Assessing Risk – Is It Possible Part III

Last week, we began to look at some of the common ways we assess for injury risk in pre-season physicals and for making return to play decisions for our athletes.  One of those tests we described was the single leg hop test for distance.  In this test, the athlete performs a maximal jump for distance on one leg and the distance is measured.  The hypothesis is that if this is within 85%-90% that the athlete is at less risk and they are able to return to play.

The single leg hop test is just one test of several that are used for making this determination.  Another test is the triple hop for distance.  This is essentially the same test except three hops are performed instead of one.  Based on the work of Johnston et al 2018 and Owusu-Akyaw et al 2018, both suggest that the mechanism of injury is dynamic valgus.  The question becomes, do these test measure these at risk motions?

Last week, we mentioned what we see anecdotally in the clinic but is this what is reflected in the literature.  What we see in the clinic is an athlete can have symmetry in these types of test regardless of biomechanics.  They may be able to perform the test within symmetry but perform the test with horrible biomechanics.    As demonstrated here with this athlete, we see that when they land they demonstrate the dynamic valgus that was mentioned in the previous studies that we need to assess for.  But if we went solely by the criteria for the hop tests, then this athlete would have been returned to play.

Considering this, we can look at a recent study published by Wren et al J Orth Sports Phy Ther 2018. 

Hop Distance Symmetry Does Not Indicate Normal Landing Biomechanics in Adolescent Athletes with Recent Anterior Cruciate Ligament Reconstruction. 

Background: Return to play following anterior cruciate ligament reconstruction often includes functional assessments such as hop for distance symmetry and triple hop for distance symmetry.  It is unclear if symmetry in these tests indicate if there is any movement deficits present that may put the athlete at risk for non-contact injuries. 

Purpose: The purpose of this study is to assess the biomechanics and symmetry of adolescent athletes following anterior cruciate ligament reconstruction (ACLR) during a single leg hop for distance test.

Methods: Forty six patients with ACLR (5-12 months post-surgical) performed the single leg hop for distance test.  A comparison of the participant demographic and clinical characteristics among groups is represented in Table 1.  During the single leg hop trials, three dimensional motion analysis data was also collected via an 8-10 camera motion capture system (Viacom).

Each participant was classified as asymmetric (operative limb hop distance <90% of non-operative limb; N=17) or symmetric (N=29).  Lower limb biomechanics were compared among operative and contralateral limbs and the 24 symmetrical controls.

Results: Compared to controls, asymmetric patients hopped a shorter distance on their operative limb (P<0.001), while symmetrical patients hopped an intermediate distance on both sides (P≥0.12).  During landing, operative limbs, regardless of hop distance, exhibited lower knee flexion moments compared to controls and the contralateral side (P≤ 0.04) with lower knee energy absorption than the contralateral side (P ≤ 0.006).

During take-off, both symmetrical and asymmetric patients had less hip extension and smaller ankle range of motion on the operative side compared to controls (P≤ 0.05).  Asymmetric patients also had lower hip range of motion on the operative, compared with the contralateral side (P =0.001).

Conclusion:  Both symmetric and asymmetric patients offloaded the operative knee, symmetric patients achieved symmetry in part by hopping a shorter distance on the contralateral side.  Therefore, hop distance symmetry may not be an adequate test of single limb function and return to sport readiness.

Next week, we will begin our discussion on how we may interpret these results and what some of the take aways are.  Stay tuned and please make sure to check out our new website at www.iceperform.com 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.