Meniscal forces and knee kinematics are affected by tibial slope modifying high tibial osteotomy.

PURPOSE

To quantify the effect of increasing the posterior tibial slope (PTS) on knee kinematics and the resultant medial and lateral meniscal forces.

METHODS

In this controlled laboratory study, a 6 degrees of freedom (DOF) robotic testing system was used to apply external loading conditions to seven fresh-frozen human cadaveric knees: (1) 200-N axial compressive load, (2) 5-N m internal tibial +10-N m valgus torque and (3) 5-N m external tibial + 10-N m varus torque. Knee kinematics and the resultant medial and lateral meniscal forces were acquired for two PTS states: (1) native PTS and (2) increased PTS. Resultant forces in the medial and lateral meniscus were calculated using the principle of superposition.

RESULTS

In response to 5-N m external tibial + 10-N m varus torque, significantly more internal tibial rotation was observed after increasing PTS at 60° (p = 0.0156) and 90° (p = 0.0156) flexion. Increasing PTS caused significantly more medial tibial translation from 30° to 90° flexion in response to 5-N m internal tibial + 10-N m valgus torque. In response to 5-N m external tibial + 10-N m varus torque, the resultant force in the medial meniscus at 60° flexion decreased significantly after increasing PTS (32.8%, p = 0.016). Resultant forces in the lateral meniscus decreased significantly after increasing PTS at 30° (34.5%; p = 0.016) and 90° (29.7%; p = 0.031) flexion in response to 5-N m internal tibial + 10-N m valgus torque.

CONCLUSION

Increasing PTS in a native knee with intact cruciate ligaments affected 6 DOF knee kinematics and decreased resultant forces in the medial and lateral meniscus by up to 35% in response to combined rotatory loads. Therefore, increasing PTS during high tibial osteotomy in a knee with intact cruciate ligaments does not increase the force carried by the entire meniscus at time zero.

LEVEL OF EVIDENCE

N/A.