1. Center for Musculoskeletal Surgery, Charité - Universitätsmedizin Berlin, Berlin, Germany
2. Department of Orthopaedic, Trauma and Plastic Surgery, University Hospital Leipzig, Leipzig, Germany
3. University Comprehensive Spine Center, University Center for Orthopedics, Traumatology and Plastic Surgery, Universitätsklinikum Carl Gustav Carus, Dresden, Germany
4. Center for Spinal and Scoliosis Surgery, Malteser Waldkrankenhaus St Marien gGmbH, Erlangen, Germany
5. Department of Orthopedics and Traumatology, Paracelsus Private Medical University Nuremberg, Nuremberg, Germany