Double-bundle PCL and posterolateral corner reconstruction components are codominant

Abstract

A more complete biomechanical understanding of a combined posterior cruciate ligament and posterolateral corner knee reconstruction may help surgeons develop uniformly accepted clinical surgical techniques that restore normal anatomy and protect the knee from premature arthritic changes. We identified the in situ force patterns of the individual components of a combined double-bundle posterior cruciate ligament and posterolateral corner knee reconstruction. We tested 10 human cadaveric knees using a robotic testing system by sequentially cutting and reconstructing the posterior cruciate ligament and posterolateral corner. The knees were subjected to a 134-N posterior tibial load and 5-Nm external tibial torque. The posterior cruciate ligament was reconstructed with a double-bundle technique. The posterolateral corner reconstruction included reattaching the popliteus tendon to its femoral origin and reconstructing the popliteofibular ligament. The in situ forces in the anterolateral bundle were greater in the posterolateral corner-deficient state than in the posterolateral corner-reconstructed state at 30 degrees under the posterior tibial load and at 90 degrees under the external tibial torque. We observed no differences in the in situ forces between the anterolateral and posteromedial bundles under any loading condition. The popliteus tendon and popliteofibular ligament had similar in situ forces at all flexion angles. The data suggest the two bundles protect each other by functioning in a load-sharing, codominant fashion, with no component dominating at any flexion angle. We believe the findings support reconstructing both posterior cruciate ligament bundles and both posterolateral corner components.

Fig. 1

The robotic system is capable of operating in position-controlled mode in which the joint is moved in space to a desired position in six-degrees-of-freedom while the UFS measures the resulting external forces and moments acting on the joint [7, 9, 27]. The robot also can be operated in a force-controlled mode using force-moment feedback from the UFS so a desired force can be applied while the resulting changes in kinematics are recorded.

Fig. 2

The PLC was reconstructed using a 5- to 6-mm doubled gracilis tendon for the PFL and by reattaching the PT to its femoral origin. The double-bundle PCL reconstruction was performed using an 11-mm Achilles tendon (AL bundle) and a 7- to 8-mm doubled semitendinosus tendon (PM bundle).

Fig. 3

In situ forces in the AL and PM bundles in the PLC-reconstructed and PLC-deficient states (mean ± standard error of the mean) under a 134-N PTL are shown. The in situ forces in the AL bundle were greater (p = 0.036) in the PLC-deficient state than in the PLC-reconstructed state at 30°. There were no differences in the in situ forces between the AL and PM bundles at any flexion angle in either PLC state.

Fig. 4

In situ forces in the AL and PM bundles in the PLC-reconstructed and PLC-deficient states (mean ± standard error of the mean) under a 5-Nm external tibial torque (ETT) are shown. The in situ forces in the AL bundle were higher (p = 0.006) in the PLC-deficient state than in the PLC-reconstructed state at 90°. There were no differences in the in situ forces between the AL and PM bundles at any flexion angle in either PLC state.

Fig. 5

In situ forces in the PT and PFL in the PCL-reconstructed state (mean ± standard error of the mean) under a 134-N PTL are shown. There were no differences detected between the PT and PFL at any flexion angle.

Fig. 6

In situ forces in the PT and PFL in the PCL-reconstructed state (mean ± standard error of the mean) under a 5-Nm external tibial torque (ETT) are shown. There were no differences detected between the PT and PFL at any flexion angle.