## 4 Discussion  
To the best of our knowledge, this is the first complex study evaluating ACL graft maturity by comparing different methods for measuring graft signal intensity, homogeneity of the graft, and evaluating the effect of sex, age, and weight-bearing being believed to have an impact on graft maturity. Moreover, we studied indirect MRI's signs of ACL graft insufficiency and its relationship to signal intensity. In 2019 [PERSON] et al. [16] performed a systematic review of papers assessing ACL graft maturation in MRI studies. He concluded that methods used across studies were too heterogeneous to conclude time frames of signal intensity. The signal intensity of the graft was poorly correlated with clinical outcomes. [PERSON] et al. [17] published a systematic review of papers assessing ACL graft maturity. He identified 10 studies with serial MRI measurements of SNQ including 479 patients (20-98 patients per study). Semi-tendinous and gracilis tendons were used for ACL reconstruction (six studies), quadriceps tendon (one study), and bone-patellar tendon-bone grafts (3 studies). Allografts were used in three studies, apart from autografts. In all studies, SNQ was calculated either by comparing signal intensity of the graft to the posterior cruciate ligament or the background. Based on available data, [PERSON] concluded that MRI SNQ was the highest at six months postoperatively and later had a gradual decrease over time. However, in his opinion, the MRI SNQ method should not be used to predict graft maturity and functional and clinical outcomes. In our study we verified different methods for evaluating ACL graft maturity: ROI and SNQ methods on axial and sagittal plane as well as rSD values. It is the first study to compare measurements obtained in both sagittal and axial planes. We showed that average values from two measurements of ACL graft taken in the sagittal plane best represent graft status. We also determined the SD of signal intensity of the graft as a new parameter for graft evaluation and prediction of graft insufficiency. The rSD was related to SNQ and overall grafts state, indicating that graft homogeneity is also an important indicator of graft  
Figure 9: **Anterior tibia subluxation. ** We observed that anterior tibia subluxation increased over the course of the study. Most importantly, we observed statistically credible differences of the anterior tibia subluxation state at week 2. Average subluxation was lower among patients who started with negative subluxation. In addition, the linear increase was noticeably stronger among this group of patients, as compared to patients who had nonnegative subluxation at week 2. _Posterior predicted marginal means (points or blue line) of the PCL subluxation. The vertical lines and shaded area show 95% credible interval. The y-axis limits span over the range of middle 95% of the data. well-being. We also evaluated the relationship between graft maturity and more subtle signs of ACL graft insufficiency, such as graft status, PCL buckling and exact measurement of anterior tibia subluxation. [PERSON] et al. [18] evaluated SNQ for ACL graft maturation in 10 multisequence MRIs performed within 50 months postoperatively. Forty-five patients with a mean age of 27 years old were included in the prospective study. All patients underwent double-bundle ACL reconstruction. Subsequently, all patients received a MRI at 3 weeks and 6, 9, 12, 18, 24, 36, 48, and 50 months after surgery. In the conclusion of the study, [PERSON] stated that at least 18 months was needed for the mean SNQ of the anteromedial bundle for normalization, whereas for the postero-lateral bundle, at least 24 months was needed. [PERSON] et al. [19] showed that even though hamstring tendons used for ACL reconstruction undergo a transformation, they do not match the ultrastructure pattern of a native ACL for up to ten years. In our study, we showed that even at 96 weeks postoperatively, signal intensity of the graft did not match values measured immediately after the reconstruction (at two weeks).