title: Splint sterilization--a potential registration hazard in computer-assisted surgery.
abstract: OBJECTIVE
  Registration of preoperative targeting information for the intraoperative situation is a crucial step in computer-assisted surgical interventions. Point-to-point registration using acrylic splints is among the most frequently used procedures. There are, however, no generally accepted recommendations for sterilization of the splint. An appropriate method for the thermolabile splint would be hydrogen peroxide-based plasma sterilization. This study evaluated the potential deformation of the splint undergoing such sterilization. Deformation was quantified using image-processing methods applied to computed tomographic (CT) volumes before and after sterilization.
  
  
  METHODS
  An acrylic navigation splint was used as the study object. Eight metallic markers placed in the splint were used for registration. Six steel spheres in the mouthpiece were used as targets. Two CT volumes of the splint were acquired before and after 5 sterilization cycles using a hydrogen peroxide sterilizer. Point-to-point registration was applied, and fiducial and target registration errors were computed. Surfaces were extracted from CT scans and Hausdorff distances were derived. Effectiveness of sterilization was determined using Geobacillus stearothermophilus.
  
  
  RESULTS
  Fiducial-based registration of CT scans before and after sterilization resulted in a mean fiducial registration error of 0.74 mm; the target registration error in the mouthpiece was 0.15 mm. The Hausdorff distance, describing the maximal deformation of the splint, was 2.51 mm. Ninety percent of point-surface distances were shorter than 0.61 mm, and 95% were shorter than 0.73 mm. No bacterial growth was found after the sterilization process.
  
  
  CONCLUSIONS
  Hydrogen peroxide-based low-temperature plasma sterilization does not deform the splint, which is the base for correct computer-navigated surgery.
authors.affiliation: Center for Biomedical Engineering and Physics, Medical University Vienna, Vienna, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Figl
authors.forename: Christoph
authors.initials: C
authors.lastname: Weber
authors.forename: Ojan
authors.initials: O
authors.lastname: Assadian
authors.forename: Cyril D
authors.initials: CD
authors.lastname: Toma
authors.forename: Hannes
authors.initials: H
authors.lastname: Traxler
authors.forename: Rudolf
authors.initials: R
authors.lastname: Seemann
authors.forename: Godoberto
authors.initials: G
authors.lastname: Guevara-Rojas
authors.forename: Wolfgang P
authors.initials: WP
authors.lastname: Pöschl
authors.forename: Rolf
authors.initials: R
authors.lastname: Ewers
authors.forename: Kurt
authors.initials: K
authors.lastname: Schicho
mesh_terms: D002070:Butadienes / Q000737:chemistry; D004058:Diffusion; D004202:Disinfectants / Q000627:therapeutic use; D004867:Equipment Design; D057918:Fiducial Markers; D006801:Humans; D006861:Hydrogen Peroxide / Q000627:therapeutic use; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D019647:Oral Surgical Procedures / Q000379:methods*; D058626:Plasma Gases / Q000627:therapeutic use; D019904:Polymethyl Methacrylate / Q000737:chemistry; D013165:Splints; D013232:Steel / Q000737:chemistry; D013242:Sterilization / Q000295:instrumentation / Q000379:methods*; D020058:Styrene / Q000737:chemistry; D013499:Surface Properties; D025321:Surgery, Computer-Assisted / Q000379:methods*; D013696:Temperature; D014057:Tomography, X-Ray Computed / Q000379:methods; D014618:Vacuum
chemical_list: D002070:Butadienes; D004202:Disinfectants; D058626:Plasma Gases; D013232:Steel; D020058:Styrene; D019904:Polymethyl Methacrylate; D006861:Hydrogen Peroxide