1. Dreifaltigkeits-Krankenhaus, Cologne, Germany
2. Department of Trauma and Orthopaedic Surgery, University of Witten/Herdecke, Cologne Merheim Medical Center, Cologne, Germany
3. Department of Gynecology and Obstetrics, Hospital Dormagen, Dormagen, Germany
4. IFOM, Institute for Research in Operative Medicine, University of Witten/Herdecke, Cologne Merheim Medical Center, Cologne, Germany