title: Comorbidities in Patients With Anterior Cruciate Ligament Reconstruction Compared With Matched Controls Without Anterior Cruciate Ligament Injury From Danish Registries.
abstract: OBJECTIVE
  To describe and compare comorbidity among anterior cruciate ligament (ACL)-reconstructed patients and a gender- and age-matched group without ACL injury. Furthermore, we sought to evaluate the impact of comorbid diseases on the risk of ACL revision surgery.
  
  
  METHODS
  This case-control study included 13,443 unilateral primary ACL-reconstructed patients from the Danish Knee Ligament Reconstruction Register matched on gender and age with a comparison group without ACL injury. Information on medical comorbid conditions was obtained from the Danish National Registry of Patients. The prevalence of all comorbid conditions was described for ACL-reconstructed patients and the comparison group in terms of (1) the Charlson Comorbidity Index (CCI); (2) International Classification of Diseases, Tenth Revision disease chapters; and (3) more common chronic diseases in a younger population. Finally, we assessed the risk of ACL revision surgery according to the more common chronic diseases in a younger population, using Cox regression analysis.
  
  
  RESULTS
  Although we found a large variety of diseases present among ACL-reconstructed patients, the percentage of patients with a CCI equal to 0 was high in both groups. ACL-reconstructed patients generally had a slightly lower prevalence of almost all International Classification of Diseases, Tenth Revision-classified comorbid disease groups compared with the comparison group without ACL injury. As expected, the prevalence of most diseases increased slightly with rising age. Furthermore, we found that having back pain or diseases of the back did alter the risk of revision surgery.
  
  
  CONCLUSIONS
  ACL-reconstructed patients are found to be generally healthy individuals with a low prevalence of serious and chronic diseases compared with an age- and gender-matched control group from the general population. A large variety of diseases are present in the ACL-reconstructed group but with very low prevalence rates and low CCIs, indicating that the severity of their illness is limited.
  
  
  METHODS
  Level III, case-control study.
authors.affiliation: Division of Sportstrauma, Department of Orthopaedic Surgery, Aarhus University Hospital, Aarhus, Denmark; Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark. Electronic address: lenerahr@dadlnet.dk.
authors.forename: Lene
authors.initials: L
authors.lastname: Rahr-Wagner
authors.affiliation: Department of Orthopaedic Surgery, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Theis Muncholm
authors.initials: TM
authors.lastname: Thillemann
authors.affiliation: Division of Sportstrauma, Department of Orthopaedic Surgery, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Martin
authors.initials: M
authors.lastname: Lind
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Alma Becic
authors.initials: AB
authors.lastname: Pedersen
mesh_terms: D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction; D016022:Case-Control Studies; D002908:Chronic Disease / Q000453:epidemiology; D015897:Comorbidity; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000453:epidemiology* / Q000601:surgery; D008297:Male; D012042:Registries; D012307:Risk Factors; D055815:Young Adult