Biomechanical Analysis of a Posterior Cruciate Ligament Reconstruction

TLDR

The study hypothesizes that posterior cruciate ligament reconstructions are often compromised by associated posterolateral injuries and evaluates this by testing isolated and combined injury models with a robotic force‑moment sensor system. Knee kinematics and in‑situ forces of native and reconstructed posterior cruciate ligaments were measured in isolated and combined injury models using a robotic/universal force‑moment sensor system under four external loading conditions. Reconstruction restores near‑intact tibial translation in isolated injuries, but posterolateral deficiency increases translation, rotation, and graft forces, rendering the graft ineffective and overloaded; thus, simultaneous reconstruction of both structures is recommended.

Abstract

We hypothesized that posterior cruciate ligament reconstructions are often compromised by associated injuries to the posterolateral structures. Therefore, we evaluated a posterior cruciate ligament reconstruction in isolated and combined injury models using a robotic/ universal force-moment sensor testing system. The resulting knee kinematics and the in situ forces in the native and reconstructed posterior cruciate ligament were determined under four external loading conditions. In the isolated injury model, reconstruction reduced posterior tibial translation to within 1.5 1.3 to 2.4 1.4 mm of the intact knee at 30° and 90° under a 134-N posterior tibial load. In the combined injury model, deficiency of the posterolateral structures increased posterior tibial translation of the reconstructed knee by 6.0 2.7 mm at 30° and 4.6 1.5 mm at 90° of flexion. External rotation increased up to 14° while varus rotation increased up to 7°. In situ forces in the posterior cruciate ligament graft also increased significantly (by 22% to 150%) for all loading conditions. Our results demonstrate that a graft that restores knee kinematics for an isolated posterior cruciate ligament deficiency is rendered ineffective and may be overloaded if the posterolateral structures are deficient. Therefore, surgical reconstruction of both structures is recommended in the setting of a combined injury.