Effect of Knee Flexion Angle and Tensile Direction on the Strength of Ligament Insertion to Bone

Abstract

This study investigated how knee flexion angle and tensile direction affect the strength of anterior cruciate ligament (ACL) insertion to tibia using swine femur-ACL-tibia complexs. Four tensile tests at displacement rate of 10 mm/min were performed at flexion angles of 0°, 45°, and 90°on the condition that the tensile direction was along the tibial axias, and at flexion angle of 90° on the condition that the tensile direction was along the femoral axis. The modes of failure and load-displacement curves were measured and compared among all tensile tests. As for the mode of failure, there was a difference between the tensile direction along the tibial axis and along the femoral axis. At flexion angles of 0°, 45°, and 90°on tensile direction along the tibial axis, the ACL failure occurred initially by failure of posterior lateral bundle followed by failure of anterior medial bundle until the complete separation of ACL to tibia, whereas at flexion angle of 90 on tensile direction along the femoral axis, the avulsion fractures suddenly occurred. As for the load-displacement curve, the maximum load at flexion angle of 0° on tensile direction along the tibial axis was significantly larger than that at flexion angle of 90°. The maximum load at flexion angle of 90°on tensile direction along the femoral axis was larger than those at flexion angles of 45° and 90° on tensile direction along the tibial axis. Therefore, the strength of ACL insertion to tibia was affected by both knee flexion angle and tensile direction.