Bone contusion patterns following anterior cruciate ligament (ACL) tears have been extensively studied in adult patients. A recent study has shown pediatric patients with ACL injuries to have the same bone contusion pattern as adults and occurred at similar rates. However, the incidence of ACL tears in skeletally immature patients who have an ACL pattern of bone contusion has not be previously investigated.
To radiographically determine the incidence of ACL tears in skeletally immature patients with the classic lateral femoral condyle (LFC) and lateral tibial plateau (LTP) bone bruise pattern that is seen in adults with ACL tears.
This retrospective cohort study was performed by performing a query for “contusion” within the MRI read for all patients between the ages of 6 and 22 years of age, with MRIs performed from 1/1/2015 to 6/30/2019. MRI images were reviewed to denote the presence of ACL, PCL, MCL, or LCL tears, meniscus tears, cartilage lesions, bone bruise pattern, and physeal status of femoral and tibial physes. MRIs were reviewed by two fellowship-trained orthopedic surgeons. The specific locations of bone contusions were recorded using zones described by the Whole-Organ Magnetic Resonance Imaging Score (WORMS) for bone contusion. The primary outcome variable was the incidence of ACL tears in patients with the presence of both central lateral femoral condyle and posterior lateral tibial plateau bone contusions. We analyzed differences in the primary outcome variable based upon physeal status using Fischer's Exact testing.
A total of 691 patients who met inclusion criteria were identified. There were 192 patients excluded (151 patellar instability, 23 history of prior ACL reconstruction, 7 with no bony contusions, 3 with fibular head contusion only, 2 with patellar fracture, 2 with tibial plateau fracture, and 2 with no viewable MRI). Of the 499 remaining patients, a total of 269 patients had the presence of both central lateral femoral condylar and posterior lateral tibial plateau bone contusions. Of these 269 patients, 259 (96.3%) had an ACL tear identified on MRI. Patients with an open femoral physis had a higher likelihood of having an intact ACL despite the presence of central LFC and posterior LTP contusions than patients with a closed femoral physis (8/74 (10.8%) vs. 2/195 (1.0%), chi-square value 14.4, p < 0.001). Patients with an intact ACL tear despite presence of central LFC and posterior LTP contusions were younger than patients with ACL tear with this contusion pattern (14.6 vs. 16.4, p = .017).
Patients who have an open femoral physis have a higher likelihood to have an intact ACL despite the presence of central LFC and posterior LTP bone contusions compared to patients who have a closed femoral physis. An ACL tear should not be assumed to be present despite the presence of typical ACL bone bruise in pediatric patients, particularly those with open physes.