title: [Accuracy of fluoroscopically navigated drilling procedures at the hip].
abstract: OBJECTIVE
  Many orthopaedic procedures require an accurate drilling in bone. The outcome is frequently dependent on the geometric accuracy of this surgical step. The precision of such a procedure can be improved with the help of fluoroscopic navigation. Reliability, accuracy and benefit of this new method for the patient, as well as for the surgical staff, need to be analysed.
  
  
  METHODS
  In a standardised in vitro trial, the drilling of a 5 mm spherical lesion implanted in an artificial femoral head was performed using a navigated drill-guide and a navigated drill. In groups A and B, the distance of the tip of the drill to the center of the lesion was analysed in a 3D CT-generated model and in macroscopic cross section. Additionally, in group B the actual direction of the drill canal was measured.
  
  
  RESULTS
  The mean distance in group A was measured to be 1 mm, with all results ranging between 0 and 2.5 mm. In group B the planned direction of the canal was reproduced with a deviation of 0 degrees to 7 degrees, the target only being missed by a mean distance of 2.5 mm and a maximum of 3.5 mm. Compared to the macroscopic and 3D-CT findings, the correlation of the data calculated by the navigation system was accurate up to a difference of 4 degrees or 2 mm.
  
  
  CONCLUSIONS
  The fluoroscopically assisted freehand navigation used during the drilling of bone led to a high accuracy of three-dimensional tip placement while reducing radiation exposure to a minimum. It represents a promising and efficient application for a variety of procedures in orthopaedic surgery.
authors.affiliation: Orthopädische Universitätsklinik, UK Aachen. johnsorge@orthopaedie-aachen.de
authors.forename: J A K
authors.initials: JA
authors.lastname: Ohnsorge
authors.forename: E
authors.initials: E
authors.lastname: Schkommodau
authors.forename: D C
authors.initials: DC
authors.lastname: Wirtz
authors.forename: J E
authors.initials: JE
authors.lastname: Wildberger
authors.forename: A
authors.initials: A
authors.lastname: Prescher
authors.forename: C H
authors.initials: CH
authors.lastname: Siebert
mesh_terms: D016477:Artifacts; D005270:Femur Head / Q000000981:diagnostic imaging / Q000601:surgery*; D005471:Fluoroscopy / Q000295:instrumentation*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation; D021621:Imaging, Three-Dimensional / Q000295:instrumentation; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D012680:Sensitivity and Specificity; D025321:Surgery, Computer-Assisted / Q000295:instrumentation*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation