In this series, we also discussed in this study what is the most common mechanism for an ACL injury in football. In the Johnston et al study in 2018, the authors found that a majority of ACL injuries in the NFL are non-contact in orientation and that the limb is in a position of dynamic valgus (as seen here). These results led the authors to suggest that there should be some targeted programs designed to assess and control valgus.
Although it is great to work with professional athletes, the majority of us don't get that opportunity and therefore the majority of our population is youth athletics. Frankly, these are the ones that should have our major attention, especially when it comes to injury prevention. This last weekend at the Andrews Institute's Annual Injuries in Football Course, Dr. John Polousky presented on the youth ACL epidemic. He stated there are some 45 million kids that participate in organized athletics and roughly 50% of all sports related injuries are due to overuse. Current literature shows that 1 in 4 elementary and middle school aged kids suffer an ACL injury at some point in their athletic career accounting for ~200,000 ACL injuries in youth athletics.
As a parent and health care provider, this is unacceptable! We have to do something about it and if we don't we are adding to the problem through our own negligence. According to the Johnston study cited above, we know movements that put the athlete at risk for non-contact ACL injuries, at least in professional players. But does that apply to youth athletics?
That will be the first thing we will look at in this series. We will start off this discussion by looking at a recent study by Owusu-Akyaw et al in the American Journal of Sports Medicine 2018.
Determination of the Position of the Knee at the Time of an Anterior Cruciate Ligament Rupture for Male Versus Female Patients by an Analysis of Bone Bruises
Background: Female athletes rupture their ACL at a rate 2 to 4 times higher than their male counterparts. As such, several studies have looked if males and females sustain ACL injuries vai different mechanisms. By understanding the mechanism, we can then create assessment tools and injury prevention programs to address.
Hypothesis: Compare the knee position at the time of the non-contact ACL injury between the sexes. It is the hypothesis of the authors that there will be no differences in the position during injury.
Methods: T2 MRI scans were retrospectively reviewed for 30 athletes (15 male and 15 female) who sustained non-contact ACL ruptures. MRIs were performed within one month of the initial injury. All participants had contusions associated with the ACL injury on both the medial and lateral articular surfaces of the femur and tibia. 3D models of the femur, tibia and bone bruises were created via segmentation on MRI (pictured to the right). The femur was positioned relative to the tibia to maximize bone bruise overlap, thereby predicting the bone positions near the time of injury. Flexion, valgus, internal tibial rotation and anterior tibial translation were measured in the predicted position of injury.
Results | Conclusion: There is no statically significant difference between male and female knee positions during the time of ACL injury. The results suggest a similar mechanism of injury for both the male and female athlete.
Obviously this is a very novel approach to determining knee position during a non-contact ACL injury. In most settings, video review would be the gold standard as you get to see actual footage of the limb position at the time of the injury. In professional sports this is great and with the amount of videoing that is occurring in practice and game time, you can be pretty much assured this will be captured. However, in youth athletics, it is rare that video footage exist where the the mechanism of injury is captured. As such, this novel approach could provide some great insight as to the limb position during injury.
Although this is based on solid biomechanics, it still is not the gold standard. As such, there are some other factors that may impact this. For example, we are basing this off the assumption that the bone bruise occurred at the time of the injury. But, what if the bone bruise did not occur at the time of the injury. What if the athlete continued to play and that resulted in the subsequent bone bruise? This would then provide a false reading and led to a misinterpretation of the limb position at the time of the injury.
This has to be considered but in reality it is most likely that the bone bruise did occur at the time of the initial injury. The mechanism of injury (flexion, valgus and internal rotation), is very similar to what other studies have reported and what the previous Johnston study reported on video review of non-contact ACL injuries. Based on the results of these studies, as well as numerous others, it is clear we need to assess the ability to control dynamic valgus at the knee. Not only do we need to assess that but we need to:
- Assess ability to control during single limb performance
- Assess ability to control during multidirectional tasks
- Assess ability to control both the motion and speed at which that motion occurs