The meniscal extrusion index is a reliable indirect sign of different meniscal lesion patterns: a classification based on percentage of meniscal extrusion

Abstract

Purpose This study's goal is to propose a straightforward classification system based on the MEI (Meniscal Extrusion Index), a measure of meniscal extrusion, that relates to various meniscal lesion patterns and has clinical and biomechanical significance. The study's secondary goal is to determine whether the standard 3 mm meniscal extrusion parameter still has value by correlating the MEI with it. Methods 1350 knee MRIs that were performed over the course of 2 years made up the study cohort. Following the application of inclusion and exclusion criteria, 200 of those patients were qualified to participate in the study. All the measurements examined for this study underwent an interobserver reliability test. Results In the 1350 MRIs that were examined for this study, meniscal extrusion of any grade was present 18.9% of the time. The use of the MEI revealed three groups of patients: those with a MEI < 20%, who are likely para-physiological; those with a MEY between 20% and 40%, who are in a grey area; and those with a MEY > 40%, who have lesions that are impairing the proper meniscal function. According to the authors' findings, the percentage of meniscal extrusion did not correlate with the finite number (3 mm), making the 3 mm parameter an unreliable evaluation method. Conclusions This study is clinically relevant, because it proposes a simple and reproducible classification of meniscal extrusion that may aid in evaluating the severity of an extrusion and help in the diagnosis of lesions that might be difficult to identify on MRI. Level of evidence Level IV.

Meniscal extrusion consensus statement: A collaborative survey within the Meniscus International Network (MenIN) Study Group

“…Considering the implications of a meniscal extrusion classification system, respondents in the current study advocated for a classification addressing OA progression, treatment approaches, a grading system, clinical outcomes/prognosis, stability or progression of meniscal extrusion, dynamic factors, centralization procedures and reducibility [23]. Various classification systems have been proposed to categorize meniscal extrusion, and these existing systems aim to provide clinicians with standardized frameworks for assessing the severity, stability and prognostic implications of meniscal extrusion [1, 3]. One commonly cited classification system is the Stoller classification, which categorizes meniscal extrusion into three grades based on the extent of extrusion relative to the tibial plateau [27].…”

“…Meniscal extrusion has garnered substantial attention amongst knee surgeons, with recent years witnessing the emergence of numerous studies and classification systems designed to improve understanding of the pathology and clinical implications [3,14,20,29]. These frameworks aim to augment our understanding of the aetiology, biomechanical repercussions and clinical implications of meniscal extrusion.…”