Impingement analysis with 3-D geometric characterizations of ACL pseudofibers and intercondylar notch

Impingement of the anterior cruciate ligament (ACL) against the intercondylar notch (ICN) may play a significant role in ACL injuries. However, there is a lack of convenient and accurate methods for evaluating ACL impingement with consideration of the three-dimensional (3-D) notch shape and ACL fibers. In the current study, ACL impingement was modeled using a 3-D geometric knee model that includes multiple ACL pseudofibers, which allowed us to identify the sites of ACL impingement during simulated tibiofemoral movements. The simulation results were compared with impingement force data measured in three cadaveric knees with ACL impingement. Results show that ACL impingement can occur on fibers at the anterolateral aspect of the anteromedial band of the ACL during tibial external rotation and abduction. The computed peak ACL strains of the three knees were 5-8%. The proposed analysis is a practical method for quantitatively evaluating ACL impingement against the ICN, and may lead to useful tools for evaluating ACL impingement in individual patients based on their magnetic resonance imaging data. These analytical tools may guide individualized rehabilitation and reduce potential ACL impingement against the ICN during strenuous tibiofemoral movements.