1. Department for Trauma Surgery, University Medical Center Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany
2. Centrum für Muskuloskeletale Chirurgie, Universitätsmedizin Berlin, Charitéplatz1, 10117 Berlin, Germany
3. Department of Spine Surgery, Schulthess Clinic Zurich, Lenghalde 2, 8008 Zurich, Switzerland