title: Navigated versus conventional transfixation of AC joint injuries: feasibility and accuracy.
abstract: OBJECTIVE
  Transfixation of the acromioclavicular (AC) joint is a well-established technique for treating Rockwood IV to VI lesions. However, several complications, including pin breakage or pin migration due to incorrect placement, have been reported in the literature. A cadaveric study was performed to investigate whether the use of 3D navigation might improve the accuracy of AC joint transfixation.
  
  
  METHODS
  Seventeen transfixations of the AC joint (8 non-navigated, 9 navigated) were performed minimally invasively in cadaveric shoulders. For the navigated procedures, a 3D C-arm (Ziehm Vision FD Vario 3D) and a navigation system (BrainLab VectorVision) were used. Reference markers were attached to the spina scapulae, then a 3D scan was performed and the data transferred to the navigation system. Two Kirschner wires (K-wires) were placed either freehand under fluoroscopic control (in the non-navigated group) or with the use of a navigated drill guide. Radiological analysis was performed with OsiriX software, measuring the distance of the K-wires from the center of the AC joint. For statistical analysis, Student's t-test was performed, with the significance level being set to p < 0.05.
  
  
  RESULTS
  The maximum distance of the K-wires from the center of the AC joint was 5.4 ± 1.1 mm for the freehand non-navigated group and 3.1 ± 1.6 mm for the navigated group (p = 0.0054). The minimum distance of the K-wires from the AC joint center was 3.0 ± 0.6 mm for the freehand group and 1.6 ± 0.6 mm for the navigated group (p = 0.0002). The radiation time was significant lower for the freehand group (41.25 ± 20.4 seconds versus 79.5 ± 13.3 seconds for the navigated group, p = 0.004). There was no statistical difference between the groups with respect to the time required for surgery (11.25 ± 3.6 min for the freehand group and 12.6 ± 4.6 min for the navigated group; p = 0.475). In the freehand group, the AC joint was penetrated by both K-wires in 87.5% of the procedures, compared to 100% in the navigated group. Both K-wires were placed completely intraosseously in the clavicula in 50% of the procedures in the freehand group, compared to 88% in the navigated group.
  
  
  CONCLUSIONS
  Three-dimensional navigation may improve the accuracy of AC joint transfixation techniques. However, the radiation time is increased when using the navigated procedure, while the overall operation time remains comparable. Nevertheless, a 3D C-arm with a variable isocentric design is recommended for the acquisition of the shoulder scans.
authors: Trauma Department, Hannover Medical School, Hannover, Germany. stuebig.timo@mh-hannover.de
authors: Timo
authors: T
authors: Stübig
authors: Torsten
authors: T
authors: Jähnisch
authors: Maximilian
authors: M
authors: Petri
authors: Nael
authors: N
authors: Hawi
authors: Christian
authors: C
authors: Zeckey
authors: Christian
authors: C
authors: Krettek
authors: Musa
authors: M
authors: Citak
authors: Rupert
authors: R
authors: Meller
mesh_terms: D000173:Acromioclavicular Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D000368:Aged; D002102:Cadaver; D004867:Equipment Design; D005240:Feasibility Studies; D005260:Female; D005471:Fluoroscopy / Q000379:methods*; D006801:Humans; D007593:Joint Instability / Q000601:surgery*; D008297:Male; D019637:Orthopedic Procedures / Q000295:instrumentation*; D015203:Reproducibility of Results; D025321:Surgery, Computer-Assisted / Q000295:instrumentation*