2017 ISAKOS Biennial Congress ePoster #1602

 

A Biomechanical and Histological Comparison of the Supra- & Infra-Meniscal Fibers of the Anterolateral Ligament

Gillian Corbo, MSc, London, ON CANADA
Alan Getgood, MD, FRCS(Tr&Orth), DipSEM, London, ON CANADA
Maddie Norris, MSc, London, ON CANADA
Timothy A. Burkhart, PhD, London, ON CANADA

Western University, London, ON, CANADA

FDA Status Not Applicable

Summary

The infra- and supra-meniscal ALL sections have different material properties such that the infra-meniscal fibers are stronger and stiffer than the supra-meniscal sections

Abstract

Introduction

Injury to the anterolateral ligament (ALL) of the knee, is highly correlated with injury to the ACL and the lateral meniscus. Recent evidence suggests that the ALL’s anatomic connection to the lateral meniscus may be responsible for the creation of lateral meniscus tears. Furthermore, it is has been shown that the ALL is divided into two sections: supra-meniscal fibers running from the femoral origin to the meniscus, and infra-meniscal fibers running from the tibial insertion to the meniscus. However, the biomechanical effect of this ALL bifurcation is not well understood. Therefore, the purpose of this research was to determine if differences exist between the structural properties of the supra- and infra-meniscal parts of the ALL.

Methods

Nine cadaveric knee specimens (mean (SD) age = 79 (14.6) years) were dissected to isolate and identify the ALL. The specimens were then randomly assigned to one of two groups: i) supra-meniscal – the ALL below the meniscus was sectioned leaving only the supra-meniscal ALL intact; and ii) infra-meniscal – the ALL above the meniscus was sectioned leaving only the infra-meniscal attachment intact. The specimens were rigidly secured within an Instron materials testing machine. The specimens were statically pre-loaded to 20N for two minutes followed by a cyclic preload between 10N and 30N for 10 cycles at 1 Hz. Following pre-loading, the specimens were subjected to a pull to failure test at 1 mm/s. The mechanical properties of each ALL-meniscus construct were categorized with the load to failure, stiffness, and peak stress. One additional specimen was dissected to separate the infra- and supra meniscal sections and a mason’s Trichome histological analysis was performed.

Results

There was a significant difference between infra- and supra-meniscal attachments such that the infra-meniscal fibers were significantly stronger and stiffer than the supra-meniscal fibers (p=0.028) and (p=0.02) respectively. The peak stress was also significantly greater in the infra-meniscal sections (p=0.04). For the five supra-meniscal specimens, failure of the ALL occurred by three mechanisms: mid-ligamentous tear (n=3), ligamentous tear at the femoral origin (n=1) and failure near the meniscal insertion (n=1). For the four infra-meniscal specimens, failure of the ALL occurred by two mechanisms: mid-ligamentous tear (n=3) and avulsion of the bony tibial attachment (Segond fracture) (n=1). The histology confirmed that the organization of collagen was consistent with ligamentous tissue with fiber organization relatively consistent between the two ALL sections.

Discussion And Conclusion

The significantly stronger infra-meniscal fibers may explain the reported incidence of Segond fractures, where the lateral aspect of the tibia is avulsed from the bone3. The strong connection at the ALL-meniscus interface is evidenced by only one specimen failing near the meniscal insertion and would suggest that any damage to the lateral meniscus caused by the ALL would be within the horns rather than the body of the meniscus1. The results of this study indicate that there is a clear difference in the tensile strength between the two sections of the ALL.