1. Department of Orthopaedic and Trauma Surgery, University Medical Center, Albert-Ludwigs University Freiburg, Freiburg, Germany.
2. Department of Orthopaedic Sports Medicine, Klinikum rechts der Isar, Technische Universitaet Muenchen, Munich, Germany.
3. Musculoskeletal Regeneration Program, AO Research Institute, Davos, Switzerland.