Meniscal Extrusion Measurements After Posterior Medial Meniscus Root Tears: A Systematic Review and Meta-analysis

Abstract

Background: Meniscal extrusion has become increasingly utilized when evaluating meniscus root abnormalities. However, no consensus definition or approach exists on how to measure extrusion. Purpose/Hypothesis: The purpose of this study was to evaluate the extent of heterogeneity in meniscal extrusion measurement techniques and reported extrusion values in knees with posterior medial meniscus root tears (PMMRTs). We hypothesized that meniscal extrusion measurement techniques would vary considerably throughout reported studies, with resultant wide-ranging published extrusion values. Study Design: Systematic review; Level of evidence, 4. Methods: A systematic review was conducted according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement. The inclusion criteria consisted of all clinical and cadaveric studies reporting on meniscal extrusion after PMMRTs, excluding studies lacking data in full extension, those presenting only semiquantitative analyses, articles reporting only differences in meniscal extrusion, and review articles. Results: A total of 45 studies were included. Imaging modality types included magnetic resonance imaging (89%), 3-dimensional reconstruction with computed tomography (7%), linear displacement transducers (2%), and a combination of magnetic resonance imaging and ultrasound (2%). The 3 most commonly used landmarks to acquire coronal images for meniscal extrusion measurements were the medial collateral ligament (38%), the midpoint of the anterior-posterior length of the medial meniscus (23%), and the middle of the medial femoral condyle (19%). The pooled mean extrusion values according to the measurement location were 3.5 ± 0.7 mm, 3.9 ± 0.8 mm, and 4.5 ± 2.1 mm, respectively, with no significant differences noted between the modality types ( P = .23). The pooled mean meniscal extrusion from all included studies was 3.2 ± 2.0 mm. Conclusion: Substantial variation exists in measurement techniques for meniscal extrusion, particularly as it relates to the coronal cross-sectional reference location. Further studies should aim to provide clear descriptions of the measurement method and have uniform measurement methodology to allow comparisons and pooling between studies.

Measuring Technique for Meniscal Extrusion Using Ultrasound in the Setting of Posterior Medial Meniscal Root Tears

“…With respect to measurement techniques, most available studies report using a reference line representing 0 mm of ME based on the location of only the medial tibial plateau, rather than a line connecting the vertices of the tibial and femoral cortices at the joint line. 11 , 15 The latter approach is difficult to reproduce, given that the femoral condyle is convex; therefore, identifying the vertex where the joint line begins on the femur is challenging to identify. In turn, an accurate reference line becomes challenging to consistently create.…”

“…A recent meta-analysis demonstrated that ME pooled from all patients with PMMRTs was 3.2 ± 2.0 mm—a wide range. 11 In addition, they also found that authors measured ME at various landmarks, including the medial collateral ligament in 38% of studies, the midpoint of the anterior−posterior length of the medial meniscus in 23% of studies, the middle of the medial femoral condyle in 19% of studies, and more. Given its low absolute measured values in the order of millimeters, ME is a fragile metric and requires a systematic and reproducible measurement technique so quantitative values can be meaningful.…”

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

“…Abnormal medial meniscus extrusion is deined as protrusion of the body of the medial meniscus beyond the tibial plateau [15]. In literature the presence of a meniscal lesion is often associated with meniscal extrusion [7,8,23]. Due to the anatomy of the medial meniscus, various lesions are described as more or less responsible for meniscal extrusion [9,11,18].…”

Radiographic OA, bone marrow lesions, higher body mass index and medial meniscal root tears are significantly associated with medial meniscus extrusion with OA or medial meniscal tears: a systematic review and meta-analysis

“…In this study, the definition of MME was based on the extrusion of the medial meniscus ≥ 3 mm [16, 50] and meniscal extrusion score ≥ 1 (0 = no extrusion, 1 = partial meniscal extrusion, and 2 = complete meniscal extrusion) on the coronal plane of MRI [38]. The inclusion criteria for this study were as follows: (1) articles reporting at least one factor associated with concomitant MME with OA or MMT; (2) study design included cross‐sectional, case–control, prospective or retrospective, and cohort studies; (3) study sample size was > 10 patients.…”

“…The medial meniscus on the tibial plateau serves an important function in the knee joint by facilitating shock absorption, load distribution, and reducing friction, thereby enhancing knee stability [9]. Medial meniscus extrusion (MME) refers to the protrusion of the medial meniscus beyond the tibial edge by more than 3 mm, leading to compromised hoop strain [16]. Biomechanical studies have demonstrated that MME reduces the tibiofemoral contact area and directly affects the ability of joints to adapt to load, increasing the risk of osteoarthritis (OA) [12].…”