A regional approach to the classic metaphyseal lesion in abused infants: the proximal humerus

OBJECTIVE: The purpose of this study was to systematically analyze the spectrum of morphologic alterations of the classic metaphyseal lesion (CML) involving the proximal humerus of abused infants and to identify radiologic features that aid in the diagnosis and assessment of healing. MATERIALS AND METHODS: Thirty-one infants who died with evidence of inflicted skeletal injury were studied with high-detail skeletal surveys, resected specimen radiography, and histologic analysis. In each infant, the number of fractures, the involved portions of the proximal humeral metaphyses, and the age of the lesion were assessed. RESULTS: Seven proximal humeral CMLs were seen in four infants. Radiography of the only infant with an acute injury revealed no fracture; however, evidence of trabecular disruption was found histologically. Radiographic patterns in the six healing injuries included focal corner-fracture appearance, transmetaphyseal radiolucency, irregularity of the metaphyseal margin, and flame-shaped mineralized extensions into the physeal cartilage. Histologically, all CMLs undercut the lateral subperiosteal bone collar, explaining the corner-fracture appearance. Focal and diffuse thickening of the zone of hypertrophic chondrocytes was seen, and peninsulas of primary spongiosa surrounded by hypertrophied cartilage corresponded to the flame-shaped densities revealed radiographically. The fracture morphology was better seen on specimen radiography than on skeletal survey images. CONCLUSION: CML of the proximal humerus has distinctive radiologic and histopathologic characteristics that relate to the anatomy of the region. In our study, changes at the chondroosseous junction revealed by radiography correlated well with histologic evidence of healing. Although the proximal humerus is a less common location for CML than the lower extremity, the proximal humerus should be carefully scrutinized on high-detail radiographs in cases of suspected infant abuse