Biomechanical study of a computer simulated reconstruction of the anterior cruciate ligament (ACL)

The purpose of the study was to use a computer simulation of various surgical techniques for reconstruction of the anterior cruciate ligament (ACL) to study graft biomechanics. To ensure the normal function of the cruciate ligament and, consequently, normal kinematics of the knee joint, the complex structure of the normal ACL must be built into the graft.

First the ACL was modeled and then a reconstruction of the ACL was simulated on a computer model of the cadaveric knee. Biomechanical patterns of the ACL and the modeled grafts in different spatial orientations and positions of the femoral attachments were studied. Isometricity of the peripheral and central fibers of the ACL and grafts was measured and the average fiber length change and isometric pattern of fibers in the graft were compared.

None of the ACL fibers is isometric and fiber length change varies with individual fibers of the original ligament or graft. The average length change of graft fibers depends on the position of the femoral attachment in the sagittal plane. It is smaller in anterior positions in relation to the geometric center of the femoral origin of the ACL, and larger in posterior positions. The isometric pattern of fibers in the graft in isometric orientations resembles most closely the pattern of the original ACL.

A computer simulation of various surgical techniques of reconstruction of the ACL can be successfully used for the study of biomechanics. The most significant kinematic characteristics of the ACL is gradual recruitment of graft fibers during knee extension, which can be defined as the pattern of isometricity. The isometric pattern of the graft is primarily influenced by spatial orientation.