Orthogonal experiment on the influence of single tunnel on bone's strength in anterior cruciate ligament reconstruction surgery

A three dimensional femur-tibia model is built based on the use of the gray value difference between the compact bone and the cancellous bone in the knee joint under CT imaging and the selection of an appropriate gray threshold. Meanwhile, given the start and the end sites of the single anterior cruciate ligament (ACL) reconstruction tunnel obtained by visual navigation, the femur-tibia containing the ACL reconstruction tunnel model is built according to three variables of the tunnel in the orthogonal experiment (pore diameter D, coronal plane angle α and sagittal plane angle β). This experiment is conducted in 5 levels, where based on the principle that the load force transfers isodynamically when the orthostatic femur and tibia are in static balance. The finite element analysis is carried out by applying the compressing and bending forces to the femur and tibia models respectively. The results show that the range of the three variables has little influence on femur's stresses (less than 7.93%), but affects tibia's stress significantly: stresses of coronal plane angle α and sagittal plane angle β increase up to 39.10% and 36.88% respectively under the compressing loads, and the contact stresses of sagittal plane angle β increase up to 24.66% under bending loads.