Monday, May 21, 2018

Assessing Risk - Is It Possible: Part II

From our last series, we know that previous knee injury does impact future performance.  During that discussion, we highlighted a study by Johnston et al that looked at the position of the lower kinetic chain at the time of injury.  This study was done via video analysis of footage of NFL game and practices during the time of the athlete's ACL injury.  We know from this study that non-contact ACL injuries occur when the limb is place in a position of dynamic valgus and under high loads (shifting position).

Last week we began the discussion to see if this is the position just for professional players or do younger athletes also present with a similar position during non-contact ACL injuries.  For this discussion we looked at recent study by Owusu-Akyaw et al which analyzed bone bruise patterns in younger athletes.  Based on these results, the dynamic valgus position (flexion, valgus and internal rotation) is a position that results in ACL rupture in male and female athletes under high loads.  Based on the results of both of these studies, then it would make sense that we must find ways to assess this in our athletes.  To do so, we should look at the literature and see what is currently being used to assess athletes for risk.

One test that is being used to assess athletes for risk is the single leg hop test for distance.  During this test, the athlete stands on the leg to be tested.  They will then hop as far as possible and land on the same limb.  This is repeated on the contralateral limb.  This is typically performed three times and the distance is measured for each.  Using the average of the three, the assessor is looking for limb symmetry (being equal on both sides) within 85%-90%.  The assumption is that if limb symmetry is achieved that the athlete is not at risk.  This is a common tool that is being used to assess risk in pre-participation physicals and for return to play following ACLR.

In 2015, Rohman et al published a paper in the Am J Sport Med looking at limb symmetry in athletics.  What they found was that 93% of norms had limb symmetry greater than or equal to 85%.  So if norms have 85% limb symmetry, what should be the number for those at risk.  Most physicians will use 85%-90% of the contralateral limb.  Considering this study however makes us question if an athlete is at 85% are they really at risk?  I am not sure if we know the answer to this question but it is something we need to consider when making these kinds of calls with the above mentioned test.  

For demonstration purposes, let's suppose the athlete has 95% limb symmetry on the single leg hop for distance test.  Is this athlete at risk or are they ready to return to play.  If we only consider the above information, we might say yes.  According to the Johnston et al study and the Owusu-Akyaw et al previously mentioned, we need to measure dynamic valgus to assess risk as these are the movements that rupture the ACL under athletic types conditions.  If an athlete is demonstrating 95% limb symmetry on this test, is this indicative that these movement patterns are not occurring?

Or, could an athlete perform this test and be 95% symmetrical and still demonstrate the movement patterns shown here.  The assumption is that with all of the hop tests (single leg hop for distance, triple hop for distance and lateral hop) that symmetry = good biomechanics.  But is this the case?  What we see anecdotally is this is not the case.

This is what we see but what does the literature tell us.  Next week we will look into this.  Make sure to stay tuned.  Please make sure to check out our new website at where our goal is to help you help others.  #ViPerformAMI

Dr. Nessler is a practicing physical therapist with over 20 years sports medicine clinical experience and a nationally recognized expert in the area of athletic movement assessment.  He is the founder | developer of the ViPerform AMI, the ACL Play It Safe Program, Run Safe Program and author of a college textbook on this subject.  Trent has performed >5000 athletic movement assessments in the US and abroad.  He serves as the National Director of Sports Medicine Innovation for Select Medical, is Vice Chairman of Medical Services for USA Obstacle Racing and movement consultant for numerous colleges and professional teams.  Trent is also a competitive athlete in Brazilian Jiu Jitsu. 

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