Background: Bone bruises are commonly seen on magnetic resonance imaging (MRI) in acute anterior cruciate ligament (ACL) injuries and can provide insight into the underlying mechanism of injury. There are limited reports that have compared the bone bruise patterns between contact and noncontact mechanisms of ACL injury.
Purpose: To examine and compare the number and location of bone bruises in contact and noncontact ACL injuries.
Study design: Cross-sectional study; Level of evidence, 3.
Methods: Three hundred twenty patients who underwent ACL reconstruction surgery between 2015 and 2021 were identified. Inclusion criteria were clear documentation of the mechanism of injury and MRI within 30 days of the injury on a 3-T scanner. Patients with concomitant fractures, injuries to the posterolateral corner or posterior cruciate ligament, and/or previous ipsilateral knee injury were excluded. Patients were stratified into 2 cohorts based on a contact or noncontact mechanism. Preoperative MRI scans were retrospectively reviewed by 2 musculoskeletal radiologists for bone bruises. The number and location of the bone bruises were recorded in the coronal and sagittal planes using fat-suppressed T2-weighted images and a standardized mapping technique. Lateral and medial meniscal tears were recorded from the operative notes, while medial collateral ligament (MCL) injuries were graded on MRI.
Results: A total of 220 patients were included, with 142 (64.5%) noncontact injuries and 78 (35.5%) contact injuries. There was a significantly higher frequency of men in the contact cohort compared with the noncontact cohort (69.2% vs 54.2%, P = .030), while age and body mass index were comparable between the 2 cohorts. The bivariate analysis demonstrated a significantly higher rate of combined lateral tibiofemoral (lateral femoral condyle [LFC] + lateral tibial plateau [LTP]) bone bruises (82.1% vs 48.6%, P < .001) and a lower rate of combined medial tibiofemoral (medial femoral condyle [MFC] + medial tibial plateau [MTP]) bone bruises (39.7% vs 66.2%, P < .001) in knees with contact injuries. Similarly, noncontact injuries had a significantly higher rate of centrally located MFC bone bruises (80.3% vs 61.5%, P = .003) and posteriorly located MTP bruises (66.2% vs 52.6%, P = .047). When controlling for age and sex, the multivariate logistical regression model demonstrated that knees with contact injuries were more likely to have LTP bone bruises (OR, 4.721 [95% CI, 1.147-19.433], P = .032) and less likely to have combined medial tibiofemoral (MFC + MTP) bone bruises (OR, 0.331 [95% CI, 0.144-0.762], P = .009) compared with those with noncontact injuries.
Conclusion: Significantly different bone bruise patterns were observed on MRI based on ACL injury mechanism, with contact and noncontact injuries demonstrating characteristic findings in the lateral tibiofemoral and medial tibiofemoral compartments, respectively.
Keywords: anterior cruciate ligament; bone bruise patterns; contact ACL injury; mechanism of injury; noncontact ACL injury.