[1] Univ Helsinki, Dept Neurosurg, Helsinki, Finland
[2] Helsinki Univ Hosp, Helsinki, Finland
[3] Univ Helsinki, Finnish Ctr Evidence Based Orthoped FICEBO, Helsinki, Finland
[4] Univ Helsinki, Dept Orthopaed & Traumatol, Helsinki, Finland
[5] Turku Univ Hosp, Dept Neurosurg, Div Clin Neurosci, Turku, Finland
[6] Univ Turku, Turku, Finland
[7] Kuopio Univ Hosp, Dept Neurosurg, Kys, Finland
[8] Univ Eastern Finland, Kys, Finland
[9] Univ Oulu, Neurosurg, Unit Clin Neurosci, Oulu, Finland
[10] Med Res Ctr, Oulu, Finland
[11] Helsinki Univ Hosp, Div Anaesthesiol, Dept Anaesthesiol Intens Care & Pain Med, Helsinki, Finland
[12] Orthopaed Hosp Orton, Dept Anaesthesia, Helsinki, Finland