Discoid lateral meniscus in children: magnetic resonance imaging after arthroscopic resection

Purpose The discoid meniscus is a common meniscal anomaly. Symptomatic discoid menisci treated by arthroscopic surgery were examined preoperatively and postoperatively by magnetic resonance imaging (MRI). Aim of this study was to quantify the amount of meniscal resection when treating discoid meniscus in children by partial meniscectomy. The hypothesis was that partial meniscectomy left sufficient amounts of meniscal tissue. Methods A quantitative evaluation of meniscal size comparing preoperative and postoperative data after partial meniscectomy was performed by MRI ( n = 6). The anteroposterior meniscal diameter and anterior and posterior thickness were measured. The relative postoperative thickness to preoperative thickness was defined. All patients were graded according to Lysholm score and Ikeuchi knee scale. Results The quantitative MRI evaluation showed a pronounced reduction of the anteroposterior meniscal diameter (42%) and anterior thickness (41%) after partial meniscectomy, whereas the posterior thickness showed a mean increase of 50%. According to Ikeuchi, all clinical postoperative findings were excellent and displayed an increase in Lysholm score. Conclusions MRI findings showed that the amount of remaining tissue after partial meniscectomy was smaller than aspired. Especially in the anterior joint, the final size of remaining meniscal tissue was overestimated intraoperatively. It may be concluded that in arthroscopic partial meniscectomy, the final meniscal size, especially in the anterior part of the joint, is difficult to assess. As it is known that the extent of meniscal resection plays a crucial role in the clinical course of discoid menisci, these data claim retentiveness in resecting meniscal tissue. Level of evidence Therapeutic case series, Level IV.