ACL Injury Prevention CPG, Copers, and Non-Copers

ACL injuries are one of the most studied orthopedic injuries, and we just couldn't get everything we'd like to say about them into the knee ligament sprain episode. So in this episode, David covers mechanisms behind non contact ACL injuries, the ACL injury prevention CPG, and ACL-deficient copers and non-copers.

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Transcript

Hello and thanks for tuning in again. In our last episode, Austin did a great job of condensing the entire knee ligament sprain CPG into a relatively short 30-minute episode. But ACL injury is one of those topics where there has been so much research done that it really deserves its own series of episodes separate from the other ligament sprains. We’re not going to cover everything that could possibly be said about ACL injuries today, but we are going to cover some highlights that didn’t fit well into the last episode. We’re going to review some features of ACL injuries, cover the ACL injury prevention CPG, and wrap up by discussing ACL-deficient copers and non-copers.

First, let’s review a few features of ACL injuries. Approximately 70% of ACL injuries are non-contact injuries. Non-contact ACL injuries are most likely to occur during deceleration or acceleration motions with excessive quadriceps contraction and reduced hamstring cocontraction at or near full extension. This makes sense, because the ACL resists anterior translation of the tibia, and a quadriceps contraction causes anterior translation of the tibia. The hamstrings, on the other hand, work with the ACL to resist anterior tibial translation. So a strong quadriceps contraction with reduced hamstring cocontraction at or near full extension is the typical mechanism of injury for non contact ACL injuries. The ACL is further loaded and at even greater risk of rupture when these forces are combined with knee internal rotation, or a valgus load combined with knee internal rotation, or excessive valgus load during weight-bearing decelerating activities. I’ll say all of that one more time: the perfect recipe for non contact ACL rupture is excessive quadriceps contraction and reduced hamstring cocontraction at or near full extension combined with knee internal rotation, or a valgus load with knee internal rotation, or valgus load during weight bearing deceleration.

ACL injury and ACL reconstruction are very common; in fact, ACL reconstruction is the sixth most common orthopedic procedure in the United States. One of the interesting things about ACL reconstructions is how often they fail. The so-called “second ACL injury” rate is estimated to be 15% overall, but in athletes younger than 25 who return to sports, the rate is 23%. Almost one in four! About half of these second injuries occur on the operative side, but half occur on the nonoperative side. And our return-to-sport criteria does a poor job of predicting who will sustain a second ACL injury. If you recall, the Ligament Injury CPG recommends triple hop testing be used as one of the outcome measures in determining return-to-sport readiness. And symmetry with triple hop testing does predict likelihood of returning to full prior level of function. But it does not predict second injury risk.

One of the factors that does help predict injury risk is time. An article by Beischer et al published in the February 2020 edition of JOSPT identified that athletes who returned to sport in less than 9 months after ACL reconstruction were seven times as likely to sustain a second ACL injury. This same study found no correlation between symmetrical muscle function and second ACL injury or quadriceps strength and second ACL injury.

So if you are asked to identify a reasonable return-to-sport timeline for a patient who has had ACL reconstruction, that timeline should be greater than 9 months.

So with ACL reconstructions being so costly, and with second injuries happening so frequently, ACL injury prevention is a big topic. And a lot of money and research has been poured into programs to reduce the risk of initial ACL injury. So that brings us to the ACL injury prevention CPG.

There are a lot of programs that have attempted to decrease the odds of sustaining an ACL injury. These programs have been performed with large numbers of participants and then analyzed in multiple meta-analyses and meta-regressions. Researchers have found that there are quite a few programs that are effective at reducing ACL injuries—particularly in female soccer players. Among them is one that I recommend and have used a lot, the FIFA 11+ program. I do not think you need to memorize the names of the specific programs listed in the CPG, because it’s a long list, and it wouldn’t be a particularly useful question for the OCS exam writers to ask. But if you’re looking for a prepackaged ACL injury prevention program for your athletes, you can go back to the CPG and look for yourself.

What I do think the OCS exam writers could ask about are the recommendations about content and dosage of ACL injury prevention programs. Because we have so many meta-analyses on such large cohorts, we have a pretty good breakdown of what an ACL injury prevention program needs. First, it needs more than one exercise component. It will come as no shock to any of you brilliant PTs that there is no single magic ACL-prevention exercise. We need multiple exercises. Next, we need to include proximal control exercises, such as trunk or core strengthening and stability exercises. Programs that lacked proximal control exercises failed to reduce the incidence of ACL injuries. Third, programs should include both plyometric and strengthening components. Programs that lacked one of these components were not as effective as those that included both. Fourth, and perhaps most surprising, is that balance exercises may not be necessary for an effective program. In fact, one study found that as the duration of time spent performing balance exercises within a program increased, the protective effect on the program decreased.

And that brings us to dosage. How much time should be spent on a program, and how frequently? The programs that were found to be most effective lasted longer than 20 minutes and were performed multiple times per week. We have evidence that these programs can be effective as in-season only programs or as pre-season and in-season programs, but pre-season only programs were not effective. So if you’re building your own ACL prevention program, sessions need to be longer than 20 minutes and performed multiple times per week during the season or during both pre-season and in-season.

And I think that covers the most important material from the ACL prevention CPG. Here’s a quick quiz to make sure you got it: you are working with the coach of a high school soccer team to design an ACL injury prevention program. Which of the following is likely to be the LEAST important component of an effective program? A. Plyometric hopping. B. Single leg stance on a rocker board. C. Planking exercises. D. Band-resisted lateral stepping. The correct answer here is B. Single leg stance on a rocker board is likely to be the least important component of an effective program. Don't get me wrong—I love single leg rocker board work. But the data we have on large-scale ACL injury prevention programs shows strong evidence for all the other components—plyometrics, strengthening, and core stability—with conflicting evidence for balance exercises.

Now let’s move on from the prevention CPG and fast-forward to immediately after an ACL injury. When an ACL injury occurs, people tend to immediately start thinking and talking about surgical management. However, multiple randomized controlled trials and meta-analyses have shown no difference in functional outcomes between ACL ruptures treated surgically and ACL ruptures treated conservatively. These studies do have their methodological limitations, so there’s still a lot we don’t know. But just let it sink in that—in the data we have—on average, individuals who get ACL reconstructive surgery and those who don’t have similar outcomes. Now, I don’t think this means that ACL reconstruction should never be done and conservative management is the only way to go. But this does show that there are a significant number of people who tear their ACL and are able to function just fine (and even return to sport!) with conservative management and no surgery.

In the literature, these people who can function without an ACL are called, “copers.” Those who are unable to function without an ACL and require surgery are called, “non-copers.” Several studies have attempted to find criteria that identify copers so that we can better match surgical management to those who need it and spare it for those who don’t. Eastlack et al developed a screen to identify copers in 1999 that has held up in several other studies since then. First, the patient has to meet a few criteria: the injury has to be an isolated ACL tear without other comorbid injuries. The knee has to have full pain-free ROM and no joint effusion. In other words, the knee has to recover effectively from the acute phase of the injury. And then the MVIC—the maximum voluntary isometric contraction—of the quadriceps on the involved side must be at least 70% as strong as the uninvolved side. All of this—the isolated injury, full pain-free ROM, no joint effusion, and at least 70% quad strength—just qualifies the patient to participate in the screening process. If the patient qualifies, they have to meet the following four criteria to be considered a likely coper: 1) they have to report no more than one episode of the knee “giving way” since the injury, 2) they have to have at least 80% symmetry in the timed 6 meter hop test, 3) they need to score at least 80% on the Knee Outcome Survey-Activities of Daily Living (or KOS-ADL), and 4) They need to score at least 60% on the Global Rating of Knee Function.

It’s possible that you may have to identify a coper or a non-coper and make a recommendation about conservative or surgical management on the OCS exam. It may be helpful to think about these criteria in reverse: if an individual has a complex injury involving more than just the ACL, this screening process does not apply to them, and they are less likely to be a coper. If it’s a simple ACL injury, but the patient lacks full pain-free knee ROM or has repeated episodes of joint effusion, they either need a little more time to recover from the injury or they’re not a likely coper. If their quadriceps strength on the affected side is <70% of the unaffected side, then again, they either need a little more time to recover, or they’re not a likely coper. If they have more than one episode of the knee “giving way,” they shouldn’t be categorized as a likely coper. And if they have less than 80% symmetry on hop testing, less than an 80% on the KOS-ADL outcome measure, or less than 60% on the Global Rating of Knee Function, they are, again, unlikely to be a coper.

As I wrap this up, I’m going to briefly point out something that is unlikely to be on the exam, but I want to mention it for the sake of your clinical practice. A moderately large study by Thoma et al. that was published in the American Journal of Sports Medicine in 2019 demonstrated that it is possible to take ACL-deficient individuals who failed some of the criteria, and—with neuromuscular and strength training—help them meet the criteria to become potential copers. In this study, nearly half of the individuals who were initially “non-copers” could be classified as “potential copers” after 10 sessions of training. So there is massive potential for physical therapy to be effective in ACL-deficient individuals—even those who might not immediately be categorized as likely copers. There’s a lot more I would love to say about ACL injuries and management of ACL-deficient athletes, but you’re here to study for the OCS exam, not to listen to me on my soap box.

So with that, I’m going to wrap up this episode on ACL injury, ACL injury prevention, and ACL-deficient copers. As always we appreciate your feedback and look forward to sharing another episode with you soon.