Summary

Contact ACL injuries demonstrated significantly different bone bruise patterns than those seen in non-contact injuries; in contact ACL injuries, the significantly higher rates of combined lateral tibiofemoral bone bruises and lower rates of combined medial tibiofemoral bone bruises may suggest a more predominant valgus mechanism compared to non-contact injuries.

Abstract

Objectives: Tibiofemoral bone bruises on preoperative magnet resonance imaging (MRI) are commonly reported in non-contact anterior cruciate ligament (ACL) injuries and provide important insight into the mechanism of injury. However, there is a lack of evidence describing the differences in bone bruise patterns between ACL injuries that occur from contact and non-contact mechanisms. The purposes of this study were: (1) To compare the number of bone bruises and their location in contact and non-contact ACL injuries; (2) To compare the rates of concomitant meniscal injuries between these same patients.

Methods

A total of 302 patients who underwent ACL reconstruction surgery from 2015 to 2021 at our institution were identified. Inclusion criteria included a clear documentation of the mechanism of injury, preoperative MRIs within 30 days of the injury on a 3T scanner, and no multiligament knee injury, and/or previous ipsilateral knee injury. Patients were then stratified into two separate groups based on a non-contact or contact mechanism of ACL injury. Preoperative MRIs were retrospectively reviewed by two musculoskeletal radiologists for bone bruises. The number and location of the bone bruises were recorded in the coronal and sagittal plane using fat-suppressed T2-weighted images and a standardized mapping technique. Lateral and medial meniscal injuries were recorded from the operative notes. The number and distribution of bone bruises and the rates of concomitant meniscal injuries were compared amongst the two cohorts.

Results

In total, 240 patients who underwent ACL reconstruction surgery met the inclusion criteria for this study. 142 (59.1%) patients sustained non-contact injuries while 78 (40.8%) patients sustained contact ACL injuries. In the coronal plane, contact injuries had significantly higher rates of combined lateral tibiofemoral (LFC + LTP) bone bruises (82.1% vs 48.6%, P < 0.001) and significantly lower rates of combined medial tibiofemoral (MFC + MTP) bone bruises (39.7% vs 65.5%, P<0.001) compared to non-contact ACL injuries. In the sagittal plane, contact injuries had significantly higher rates of posterior LTP bruises (85.9% vs 32.4%, P < 0.001) and significantly lower rates of posterior MFC bruises (3.8% vs 67.6%, P < 0.001) and posterior MTP bruises (52.6% vs 66.2%, P < 0.001) compared to non-contact injuries. There were no significant differences in the rates of lateral meniscus (34.6% vs 41.5%, P=0.313) and medial meniscus injuries (35.9% vs 26.1%, P=0.126) between contact and non-contact injuries, respectively.

Conclusion

Contact ACL injuries demonstrated significantly different bone bruise patterns than those seen in non-contact injuries. In contact ACL injuries, the significantly higher rates of combined lateral tibiofemoral bone bruises and lower rates of combined medial tibiofemoral bone bruises may suggest a more predominant valgus mechanism compared to non-contact injuries. In addition, there were no significant differences in the number of lateral and medial meniscal injuries between the two mechanisms of ACL injury.