ARRS 2022 Abstracts

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E1146. Anterior Cruciate Ligament Imaging in Children and Adolescents
Authors
  1. Augustah Poutre; Cincinnati Children's Hospital
Background
There are key differences encountered when imaging the anterior cruciate ligament (ACL) in children versus adults. First, congenital dysplasia or absence of the ACL is a rare condition that can be associated with other congenital limb abnormalities. These children may present with symptoms from chronic knee laxity and have distinct radiographic and MR imaging features. Also, children have a higher incidence of avulsion injuries of the ACL than adults. This most commonly occurs at the distal attachment site and specific imaging findings should be reported to guide treatment. Finally, increased participation in high-level sports activities at earlier ages has led to an increasing frequency of intra-substance ACL injuries in children. The type of ACL injury and the degree of skeletal maturity (particularly the degree of physeal closure) determines which ACL reconstruction technique is appropriate. There are unique differences between pediatric and adult ACL reconstruction techniques, each of which have differing postoperative appearances on imaging. The purpose of this exhibit is to review these key differences when imaging the pediatric versus the adult ACL.

Educational Goals / Teaching Points
The goals of this exhibit are to identify the imaging findings of congenital dysplasia or absence of the ACL; describe differences in the types of ACL injuries seen in children versus adults; and describe various pediatric ACL reconstruction techniques and show how they differ from conventional adult ACL reconstruction techniques.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
In children who are skeletally immature or are near skeletal maturity, the bone is the relative weak link in bone-ligament complexes, resulting in a greater frequency of avulsion injuries in children versus adults. This is true for ACL avulsions as well as other areas throughout the pediatric skeleton. ACL avulsions, at the tibial eminence or less commonly at the femoral insertion, may be subtle but can usually be diagnosed on radiographs. Additionally, there are important imaging findings that should be reported when evaluating these avulsions on MRI. Another crucial anatomic difference between children and adults, which is important when an ACL reconstruction procedure is being planned, is the status of the distal femoral and proximal tibial physis. A variety of ACL reconstruction techniques are used in children and adolescents depending upon the degree of skeletal maturity including physeal sparing, transphyseal, and adult-type reconstruction techniques.

Conclusion
Radiologists who interpret pediatric musculoskeletal imaging need to be aware of some key differences in the imaging of the pre- and postoperative ACL in children versus adults.