The biomechanical interdependence between the anterior cruciate ligament replacement graft and the medial meniscus

To establish a quantitative biomechanical relationship between the anterior cruciate ligament graft and the medial meniscus, 10 human cadaveric knees were examined using the robotic/universal force-moment sensor testing syste m. In response to a combined 134-N anterior and 200-N axial compressive tib ial load, the resulting kinematics of the knee and the in situ forces in th e anterior cruciate ligament, the anterior cruciate ligament graft, and the medial meniscus were measured. Anterior tibial translation significantly i ncreased after anterior cruciate ligament transection, between 6.8 +/- 2.3 mm at full extension and 12.6 +/- 3.3 mm at 30 degrees of flexion. Conseque ntly, the resultant forces on the medial meniscus, ranging from 52 +/- 30 N to 63 +/- 51 N between full extension and 90 degrees of knee flexion in th e intact knee, were doubled as a result of anterior cruciate ligament defic iency. However, after anterior cruciate ligament reconstruction, anterior t ibial translations were restored to the levels of the intact knee, and thus the forces on the medial meniscus were restored as well. Likewise, the in situ forces in the anterior cruciate ligament replacement graft increased b etween 33% and 50% after medial meniscectomy.