In our first section, we discussed what we should be assessing to determine risk. Whether you are a NFL player, an elite athlete or a high school athlete, the literature is pretty clear that dynamic valgus is something we need to make sure to assess. Yet, the majority of testing in the NFL uses assessments (movement screens) that have not been well validated in the research to be predictive of injury and which do not assess dynamic valgus. In addition, many teams also use test which assess limb symmetry index. Limb symmetry index (LSI) is the variance between your right leg and left leg during functional testing (single leg hop, single leg hop for distance, single leg triple hop). Most of the research indicates if you have >15% variance then you are at greater risk for injury. But, is that good enough?
It makes sense if you have a huge variance between the right side and the left side that you are at greater risk. That would mean that you would always be putting more wear and tear on one side and the side that is weaker would be at greater risk because it is underdeveloped and may not be as resistance to the high forces associated with the sport when you are force to use it. However, does an LSI of 100% mean you are at less risk?
Take the athlete depicted here. In single limb testing, this athlete may present as 100% symmetrical. But is that 100% of good movement? I think we would all agree, this athlete is still at risk despite the fact that she is 100% symmetrical. That is exactly what a study by Wellsandt et al in the 2017 Journal of Orthopedic & Sports Physical Therapy showed.
70 athletes completed quadriceps strength and 4 single leg hop tests before ACLR and 6 months after ACLR. LSI for each test compared 6 month post op involved limb measures to involved 6 months post op measures. Second ACL injuries were tracked for a minimum follow up of 2 years after ACLR.
57.1% (40) patients achieved 90% LSI for quadriceps strength and all single leg hop tests. 11 (15.7%) of patients sustained a 2nd ACL injury in the 2 year follow up period. 8 of the 11 patients with second ACL injury passed the 90% LSI return to sport criteria in quadriceps strength and single leg hop tests 6 months after the initial ACLR.
72.7% (8 of 11) of the patients who suffered a second ACL injury achieved 90% LSI. Although that is only 20% (8 of the 40) of those who achieved 90% LSI, it begs the question on whether LSI should be the sole measure of return to play. In many cases and as a standard of practice, this is often the case.
So is the answer adding additional tests to capture true deficits? Toole et al in the 2017 Journal of Orthopedic & Sport Physical Therapy looked at this in youth athletics. What the authors found is when you add the recommended tests from the literature for RTPlay following ACLR reconstruction, you end up with:
- IKDC - score 90 or better
- 90% LSI on:
- Quad/Ham strength
- SL Hop
- Triple Hop
- Cross over hop
- 6 meter timed test
- 13.9% met all the criteria
- 43.5 to 78.3% met criteria on the individual tests
So, is it that our rehabilitation is not preparing people properly for functional testing and return to play or that we are not measuring the right things? If we think back to part I of this discussion, we know we need to measure dynamic valgus and yet none of these tests are doing that. So, do we continue to do the same thing and expect different results or do we try something different?
With the advent of wearable sensor technology we now have a way to accurately measure dynamic valgus. Not only can we capture the magnitude of motion that occurs but also the speed at which it occurs. Finally, we have a solution. Once those at risk have been identified, we can now create programs to change those movements. There are multiple programs out there that can efficiently impact these pathokinematics and improve the movements that put athletes at risk.