Executing a Collaborative Prospective Risk-Factor Study: Findings, Successes, and Challenges

Abstract

M oderate evidence 1 demonstrates that injury-prevention training programs can substantially reduce the risk of anterior cruciate ligament (ACL) injury in athletes. Yet the current literature [2][3][4] contains both positive and negative results for ACL injury prevention. Researchers must identify the prospective risk factors for noncontact/indirect-contact ACL injury to ultimately improve the effectiveness of existing ACL injury-prevention programs. PROSPECTIVE RISK FACTORS VERSUS MECHANISMS OF INJURYA critical distinction needs to be made when describing prospective risk factors for ACL injury. This involves differentiating between ACL injury mechanisms and prospective risk factors. An ACL injury mechanism can be defined as the combinations of joint forces, moments, and movements that cause failure of the ACL and occur at the time of injury. However, ACL injury prospective risk factors are variables that are useful for screening purposes. Also, prospective risk factors for ACL injury are not necessarily the same as mechanisms of ACL injury or loading. Prospective risk factors are variables that can be identified years before an ACL injury mechanism is experienced. Therefore, prospective risk factors for ACL injury can be defined as those variables (eg, signature movement patterns, age, sex, injury history) that identify individuals who will later experience an ACL injury mechanism.Risk factors and injury mechanisms are related in 2 ways. First, risk factors may work in a synergistic manner to raise the probability that a certain individual is exposed to high-risk biomechanical forces that create injury mechanisms. For example, knee laxity and poor neuromuscular control of the hamstrings muscles are independent risk factors that might interact to increase the probability of an injury mechanism occurring. Second, risk factors might be ''proxies'' or ''markers'' for unknown factors that predispose an individual to injury mechanisms; for example, sex may be a proxy for poor neuromuscular control in high school-aged athletes.Improving our understanding of mechanisms for ACL injury has been accomplished through cadaver-based and computer-simulation research. Cadaver-based research has provided insight into how internal and external loads at the knee may facilitate stress and strain on the ACL. [5][6][7] Recently, computer simulations of ACL loading mechanisms have enhanced our understanding of the loading combination most likely to facilitate an ACL injury mechanism. 8-13 Even though cadaver-based and computer-simulation-based research has greatly improved our understanding of ACL injury mechanisms, this research does not identify prospective risk factors. Thus, we still have a very limited understanding of prospective risk factors for ACL injury because injury mechanisms and prospective risk factors, although related, are not identical.The prospective cohort design is considered the strongest method for identifying prospective risk factors for ACL injury. 14 This design requires testing of participants before they ...

ACL Research Retreat VII: An Update on Anterior Cruciate Ligament Injury Risk Factor Identification, Screening, and Prevention

“…155,156,[158][159][160] Lower Extremity Alignment. Although the results of 2 large prospective studies are not yet available 161 (see also Beynnon et al 1 ), no clear consensus in the literature consistently links any 1 lower extremity alignment factor to ACL injury. Lower extremity alignment differs among maturational groups and also develops at different rates in males and females within those groups.…”

The Landing Error Scoring System as a Screening Tool for an Anterior Cruciate Ligament Injury–Prevention Program in Elite-Youth Soccer Athletes

“…9,10 Data regarding ACL loading and injury mechanisms help clinicians understand what occurs at the time of injury. 11 Prospective risk factors, however, provide information for identifying individuals at risk for sustaining injuries, potentially years before injury. 11 Only a small body of evidence exists on prospective biomechanical risk factors for ACL injury.…”

“…11 Prospective risk factors, however, provide information for identifying individuals at risk for sustaining injuries, potentially years before injury. 11 Only a small body of evidence exists on prospective biomechanical risk factors for ACL injury. A limitation of these studies is the use of laboratory-based instrumentation and testing procedures.…”

Seven Steps for Developing and Implementing a Preventive Training Program

“…The JUMP ACL study began as a multi-site prospective cohort study investigating biomechanical and neuromuscular risk factors for non-contact / indirect contact ACL injury at The United States Military, Naval, and Air Force Academies. 13 The second phase of JUMP ACL has focused on developing and implementing a PTP as part of a cluster randomized controlled trial at the United States Military Academy at West Point from 2010 to 2014. The PTP was delivered as a set of exercises performed as a dynamic warm up prior to physical training.…”