title: A non-response analysis of 2-year data in the Swedish Knee Ligament Register.
abstract: OBJECTIVE
  To analyse the non-response group in the Swedish Knee Ligament Register (SKLR).
  
  
  METHODS
  All 3588 patients in the SKLR who had undergone anterior cruciate ligament surgery in 2010 were included. Respondents (n = 1865) and non-respondents (n = 1723) at the 2-year follow-up survey were assessed for potential differences in demographics and baseline data. KOOS/EQ5D questionnaires were sent to non-respondents together with a non-response survey asking questions about reasons for dropout.
  
  
  RESULTS
  Respondents had a significantly higher mean age (27.8 years, range 9-64) than non-respondents (25.9 years, range 12-65) (p < 0.001). Women had a higher rate of response 927 (62.8 %) than men 938 (44.4 %) even after correction for age (p < 0.001). Alpine/telemark skiing was the only activity at time of injury that showed higher rate of respondents 280 (62.5 %) compared to non-respondents 168 (37.5 %) (p < 0.001). No differences in EQ5D at 2-year follow-up were found between the groups. The change in KOOS from 0 to 2 years showed difference in the subscale pain with 9.4 in the response group compared to 6.3 in the late-response group (p < 0.05) and the subscale quality of life with a difference of 26.1 and 22.6, respectively (p < 0.05). The non-response questionnaire showed shortcomings in patient information regarding the importance of the SKLR.
  
  
  CONCLUSIONS
  The register is valid concerning baseline surgical data, but higher age, female gender and perhaps higher socioeconomic status improve the response rates. KOOS showed small differences of questionable clinical significance. The SKLR patient information could be improved.
  
  
  METHODS
  Retrospective comparative study, Level III.
authors.affiliation: Department of Molecular Medicine and Surgery, Stockholm Sports Trauma Research Center, Karolinska Institutet, 114 86, Stockholm, Sweden.
authors.forename: John
authors.initials: J
authors.lastname: Reinholdsson
authors.affiliation: Department of Molecular Medicine and Surgery, Stockholm Sports Trauma Research Center, Karolinska Institutet, 114 86, Stockholm, Sweden. jesper.kraus.schmitz@ki.se.|Department of Orthopaedics, Visby Hospital, 621 84, Visby, Sweden. jesper.kraus.schmitz@ki.se.
authors.forename: Jesper
authors.identifier: http://orcid.org/0000-0002-6543-9714
authors.initials: J
authors.lastname: Kraus-Schmitz
authors.affiliation: Department of Molecular Medicine and Surgery, Stockholm Sports Trauma Research Center, Karolinska Institutet, 114 86, Stockholm, Sweden.|Capio Artro Clinic, Valhallavägen 91, 114 86, Stockholm, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Forssblad
authors.affiliation: Department of Molecular Medicine and Surgery, Stockholm Sports Trauma Research Center, Karolinska Institutet, 114 86, Stockholm, Sweden.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Edman
authors.affiliation: Department of Molecular Medicine and Surgery, Stockholm Sports Trauma Research Center, Karolinska Institutet, 114 86, Stockholm, Sweden.
authors.forename: Martina
authors.initials: M
authors.lastname: Byttner
authors.affiliation: Department of Molecular Medicine and Surgery, Stockholm Sports Trauma Research Center, Karolinska Institutet, 114 86, Stockholm, Sweden.|Capio Artro Clinic, Valhallavägen 91, 114 86, Stockholm, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Stålman
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000070598:Anterior Cruciate Ligament Injuries / Q000601:surgery*; D059549:Anterior Cruciate Ligament Reconstruction; D002648:Child; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D010352:Patient Dropouts / Q000706:statistics & numerical data*; D011788:Quality of Life; D012042:Registries; D012189:Retrospective Studies; D011795:Surveys and Questionnaires; D013548:Sweden; D055815:Young Adult
keywords: ACL reconstruction; Non-response analysis; Outcome data; Register