[An experimental study of split-double-bundle posterior cruciate ligament reconstruction in single femoral tunnel]

To compare the single femoral tunnel split-double-bundle posterior cruciate ligament (PCL) reconstruction with the single-bundle PCL reconstruction and to discuss the advantages of the modified reconstruction method.

Fourteen donated fresh-frozen human knee specimens were biomechanically tested, which included knee specimens from 12 males and 2 females, and their ages ranged from 20 to 31 years. The specimen length of the femur and the tibia was 20 cm. The tibial posterior translation and the PCL strains were first measured when PCL was in an intact state (the intact group, n=14). Then, PCL was cut (the cut group, n=14). The posterior translation was measured when a posterior load was applied. After that, the specimens were randomly divided into two groups: the single-bundle group (n=7) and the double-bundle group (n= 7). When the posterior load was applied to the tibia, the bundle strain and the tibial posterior translation were measured with the knees flexed at 0, 30, 60, 90 and 120 degrees, respectively.

While a 100 N posterior force was applied, the posterior tibial displacement of the intact PCL knee ranged from 1.97+/-0.29 mm to 2.60+/-0.23 mm at the different knee flexion angles. In the PCL-cut state, the tibial displacement increased significantly from 11.27+/-1.06 mm to 14.94+/-0.67 mm (P<0.05). After the single-bundle reconstruction, the posterior tibial translation ranged from 1.99+/-0.19 mm to 2.72+/-0.38 mm at the different knee flexion angles. In the split-double-bundle reconstruction, the posterior tibial translations ranged from 2.27+/-0.32 mm to 3.05 +/- 0.44 mm. The graft of the single-bundle reconstruction was tensioned from 0 degrees to 120 degrees, and the tibial displacement increased significantly at 90 degrees compared with that at the other angles (P<0.05). In the double-bundle reconstruction, the anterolateral bundle and the posteromedial bundle were tensioned in a reciprocal fashion, and the tibial displacement had no significant difference at the five kinds of the flexion angles.

The single femoral tunnel split-double-bundle PCL reconstruction can restore the posterior tibial displacement at different flexion angles, and the tibial displacement in the single-bundle PCL reconstruction knee can be increased when the knee flexion is at 90 degrees. In the double-bundle reconstruction, the graft can be tensioned in a reciprocal fashion and the biomechanical features can be nearer to those of the normal PCL bundles.