Confirming the Presence of Unrecognized Meniscal Injuries on Magnetic Resonance Imaging in Pediatric and Adolescent Patients With Anterior Cruciate Ligament Tears

Background: Prior research has shown decreased accuracy of meniscal injury detection using magnetic resonance imaging (MRI) for anterior cruciate ligament (ACL)-deficient adult patients as well as ACL-deficient pediatric and adolescent patients. The objectives of this study were the following: (1) assess the diagnostic ability of MRI in detecting meniscal injuries for pediatric and adolescent patients undergoing arthroscopic ACL reconstruction and (2) characterize the unrecognized meniscal injuries. Methods: The sensitivity, specificity, positive predictive value, and negative predictive value of meniscal tears (medial, lateral, or both) on MRI were calculated for the 107 patients in this cohort. Fisher exact tests were used to compare event frequencies between medial meniscal (MM) and lateral meniscal (LM) tears. One-way analysis of variance tests were performed to compare event rates between the location and type of unrecognized meniscal tears. Results: The median age of the cohort was 15 (range: 7 to 18). The sensitivity, specificity, positive predictive value, and negative predictive value of MRI in detecting meniscal tears (medial, lateral, or both) in ACL-deficient pediatric and adolescent patients was 62.3%, 68.4%, 78.2%, and 50.0%, respectively. There were 26 (24.3%) cases in which a meniscal injury was not detected on MRI, but was discovered arthroscopically (MM: 5 knees, LM: 20 knees, both: 1 knee). These unrecognized meniscal injuries were more commonly the LM than the MM (77.8%, P-value=0.100), a vertical/longitudinal tear type (77.8%, P-value <0.001), and located in the posterior horn (74.1%, P-value <0.001). Conclusions: In this ACL-deficient pediatric and adolescent cohort, there were 26 (24.3%) patients with unrecognized meniscal injuries. A vertical tear in the posterior horn was the most commonly unrecognized meniscal injury, supporting the findings of prior research postulating that the location and configuration of a tear influence the accuracy of MRI in detecting these injuries. More research is needed to investigate strategies to improve the detection of meniscal tears in pediatric and adolescent patients preoperatively. These findings have implications with regard to patient counseling, operative planning, anticipatory guidance with regard to postoperative rehabilitation, recovery expectations, and surgical outcomes.