1. Spine Care Institute, Hospital for Special Surgery, New York, NY
2. Department of Orthopaedic Surgery, Showa University School of Medicine, Tokyo, Japan
3. Department of Orthopedic Surgery, University of Ulm, Ulm, Germany
4. Center for Musculoskeletal Surgery, Charité—Universitätsmedizin Berlin, Berlin, Germany
5. Weill Cornell Medicine, New York, NY
6. Department of Orthopedic Surgery and Traumatology, University Hospital Duesseldorf, Duesseldorf, Germany