THE EFFECT OF THE ACL SINGLE-BUNDLE/DOUBLE-BUNDLE RECONSTRUCTION ON THE BIOMECHANICS OF TIBIO-FEMORAL JOINT AT DIFFERENT FLEXION ANGLES

In this paper, through the simulation of the clinical pivot test at knee flexion angle of 0? for the models A and B, the accuracy and validity of the pairs of models for healthy adult A were proved. After that, MRI images of the normal human knee at different flexion angles of 0?/25?/60?/80? were obtained through SONATA MAESTRO 1.5T Scanning. Then, the corresponding 3D tibio-femoral joint models of normal/ACL single bundle/double bundle reconstruction were established. In the experiment, axial force and combined loads (axial force and torque) were applied to these models to analyze and compare the changes of the stress distribution of cartilages/meniscus/ligaments and the tension characteristic of ligaments before and after the ACL reconstruction. The results show that: (1) The stresses on cartilages and meniscus after ACL single bundle/double bundle reconstruction change with the flexion angles, and especially the stress distributions on the cartilages change significantly at some angle. (2) Single-bundle reconstruction can lead to the obvious increment of the equivalent stresses on cartilages and meniscus, and the maximum increment is to 40%. However, the corresponding values after double bundle reconstruction at different flexion angles are closer than that after single-bundle reconstruction. (3) Although ACL single-bundle reconstruction will reduce the equivalent stress on PCL, stress on medial/lateral collateral ligament will significantly increase at high-flexion angle. The maximum stress on MCL changes obviously with the flexion angles after double-bundle reconstruction, but the maximum stress on LCL and PCL show the corresponding trend to normal joint. (4) The average tension of MCL is higher than that of the other two after single or double bundle reconstruction. Besides, the tension characteristic of ligaments after the double-bundle reconstruction is closer to the normal joint than that after single-bundle. In short, considering the stress and tension of cartilages, meniscus and ligaments after ACL reconstruction, the tibio-femoral joint mechanical contact characteristic after ACL double-bundle reconstruction is closer to the normal joint than that after single-bundle reconstruction. And whether ACL single-bundle or double bundle reconstruction, the change of stress distribution and the increase of peak stress on cartilages, meniscus and ligaments would induce chronic degeneration of joints and be the main reason for the disease knee.