Summary

Meniscal extrusion is a common finding in patients over 50 years of age with suspected meniscal injury. It is associated with meniscal tears, especially in the posterior horn.

Abstract

Introduction

Even though meniscal extrusion alters the biomechanics of the meniscus, leading to accelerated degeneration, its clinical implications are still unclear. Magnetic Resonance Imaging (MRI) has an excellent diagnostic capacity for the study of these meniscal abnormalities. There are various factors associated with meniscal extrusion, however, there is little evidence on its incidence when meniscal disease is suspected.

Objectives
To describe the incidence rate of meniscal extrusion on MRI in patients >50 years of age with clinical suspicion of meniscopathy, and to assess its association with meniscal tears, maceration and BMI.

Methods

Randomized retrospective cohort between 2019 and 2021. Patients >50 years old with suspected meniscal injury with knee MRI done at Clínica Alemana de Santiago were included. Those <50 years old, with fractures or ligamentous injuries of the studied knee, and those with meniscal tears or previous knee surgery were excluded. 50 knees were randomly selected. Demographic and imaging variables were measured. Extrusion was defined as the protrusion of the meniscus ?3 mm from the tibial edge. Quantitative variables were described using mean and SD, and compared using Student's t-test. Categorical variables were described using frequency and percentage and compared using Fisher's exact test. The exploration of prognostic variables was done using logistic regression. 95% confidence intervals were constructed for the proportion of meniscal extrusion. A statistical significance of 5% was used and the data was processed in MiniTab 18.0.

Results

50 knees were analyzed; 54% men; mean age 60 years (± 7.4 SD); mean BMI 26.3 (± 4.2 SD); and 74% with suspected internal meniscal injury. Relevant imaging results include: 44% (22) presented extrusion, with an average of 4.4 mm (± 1.3 SD); and 58% (29) had a meniscal tear. There was no extrusion of the lateral meniscus. Of the knees with extrusion, 68.2% (15) presented tears, 60% corresponding to degenerative tears and 20% to maceration. Of the knees with extrusion and meniscal tears, 66.7% were complex tears, 20% horizontal; 86.7% were located in the posterior horn and body, 20% in the anterior horn, and 13.3% in the posterior root. There is an association between extrusion and tears of the posterior horn (p= 0.01). It is possible to highlight that there was no maceration in the knees without extrusion. Meniscal tear and BMI were not statistically significantly associated with extrusion.

Conclusion

Meniscal extrusion is a common finding in patients over 50 years of age with suspected internal meniscal injury. It is associated with meniscal tears, especially in the posterior horn.