1. Department of Surgical Sciences, Uppsala University Hospital, Uppsala, Sweden;
2. Neuro-Orthopaedic Center, Jönköping, and Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden;
3. Department of Radiology, Uppsala University Hospital, Uppsala, Sweden; and
4. Department of Learning, Informations, Management and Ethics (LIME), Medical Management Center, Health Economics and Health Evaluation Research Group, Karolinska Institutet, Stockholm and Center for Spine Surgery in Stockholm, Sophiahemmets Sjukhus, Stockholm, Sweden