Sports Medicine Research: In the Lab & In the Field: Balance Assessments Unable to Predict ACL Injury in Elite Female Athletes (Sports Med Res)


Wednesday, March 15, 2017

Balance Assessments Unable to Predict ACL Injury in Elite Female Athletes

No Association Between Static and Dynamic Postural Control and ACL Injury Risk Among Female Elite Handball and Football Players: A Prospective Study of 838 players

Steffen K, Nilstad A, Krosshaug T, Pasanen K, Killingmo A, & Bahr R. Br J Sports Med. 2017; 51:253-259. doi: 10.1136/bjsports-2016-097068

Take Home Message: Balance assessments were not associated with anterior cruciate ligament injury risk among elite female handball and soccer athletes. 

Clinicians and researchers are seeking screening tests to determine who is at greater risk for an anterior cruciate ligament (ACL) injury.  Balance exercises are often integrated into ACL prevention programs since many believe poor balance is associated with increased lower extremity injury risk.  However, there is little research to quantify the ACL injury risk associated with balance deficits.  The authors of this prospective study screened 838 elite female handball and football players and followed them to see if they suffered an ACL injury over an eight-year period. After an initial baseline screening, new athletes and athletes on new teams to the premier leagues were evaluated. Balance screening consisted of a single leg stabilization on a foam pad on a balance platform (static and following a drop down), as well as dynamic stability through a simplified star excursion balance test.  The investigators assessed balance on both legs. They also assessed the consistency of the balance assessment among a subset of people at 1 to 5 years after the initial screening. The authors recorded all complete ACL injuries, which were verified with MRI or surgery, and asked the athletes if the injury was direct contact, indirect contact, or noncontact. Eighty-one players reported a history of ACL injury prior to screening. Among these athletes, 12 players experienced another ACL injury during the follow-up period.  Over the follow-up period 67 athletes had 80 ACL injuries. The most common ACL injury mechanism was non-contact, and there was a total of 55 new non-contact ACL injuries analyzed during the study period.  Within those that suffered noncontact ACL injuries, there were no differences between the uninjured and injured legs for static balance, drop-down balance, or dynamic balance.  There were also no differences between those who did and did not suffer a noncontact ACL injury in any of the 3 baseline balance assessments.  The only significant finding was that a previous ACL injury history tripled the risk for suffering another ACL injury.

This study shows that baseline balance data are poor predictors for ACL injury risk.  The authors noted that these balance tests had poor reproducibility because people demonstrated an improvement over time.  These assessments may be inappropriate among elite female athletes. Therefore, we need to wonder if another test may be better suited for screening or if screening needs to occur every preseason.  It would have been interesting to see how balance assessments changed over the years, and whether there were any clinically meaningful changes over the course of the study.  The authors indicated that fatigue may have been a factor in how the players performed on the tests.  It would be interesting to further investigate this idea.  Some people think that fatigue can adversely affect performance and increase injury risk. Hence some think that you should try to prevent fatigue to prevent injury.  Most importantly, we need to increase our efforts in primary prevention of an ACL tear since that is the strongest risk factor for suffering an ACL tear.  Bottom line based on this research study, is that clinicians lack a balance-screening test to identify elite athletes at risk for ACL injury. This study also highlights that primary prevention among young athletes is critical.    

Questions for Discussion:  What do you use for ACL injury risk assessments?  What are your thoughts on fatigue and injury risk?    

Written by: Nicole Cattano
Reviewed by: Jeffrey Driban

Related Posts:

Steffen K, Nilstad A, Krosshaug T, Pasanen K, Killingmo A, & Bahr R (2017). No association between static and dynamic postural control and ACL injury risk among female elite handball and football players: a prospective study of 838 players. British Journal of Sports Medicine, 51 (4), 253-259 PMID: 28148513


Haley said...

I thought this article brought up some good points. ACL injury screening risk assessments should include some type of balance/neuromuscular control assessment. In terms of single-leg stabilization on a foam pad, the knee is in a more at-risk position when slightly bent as opposed to locked out. I believe single-leg balance on a foam pad is more focused for the ankle and by bending the knee to an athletic position, the knee will become less stable and more likely to show risk for injury. I think fatigue plays a huge role in injury risk. When we test athletes in a rested state, it isn't clinically applicable because athletes become injured when they're fatigued towards the ends of games or halves of games. If we test athletes in a fatigued state, it will be a more realistic test of risk for injury.

Aleah Kirsch said...

I thought this was a valuable article to read. It was nice to have the study based on a large sample size and long duration. I personally believe that balance assessments are more valuable to analyze when a clinician is returning an athlete to play after ACL-R vs using balance as an indicator of risk. This study states that balance is unable to predict risk of injury but that is what I personally would expect. Going along with what Haley stated in the previous comment, I think taking the knee out of a closed packed position would allow the clinician to get more valuable information of function of the ACL instead of having it in a fully extended, locked positon. If this were to be done post ACL-R I believe that balance tasks would be able to discriminate between healthy and ACL-R knees. I do believe that fatigue plays a huge roll in risk for ACL injury. I know form growing up a soccer player that our coaches would preach technique and not getting “sloppy” when we got tired after lifting or even at practice. Once fatigue is induced, an athlete loses their ability to maintain proper technique which inherently puts them at risk for serious injury. Due to this, I think it is important to test athletes for risk of ACL injury once fatigue is induced to get a better picture of actual risk instead of risk in a lab setting.

Jeffrey Driban said...

Hi Haley and Aleah: Thanks for the comments. I agree that it would be interesting to screen athletes while fatigued. It would be an interesting study to see if screening tools perform better when the athlete was fatigued vs rested.
The authors didn't coach the participants how to balance (e.g., bent knee vs locked knee) but in addition to static balance they also assessed balance following a drop down from 30 cm height, which would be a more functional movement than just static balance. It will probably always be challenging to predict who is at risk for injury because injuries may have different mechanisms (hence, may have different risk factors) and many studies will only have a small number of ACL injuries, which makes it hard to find a risk factor unless it is strongly related to risk of injury. Thanks for the comments.

Abbis Haider said...

I think this was an interesting study. Prospective cohort studies are always interesting and require a lot of effort to be done. This was kind of surprising for me that balance performance was unable to predict future injuries/injury risk. Well! I think balance is a very important assessment which takes into accounts neuromuscular component for maintaining stability. In regards to static balance, I think, we don`t see any risk identification perhaps because of the "not so challenging" nature of static balance assessments. Single-leg stance may not be that challenging for subjects involved in higher level sports. Static balance assessments are not that robust in identifying the potential injuries. However, not seeing anything on SEBT was kind of unexpected as it has shown in the past to identify the balance deficits, if present. I also think that more tasks or tests should have been used for balance assessment that could have been more demanding. I think SEBT more so takes in to consideration the range of motion at ankle joint than knee or hip ROM or balance. This might also be a reason that we didn`t see SEBT a strong predictive tool in case of ACL-R. I also agree that testing participants when they are fatigued would have been better. Conclusively, I think it would have been better if participants were screened with more balance tools than what are used in this study. Nevertheless, it was an interesting study.

Jeffrey Driban said...

Thanks Abbis. It's always valuable to have a study challenge the use of existing screening tools. With an increased awareness that these may not be optimal in this population, I agree that it's time to try more challenging balancing tasks/tools. What tasks would you try?

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