Ideal remaining meniscus width and risk factors for decrease in meniscus width after reshaping surgery in pediatric patients with discoid lateral meniscus

Purpose: This study aimed to determine the ideal remaining discoid meniscal width after reshaping surgery and to investigate the preoperative risk factors for changes in the meniscal width. Methods: Twenty-nine pediatric patients (39 knees) who underwent arthroscopic reshaping for symptomatic discoid lateral meniscus (DLM) were retrospectively analyzed. MRI was performed postoperatively and at 6 months or 1–2 years. Changes in meniscal width were measured, and logistic regression and receiver operating characteristic (ROC) curve analyses identified risk factors and cut-off values. Results: The meniscal width gradually decreased, particularly in the midbody (25.7 % at 6 months and 38.1 % at 1–2 years, postoperatively). Risk factors for width reduction included a complete-type DLM (β = 26.0, P = 0.036) and a smaller preoperative meniscal height (β = −4.51, P = 0.048). The ROC curve analysis indicated that a preoperative meniscal height of ≤ 3.3 mm and preserving a meniscal width of ≤ 8.5 mm after surgery may result in a residual meniscal width of less than 5 mm. Conclusion: The ideal remaining meniscal width after reshaping surgery should be > 8.5 mm to minimize the risk of postoperative degeneration. Surgeons should consider preserving additional meniscal tissue, especially in patients with risk factors such as complete DLM or a meniscal height of less than 3.3 mm, to improve long-term joint preservation.