1. University of Ulm, Ulm, Germany
2. Ludwig Maximilian University of Munich, Munich, Germany
3. Orthopedic Clinic Munich-Harlaching, Munich, Germany
4. AO Foundation, Clinical Investigation and Documentation (AOCID), Zurich, Switzerland
5. University of Tennessee, Semmes-Murphey Neurologic and Spine Institute, Memphis, TN, USA
6. Weill Cornell Medical College, New York Presbyterian Hospital, New York, NY, USA