1. Division of Plastic- Reconstructive- and Handsurgery, Kantonsspital Aarau, Tellstrasse, CH 5001 Aarau, Switzerland
2. Orthopedic Department, Balgrist University Hospital, Forchstrasse 340, 8008 Zürich, Switzerland
3. University of Zürich, Biostatics unit, Institute for Social- and Preventive Medicine, Hirschengraben 84, 8001 Zürich, Switzerland