Size of Initial Bone Bruise Predicts Future Lateral Chondral Degeneration in ACL Injuries: A Radiographic Analysis

BACKGROUND: Bone marrow contusions are common after an acute anterior cruciate ligament (ACL) injury. It is unknown whether the severity of this initial bruise can predict the potential of developing chondral changes even after ACL reconstructive surgery (ACLR). PURPOSE: To investigate whether the initial bone bruise area could be predictive of progressive chondral defects. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: A retrospective chart review was performed to capture patients with an acute ACL injury with pre- and post-ACLR magnetic resonance imaging (MRI) between January 2000 and December 2017. Lesion areas were measured on initial MRI, and chondral wear was graded on final imaging by use of the modified Outerbridge classification. An ordinal model was created to determine whether the initial area was a significant predictor for future chondral degeneration. RESULTS: A total of 40 patients with a mean age of 34.5 ± 12.6 years were included for analysis. All patients underwent ACLR at a mean 139 ± 64 days from initial injury. A lateral tibial and femoral bone bruise was most commonly present in patients (77.5% and 62.5%, respectively). A medial femoral bone bruise was found in only 12.5% (5/40) of patients. The initial contusion area significantly correlated with increasing chondral wear over time in the tibia and lateral femoral condyle (P < .001). Patients with a bone bruise encompassing 100% of the lateral femoral compartment on MRI had a 74% chance of having grade 3 or 4 chondral changes at 5 years (P = .001). Absence of a bone bruise on initial MRI was the greatest predictor of no cartilage wear at 5 years in all compartments (P < .001). The presence of a concomitant lateral meniscal injury increased the risk of developing type 3 or 4 chondral wear in the lateral tibial plateau (P = .012) but did not pose increased risk of femoral wear (P = .23). CONCLUSION: A significant relationship between area of initial bone bruise at the time of injury and progressive posttraumatic chondral disease was found in the tibial and lateral femoral compartments.