Correction to: High prevalence of symptomatic spinal stenosis in Norwegian adults with achondroplasia: a population-based study. - Fredwall SO; Steen U; de Vries O; Rustad CF; Eggesbø HB; Weedon-Fekjær H; Lidal IB; Savarirayan R; Månum G (Orphanet journal of rare diseases, 2020)