Effects of tibial and femoral tunnels on menisci contact stress

Based on CT and MRI data, a three dimensional tibio-femoral joint model containing cartilages and menisci was built, and the three objectives of this study were as follows. 1) To analyze the effects of loads on the contact stress of medial and lateral menisci when variable forces were applied on the intact, single-tunnel and double-tunnel finite element joint models respectively. 2) To construct tibio-femoral joint models during flexion by using parallel mechanism theory and simulating with ADAMS software. 3) To analyze the effects of graft tunnels on the contact stress distribution of the menisci as the joint flexion angle changed (0°, 30°, 60° or 90°, finite element analysis was done on the models under the same loads, while neglecting the influence of tunnels on the tibia's position and pose relative to the femur. The obtained results show that menisci contact stress and force have a good linear relationship, and the contact stress of medial meniscus remains nearly unchanged in full extension position as graft tunnels inserted. However, the contact stress of medial and lateral menisci increases significantly during 30° or 60° flexion. Therefore, it's concluded that the possibility of menisci chronic degradation exists after ACL reconstruction surgery.