Computational modelling of the graft-tunnel interaction in single-bundle ACL reconstructed knee

Objectives: Tunnel enlargement and graft failure are common complications associated with ACL reconstruction. The mechanical interaction between the graft and the tunnel aperture may play a more important role. This study aims to evaluate graft position within femoral tunnel and the graft force under external loads. Methods: An FE model of the femur-graft-tibia complex was constructed from CT images of an anatomically reconstructed knee specimen. The model was subjected to kinematics of passive flexion extension, anterior/posterior translation, internal/external rotation and valgus kinematics, which were collected from experimental testing. Graft shift and rotation of graft-tunnel contact region during flexion/extension and external loadings were recorded and compared to experimental measurements. Results: Model showed that the graft shifted in the femoral tunnel during flexion and under external loads. The graft-tunnel contact area rotated by up to 55 degrees during flexion from full extension to 90 degrees of extension implying that the so-called wiper effect occurs during most of flexion angles. Conclusions: Different regions of the femoral tunnel aperture, particularly the anterior region, were under significantly more contact force from the graft than other areas of the aperture during the anterior translation test, potentially leading to femoral tunnel enlargement to the anterior side of the aperture.

Automated summary

This study aimed to evaluate the position of the graft within the femoral tunnel and the force exerted on the graft under external loads in ACL reconstruction. The model showed that the graft shifted within the femoral tunnel during flexion and under external loads. The anterior region of the tunnel aperture was under significantly more contact force from the graft, potentially leading to tunnel enlargement.