title: Precision of computer-assisted core decompression drilling of the femoral head.
abstract: BACKGROUND
  Osteonecrosis of the femoral head is a local destructive disease with progression into devastating stages. Left untreated it mostly leads to severe secondary osteoarthrosis and early endoprosthetic joint replacement. Core decompression by exact drilling into the ischemic areas can be performed in early stages according to Ficat or ARCO. Computer-aided surgery might enhance the precision of the drilling and lower the radiation exposure time of both staff and patients. The aim of this study was to evaluate the precision of the fluoroscopically based VectorVision navigation system in an in vitro model.
  
  
  METHODS
  Thirty sawbones were prepared with a defect filled up with a radiopaque gypsum sphere mimicking the osteonecrosis. Twenty sawbones were drilled by guidance of an intraoperative navigation system VectorVision (BrainLAB, Munich, Germany) and 10 sawbones by fluoroscopic control only.
  
  
  RESULTS
  No gypsum sphere was missed. There was a statistically significant difference regarding the three-dimensional deviation (Euclidian norm) as well as maximum deviation in x-, y- or z-direction (maximum norm) to the desired mid-point of the lesion, with a mean of 0.51 and 0.4 mm in the navigated group and 1.1 and 0.88 mm in the control group, respectively. Furthermore, significant difference was found in the number of drilling corrections as well as the radiation time needed: no second drilling or correction of drilling direction was necessary in the navigated group compared to 1.4 in the control group. The radiation time needed was less than 1 s compared to 3.1 s, respectively.
  
  
  CONCLUSIONS
  The fluoroscopy-based VectorVision navigation system shows a high feasibility of computer-guided drilling with a clear reduction of radiation exposure time and can therefore be integrated into clinical routine. The additional time needed is acceptable regarding the simultaneous reduction of radiation time.
authors.affiliation: Orthopaedic Clinic of the University of Regensburg, Asklepios Klinik Bad Abbach, Kaiser-Karl-V-Allee 3, 93077 Bad Abbach, Germany. j.beckmann@asklepios.com
authors.forename: J
authors.initials: J
authors.lastname: Beckmann
authors.forename: J
authors.initials: J
authors.lastname: Goetz
authors.forename: H
authors.initials: H
authors.lastname: Baethis
authors.forename: T
authors.initials: T
authors.lastname: Kalteis
authors.forename: J
authors.initials: J
authors.lastname: Grifka
authors.forename: L
authors.initials: L
authors.lastname: Perlick
mesh_terms: D019299:Decompression, Surgical / Q000379:methods*; D005270:Femur Head / Q000601:surgery*; D005471:Fluoroscopy; D006801:Humans; D008953:Models, Anatomic; D010020:Osteonecrosis / Q000601:surgery*; D025321:Surgery, Computer-Assisted / Q000295:instrumentation / Q000379:methods*