A regional approach to the classic metaphyseal lesion in abused infants: the distal femur.

OBJECTIVE: The purpose of this study was to analyze the spectrum of morphologic alterations of the classic metaphyseal lesion involving the distal femur of abused infants and to identify features that aid in radiologic 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. We recorded the number of fractures, the portions of the distal femoral metaphyses involved, and the age of the lesions.
RESULTS: Fifteen classic metaphyseal lesions of the distal femur were seen in 11 infants. The lesions were bilateral in four infants and unilateral in seven. Nine healing and three acute classic metaphyseal lesions were found. In the remaining three lesions, the age of the lesions was indeterminate. Fractures always involved the posteromedial aspect of the femur; anterior and lateral extension occurred in more diffuse lesions. Fractures tended to be less conspicuous when they were acute and were more easily recognized with healing, especially with specimen radiography. Histologically, the fracture line consistently undercut the medial subperiosteal bone collar. Extension of hypertrophic chondrocytes from the growth plate into the region of fracture was found in all nine healing lesions.
CONCLUSION: The classic metaphyseal lesion of the distal femur has distinctive radiologic and histopathologic characteristics that relate to the anatomy of the region. Because the distal femur is a common site for this strong indicator of infant abuse, the region should be carefully evaluated with well-collimated, high-detail skeletal radiographs in all cases of suspected infant abuse.