Purpose or Case Report: Mensicocapsular injury (ramp lesion) occurs in 9-17% of ACL tears. These injuries are a risk factor for instability and failure following ACL reconstruction. The far peripheral location has contributed to under-diagnosis during routine anterior-approach arthroscopy. While there has been increasing interest in the identification and treatment of these lesions in adults, there is a paucity of published data on children and the proposed MRI features lack specificity. Therefore, the purpose of this study was to investigate the performance of MRI criteria for identifying ramp lesions in children.
Methods & Materials: This IRB-approved, HIPPA-compliant retrospective study included patients with primary ACL tears, who underwent pre-operative MRI, performed between Feb 1, 2017 and July 30, 2019, and diagnostic arthroscopy with attention to the medial meniscocapsular junction (MCJ). Each MRI examination was blindly retrospectively re-reviewed to determine the presence or absence of a suprapatellar joint effusion, medial joint findings (meniscus tear, peripheral meniscal irregularity, MCJ ligament tear, junctional T2-weighted signal, tibial plateau marrow edema), and lateral joint findings (meniscus tear, tibial plateau marrow edema). Chi-square, Fisher’s exact, and Mann-Whitney U tests were used to compare MRI findings between those with and without arthroscopically-confirmed ramp lesions.
Results: Seventy-one subjects (40 had ramp lesions at arthroscopy: 24 boys and 16 girls, 16.4 + 2.1 years; 31 did not have ramp lesions at arthroscopy: 12 boys and 19 girls, 15.1 + 2.1 years) were identified from the 312 patients whom underwent primary ACL reconstruction. Subjects who had ramp lesions were significantly older at arthroscopy (p=0.018) than those who did not have ramp lesions, but there were no differences in the distribution of sex (p=0.075), days between injury and MRI (p=0.067), or days between MRI and surgery (p=0.133) between the two groups. Knees with ramp lesions were more likely to have a suprapatellar effusion (p=0.047), medial meniscus tear (p=0.023), MCJ ligament tear (p=0.003), and junctional T2-weighted fluid-high signal (p<0.001). No association was found between ramp lesions and meniscal irregularity (p=0.070), size of the torn meniscal fragment (p=0.061), lateral meniscus tear (0.704), or tibial edema (p=0.929).
Conclusions: MRI findings predictive of a ramp lesion include a suprapatellar effusion, medial meniscus tear, MCJ ligament tear, and junctional T2-weighted fluid-high signal.