Biomechanical Evidence on Anterior Cruciate Ligament Reconstruction.

Anterior cruciate ligament (ACL) reconstruction is recommended in athletes with high physical demands. Several techniques are used in reconstruction; however, the most relevant question still is the best biomechanical positioning for the graft. The present study aimed to analyze the biomechanical effect of the position of bone tunnels on load distribution and joint kinetics, as well as the medium-term functional outcomes after ACL reconstruction.  A biomechanical study using a finite element model of the original knee (without anterior cruciate ligament rupture) and reconstruction of the ACL (neoACL) was performed in four combinations of bone tunnel positions (central femoral-central tibial, anterior femoral-central tibial, posterosuperior femoral-anterior tibial, and central femoral-anterior tibial) using the same type of graft. Each neo-ACL model was compared with the original knee model regarding cartilaginous contact pressure, femoral and meniscal rotation and translation, and ligamentous deformation.  No neo-ACL model was able to fully replicate the original knee model. When the femoral tunnel was posteriorly positioned, cartilage pressures were 25% lower, and the mobility of the meniscus was 12 to 30% higher compared with the original knee model. When the femoral tunnel was in the anterior position, internal rotation was 50% lower than in the original knee model.  Results show that the femoral tunnel farther from the central position appears to be more suitable for a distinct behavior regarding the intact joint. The most anterior position increases rotational instability.