Summary

When the postoperative MRI were evaluated in both groups (discoid lateral meniscus group vs normal group), the width of the remained meniscus in discoid group was comparable with that of normal subjects. However, the subluxation of remained meniscus in discoid group was found to anteriorly and laterally compared with normal subjects.

Abstract

Purpose

Current treatments for discoid lateral meniscus (DLM) favor partial meniscectomy, but no studies to date have compared the resulting position and size with that of normal lateral meniscus. To evaluate the postoperative position and size of DLM compared with that of normal lateral meniscus using magnetic resonance imaging (MRI).

Methods

This retrospective study involved 52 symptomatic DLMs (discoid group) who underwent arthroscopic partial meniscectomy with or without repair and 50 normal controls (control group) who had no pathologic lesions. MRI evaluations including height, width, and relative percentage of extrusion (RPE) were performed. Sagittal position parameters, including the distances from the articular cartilage center to anterior meniscus (CAMD), from the anterior articular cartilage margin to anterior horn (ACMD), from the articular cartilage center to posterior meniscus (CPMD), and from the posterior articular cartilage margin to posterior horn (PCMD), were also assessed. Logistic regression analysis was performed to find associated factors with extrusion of remaining DLM.

Results

Height of the discoid group was significantly lower than control group (discoid vs normal: 5.0 ± 1.5 mm vs. 6.7 ± 1.1 mm; p = 0.000), although the width was not significantly different (9.0 ± 4.1 mm vs. 9.9 ± 2.1 mm; p = 0.148). RPE in the discoid group were significantly larger than in control group (p = 0.005). Only CAMD and ACMD in discoid group were significantly different (positioned more anteriorly) from the control group (p = 0.000). Presence of preoperative meniscal shift [odds ratio (OR): 12.448, 95% confidence interval (CI): 1.465–92.733; p = 0.003] and operative technique, especially partial meniscectomy with repair (OR: 19.125, 95% CI: 4.29–85.257; p = 0.000), were the major factors associated with extrusion postoperatively.

Conclusion

Width of the remaining DLM was comparable to that of normal controls, but the position was found to be more anterior in sagittal plane and more lateral in coronal plane than that of normal controls. Preoperative meniscal shift and combined meniscus repair were the major factors for smaller width and greater meniscus extrusion; thus, surgeons should address these factors before surgery.