1. Department of General Practice and Health Services Research, University Hospital of Heidelberg, Vossstrasse 2, 69115 Heidelberg, Germany
2. Institute of Family Medicine, University of Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany
3. Orthopedic Practice, Wilhelm-Becker-Strasse 11 b, 75179 Pforzheim, Germany
4. Institute of General Practice, University Hospital of Tübingen, Österbergstraße 9, 72074 Tübingen, Germany