1. Department of Orthopedic Surgery, Hannover Medical School, Germany,
2. Department of Orthopedic Surgery, Univeristy of Duesseldorf, Germany
3. Department of Orthopedic Surgery, University of Leipzig, Germany
4. Department of Orthopedics, Hessing Stiftung Augsburg, Germany
5. Department of General Pediatrics, University of Duesseldorf, Germany