Summary

Arthroscopic Centralization Protects a Medial Meniscus Posterior Root Repair - A Biomechanical Investigation

Abstract

Background

In addition to the anterior and posterior root, the meniscus is anchored to the tibia and femur by the meniscotibial-and meniscofemoral attachment. However, the interaction and load sharing between the roots and these peripheral attachments is not known.

Purpose

To investigate the influence of an insufficiency of the peripheral attachments on the forces acting on a posterior medial meniscus root repair in both neutral and varus alignment, and to explore whether meniscal centralization reduces these forces.

Methods

In eight fresh-frozen human cadaveric knees an arthroscopic transosseous root repair (step 1) was performed after sectioning the posterior root of the medial meniscus. The pullout suture was connected to a load cell, to allow measurement of the forces acting on the root repair. A medial closing wedge distal femoral osteotomy was performed to change the mechanical axis from neutral to 5° varus alignment. The meniscus was released from its peripheral attachments (step 2), followed by transosseous arthroscopic centralization (step 3). Each step was tested in both neutral and varus alignment. The specimens were subjected to non-destructive dynamic varus loading under axial compression of 300 N, in 0°, 15°, 30°, 45°, and 60° of flexion. The changes in force acting on the posterior medial meniscus root repair were statistically analyzed using a mixed linear model.

Results

Axial loading in neutral alignment led to increassed foraces at the root repair ranging from 3.2 ± 3.1 N (in 0°) to 6.3 ± 4.4 N (in 60°). In varus alignment, forces increased significantly from 30° (3.5 N; 95 % CI 1.1 – 5.8 N; P = 0.01) to 60° (7.1 N; 95 % CI 2.7 – 11.5 N; P = 0.007), in comparison to the neutral alignment. Cutting of the peripheral attachments in neutral alignment led to a significant increase of root repair forces in all flexion angles, from 7.0 N (95 % CI 1.0 – 13.0 N; P = 0.02) to 9.1 N (95 % CI 4.1 – 14.1 N; P = 0.003), in comparison to the intact state. Varus alignment significantly increased the forces in the cut states between 4.8 N (95 % CI 1.0 – 8.5 N; P = 0.02) to 11.1 N (95 % CI 4.2 – 18.0 N; P = 0.006), from 30° to 60°, in comparison to the neutral alignment. Arthroscopic centralization led to restoration of the native forces in both neutral and varus alignment, with no significant differences between the centralized and intact states.

Conclusion

An insufficiency of the peripheral attachments of the medial meniscus, as well as varus alignment, leads to increased forces acting on a posterior medial meniscus root repair. These forces were reduced by an arthroscopic meniscal centralization, which might therefore be used to protect meniscal root repairs