1. Department of Neurosurgery, Geisinger Neuroscience Institute, Danville, Pennsylvania, USA;
2. Department of Neurological Surgery, The University of Washington, Seattle, Washington, USA;
3. Department of Orthopedics and Trauma Surgery, Faculty of Medicine, University of Cologne, Cologne, Germany;
4. Department of Neurosurgery, Houston Methodist Neurological Institute, Houston, Texas, USA;
5. Kentucky College of Osteopathic Medicine, University of Pikeville, Pikeville, Kentucky, USA;
6. Geisinger Commonwealth School of Medicine, Scranton, Pennsylvania, USA;
7. Department of Neurosurgery, University of Michigan, Ann Arbor, Michigan, USA;
8. University Hospital Cologne, Cologne, Germany;
9. Department of Orthopedics and Trauma Surgery, Krankenhaus Porz am Rhein, University of Cologne, Cologne, Germany;
10. Department of Orthopedic Surgery, Vanderbilt University, Nashville, Tennessee, USA;
11. Golden State Orthopedics and Spine, Oakland, California, USA;
12. Department of Neurosurgery, Warren Alpert School of Medicine of Brown University, Providence, Rhode Island, USA