## 4 Discussion

Table 4: _Cont._Our results confirmed the previous report by [PERSON] et al., which compared MRI of the knee after ACL-R using a hamsring with the opposite knee [43]. This analysis showed no statistically significant articular cartilage damage in the knees after ACL-R at 9 years after surgery [43]. Based on the literature, it is known that the number of arthoscopies required to eradicate infection after ACL-R ranges between 1.3 and 3 [20; 21; 32; 44]. Most authors initially suggest leaving the graft, and performing arthroscopic lavage and debridement combined with intravenous antibiotic therapy [17; 32]; however, this initial treatment achieved success in 85.5% of patients affected by this complication [44]. In addition to arthroscopic lavage and debridement combined with intravenous antibiotic therapy, we also used flow drainage with vancomycin (1 g/3 L in 0.9% NaCl) for an average of 9 days, which caused the flushing of pro-inflammatory mediators and bacterial debris and led to faster eradication of the infection. This is evidenced by the faster return of CRP to normal values, which was observed after 9 days (range, 7-12 days). Based on the literature, the fastest CRP return after arthroscopic lavage and debridement combined with intravenous antibiotic therapy alone was observed after an average of 14-21 days [32]. If we objectively compare the arguments for multiple arthroscopy and close drainage, the second option is a more rational choice [21; 32; 44]. It is also known that postinfectious synovitis persists after SA following an ACL-R [3]: this is because after eradicating the infection, sterile microbial fragments and inflammatory mediators remain in the joint environment for a long time, initiating a continuous inflammatory response, leading to articular cartilage damage and the development of OA [2; 3; 8; 42]. We consider the use of flow drainage, by flushing out sterile microbial fragments and inflammatory mediators, to significantly reduce postinfectious synovitis, as shown in the much faster return of CRP to normal values that we observed in our patients. According to [PERSON] et al., patients who had a single arthroscopic lavage and debridement resulting in the eradication of infection had a higher success rate [44]. When performing arthroscopic irrigation and debridement, we did not perform additional surgical accesses or extensive synovectomy to avoid additional surgical trauma, damaging the natural protective barrier of the synovium and reducing the risk of arthofibrosis. In fact, synovectomy is unnecessary because in acute infection, the synovial membrane is in a phase of swelling and inflammatory congestion. Moreover, removing fibrous deposits and small adhesions without synovectomy eliminates postoperative bleeding, which can be a source of material blocking the free flow in the drains. The flow drainage we used (1 g of vancomycin in 3 L of 0.9% NaCl administered daily) proved to be completely safe and did not result in any adverse general symptoms. Recent publications also confirm that a vancomycin concentration of 0.3 mg/mL is completely safe for ligament grafting [45]. The faster return of CRP to normal values observed in our study is associated with a shorter duration of hospitalization and a shorter period of intravenous antibiotic administration. Based on literature data, the length of hospitalization during treatment of this complication is 29.7 \(\pm\) 11.6 days [32]. Our patients were hospitalized for an average of 16.2 days, the entire period of intravenous antibiotic therapy (Table 1). Our later experience and observations allowed us to reduce this time even further, and patients were discharged from the hospital the day after CRP returned to normal values. In addition, none of our patients required repeated arthroscopy because of failure to eradicate the infection. The much shorter hospitalization time and lack of need for further arthroscopies significantly reduced the cost of treatment for this complication.