1. Department of Orthopaedic Surgery, University of Minnesota, Minneapolis, MN, USA
2. Department of Orthopaedic Surgery, Emory University, Atlanta, GA, USA
3. Department of Neurosurgery, Kantonsspital St.Gallen, Switzerland
4. Department of Orthopaedic Surgery, Keio University School of Medicine, Tokyo, Japan
5. Department of Neurosurgery, BG Klinikum Bergmannstrost Halle, Germany
6. Gerling Institute, Brooklyn, NY, USA
7. Department of Orthopedic Surgery, NYU Grossman School of Medicine, New York, NY, USA