title: Effect of one- and two-pin reference anchoring systems on marker stability during total knee arthroplasty computer navigation.
abstract: OBJECTIVE
  This study investigated different infrared marker reference base attachments in cadaveric bone and their effects on alignment outcome when different loads were applied.
  
  
  METHODS
  Five cadaveric specimens were used to test four reference base attachments: a locking one-pin (4.0 mm and 5.0 mm pins) and a two-pin clamp (Hoffman fixator, 3.0 mm and 5.0 mm pins, Stryker Inc., NJ). Each was tested with metaphyseal and diaphyseal attachments. A navigation system (Stryker Navigation, MI) was used for testing with applied incremental loads and torques (65 N and 1.0 Nm) to the different reference base configurations.
  
  
  RESULTS
  With 65 N the maximum change in distance to a verification point was 4.3 + 1.6 mm with the 4.0 mm locking pin in metaphyseal bone. No difference in verification point distances was found with any two-pin configuration. Alignment changes greater than 4 degrees resulted with the 65 N loads and a 4.0 mm pin.
  
  
  CONCLUSIONS
  The results may prove beneficial in comparing the resulting error of different manufacturers and allow surgeons to realize the variability that may occur through incidental contact in the operating room.
authors.affiliation: Department of Orthopaedic Surgery, University of Virginia, Charlottesville, 22908, USA. wmm4n@virginia.edu
authors.forename: William M
authors.initials: WM
authors.lastname: Mihalko
authors.forename: Thomas
authors.initials: T
authors.lastname: Duquin
authors.forename: Jethro R
authors.initials: JR
authors.lastname: Axelrod
authors.forename: Mary
authors.initials: M
authors.lastname: Bayers-Thering
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Krackow
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation*; D002102:Cadaver; D005269:Femur / Q000601:surgery; D006801:Humans; D066298:In Vitro Techniques; D016268:Internal Fixators; D015203:Reproducibility of Results; D025321:Surgery, Computer-Assisted / Q000379:methods*