title: Incidence of contralateral and ipsilateral anterior cruciate ligament (ACL) injury after primary ACL reconstruction and return to sport.
abstract: OBJECTIVE
  Incidence rate (IR) of an ipsilateral or contralateral injury after anterior cruciate ligament reconstruction (ACLR) is unknown. The hypotheses were that the IR of anterior cruciate ligament (ACL) injury after ACLR would be greater than the IR in an uninjured cohort of athletes and would be greater in female athletes after ACLR than male athletes.
  
  
  METHODS
  Prospective case-control study.
  
  
  METHODS
  Regional sports community.
  
  
  METHODS
  Sixty-three subjects who had ACLR and were ready to return to sport (RTS) and 39 control subjects.
  
  
  METHODS
  Second ACL injury and sex.
  
  
  METHODS
  Second ACL injury and athletic exposure (AE) was tracked for 12 months after RTS. Sixteen subjects after ACLR and 1 control subject suffered a second ACL injury. Between- and within-group comparisons of second ACL injury rates (per 1000 AEs) were conducted.
  
  
  RESULTS
  The IR of ACL injury after ACLR (1.82/1000 AE) was 15 times greater [risk ratio (RR) = 15.24; P = 0.0002) than that of control subjects (0.12/1000 AE). Female ACLR athletes demonstrated 16 times greater rate of injury (RR = 16.02; P = 0.0002) than female control subjects. Female athletes were 4 (RR = 3.65; P = 0.05) times more likely to suffer a second ACL injury and 6 times (RR = 6.21; P = 0.04) more likely to suffer a contralateral injury than male athletes.
  
  
  CONCLUSIONS
  An increased rate of second ACL injury after ACLR exists in athletes when compared with a healthy population. Female athletes suffer contralateral ACL injuries at a higher rate than male athletes and seem to suffer contralateral ACL injuries more frequently than graft re-tears. The identification of a high-risk group within a population of ACLR athletes is a critical step to improve outcome after ACLR and RTS.
authors.affiliation: Sports Health and Performance Institute, The Ohio State University Medical Center, Columbus, Ohio, USA. mark.paterno@cchmc.org
authors.forename: Mark V
authors.initials: MV
authors.lastname: Paterno
authors.forename: Mitchell J
authors.initials: MJ
authors.lastname: Rauh
authors.forename: Laura C
authors.initials: LC
authors.lastname: Schmitt
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Ford
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Hewett
mesh_terms: D000293:Adolescent; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D000070598:Anterior Cruciate Ligament Injuries; D001265:Athletic Injuries / Q000453:epidemiology* / Q000601:surgery*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D011446:Prospective Studies; D012008:Recurrence; D018570:Risk Assessment; D012737:Sex Factors