Is Delayed Anterior Cruciate Ligament Reconstruction Associated With a Risk of New Meniscal Tears? Reevaluating a Longstanding Paradigm.

Background: Delayed anterior cruciate ligament (ACL) reconstruction has been associated with an increased risk of meniscal tears. However, studies comparing early versus delayed ACL reconstruction have not clearly demonstrated that meniscal tears diagnosed arthroscopically are new injuries as opposed to concomitant injuries sustained during ACL rupture. Purpose: To determine whether and how delay of ACL reconstruction is associated with risk of "new" meniscal tears (defined as those visualized arthroscopically that had not been detected on magnetic resonance imaging [MRI]) in adult and pediatric patients. Study Design: Cohort study; Level of evidence, 3. Methods: We retrospectively identified patients who underwent primary ACL reconstruction between 2013 and 2022 at our institution. To ensure that MRI reflected initial intra-articular pathology, we included only patients who had an MRI scan within 3 weeks after injury (173 pediatric and 369 adult patients). Multivariate Poisson regression was performed to calculate the adjusted relative risk (ARR) of new meniscal tears after delayed (≥8 weeks from injury) operative treatment. Results: The mean (± SD) time from injury to MRI was 1.0 ± 0.8 weeks for pediatric patients and 1.1 ± 0.7 weeks for adults. Less than half of the meniscal tears observed arthroscopically had been absent on initial MRI. New medial meniscal tears occurred in 15% of pediatric patients and 16% of adults. New lateral meniscal tears occurred in 48% of pediatric patients and 34% of adults. Among pediatric patients, delayed ACL reconstruction was associated with higher risk of new medial tears (ARR, 3.9; 95% CI, 1.5-10) but not lateral tears (ARR, 0.8; 95% CI, 0.4-1.5). In contrast, adults had no significant increase in risk of meniscal tears associated with operative delay. Conclusion: Delayed ACL reconstruction may be acceptable in adults, who may be less active and less injury-prone than children and adolescents.