Spectrum of injuries associated with paediatric ACL tears: an MRI pictorial review

Abstract

ObjectiveMagnetic resonance imaging (MRI) findings in anterior cruciate ligament (ACL) injury are well known, but most published reviews show obvious examples of associated injuries and give little focus to paediatric patients. Here, we demonstrate the spectrum of MRI appearances at common sites of associated injury in adolescents with ACL tears, emphasising age-specific issues.MethodsPictorial review using images from children with surgically confirmed ACL tears after athletic injury.ResultsACL injury usually occurs with axial rotation in the valgus near full extension. The MRI findings can be obvious and important to management (ACL rupture), subtle but clinically important (lateral meniscus posterior attachment avulsion), obvious and unimportant to management (femoral condyle impaction injury), or subtle and possibly important (medial meniscocapsular junction tear). Paediatric-specific issues of note include tibial spine avulsion, normal difficulty visualising a thin ACL and posterolateral corner structures, and differentiation between incompletely closed physis and impaction fracture.ConclusionACL tear is only the most obvious sign of a complex injury involving multiple structures. Awareness of the spectrum of secondary findings illustrated here and the features distinguishing them from normal variation can aid in accurate assessment of ACL tears and related injuries, enabling effective treatment planning and assessment of prognosis.Teaching points• The ACL in children normally appears thin or attenuated, while thickening and oedema suggest tear.• Displaced medial meniscal tears are significantly more common later post-injury than immediately.• The meniscofemoral ligaments merge with the posterior lateral meniscus, complicating tear assessment.• Tibial plateau impaction fractures can be difficult to distinguish from a partially closed physis.• Axial MR sequences are more sensitive/specific than coronal for diagnosis of medial collateral ligament (MCL) injury.

Seventeen-Year Follow-up After Meniscal Repair With Concomitant Anterior Cruciate Ligament Reconstruction in a Pediatric and Adolescent Population

“…The correlation between ACL tear and concomitant meniscal tear in the pediatric population has been well reported. 4,21,36,50 Vavken et al 50 recently examined 208 patients undergoing ACL reconstruction over 1 year at a tertiary children’s hospital and found that 67% had concomitant meniscal tears. These findings demonstrate the importance of follow-up studies to examine outcomes of meniscal repair and concomitant ACL reconstruction in this population.…”

MRI Anatomy of the Tibial ACL Attachment and Proximal Epiphysis in a Large Population of Skeletally Immature Knees

“…However, ACL integrity is accurately assessed on MRI, and tears are typically proximal, rather than at the tibial attachment fibers studied here. 12 Third, our study was not designed to demonstrate the validity, through anatomic correlation, of the MRI parameters measured. Small errors between the MRI-estimated and actual locations may exist, although these are unlikely to affect the clinical utility of these measurements.…”

“…A total of 570 patients were included. One hundred consecutive patients from 5 age groups (11,12,13,14, and 15 years) were included in the study. We also included 10 consecutive patients aged 6, 7, and 8 years as well as 20 patients aged 9 and 10 years because of more limited availability of knee MRI in these younger age groups.…”

Intrasubstance Anterior Cruciate Ligament Injuries in the Pediatric Population

“…Both soft tissue and osteochondral injuries have been described to have an association with pediatric ACL tears. 20 21 22 Impaction forces at the time of injury lead to bony edema secondary to trabecular microfracture. This is classically seen in the middle third of the lateral femoral condyle and the posterior third of the lateral tibial plateau.…”

“…This is classically seen in the middle third of the lateral femoral condyle and the posterior third of the lateral tibial plateau. 20 23 While it is unclear whether these findings independently lead to long term sequelae, subchondral changes can persist on magnetic resonance imaging (MRI) for several years after injury. 23 24 …”