Utilization of ACL Injury Biomechanical and Neuromuscular Risk Profile Analysis to determine the effectiveness of Neuromuscular Training
Authors: Hewett Timothy E. , Ford Kevin R. , Xu Yingying , Khoury Jane , Myer Gregory D. 
Published: August 2015

Objectives: Over 125,000 anterior cruciate ligament (ACL) injuries occur each year in the United States. External loads on the knee in the frontal plane, specifically the knee abduction moment (KAM), predict future ACL injury with high sensitivity and specificity. The purpose of this randomized controlled trial (RCT) was to determine if biomechanical and neuromuscular factors could be used to characterize athletes by distinct factor profiles, to examine if neuromuscular training (NMT) would decrease the potential risk factors, and if NMT would preferentially benefit athletes that exhibited specific risk profiles. The hypotheses tested were: 1) a priori chosen biomechanical and neuromuscular factors would characterize subjects into distinct at-risk profiles, 2) NMT would decrease biomechanical and neuromuscular factors related to increased injury risk and 3) the decrease in these biomechanical and neuromuscular factors would be greater in those athletes characterized by the overall higher risk profiles. Methods: A total of 624 female athletes from 52 basketball, soccer and volleyball teams participated and were screened prior to their competitive season. During the pre-season testing, the athletes performed 3 different types of tasks for which biomechanical measures were taken: 1) drop vertical jump (DVJ), 2) single leg drop (SLD), and 3) single leg cross drop (SCD) landings. Using data from these tasks a latent profile analysis (LPA) was conducted to identify distinct profiles based on pre-intervention biomechanical and neuromuscular measures. As a validation, we examined whether the profile membership was significant predictor of KAM. Analysis of Co-Variance (ANCOVA) was used to examine treatment effects of NMT on biomechanical and neuromuscular measures in the 375 athletes who completed both pre- and post-intervention tasks. Differences were considered statistically significant at p<0.05. Results: LPA using six pre-intervention biomechanical measures selected a priori resulted in three distinct profiles. Athletes in profiles II and III had significant higher KAM, compared to Profile I. The Core/Trunk-based NMT significantly increased hip external rotation moments and moment impulse and increased peak trunk flexion and decreased extension. In addition, the treatment effect of NMT varied by pre-intervention risk profile. Athletes with pre-intervention risk Profile II and III (higher risk) had a more significant treatment effect of NMT than Profile I. Conclusion: This is the first study to use LPA analysis of biomechanical landing data to create KAM and potentially ACL injury risk profiles. The LPA of multiple biomechanical and neuromuscular measures identified three distinct risk groups; associated with differences in peak KAM Analysis of the RCT showed that NMT significantly increased hip external rotation moments and moment impulse and increased peak trunk flexion and decreased extension, and that alterations in risk factors are different across risk profile group, with higher risk groups showing an overall significant improvement in KAM. These findings show the existence of discernable groups of athletes that are more appropriate for NMT intervention; further study is needed in even larger cohorts to investigate ACL injury as our primary outcome variable.