title: Comparison of different registration methods for surgical navigation in cranio-maxillofacial surgery.
abstract: BACKGROUND
  Surgical navigation requires registration of the pre-operative image dataset with the patient in the operation theatre. Various marker and marker-free registration techniques are available, each bearing an individual level of precision and clinical practicability. In this study the precision of four different registration methods in a maxillofacial surgical setting is analyzed.
  
  
  METHODS
  A synthetic full size human skull model was registered with its computer tomography-dataset using (a) a dentally mounted occlusal splint, (b) the laser surface scanning, (c) five facial bone implants and (d) a combination of dental splint and two orbital bone implants. The target registration error was computed for 170 landmarks spread over the entire viscero- and neurocranium in 10 repeats using the VectorVision2 (BrainLAB AG, Heimstetten, Germany) navigation system. Statistical and graphical analyses were performed by anatomical region.
  
  
  RESULTS
  An average precision of 1mm was found for the periorbital region irrespective of registration method (range 0.6-1.1mm). Beyond the mid-face, precision linearly decreases with the distance from the reference markers. The combination of splint with two orbital bone markers significantly improved precision from 1.3 to 0.8mm (p<0.001) on the viscerocranium and 2.3-1.2mm (p<0.001) on the neurocranium.
  
  
  CONCLUSIONS
  An occlusal splint alone yields poor precision for navigation beyond the mid-face. The precision can be increased by combining an occlusal splint with just two bone implants inserted percutaneously on the lateral orbital rim of each side.
authors.affiliation: Clinic for Cranio-Maxillofacial Surgery, University Hospital of Zurich, Frauenklinikstrasse 24, CH-8091 Zurich, Switzerland. heinz-theo.luebbers@usz.ch
authors.forename: Heinz-Theo
authors.initials: HT
authors.lastname: Luebbers
authors.forename: Peter
authors.initials: P
authors.lastname: Messmer
authors.forename: Joachim Anton
authors.initials: JA
authors.lastname: Obwegeser
authors.forename: Roger Arthur
authors.initials: RA
authors.lastname: Zwahlen
authors.forename: Ron
authors.initials: R
authors.lastname: Kikinis
authors.forename: Klaus Wilhelm
authors.initials: KW
authors.lastname: Graetz
authors.forename: Felix
authors.initials: F
authors.lastname: Matthews
mesh_terms: D001863:Bone Screws; D003287:Contrast Media; D005147:Facial Bones / Q000601:surgery*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007834:Lasers; D008953:Models, Anatomic; D017090:Occlusal Splints; D009915:Orbit; D010347:Patient Care Planning; D019047:Phantoms, Imaging; D025321:Surgery, Computer-Assisted; D014057:Tomography, X-Ray Computed
chemical_list: D003287:Contrast Media