[1] Oslo Metropolitan Univ, Dept Physiotherapy, Oslo, Norway
[2] Oslo Univ Sykehus Ulleval, Res & Commun Unit Musculoskeletal Hlth, Oslo, Norway
[3] Oslo Metropolitan Univ, Dept Nursing & Hlth Promot, Oslo, Norway
[4] Oslo Univ Sykehus Ulleval, Res & Commun Unit Musculoskeletal Disorders, Oslo, Norway
[5] Hosp Ostfold HF, Dept Rheumatol, Gralum, Norway
[6] Nasjonalt folkehelseinst, Div Hlth Serv, Oslo, Norway
[7] Res & Commun Unit Musculoskeletal Hlth FORMI, Oslo, Norway
[8] Oslo Metropolitan Univ, Fac Hlth Sci, Oslo, Norway
[9] Univ Hosp North Norway, Neurosurg, Tromso, Norway
[10] North Norway Hlth Author, Norwegian Registry Spine Surg, Tromso, Norway
[11] Oslo Univ Hosp, Dept Neurol, Oslo, Norway
[12] Oslo Univ Hosp, FORMI, Oslo, Norway
[13] Univ Oslo, Fac Med, Oslo, Norway