The Norwegian registry for spine surgery (NORspine): cohort profile. - Mikkelsen E; Ingebrigtsen T; Thyrhaug AM; Olsen LR; Nygaard ØP; Austevoll I; Brox JI; Hellum C; Kolstad F; Lønne G; Solberg TK (European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society, 2023)