title: Incidence of Second Anterior Cruciate Ligament Tears (1990-2000) and Associated Factors in a Specific Geographic Locale.
abstract: BACKGROUND
  Second anterior cruciate ligament (ACL) tears after reconstruction occur at a reported rate of 20% to 30%. This high frequency indicates that there may be factors that predispose an athlete to graft failure and ACL tears of the contralateral knee.
  
  
  OBJECTIVE
  To determine the incidence of second ACL injuries in a geographic population-based cohort over a 10-year observation period.
  
  
  METHODS
  Descriptive epidemiological study.
  
  
  METHODS
  International Classification of Diseases, 9th Revision (ICD-9) codes relevant to the diagnosis of an ACL tear and the procedure code for ACL reconstruction were searched across the Rochester Epidemiology Project, a multidisciplinary county database, between the years of 1990 and 2000. This cohort of patients was tracked for subsequent ACL injuries through December 31, 2015. The authors identified 1041 patients with acute, isolated ACL tears. These patients were stratified by primary and secondary tears, sex, age, activity level, side of injury, sex by side of injury, and graft type.
  
  
  RESULTS
  Of the 1041 unique patients with a diagnosed ACL tear in Olmsted County, Minnesota, from 1990 to 2000, there were 66 (6.0%) second ACL tears; 66.7% of these tears occurred on the contralateral side. A second ACL injury was influenced by graft type ( P < .0001), election of ACL reconstruction ( P = .0060), and sex by side of injury ( P = .0072). Nonparametric analysis of graft disruption by graft type demonstrated a higher prevalence of second ACL tears with allografts compared with hamstring ( P = .0499) or patellar tendon autografts ( P = .0012).
  
  
  CONCLUSIONS
  The incidence of second ACL tears in this population-based cohort was 6.0%, with 66.7% of these tears occurring on the contralateral side from the original injury. There was a high population incidence of second ACL injuries in female patients younger than age 20 years. The utilization of patellar tendon autografts significantly reduced the risk of second ACL injuries compared with allografts or hamstring autografts in this cohort.
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota, USA.|Sports Medicine Center, Mayo Clinic, Rochester, Minnesota, USA.|Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Nathan D
authors.initials: ND
authors.lastname: Schilaty
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota, USA.|Sports Medicine Center, Mayo Clinic, Rochester, Minnesota, USA.|Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Nathaniel A
authors.initials: NA
authors.lastname: Bates
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Sanders
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota, USA.|Sports Medicine Center, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Krych
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota, USA.|Sports Medicine Center, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Stuart
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota, USA.|Sports Medicine Center, Mayo Clinic, Rochester, Minnesota, USA.|Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA.|Department of Physical Medicine & Rehabilitation, Mayo Clinic, Rochester, Minnesota, USA.|Department of Biomedical Engineering, The Ohio State University, Columbus, Ohio, USA.
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Hewett
mesh_terms: D000293:Adolescent; D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries / Q000145:classification / Q000453:epidemiology* / Q000209:etiology; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D008910:Minnesota / Q000453:epidemiology; D017847:Patellar Ligament / Q000601:surgery; D012307:Risk Factors; D014182:Transplantation, Autologous / Q000706:statistics & numerical data; D055815:Young Adult
keywords: anterior cruciate ligament (ACL); epidemiology; graft tear; incidence; secondary