Limb Symmetry Index - What is it and Is it important - Part II

Last week we started our discussion about limb symmetry index (LSI) and specifically related to the lower kinetic chain.  We also know this is a measure that is commonly used by physicians and in sports medicine when making return to play decisions.  Based on some of the information provided last week, we have questioned on whether this is truly providing us a measure of risk, especially when looking at return to play.  Last week, we discussed a study by Rohman et al that looked at changes in LSI with ACLR rehabilitation but then also discussed the Adams et al study which showed that 93% of normal uninjured athletes LSI index was below or at the standard currently being used to determine return to play. 

This week, we will look at another study by Wellsandt et al J Ortho Sports Phys Ther 2017 which dives into this subject a little deeper.  The objective of this particular study was to evaluate LSI in return to sport testing and its relation to reinjury rates after ACLR.

Methods: Seventy athletes completed quadriceps strength and 4 single leg hop tests before ACLR and 6 months after ACLR.  LSI for each test compared to the involved limb measures at 6 months to uninvolved measures at 6 months.  Estimated preinjury capacity (EPIC) levels for each test compared the involved limb measures at 6 months to uninvolved limb measures before ACLR.  Reinjury rates were tracked for a minimum of 2 years post ACLR.

Results: Forty (57%) of patients achieved 90% LSI for quadriceps strength and on all hop tests.  20 patients (28.6%) met 90% EPIC levels for quadriceps strength and all hop tests.  Twenty four patients (34%) who achieved 90% LSI for all measures at 6 months after ACLR did not achieve 90% EPIC levels.  11 patients (27%) sustained a 2nd ACL injury at 78 weeks (median time).  8 of the 11 patients (73%) with the 2nd ACL injury passed with 90% LSI at 6 months.  But 6 of these 8 (75%) did not achieve 90% EPIC levels.  EPIC levels was superior at predicting 2nd ACL injury.

Despite previous studies stating there is little to no degradation of the noninvolved limb post ACLR, EPIC levels might indicate the contrary.  In this study, the most sensitive measure appears to be comparing the involved limb post ACLR numbers to pre-operative uninvolved numbers.  From a rehabilitation standpoint, if we can get pre-operative numbers, it would make sense to use EPIC levels when trying to determine return to play. 

That being said, it also leads us to the question, wouldn't it be even better if we had baseline movement data to compare to.  What if we had pre-participation movement data taken in physicals, would this be even more sensitive data to compare to.  For those of us that treat athletes who have had an ACLR, we know right after the injury the athlete is definitely going to be hesitant with movement.  Especially with hopping types of motions for the fear of landing on the involved injured limb.  So, would it be better to compare this to movement where there is not that hesitation at all?

All that said, are these LSI measures (whether done in traditional LSI measurement calculation or EPIC calculations) really providing information about "movement quality".  If the athlete had horrible movement prior to surgery on both legs, are we truly measuring risk?  When looking at the athlete depicted here, if this is the preoperative test on the uninvolved side, does his LSI or even his EPIC levels truly depict his risk for reinjury?  Are we missing something here or are we not using enough measures to measure this correctly?

Next week, we will look at some of the common battery of tests used for testing LSI and what they are telling us.  So make sure to stay tuned.  If you enjoy this blog, please share and follow us on instagram @ bjjpt_acl_guy and on twitter @ ACL_prevention.  #ViPerformAMI #ACLPlayItSafe

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 and ACL injury prevention.  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.