Biomechanical comparisons of three different tibial tunnel directions in posterior cruciate ligament reconstruction

To investigate the effects of 3 different tunnel directions on the outcomes of posterior cruciate ligament (PCL) reconstruction surgery based on the forces exerted on the replacement ligament from a biomechanical point of view. The 3 tunnel directions in the proximal tibia are medial, central, and lateral.

Biomechanical study.

The forces exerted on the replaced PCL were calculated using finite element analyses as well as measurements from 6 cadavers. The results of the 3 surgical approaches were then compared. In the finite element analyses, the replaced ligament was assumed to have nonlinear elastic as well as viscoelastic properties. To simulate the overload in exercise, the femur was forced to move in the anterior direction abruptly while the tibia was held. From numerical analyses, the resultant forces, von Mises stresses, and maximum shear stresses on the replacement PCLs were calculated and compared. In the cadaveric study, a pressure-sensitive thin film was inserted between the replacement PCL and the killer turn area of the tibia. The color changes in films were evaluated using digital image processing in each case.

The medial approach showed remarkably higher stresses and forces on the interface between the replaced PCL and the killer turn in both the numerical and cadaveric study. In contrast, the lateral approach showed the lowest stresses.

The numerical and cadaveric studies indicate that the lateral approach is highly promising compared with the other approaches.

The lateral approach has been shown to minimize stress concentration around the killer turn during in vitro experiments and a computer simulation of PCL reconstruction for long-term stability. The lateral approach technique appears to provide a promising clinical outcome in patients undergoing PCL reconstruction.