Monday, March 17, 2014

Are You At Risk For A 2nd ACL Injury?

Anterior Cruciate Ligament (ACL) injuries are one of the sports injuries that most of us know about.  It is one of the sports injuries that get the most press and media attention.  Why?  Although there are a lot of reasons for that, a lot of it has to do with:

  • Prevalence and cost of the injury – over 250,000 in the US alone at average cost of $25,000 to $50,000, this is a $5B health care cost annually
  • Time on the disabled list – due to the injury, surgery and rehabilitation, it is one of the injuries that results in the largest amount of time on the DL for players
  • Impact on future performance – although percentage of players that return to play is debatable, the percentage that return at the previous level of play is ~40%.
  • Impact on future joint health – studies show 79% have osteoarthritis in 12 years and 20% have second ACL injury in 2 years.

When discussing ACL injuries, it is important to consider the mechanism of injury.  For our purposes, we will classify these as:

  • Contact ACL Injury – ACL injury that results from contact with another player or object
  • Non-contact ACL injury – where there is no contact with another player.  These account for the majority of ACL injuries and are the ones targeted by most ACL Injury Prevention programs.

It is the non-contact ACL injuries that plague most sports.  Although we know what the intrinsic and extrinsic factors are that lead to the primary non-contact ACL injuries and have various programs developed to address, there has only been a 1.5% reduction in injury rates over the last 5 years.  So developing a better understanding is important to preventing.  Knowing that those who have had an ACL reconstruction (ACLR) are at risk for a 2nd ACL injury, it is important to identifying factors which put them at risk for a second injury so that this risk can also be minimized.  Identifying the pre-injury and post-injury risk factors will aid us in development of interventions and programs to better address.    

In the September issue of the American Journal of Sports Medicine, the authors of the study entitled Risk Factors for Recurrent Anterior Cruciate Ligament Reconstruction: A Population Study in Ontario, Canada, With 5 Year Follow Up, attempted to identify some of those risk factors. 

Methods:  Using the Ontario Administrative Health Care Database and the Registered Persons Database, the authors were able to identify all primary elective ACLR procedures performed in Ontario from July 2003 to March 2008.  This included a total of 12,967 ACLR procedures with patients aged 15 to 60 years of age.  Using these same databases, revisions and contralateral ACLR were sought until January 2012.  Comparisons were done for patient factors (age, sex, comorbidity, etc), provider factors (surgeon volume, academic hospital status, etc) and surgical factors (allograft vs. autographft, fixation type, etc).

Results:  For the 12,967 ACLR performed, these had a mean follow-up of 5.2 years.  For all the subjects included in the study, the revision rate was 2.6% and the rate of the primary contralateral ACLR was 4.6%.  ACLR performed at an academic hospital and the use of allograft significantly increased the risk of revision of the ACLR.  Younger age was the only patient factor that increased risk for contralateral ACLR.

Discussion:  The numbers reported in this study are much lower than previous studies looking at ACL revisions or risk for 2nd ACL injury.  In an effort to determine which is more relevant to our patients and our setting in the US, we must consider all the factors.  Considering the design of the study, there may be several reasons for these lower reported numbers.

  1. Health Care Delivery System:  This study was performed in Ontario, Canada and hence could account for the variance in US published studies vs. Canadian.  So, does this mean that ACLR procedures there have better long term outcomes than the US or is it a result of the health care delivery model?  In Canada, there is a substantial waiting period between the onset of the injury and the actual surgery itself (up to several months).  This waiting period may result in some choosing to opt out of having surgery, which may impact.  This is also insurance driven data base.  Therefore, any athlete that chooses to self-pay for this surgery is not included in this data.
  2. Age of Participants:  This study also includes individuals up to 60 years of age whereas most of the studies in the US use a much younger population.  In this study, over 45% of the subjects were over the age of 30.  Although you would think this would add to more revisions, the opposite is true.  Since younger individuals are more likely to return to sport and more aggressive sports, if ½ of your study population is not returning to sport and at less risk then this would skew your data.
  3. Database driven information:  Since this is database driven, there is no outcome information included so we have no idea what the outcome is.  Without this information, we have no idea of what the activity level is with these patients post ACLR.  Were they able to return to their prior level of activity or where they limited in their ability?  Are those in the US more likely to have revision due to the fact that they return to a higher level of activity?  This study also only looks at ACLR.  What about patients who had surgery down the line for meniscal tears, OA, etc that all resulted from the primary ACLR?  These questions are unknown.

So in considering this study, we must consider all these factors.  Based on the above, what does this tell us clinically?  We do know that our patients are at greater risk for second ACLR if:

  • They are younger – hence why it is important to ensure we are incorporating injury prevention techniques to address “root cause” of the primary ACL injury
  • If they have surgery at an academic institution – several studies correlate outcomes to frequency or number of ACLR performed by the surgeon.  Therefore the more a surgeon has done, typically correlates to improved outcome. 
  • Use of allograph can lead to higher risk of 2nd ACLR

Considering previously posted articles, you should also determine the “root cause” for the non-contact ACL injury and address the psychology of the injury as well.


Wasserstein D, Khoshbin A, Dwyer T, Chahal J, Gandhi R, Mahomed N, Harris D.  “Risk Factors for Recurrent Anterior Cruciate Ligament Reconstruction: A Population Study in Ontario, Canada, With 5 Year Follow Up”.  Am j sport med.  41:2000-2107.  2013.

Brophy, R; Schmitz, L; Wright, R; Dunn, W; Parker, R; Andrish, J; McCarty, E; Spindler, K.  “Return to Play and Future ACL Injury Risk After ACL Reconstruction in Soccer Athletes From a Multicenter Orthopaedic Outcomes Network (MOON) Group”.  Am j sports med.  40:2517-2522, 2012.

Holm, I; Oiestad, B; Risberg, M; Gunderson, R; Aune, A.  “No Difference in Prevalence of Osteoarthritis or Function After Open Versus Endoscopic Technique for Anterior Cruciate Ligament Reconstruction: 12 Year Follow-up Report of Randomized Controlled Trial”.  Am j sports med.  40:2492-2498, 2012

McCullough, K; Phelps, K; Spindler, K; Matava, M; Dunn, W; Parker, R; Reinke, E.  “Return to High School – and College-Level Football After Anterior Cruciate Ligament Reconstruction: A Multicenter Orthopaedic Outcomes Network (MOON) Cohort Study.  Am j sports med.  40:2523-2529, 2012

No comments:

Post a Comment