Differentiation of rickets and classic metaphyseal lesions on radiographs

Noting both high interobserver agreement and diagnostic performance for differentiating the two entities in this 7-center study, “recognition that CMLs mostly occur in children younger than 6 months and are unusual in children older than 1 year may assist interpretations,” wrote corresponding author Boaz Karmazyn from the Riley Hospital for Children in Indianapolis, IN.

Karmazyn and colleagues’ retrospective study included children younger than 2 years old who underwent knee radiographs from January 2017 to December 2018 and who either had rickets (25-hydroxy vitamin D <20 ng/mL and abnormal knee radiographs) or knee CMLs and a diagnosis of child abuse from a pediatrician. Eight radiologists independently interpreted radiographs for rickets or CML diagnoses, rating confidence levels and logging associated radiographic signs.

Ultimately, children with CML were younger than children with rickets (3.9% vs 65.7% >1 year old). The rate of false-positive moderate or high-confidence interpretations was 0.6% for CML and 1.6% for rickets. Only a single child with CML and low vitamin D received an interpretation of combined CML and rickets.

Reiterating that less- and more-experienced pediatric and non-pediatric radiologists had high diagnostic performance in differentiating rickets and CML — regardless of the presence of vitamin D deficiency, with few false-positive interpretations for these diagnoses — “findings suggestive of both rickets and CML should be viewed as indeterminate,” the authors of this AJR article concluded.

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