1. Department of Orthopaedic Surgery, University of Bonn, Sigmund-Freud-Strasse 25, D-53105 Bonn, Germany.
2. Orthopaedic Department, Landeskraukenhaus Feldkirch, Cannagasse 47, A-6807 Feldkirch, Austria.
3. Orthopaedic Department, Annastift Hannover, Anna-von-Borries-Strasse 1–7, D-30625 Hannover, Germany.