Extension of growth-plate cartilage into the metaphysis: a sign of healing fracture in abused infants.

The present study was carried out to determine if healing metaphyseal injury in abused infants is accompanied by an increase in the thickness of the growth-plate zone of hypertrophic cartilage and if a radiolucent extension from the growth plate into the metaphysis correlates with this histologic indicator of healing fracture. The radiologic studies of 13 infants who died with evidence of inflicted injury were reviewed. Thirteen distal metaphyseal fractures were identified. Histologically, nine of these fractures were noted to be healing and four showed no evidence of healing. The nine healing injuries were accompanied by statistically significant thickening of the zone of hypertrophic cartilage. Seven of these demonstrated localized areas of hypertrophic cartilage extension; in six of these, corresponding radiolucent extensions of the growth plate into the metaphysis were seen. The extensions tended to be single and focal with minimal osseous injury and broad and multiple with extensive injury. No similar extension was visible in the four acute injuries. Because metaphyseal injuries are notoriously difficult to date, the presence of a reliable radiologic indicator of healing metaphyseal fracture can be important in the evaluation of infant abuse. Because the radiologic findings reflect the histologic alterations, extension of the growth-plate cartilage into the metaphysis may have implications for estimating fracture age.