Ultrasound findings in classic metaphyseal lesions: emphasis on the metaphyseal bone collar and zone of provisional calcification

Abstract

Background The classic metaphyseal lesion (CML) is highly specific for non-accidental trauma in infants. While the radiographic findings are well documented, there is little literature on the ultrasound (US) appearance. Objective To evaluate US findings in CMLs identified on radiographs. Material and methods This institutional review board-approved, retrospective evaluation of targeted US of CMLs was performed in selected groups of children from 2014 to 2017. Only CMLs confidently identified on radiography by a consensus of two radiologists were included. US images were obtained with a linear transducer, including longitudinal images at lateral, anterior, medial and posterior aspects. Two pediatric radiologists evaluated the US appearance, specifically the metaphyseal bone collar for thickness, deformity and fracture, as well as the sonographic zone of provisional calcification for irregularity and appearance of multiple lines. Radiography was the reference standard. Results Twenty-two patients (13 female; mean age: 4.2 months) were identified, with 39 CMLs in the tibia (n=22), femur (n=11), humerus (n=3), radius (n=2) and fibula (n=1). Thirty-three of the 39 CMLs (85%) were identified on US, while 6 (15%) were not seen (false negatives). Thirty of the 39 (77%) had metaphyseal bone collar thickening, 29 (74%) had collar deformity and 12 (31%) had visible fracture of the collar. At the sonographic zone of provisional calcification, 16/39 (41%) had irregularity and 5 (13%) had multiple lines visible. Conclusion Identifying metaphyseal bone collar and zone of provisional calcification abnormalities is key to recognizing CMLs on US. While additional studies are necessary to evaluate the accuracy of US in the diagnosis of CMLs, our findings suggest US may have a potential role in either confirming or evaluating radiographically equivocal/occult CMLs.