1. Department of Orthopaedic and Trauma Surgery, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
2. St. Barbara-Hospital Gladbeck, Clinic for Orthopaedic and Trauma Surgery, Gladbeck, Germany
3. University Hospital Essen, Institute of Pharmacogenetics, University of Duisburg-Essen, Essen, Germany
4. Department of Orthopaedic and Trauma Surgery, University Hospital Freiburg, Freiburg, Germany