## 4 Discussion  
The main finding of this study is that both mosaicplasty and MACT techniques provided satisfactory clinical results at long-term follow-up in two homogeneous groups of patients affected by knee cartilage defects. Additionally, the MRI evaluation suggested a good and durable quality of repair tissue, although without correlations with the clinical outcomes. The comparative analysis of the two procedures suggested that while similar results were obtained for small lesions, MACT should be preferred versus mosaicplasty when addressing larger knee cartilage defects. The overall clinical results reported in this study are in line with other recently published long-term studies, showing that both mosaicplasty and MACT may offer satisfactory and durable results when applied for the treatment of relatively small chondral lesions of knee femoral condyles [17; 24; 25; 26]. In the largest available study of mosaicplasty that included 831 patients evaluated at 10 years of follow-up, [PERSON] et al. reported 92% good-to-excellent results with a low complication rate [26]. Similarly, [PERSON] et al. performed a long-term evaluation at 15 years of follow-up in 113 patients treated with MACT, reporting a significant and stable clinical scores improvement. Even the failures rates reported in this study reflect the literature findings, with higher failure rates documented in patients treated with mosaicplasty technique compared to MACT. [PERSON] et al. [13] found that, at an average follow-up of 10 years, patients who underwent mosaicplasty had an overall failure rate of 28% and a reoperation rate of 19%, thus reflecting the results obtained in the current study (overall failure rate of 25% and a reoperation rate of 10%). The survival of MACT of the present study appears to be actually higher than previous findings. A systematic review reported a failure rate of 10.4% at mid-long term follow-up in patients treated with MACT [27]. However, these differences may be due to the different populations of patients considered; other studies demonstrated a higher failure rate in some patients categories, such as knee osteoarthritis and patellar defects [25; 28], and these types of patients were excluded in the current study, where no failures were documented in the MACT group. Long-term results of both mosaicplasty and MACT have also been evaluated in comparison with other cartilage repair techniques. Compared to microfractures, mosaicplasty resulted in significantly better outcomes in several studies at long-term follow-up [29; 30; 31]. In particular, even though both mosaicplasty and microfractures presented a worsening of results at 10 years, [PERSON] et al. [32] reported significantly better results in patients treated with mosaicplasty, which presented a higher  
Figure 5: Evaluation of the defect size effect on the International Knee Documentation Committee (IKDC) subjective score and the percentage Tegner Score improvement at a final follow-up of 12 years in both groups of patients. The asterisk (*) indicates for the MACT group a tendency for higher subjective results compared to the mosaicplasty group for the defect area \(>\) 2 cm\({}^{2}\) (p = 0.092). The double asterisk (**) indicates a lower improvement in terms of Tegner Score for the defect area \(>\) 2 cm\({}^{2}\) in the mosaicplasty group (p = 0.014). activity level, a lower failure rate, and a lower radiographic evidence of osteoarthritis degenerative progression. These results may be explained by the better quality of repair tissue provided by the use of autologous graft compared to fibrocartilage obtained with bone marrow stimulation techniques [32]. Similarly, MACT also presented better patient-reported outcome scores and lower failures compared to microfractures [33; 34]. Additionally in this case, the excellent durability of MACT results could be explainable by the hyaline-like tissue restored [35], compared to the fibrocartilaginous repair tissue provided by microfractures as demonstrated by MRI studies [36; 37].