Morphometric analysis of the bone growth plate in sudden infant death syndrome

Abstract

It has been proposed that maturational delay and suboptimal growth may increase the risk of sudden death in early life, however, estimates of the percentage of growth-retarded infants in the SIDS group have varied widely. While other growth parameters have been examined in detail, morphometric assessment of the growth plate has not been performed to any extent in these infants. In this study rib growth plates from 20 randomly chosen SIDS infants and 20 age-matched controls were decalcified, multiply sectioned and stained with acid-fuschin. Each section was analysed at ×20 objective magnification with a 10×10 eyepiece graticule aligned parallel to the growth plate interface. The volume fraction of cartilage and bone together with the number of cartilagenous and bone trabeculae per unit length of growth plate were measured to a depth of seven grid lengths from the starting point. Using this protocol the growth plate trabecular structure was sampled systematically at 0.18mm intervals to a depth of approximately 4mm. No differences were found between the SIDS group and the controls In cartilage/bone volume. However, numbers of cartilage/bone trabeculae per unit length were found to be significantly different in the hypertrophic zone of the growth plate (p<0.001) and in adjacent portions of the proliferative zone and metaphysis in the SIDS cases. Although a smaller pilot study by this group failed to demonstrate differences between SIDS infants and controls, these data indicate an apparent abnormality in bone growth plate architecture In the SIDS group. This is the first time that abnormal growth plate structure in SIDS Infants has been quantified over the time prior to death, and supports the concept that certain infants who die of SIDS have not had normal growth.