Summary

Valgus Malalignment Leads to Increased Loading of a Medial Collateral Ligament Reconstruction under Dynamic Valgus Loading

Abstract

Background

Valgus malalignment has been considered an important risk factor for failure of medial collateral ligament reconstructions (MCLR). Thus, the aim of this study was to analyze the forces on a MCLR in valgus maligned knees.

Methods

Eight fresh-frozen human cadaveric knees (72.9  9.5 years) were subjected to dynamic valgus loading using a custom-made kinematics rig at 400N axial loading. After resection of the superficial medial collateral ligament, a single bundle MCLR with a hamstring tendon autograft was performed. The tibial side of the reconstruction was connected to a custom-made tensioning device connected to a force sensor, which allowed measurement of the forces acting on the reconstruction with an accuracy of ± 0.1 N. A medial opening wedge distal femoral osteotomy was performed and fixed with an external fixator to gradually adjust the alignment in five degree increments: 0° valgus (force vector passing through the center of the tibial spine), 5° valgus (force vector passing through 75% of the distance between the most medial and lateral aspects of the tibial plateau), and 10° valgus (force vector passing through 100% of the distance between the most medial and lateral aspects of the tibial plateau). For each degree of valgus deformity, the resulting forces on the MCLR were captured from 0° to 60° of knee flexion.

Axial loading of the knee in neutral alignment led to a mean increase of force on the MCLR of 10.2 ± 14.2 N in 0°, 8.9 ± 12.7 N in 15°, 7.6 ± 12.3 N in 30°, 10.3 ± 11.4 N in 45°, and 9.4 ± 11.5 N in 60°. Moderate valgus malalignment significantly increased the forces on the MCLR in all flexion angles between 6.3 N and 9.7 N (p < 0.05). A severe valgus malalignment resulted in a further increase of the forces at the MCLR at all flexion angles between 29.4 N and 40.0 N in comparison to the neutral alignment (p < 0.05).

Conclusion

Increasing valgus alignment of the knee leads to increased forces on the reconstructed MCL, possibly leading to secondary deficiency of a reconstruction with subsequent re-instability. In case of chronic medial instabilities, valgus deformities ≥ 5° should be corrected concomitantly to a MCLR.