1. Department of Neuromedicine and Movement Science, Norwegian University of Science and Technology, Trondheim, Norway
2. National Advisory Unit on Spinal Surgery, St Olavs Hospital, Trondheim, Norway
3. Department of Neurosurgery, St Olavs University Hospital, Trondheim, Norway
4. Department of Clinical and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway
5. Institute of Neuroscience and Physiology, Sahlgrenska Academy, Gothenburg, Sweden
6. Department of Public Health and Nursing, Norwegian University of Science and Technology, Trondheim, Norway