Effectiveness of surgery for sciatica with disc herniation is not substantially affected by differences in surgical incidences among three countries: results from the Danish, Swedish and Norwegian spine registries. - Lagerbäck T; Fritzell P; Hägg O; Nordvall D; Lønne G; Solberg TK; Andersen MØ; Eiskjær S; Gehrchen M; Jacobs WC; van Hooff ML; Gerdhem P (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, 2019)