1. Spine Unit, Department of Orthopedic Surgery Zealand University Hospital Roskilde Denmark
2. Spine Surgery and Research Spine Center of Southern Denmark, Lillebaelt Hospital Middelfart Denmark
3. Department of Orthopaedic Surgery Rush University Medical Center Chicago Illinois USA
4. International Spine Research and Innovation Initiative Rush University Medical Center Chicago Illinois USA
5. Medical Research Center Oulu Oulu University Hospital and University of Oulu Oulu Finland
6. Rehabilitation Services of South Karelia Social and Health Care District Lappeenranta Finland
7. Vanderbilt University Medical Center Nashville Tennessee USA