC) drill on selected registration procedures.
  
  
  METHODS
  The target registration error of the instrument and the maximum proximity to a typical high-risk structure (facial nerve) were determined within an artificial petrous bone.
  
  
  METHODS
  The studies took place in two groups: group 1, navigation bow with six integrated markers and attachment at the upper jaw, and group 2, landmark registration with four titanium microscrews. Measurement of the target registration error took place at three targets (3 titanium screws) with 20 repeated registration procedures via evaluation of the deviation between a target and the indicated position in the navigation data.
  
  
  METHODS
  For measurement of the conversion accuracy of the planned cavity, 20 petrous bone models were milled by inexperienced test subjects. The evaluation of 20 cavities was conducted via a microscope by five jurors.
  
  
  RESULTS
  Registration accuracy showed a maximum deviation between the actual position achieved and the computed position in the navigation system of 1.73 mm in group 1 and 0.93 mm in group 2. In group 1, the nerve in five of 20 cases was damaged, and a maximum penetration into the nerve of 1.5 mm (0.25 mm SD; milled beyond) was measured. In group 2, the facial nerve was not damaged at all, and a maximum deviation of 0.5 mm (0.63 mm SD; stopped before) was measured.
  
  
  CONCLUSIONS
  The results for registration and conversion accuracy are significantly better for the landmark-based registration than with the registration of the patient model with registration bow on the upper jaw.
authors.affiliation: Department of Otorhinolaryngology/Plastic Surgery, University Hospital Leipzig, Leipzig, Germany. Mathias.Hofer@medizin.uni-leipzig.de
authors.forename: Mathias
authors.initials: M
authors.lastname: Hofer
authors.forename: Elmar
authors.initials: E
authors.lastname: Dittrich
authors.forename: Christian
authors.initials: C
authors.lastname: Baumberger
authors.forename: Mario
authors.initials: M
authors.lastname: Strauss
authors.forename: Andreas
authors.initials: A
authors.lastname: Dietz
authors.forename: Tim
authors.initials: T
authors.lastname: Lüth
authors.forename: Gero
authors.initials: G
authors.lastname: Strauss
mesh_terms: D001863:Bone Screws; D002138:Calibration; D006801:Humans; D008953:Models, Anatomic; D010579:Petrous Bone / Q000033:anatomy & histology / Q000601:surgery*; D012016:Reference Values; D012984:Software; D025321:Surgery, Computer-Assisted / Q000379:methods*; D013525:Surgical Instruments