title: Incidence of Second ACL Injuries 2 Years After Primary ACL Reconstruction and Return to Sport.
abstract: BACKGROUND
  The incidence of second anterior cruciate ligament (ACL) injuries in the first 12 months after ACL reconstruction (ACLR) and return to sport (RTS) in a young, active population has been reported to be 15 times greater than that in a previously uninjured cohort. There are no reported estimates of whether this high relative rate of injury continues beyond the first year after RTS and ACLR.
  
  
  OBJECTIVE
  The incidence rate of a subsequent ACL injury in the 2 years after ACLR and RTS would be less than the incidence rate reported within the first 12 months after RTS but greater than the ACL injury incidence rate in an uninjured cohort of young athletes.
  
  
  METHODS
  Cohort study; Level of evidence, 2.
  
  
  METHODS
  Seventy-eight patients (mean age, 17.1 ± 3.1 years) who underwent ACLR and were ready to return to a pivoting/cutting sport and 47 controls (mean age, 17.2 ± 2.6 years) who also participated in pivoting/cutting sports were prospectively enrolled. Each participant was followed for injury and athlete exposure (AE) data for a 24-month period after RTS. Twenty-three ACLR and 4 control participants suffered an ACL injury during this time. Incidence rate ratios (IRRs) were calculated to compare the rates (per 1000 AEs) of ACL injury in athletes in the ACLR and control groups. For the ACLR group, similar comparisons were conducted for side of injury by sex.
  
  
  RESULTS
  The overall incidence rate of a second ACL injury within 24 months after ACLR and RTS (1.39/1000 AEs) was nearly 6 times greater (IRR, 5.71; 95% CI, 2.0-22.7; P = .0003) than that in healthy control participants (0.24/1000 AEs). The rate of injury within 24 months of RTS for female athletes in the ACLR group was almost 5 times greater (IRR, 4.51; 95% CI, 1.5-18.2; P = .0004) than that for female controls. Although only a trend was observed, female patients within the ACLR group were twice as likely (IRR, 2.43; 95% CI, 0.8-8.6) to suffer a contralateral injury (1.13/1000 AEs) than an ipsilateral injury (0.47/1000 AEs). Overall, 29.5% of athletes suffered a second ACL injury within 24 months of RTS, with 20.5% sustaining a contralateral injury and 9.0% incurring a retear injury of the ipsilateral graft. There was a trend toward a higher proportion of female participants (23.7%) who suffered a contralateral injury compared with male participants (10.5%) (P = .18). Conversely, for ipsilateral injuries, the incidence proportion between female (8.5%) and male (10.5%) participants was similar.
  
  
  CONCLUSIONS
  These data support the hypothesis that in the 24 months after ACLR and RTS, patients are at a greater risk to suffer a subsequent ACL injury compared with young athletes without a history of ACL injuries. In addition, the contralateral limb of female patients appears at greatest risk.
authors.affiliation: Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA Division of Occupational Therapy and Physical Therapy, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA Department of Pediatrics, College of Medicine, University of Cincinnati, Cincinnati, Ohio, USA mark.paterno@cchmc.org.
authors.forename: Mark V
authors.initials: MV
authors.lastname: Paterno
authors.affiliation: Doctor of Physical Therapy Program, San Diego State University, San Diego, California, USA.
authors.forename: Mitchell J
authors.initials: MJ
authors.lastname: Rauh
authors.affiliation: Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA Division of Physical Therapy, School of Health and Rehabilitation Sciences, The Ohio State University, Columbus, Ohio, USA Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.
authors.forename: Laura C
authors.initials: LC
authors.lastname: Schmitt
authors.affiliation: Department of Physical Therapy, School of Health Sciences, High Point University, High Point, North Carolina, USA.
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Ford
authors.affiliation: Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA Department of Pediatrics, College of Medicine, University of Cincinnati, Cincinnati, Ohio, USA Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA Department of Orthopaedic Surgery, College of Medicine, and the Departments of Biomedical Engineering and Rehabilitation Sciences, University of Cincinnati, Cincinnati, Ohio, USA Ohio State University Sports Medicine, Sports Health & Performance Institute, Departments of Orthopaedic Surgery, Family Medicine, Physiology and Cell Biology, College of Medicine, and the 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; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D056352:Athletes; D016022:Case-Control Studies; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D007718:Knee Injuries / Q000453:epidemiology* / Q000601:surgery; D008137:Longitudinal Studies; D008297:Male; D011446:Prospective Studies; D000068958:Return to Sport / Q000706:statistics & numerical data*; D013177:Sports; D055815:Young Adult
keywords: anterior cruciate ligament reconstruction; incidence rate; second injury; subsequent injury
references.citation: J Bone Joint Surg Am. 2011 Jun 15;93(12):1159-65
references.pmid: 21776554
references.citation: Am J Sports Med. 2012 Mar;40(3):595-605
references.pmid: 22184280
references.citation: Am J Sports Med. 2007 Jul;35(7):1131-4
references.pmid: 17452511
references.citation: Clin J Sport Med. 2007 Jul;17(4):258-62
references.pmid: 17620778
references.citation: J Athl Train. 2006 Apr-Jun;41(2):207-15
references.pmid: 16791309
references.citation: Am J Sports Med. 1994 Sep-Oct;22(5):632-44
references.pmid: 7810787
references.citation: Phys Ther. 2000 Mar;80(3):251-60
references.pmid: 10696152
references.citation: Arthroscopy. 2005 Aug;21(8):948-57
references.pmid: 16084292
references.citation: J Orthop Sports Phys Ther. 2011 Aug;41(8):553-9
references.pmid: 21808100
references.citation: Am J Sports Med. 2010 Nov;38(11):2233-9
references.pmid: 20610771
references.citation: J Pediatr Orthop. 2004 Nov-Dec;24(6):623-8
references.pmid: 15502559
references.citation: Am J Sports Med. 2007 Apr;35(4):564-74
references.pmid: 17261567
references.citation: Am J Sports Med. 1999 May-Jun;27(3):294-9
references.pmid: 10352762
references.citation: Am J Sports Med. 2005 Jul;33(7):1003-10
references.pmid: 15888716
references.citation: Sports Med. 2004;34(4):269-80
references.pmid: 15049718
references.citation: J Athl Train. 2002 Sep;37(3):262-268
references.pmid: 12937583
references.citation: Am J Sports Med. 2005 Apr;33(4):492-501
references.pmid: 15722287
references.citation: Am J Sports Med. 1996 Sep-Oct;24(5):684-7
references.pmid: 8883693
references.citation: Am J Sports Med. 2012 Jan;40(1):41-8
references.pmid: 21946441
references.citation: Arthroscopy. 2007 Dec;23(12):1320-1325.e6
references.pmid: 18063176
references.citation: Am J Sports Med. 2011 Mar;39(3):538-43
references.pmid: 21098818
references.citation: J Athl Train. 2007 Oct-Dec;42(4):486-94
references.pmid: 18176621
references.citation: J Bone Joint Surg Am. 1997 Oct;79(10):1556-76
references.pmid: 9378743
references.citation: Am J Sports Med. 2010 Oct;38(10):1968-78
references.pmid: 20702858
references.citation: Cochrane Database Syst Rev. 2005 Apr 18;(2):CD001356
references.pmid: 15846618
references.citation: Sports Health. 2011 Jan;3(1):73-81
references.pmid: 23015994
references.citation: Instr Course Lect. 2002;51:315-24
references.pmid: 12064119
references.citation: Am J Sports Med. 1999 Nov-Dec;27(6):699-706
references.pmid: 10569353
references.citation: Knee Surg Sports Traumatol Arthrosc. 2009 Aug;17(8):859-79
references.pmid: 19506834
references.citation: Am J Sports Med. 2006 Mar;34(3):490-8
references.pmid: 16382007
references.citation: J Orthop Sports Phys Ther. 2012 Sep;42(9):750-9
references.pmid: 22813542
references.citation: Clin J Sport Med. 2012 Mar;22(2):116-21
references.pmid: 22343967
references.citation: Am J Sports Med. 2008 Aug;36(8):1476-83
references.pmid: 18658019
references.citation: Am J Sports Med. 2001 Mar-Apr;29(2):196-200
references.pmid: 11292045