Effect of ACL Laxity on ACL Loading: Dynamic Simulation Using Impulsive Loads

Noncontact ACL injuries are among the most common, potentially traumatic and costly sport-related injuries, approximately 200,000 injuries occurring each year. Female athletes exhibit a trend toward higher rates of ACL injuries suggesting the influence of gender-specific characteristics. ACL laxity, a direct manifestation of hormonal cycling is a crucial differentiating factor between males and females that influences the strength and compliance of ACL when stressed. However, the mechanism through which ACL laxity implicates within an injury is unknown. Therefore, using FE methods, we tested the hypothesis that a lax ACL fails to adequately restrain the tibia during dynamic activities, resulting in lower intersegmental decelerations and subsequently, higher strain in the ACL. A 2D computational model of bones, meniscus, cartilage and ACL in sagittal plane was created. An impulse load was applied for 100ms (peak:1200N at 35ms) to simulate drop landing. Multiple simulations were run with varying ACL laxity. We observed that as stiffness increased from 50% to 150%, intersegmental deceleration increased by 10.9% and ACL strain reduced by 19.4%. These results indicate that relative peak deceleration of tibia can be used to predict ACL strain and is a potential clinical measure for identifying female athletes at risk for injury.Copyright © 2011 by ASME