## 4 Discussion
At each follow-up, the radiolucency of implants was progressively more similar to radiolucency of the surrounding bone (see exemplificative Figures 1 and 2). We interpreted this evidence as supporting the thesis that SB would have been able to integrate with autologous bone tissue, favouring deposition of new bone matrix within an ongoing remodelling process: indeed, there is a clear morphological pattern on the evolution of the standard X-Ray imaging series over time which shows the substitution of the grafted material with a more homogeneous signal in the area of graft implant. As already demonstrated, the progressive remodelling together with an increase of the mineral signal cannot be dependent on the active remodelling of the graft per se given it is a decellularized matrix. Therefore, the increase in the density over time depends on novel mineral matrix apposition likely induced by the graft, as previously shown both in vivo and in vitro [7; 20]. The literature on the use of xenografts in the setting of tibial plateau fractures is still limited. In 2009, [PERSON] et al. [27] described clinical and radiological findings of a series of patient treated for tibial plateau fractures with bone xenograft, but their study did not include any quantitative assessment of outcomes. The majority of studies reported in the literature, about bone augmentation for the treatment of such fractures, involve AIBG; controlled studies comparing different types of bone graft are scarce [31]. However, innovative biomaterials for bone transplantation have demonstrated to be safe, reliable, and biocompatible tools for bone transplantation [16]. Their use resulted in most cases in reduced rate of complications, operative times, operative costs, and hospital length of stay, along with comparable or better results in term of clinical and radiological outcomes [8; 38; 39; 40; 41]. Furthermore, xenohybrid materials demonstrated that can be successfully used as carriers to locally administer drugs or MSCs, making them a useful resource for orthopaedic surgeons, in a variety of conditions [7; 20; 44; 45]. Hence, more clinical studies to better understand the role of biomaterials in orthopaedic surgery are encouraged. This study shows some limitations, like the relatively small number of patients having been chosen within the framework of an observational study, the retrospective nature of the analysis, which includes different subtypes of fractures and the lack of a pre-existing quantitative scale definingradiological outcomes; at this last regard, we had hence to develop a new protocol [20]. Also, the ROM of the contralateral (healthy) joint was not reported as it was considered as physiological, while the aim was to test the improvement in the operated joint. Finally, it would have been useful to evaluate a control group a that has been treated in the same hospital with the same clinical procedures in order to evaluate the influence of the bone substitute on the healing. Nevertheless, here we have collected strong clinical evidences already from the 1-year follow-up, being confirmed by all follow-ups (91.2%) recorded after 1.5 and 2 years, including the lack of long-term complications. Overall, collected data offers a confirmation to investigated clinical endpoints and confirms material properties too. A further study will address bone density and graft density on a selected group of patients using a novel TC protocol.