## 4 Discussion
SF-36 is a questionnaire that assesses general health status through 36 questions [23]. The results of the questions are then transformed in eight scales, each one ranging from 0 to 100. The higher the score the higher the level of healthiness related to the parameter assessed by that specific scale. The mean values of SF-36 are reported in Table 2. For each scale values are excellent and similar to those of the general population. Mean VAS decreased from \(6.33\pm 1.40\) to \(1\pm 0.79\), difference that we considered significant (\(p<0.0001\)). None of the 34 patients reported any local complication related to the implant, nor neurovascular or infectious adverse effect, which points out the safety of the graft. We used literature data within our study as a referenced historical control group. The comprehensive review of the literature published in 2013 by [PERSON] et al. [31] analysed data from 672 patients from different studies, with different biomaterials used: fracture healing was uneventful in over 90% of the cases over a variant period of time; secondary collapse of the knee joint surface was reported in 8.6% in the biological substitutes, 5.4% in the hydroxyapatite, 3.7% in the calcium phosphate cement, and 11.1% in the calcium sulphate cases. The recorded incidence of primary surgical site and donor site infection (3.6%) was not statistically significant different, however donor site-related pain was reported up to 12 months following autologous iliac bone graft (AIBG) harvest, i.e. in the most commonly performed procedure for bone augmentation in the management of tibial plateau fracture. [PERSON] et al. [36] reported good clinical outcomes in a series of patient with tibial plateau fractures treated with a hydroxyapatite bone substitute, however highlighting some complications like infections and collapses. Moreover, they considered the biodegradation process of the graft as slow. [PERSON] et al. [37] described a series of 49 patients whom bone augmentation was performed with a CaP bone cement, reporting good results with regard to return to activity and clinical outcomes; however, 7% of patients presented complications. Similar results have been obtained by other authors, using the same type of synthetic biomaterial [38; 39; 40]. Moreover, [PERSON] et al. [38] reported a significant reduction in mean duration of surgery in patients treated with the CaP bone cement if compared with patients who underwent AIBG (55 vs 101 min, \(p<0.0001\)), which have implications on overall costs of procedures [41]. We quantitatively assessed the grade of knee joint mobilisation, which is crucial to restore weight bearing, through measurement of the ROM. Our series of patients had a mean ROM of \(124\pm 6^{\circ}\) at 1-year follow-up. [PERSON] et al. [42] in a prospective, randomised, multi-centric study comparing CaP cement with AIBG, registered that 69% of patients of the study group had ROM \(>120^{\circ}\) at average 12 months follow-up. [PERSON] et al. [43] studied a group of patients treated with allograft, that reported mean ROM of \(118^{\circ}\) at 12 months; however, one patient presented osteomyelitisitis and in four cases subsidence of the joint. Comparison with the current literature is challenging, due to the lack of standardised follow-up protocols and differences in quantitative assessment of outcomes among the studies. However, the implant of SB in our series resulted in a standard return to knee mobilisation, as highlighted by the mean ROM at last follow-up and the return to partial weight bearing at 4-6 weeks. We also described no complications, like infections and joint subsidence, if compared to similar studies present in the medical literature [31]. Radiological follow-up did not show diastasis or depressions of tibial articular surface excluding the incomplete subchondral reductions documented at the first post op X-ray, which means that mechanical properties of SB were adequate for high and complex forces which the plateau commonly undergoes.