1. Faculty of Medicine, University of Marburg, 35037 Marburg, Germany
2. Department of Orthopaedics and Traumatology, University Hospital of Giessen and Marburg, 35043 Marburg, Germany
3. Department of Orthopaedics and Trauma Surgery, Lahn-Dill-Kliniken, 35683 Dillenburg, Germany
4. Department of Anesthesiology and Intensive Care Medicine, Ulm University Hospital, 89070 Ulm, Germany
5. Institute for Empirics & Statistics, FOM University of Applied Sciences, 45141 Essen, Germany