## 4 Preservation of Hamstrings Tibial Insertion  
The evidence regarding the outcomes of pedunculated hamstring procedures is summarized in Table 2.  
While reconstructing an ACL with the hamstring autograft, the benefits emerging from its tibial attachment preservation are two-fold--Biological and mechanical. First, [PERSON] et al. [19] reported in their anatomic study that pes anserinus tendons are consistently well innervated and vascularized along their course. These authors suggest that preservation of this supply may be of clinical benefit. Experimental ACL reconstructions performed in an animal model revealed that the preservation of hamstrings tibial attachment preserved the viability of the graft and enabled the bypass of the stage of avascular necrosis during graft remodeling [20,21]. Second, the cadaver study conducted by [PERSON] et al. [22] demonstrated the significantly higher pull-out strength of the pedunculated hamstring graft fixed with a tibial screw compared to the free hamstring graft, with a 65% higher load to failure in the pedunculated graft group. The load to failure in the pedunculated hamstring group without additional tibial fixation was 33% higher than in the free graft group, although the difference did not reach statistical significance. A review published in 2015 regarding the preservation of hamstring tibial insertion pointed out the great heterogeneity of available surgical techniques as well as fixation methods, which precluded authors from drawing a definitive conclusion about the superiority of insertion-preserving or insertion-sacrificing procedure over each other [23]. However, the results from reported case series were satisfactory and comparable with conventional ACL reconstructions. Since then, several studies have evaluated the functional and biomechanical outcomes of hamstring insertion-preserving procedures. [PERSON] et al. compared the ACL reconstruction with pedunculated hamstring autograft and the free hamstring autograft after 2 years of follow-up [24]. The results of their single-blinded randomized trial reported significantly higher Cincinnati knee scores, greater improvement in the Tegner activity scale and lower side-to-side difference in KT-1000 testing in favor of the pedunculated hamstring group. Nonetheless, despite the significant difference in functional outcomes, no clinically significant difference regarding these scoring systems were found. [PERSON] et al. compared the outcomes between a single-bundle ACL reconstruction \begin{table}
\begin{tabular}{c} Significantly lower incidence of femoral \\ and tibial anteromedial tunnel \\ enlargement in the \\ remnant-preserving group. \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Cont. with a free hamstring autograft and so-called functional double-bundle ACL reconstruction, which included preservation of the hamstring tibial insertion and independent fixation of semitendinosus and gracilis grafts at different tensions in the single tibial tunnel [25]. The functional outcomes including the Tegner Activity Scale, IKDC score, Knee Injury and Osteoarthritis Outcome score and Lysholm score of the functional double-bundle ACL reconstruction group were better than the outcomes of the control group. Although the translational stability was similar, the rotational stability was significantly better in the functional double-bundle ACL reconstruction group. Recently, the prospective study of [PERSON] et al. reported excellent functional outcomes in IKDC and Lysholm scores for an ACL reconstruction with pedunculated hamstring autograft [26]. Moreover, the postoperative stability and the postoperative recovery of hamstring and quadricep strength were comparable with conventional ACL reconstructions. Considering the influence of hamstring attachment preservation on the progress of ACL graft maturation, the abovementioned scientific observations have found increasing support in the data from clinical studies. [PERSON] et al.