title: The virtual isocentric aiming device: a new mechanical targeting concept.
abstract: BACKGROUND
  Minimally invasive fracture fixation can be technically demanding, especially in body regions characterised by complex bone anatomy and the presence of a significant amount of soft tissue. Hence, this procedure is associated with a high risk of implant malposition. As a consequence, radiation exposure to the patient and the surgeon increases within surgery.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the practicability and accuracy of a newly designed virtual isocentric aiming device (VIAD) as compared to the more traditional approach of the freehand insertion of K-wires. Forty polyurethane foam blocks were prepared with a reference wire (W                            (                               R                            )) and covered by sponge material to simulate soft tissue.
  
  
  METHODS
  For the sake of comparison, both an untrained and an experienced surgeon were selected for the study and were advised to insert a K-wire into the foam block so as to have the same axis as the W                            (                               R                            ) using both of the aforementioned methods. The clinical parameters of both techniques were analysed. In addition, 3-D precision data computed using CT-scans of each sample were evaluated. Device adjustment prolonged the time required for the experienced surgeon to complete the VIAD procedure when compared to the freehand method. However, using the VIAD, the number of plane changes made to the image intensifier in addition to the number of drill trials was significantly reduced by each surgeon. Furthermore, mechanical K-wire navigation leads to a decrease in the radiation exposure time for the untrained surgeon.
  
  
  RESULTS
  VIAD-guided K-wires revealed a significant lower angle of deviation in relation to W                            (                               R                            ). Tip-to-tip and tip-to-axis distances displayed a trend indicating reduced displacement values as well. The VIAD allows for simple wire insertion with increased precision as well as a reduction in radiation exposure, plane changes of the image intensifier and the number of drill trials compared to the freehand method.
  
  
  CONCLUSIONS
  The VIAD also satisfies the demand for a less invasive technique. Prospectively, the VIAD represents a useful and cost-effective alternative to the freehand method.
authors.affiliation: Department of Trauma Surgery, Employers' Liability Insurance Association Hospital Bergmannstrost, Merseburger Straße 165, 06112 Halle (Saale), Germany. thomasmendel@hotmail.com
authors.forename: Thomas
authors.initials: T
authors.lastname: Mendel
authors.forename: Markus
authors.initials: M
authors.lastname: Hänni
authors.forename: Boyko
authors.initials: B
authors.lastname: Gueorguiev
authors.forename: David
authors.initials: D
authors.lastname: Wohlrab
authors.forename: Gunther Olaf
authors.initials: GO
authors.lastname: Hofmann
mesh_terms: D001864:Bone Wires; D004867:Equipment Design; D005592:Fracture Fixation / Q000295:instrumentation* / Q000379:methods*; D055641:Mathematical Concepts; D025321:Surgery, Computer-Assisted / Q000295:instrumentation*