Summary

Biomechanical study on 24 cadaveric knees (fresh disarticulated at the hip) using the Dyneelax® laximeter, carrying out a sequential transection of the ACL and the various structures of the medial side (anteromedial capsule, superficial and deep MCL, POL,the posterior horn of the medial meniscus) defining their roles in stabilizing the knee in anterior translation,internal and external rotation

Abstract

Introduction

Ligament injuries of the medial side of the knee are frequent, grades I injuries usually have a good prognosis, but grades II and III injuries may leave sequelae. It is important to understand the contribution of each ligamentous structure of the medial side to facilitate improvement in clinical testing and management. These injuries can be isolated or associated with a rupture of the ACL, producing anteromedial or antero-anteromedial laxity.

Objective

To determine the respective role of the ACL and the different components of the medial side in the control of anterior translation and internal and external rotations

Material And Method

24 fresh-frozen cadaveric lower limbs, disarticulated at the hip, were tested in the University Anatomy Laboratory (mean age: 82 years). The following structures were isolated: the ACL, the anteromedial capsule (AMC), the medial collateral ligament (superficial and deep MCL), the posterior oblique ligament (POL) and the posterior horn of the medial meniscus to simulate a « ramp lesion ». The lower limb was positioned at 30° of flexion in neutral position on the Dyneelax® laximeter (0.1 mm and 0.1° accuracies) and underwent anterior forces of 0 to 200 N and torques (internal and external) from 0 to 5N/m. Each ligament structure was sequentially transectioned and the knee was then retested. The result (average of 5 successive tests) was presented in absolute value of translation and rotations for each structure. SIdak's tests were used to compare the gain at each step of sequential section.
Results.
Translation gains were significant for ACL, sMCL and POL transections (p<0.05).
Gains in internal rotation were significant for ACL, dMCL, POLand the posterior horn of the medial meniscus transections (p<0.05).
Gains in external rotation were significant for ALC, sMCL, dMCL, POL and the posterior horn of the medial meniscus transections (p<0.05).

The relative gains after transection of the ACL, CAM, sMCL, dMCL , POL and the posterior horn of the medial meniscus was respectively : 42.9%, 5.3%, 4.3%, 3.9%, 3.2 %, 7% in translation, 12.9%, 5.3%, 4.4%, 3.9%, 8.7%, 4% in internal rotation and 9.5%, 8%, 5.8%, 13.4%, 7.8%, 6% in external rotation.



Conclusion.
All of the medial ligament structures constitutes a functional unit in which each component has a specific passive contribution in the sagittal and rotatory control of the knee.