Meniscal allograft transplantation in discoid meniscus patients achieves good clinical outcomes and superior chondroprotection compared to meniscectomy in the long term

Purpose To compare the long-term clinical and radiological results of meniscal allograft transplantation (MAT) for discoid lateral meniscus (DLM) patients with MAT for non-discoid lateral meniscus patients and meniscectomy (ME) for DLM patients and, thus, to determine whether DLM patients are suitable candidates for MAT.Methods Eight MAT cases in DLM patients were identified (discoid MAT group), six MAT cases in non-discoid lateral meniscus patients (non-discoid MAT group) and ten total meniscectomy cases in DLM patients (discoid ME group) were matched as controls. Subjective evaluations, postoperative radiography and magnetic resonance imaging (MRI) were conducted at 5 years and 10-14 years, respectively. Joint degeneration was evaluated by the Kellgren-Lawrance (KL) grade and joint space width (JSW). MRI with T2 mapping sequences was used to quantitatively evaluate degeneration of the joint cartilage and shrinkage of the allografts. Student's t test was used to compare quantitative variables and the Mann?Whitney U test was used to compare categorical variables.Results There was no difference in Lysholm, IKDC, Tegner or VAS scores amongst the discoid MAT, non-discoid MAT and discoid ME groups at the final follow-up. No revision surgery was performed in any MAT patient. The JSW narrowing in the discoid MAT group was better than that in the discoid ME group (0.8 +/- 0.4 mm vs. 2.1 +/- 1.3 mm, p = 0.012) and worse than that in the non-discoid MAT group (0.1 +/- 0.1 mm, p = 0.003). The KL progression of the discoid MAT group was less than that of the discoid ME group (1.3 +/- 0.7 vs. 2.3 +/- 0.9, p = 0.034). The discoid ME group had worse cartilage lesion progression than the discoid MAT and non-discoid MAT groups. The allograft width of the DLM patients shrank more than that of the non-discoid patients at the meniscus midbody (3.6 +/- 0.9 mm vs. 6.2 +/- 1.9 mm, p = 0.015).Conclusion Compared to meniscectomy, MAT achieved similar long-term symptom relief and superior chondroprotection in discoid meniscus patients. Despite more graft shrinkage, the outcomes of MAT in discoid meniscus patients were comparable to those in non-discoid meniscus patients. Therefore, DLM patients may be suitable candidates for MAT procedures.