[1] Univ Bergen, Sect Orthopaed Surg, Dept Surg Sci, Bergen, Norway
[2] Forde Cent Hosp, Dept Orthopaed, N-6807 Forde, Norway
[3] Forde Cent Hosp, Dept Anaesthesiol, N-6807 Forde, Norway
[4] Sogn & Fjordane Univ Coll, Dept Hlth Studies, N-6803 Forde, Norway
[5] Forde Cent Hosp, Dept Obstet & Gynaecol, N-6807 Forde, Norway
[6] Forde Cent Hosp, Dept Phys Med & Rehabil, N-6807 Forde, Norway
[7] Forde Cent Hosp, Dept Neurol, N-6807 Forde, Norway