# The Influence of Bone Bruises on Bone Tunnel Enlargement Regarding ACL Rupture
## 4 Discussion  
The most important finding of this retrospective analysis is that the close proximity of the BBs to the bone tunnel may be a relevant factor influencing the size of BTE in the femur. The results of the retrospective analysis of MRI performed after ACL injury and after ACLR surgery demonstrated a moderate and statistically significant negative correlation between the distance from the BB to the bone tunnel and BTE in the femur, which means that decreasing the distance between the BB and the tunnel increases the size of BTE. The association was even stronger (r = \(-\)0.77) when the correlation coefficient was calculated in the largest subgroup of patients, in whom surgery was performed 31 to 60 days after ACL rupture. It is hypothesized that the relationship is also considerable in patients with BBs who underwent ACLR within 30 days after the injury since there is a greater likelihood that all the BB had not yet been resolved. Considering the impact of proximity of the BBs on bone tunnel size in the tibia, a close association was not confirmed, as there was a weak negative correlation. In the studied STGR group, there were five femoral and six tibial bone tunnels that directly passed through the BB. The intersection of the bone tunnel and BB (measured in mm\({}^{3}\)) was calculated to measure to what extent the BB collides with the tunnel. The relationship between this intersection and the increase in the diameter of the tunnel (\(\Delta\)f)d in the femur was moderate; however, the relationship in the tibia was negligible. In our group of patients, a BB was not present in the femur in six patients or in the tibia in one patient, which is consistent with the outcomes reported by [PERSON] et al. [40], who studied the prevalence of BBs in the anterior, posterior, and middle aspects of the lateral and medial compartments of the tibia. In this paper, we elucidated that because MRI is the common diagnostic tool in the examination of ACL tears, there is an opportunity to simultaneously investigate concomitant injuries such as BBs that may have an impact on ACL reconstruction success. We aimed to highlight the need for preoperative assessments of the bone environment, which constitutes support for implanted grafts and ensures proper incorporation and healing. Applying a quantitative method of measuring bone BBs in spatial relation to the bone tunnel prior to ACLR may reduce complications including BTE. In contrast to graft fixation by interference screws or EndoButton devices, bone around the tunnel is a natural material used for the fixation of transplanted tendons. Fixation develops through bone ingrowth into the tissue of the fibrovascular interface that initially forms between the outer part of the tendon and the inner bone wall [41]. In the subsequent steps, progressive mineralization of the interface  
Figure 5: Boxplots showing the measurements of the diameter of (a) the femoral bone tunnel at three parts of tunnel: \(f\)-d1—entrance, \(f\)-d2—midportion, and \(f\)-d3—exit; (b) the tibial bone tunnel at three parts of tunnel: \(t\)-d1—entrance, \(t\)-d2—midportion, and \(t\)-d3—exit. Boxplot legend: the median is shown as a square in the center of the box. The top and bottom of the boxes represent the first and third quartiles, respectively. The whiskers correspond to the maximal and minimal values within the \(1.5\times\) interquartile range (IQR). The outliers are plotted as points. tissue appears, with bone ingrowth into the outer graft and the incorporation of the graft into neighboring bone tissue [41]. This process is influenced by many different factors and may be modified for different regions of the bone tunnels [42; 43], such as the entrance, midportion, and exit [44]. To the best of our knowledge, this is the first study of its kind that highlights the influence of bone bruising on bone tunnel widening by determining the spatial locations of BBs with respect to femoral and tibial tunnels.