1. Department of Trauma Surgery; Medical University of Vienna; Waehringer Guertel 18-20 A-1090 Vienna Austria
2. Center for Medical Physics and Biomedical Engineering; Medical University of Vienna; Waehringer Guertel 18-20 A-1090 Vienna Austria
3. Division of Plastic and Hand Surgery; University Hospital Zurich; Raemistrasse 100 8091 CH-Zurich Switzerland
4. Core Unit of Medical Statistics; Medical Statistics and Informatics; BT88 University of Vienna; Spitalgasse 23 A-21090 Vienna Austria