Summary

Radial tear in case of a large/complex tear was significantly correlated with MME similarly to MMPRT.

Abstract

Introduction

Medial meniscal tears lead to decreased functions and increased risk of varus knee osteoarthritis (OA). The medial meniscus extruded from its physiological and anatomical position (MME) associated with a meniscal tear or a degenerative change is often identified in varus knee OA and induces further progression of knee OA. In general, radial tears extending to the periphery have been considered to result in reduction of meniscal hoop strength. Although it has been broadly reported that a medial meniscal posterior root tear (MMPRT) is a strong risk factor of MME, a relationship between a radial tear and MME is still unknown. The purpose of this study is to investigate the relationship between MME and meniscal tear type including radial tear.
METHODS. 153 patients (76 males and 77 females, average age: 58.0 ± 7.5 years) who underwent MRI for persistent medial knee pain concomitant with varus knee OA were included in this study. As for the measurement of the amount of MME, the image slice at the maximum meniscal extrusion on a coronal proton-density-weighted image was identified. Then, the distance from the edge of the extruded meniscus to a parallel line perpendicularly drawn from the medial tibial edge was measured and defined as the amount of the MME (ΔMME). The type of meniscal tear was divided into four types: horizontal tear, MMPRT, small radial tear detected in a single slice on MRI, and large radial tear coinciding complex tear detected in both sagittal and coronal planes on MRI (Figure 1). Difference in the ΔMME among four types of meniscal tears was statistically assessed. In addition, the correlation between patient characteristics or radiographic parameters of the lower leg and the ΔMME was evaluated using the Pearson's correlation coefficient. Subsequently, a multivariable logistic regression analysis of risk factor for development of the MME defined by more than 3 mm were conducted.

Results

The average ΔMME values were 3.36 ± 1.86 mm in the horizontal tears, 4.98 ± 1.28 mm in the MMPRTs, 4.18 ± 1.95 mm in the small radial tears and 5.0 ± 2.19 in the large/complex radial tears. The ΔMME in the MMPRTs and the large/complex radial tears were significantly larger than that in the horizontal tears (P = 0.001, P < .0001) . Significant correlations with ΔMME were observed for age and varus deformity of the lower leg (%MA, HKAA, and JLCA) . In terms of a risk factor of MME, the multivariable analysis showed that the varus deformity of the lower leg (HKAA) was not a significant risk factor. On the other hand, age and meniscal tear types such as the MMPRT and the large/complex radial tear were demonstrated as risk factors significantly associated with MME of more than 3 mm.

Discussion

The present study showed that a radial tear in case of a large/complex tear was significantly correlated with MME similarly to MMPRT.