Exploratory Anterior Cruciate Ligament Graft Stress during Medial Knee Rotation with and without Iliotibial Band–Intermuscular Septum Lateral Extra-Articular Tenodesis for Transtibial and Anteromedial Femoral Tunnels

Traditional lateral extra-articular tenodesis (LET) using fixation elements constrains medial knee rotation laxity after anterior cruciate ligament reconstruction (ACLr). However, the mechanical behavior of an LET made with an iliotibial band–intermuscular septum is unknown using different anterior cruciate ligament (ACL) reconstruction drillings and would be crucial for constraining the rotatory components of direction change movements. Thus, this study aimed to explore the maximum principal stresses and their distribution in grafts during medial knee rotation with and without iliotibial band–intermuscular septum lateral extra-articular tenodesis for the transtibial technique (TT), hybrid transtibial technique (HTT), and anteromedial portal technique (AM) in single-bundle ACLr. The maximum von Mises principal stresses and their distribution under medial knee rotation were described using a finite element model generated from a healthy knee. LET with HTT, TT, and AM decreases stress by 97%, 93%, and 86% during medial rotation compared to each technique without LET, respectively. The stress concentration for the AM portal and TT techniques was located at the femoral tunnel, and for HTT with LET, it was located across the distal thirds of the anterior aspect of the graft. In conclusion, the HTT with LET diminishes graft stress more than the HTT, TT, and AM without LET, and the TT and AM with LET during medial knee rotation. The AM portal, HTT, and TT techniques without LET show higher stress concentration patterns at the femoral tunnel, establishing a biomechanical risk of femoral tunnel enlargement when LET is not performed.