A Flat Reconstruction of the Medial Collateral Ligament and Anteromedial Structures Restores Native Knee Kinematics: A Biomechanical Robotic Investigation.

BACKGROUND

Injuries of the superficial medial collateral ligament (sMCL) and anteromedial structures of the knee result in excess valgus rotation and external tibial rotation (ER) as well as tibial translation.

PURPOSE: To evaluate a flat reconstruction of the sMCL and anteromedial structures in restoring knee kinematics in the combined MCL- and anteromedial-deficient knee.

STUDY

DESIGN

Controlled laboratory study.

METHODS

Eight cadaveric knee specimens were tested in a 6 degrees of freedom robotic test setup. Force-controlled clinical laxity tests were performed with 200 N of axial compression in 0°, 30°, 60°, and 90° of flexion: 8 N·m valgus torque, 5 N·m ER torque, 89 N anterior tibial translation (ATT) force, and an anteromedial drawer test consisting of 89 N ATT force under 5 N·m ER torque. After determining the native knee kinematics, we transected the sMCL, followed by the deep medial collateral ligament (dMCL). Subsequently, a flat reconstruction of the sMCL with anteromedial limb, mimicking the function of the anteromedial corner, was performed. Mixed linear models were used for statistical analysis (P < .05).

RESULTS

Cutting of the sMCL led to statistically significant increases in laxity regarding valgus rotation, ER, and anteromedial translation in all tested flexion angles (P < .05). ATT was significantly increased in all flexion angles but not at 60° after cutting of the sMCL. A combined instability of the sMCL and dMCL led to further increased knee laxity in all tested kinematics and flexion angles (P < .05). After reconstruction, the knee kinematics were not significantly different from those of the native state.

CONCLUSION

Insufficiency of the sMCL and dMCL led to excess valgus rotation, ER, ATT, and anteromedial tibial translation. A combined flat reconstruction of the sMCL and the anteromedial aspect restored this excess laxity to values not significantly different from those of the native knee.

CLINICAL RELEVANCE: The presented reconstruction might lead to favorable results for patients with MCL and anteromedial injuries with an anteromedial rotatory knee instability.