## 4 Discussion
Among them, age, sex, etiology and size of the defect seem to modify the failure rate, with female patients, older patients and those affected by degenerative or larger lesions, complex cases, and patients undergoing salvage treatment being more at risk of failures [13; 24; 25; 49; 50]. Such profiling of patient characteristics which may influence the outcome were not possible in this series due to the low number of patients, although interesting findings could be underlined for the most suitable treatment indication based on the lesion size. The current study has limitations that should be considered in the interpretation of the results. First of all, the retrospective design, with consequent lack of randomization, may entail an inclusion bias, with different patients treated with different procedures. Nevertheless, data were collected prospectively, and the strict patient selection by a statistician blinded to the study outcome allowed us to obtain two homogeneous groups to compare, thus allowing us to draw conclusions about the selected population. The absence of an intermediate evaluation is another limitation. Unfortunately, some patients of the two treatment groups were not evaluated at the intermediate follow-ups, hindering the possibility to better understand possible oscillations of the outcomes over time between the two techniques. Nevertheless, short and mid-term follow-ups of both procedures have already been reported in the literature. Secondarily, the relatively small number of patients evaluated hindered the possibility to confirm some correlations between outcome and influencing factors. Moreover, a slight (although not significant) heterogeneity was present between the two groups in terms of etiology, with some more degenerative cases in the mosaicplasty group. Nevertheless, the current survey represents the largest population evaluated in a comparative long-term analysis, and allowed meaningful clinical and MRI results, showing overall good results over time for both techniques, but lower results for mosaicplasty in lesions larger than 2 cm\({}^{2}\). Other limitations are the absence of arthroscopic and histologic examinations, and of a radiologic follow-up, often considered the ideal technique for evaluating cartilage quality and OA evolution. Moreover, the imaging evaluation was not available for all patients, because some patients declined to undergo MRI exam. Nevertheless, the high rate of MRI evaluations at long-term follow-up and the use of the recent MOCART 2.0 tool offered important information regarding the state of the repair tissue and of the whole joint, leaving the analysis of the degenerative progression to future studies with longer follow-up times. Alternative solutions have been explored to restore the articular surface while overcoming the drawbacks of mosaicplasty and MACT, aiming at lowering costs, simplifying the procedure, and improving long-term results [51; 52]. The most recent developments involve the use of cell sources for one-step solutions or the application of biomaterials, such as a cell-free approach [53; 54; 55; 56]. Nevertheless, while research is moving forward, it is fundamental to keep documenting the results of the most established procedures like mosaicplasty and MACT, to better understand how much and how long can patients benefit from these cartilage procedures, to detect the ideal candidates through a patient profiling, and to set a reference point to measure the potential of the other emerging solutions. Conceptualization, S.Z. and G.F.; methodology, M.B. and A.D.M. ; data curation, D.R. ; writing--original draft preparation, A.B. and L.A.; writing--review and editing, G.F.; supervision, A.D.M., M.B., G.F., and S.Z. All authors have read and agreed to the published version of the manuscript. This research received no external funding. S.Z. has received institutional support from Fidia Farmaceutici, Cartiheal, IGEA Clinical Biophysics, Biomet, and Kensey Nash; grant support from 1+; and royalties from Springer.