Full Length Article The epidemiology of scaphoid fractures in Sweden: a nationwide registry study Elin M. Swa ¨rd 1 , Thorsten U. Schriever 1 , Mikael A. Franko 1 , Anders C. Bjo ¨rkman 2 and Maria K. Wilcke 1 Abstract The epidemiology of scaphoid fractures has been described in limited populations, and incidence reports have been inconsistent. We investigated the nationwide incidence of scaphoid fractures by evaluating data on 34,377 patients in the Swedish National Patient Register for the years 2006–2015 regarding diagnosis, age, sex and treatment. The data were validated in 300 random patients, and incidence rates were adjusted accordingly. Forty-one per cent of the initially diagnosed fractures were false positives. The adjusted true fracture incidence rate was 22 per 100,000 person-years. During the decade studied incidence rates decreased in younger men and increased in middle-aged women. The incidence of surgical treatment vs. non-operative treatment did not change over time. Men were treated surgically more often than women (6% vs. 3%) and had a greater risk for nonunion (3% vs. 1%). Keywords Scaphoid fracture, epidemiology, incidence, nonunion, validation Date received: 8th November 2018; revised: 18th March 2019; accepted: 21st April 2019 Introduction The epidemiology of scaphoid fractures has been described in limited populations or over short time periods. Yearly incidence rates range from 12 to 121 per 100,000 person-years (Duckworth et al., 2012; Garala et al., 2016; Holloway et al., 2015; Hove, 1999; Larsen et al., 1992; Wolf et al., 2009). The Swedish National Patient Register (NPR) con- tains information regarding all out- and inpatient care, as well as all surgical interventions. Reporting to the inpatient register has been compulsory in both public and private settings since 1987 and has shown high validity (Ludvigsson et al., 2011). Reporting to the outpatient register has been compulsory since 2001. The validity of the outpatient data has been tested for rheumatoid arthritis (Waldenlind et al., 2014) and bullous pemphigoid (Gro ¨nhagen et al., 2017) and showed high validity. However, the validity of the outpatient register for any trauma diagnosis has not yet been examined. The first aim of this study was to describe the epi- demiology and treatment of scaphoid fractures in Sweden during the period 2005–2015 and to validate the NPR data for this diagnosis. The second aim was to investigate the incidence of nonunion after a scaphoid fracture. Methods Data extraction Data were extracted from the NPR for the years 2005–2015. The patients were identified with the International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10) code for a scaphoid fracture (S62.00/01). The identifying event was the first time an individual was reported with a scaphoid fracture during the study period. The first 12 months (i.e. year 2005) were regarded as a wash-out period to avoid includ- ing patients during follow-up after a scaphoid frac- ture. Hence, patients with a scaphoid fracture during the period 2006–2015 were not included if a scaphoid fracture was recorded during 2005. Patients with an acute fracture and a simultaneous record of a 1 Department of Clinical Science and Education, Karolinska Institute, Stockholm, Sweden 2 Department of Translational Medicine – Hand Surgery, Lund University, Lund, Sweden Corresponding Author: Elin Swa ¨rd, Handkirurgiska klinken So ¨dersjukhuset, Sjukhusbacken 10, 11883 Stockholm, Sweden. Email: elin.sward@sll.se Journal of Hand Surgery (European Volume) 0(0) 1–5 ! The Author(s) 2019 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/1753193419849767 journals.sagepub.com/home/jhs