Quantitative ultrasound for the assessment of osteopenia in preterm infants

Bone Metabolic Unit, Scientific Institute, San Raffaele Hospital, Via Olgettina 60, Milan 20132, Italy. a.rubinacci@hsr.it

OBJECTIVE: To evaluate the potential role of quantitative ultrasound (QUS) investigation in assessing the osteopenia of prematurity. DESIGN: QUS parameters measured at the time of discharge were related to the anthropometric characteristics and age (postnatal and gestational) of 51 (34 female and 17 male) preterm infants fed fortified human milk. METHODS: QUS evaluation was performed at the humerus (h) by measuring two parameters: ultrasound velocity (hSOS, in m/s) and bone transmission time (hBTT, in micros). A group of 43 term infants (29 female and 14 male) was also evaluated. RESULTS: In preterm infants, significant correlations were found for hSOS and hBTT vs gestational age (r=0.504, 0.477, P<0.0001), length (r=0.641, 0.594, P<0.0001) and weight (r=0.580, 0.562, P<0.0001) at birth, and length (r=0.341, 0.332, P<0.05) and weight (r=0.331, r=0.362, P<0.05) at QUS measurement. In preterm infants, both QUS parameters were negatively correlated with age (r=-0.536, P<0.0001, r=-0.443, P<0.001) and were significantly lower than in the term infants (hSOS: 1664+/-42 m/s vs 1734+/-28 m/s, P<0.0001; hBTT: 0.58+/-0.24 micros vs 1.06+/-0.15 micros, P<0.0001) even when adjusted for body length (P<0.05). In preterm infants, hSOS was also negatively correlated with postconceptional age (r=-0.322, P<0.05). CONCLUSIONS: This study suggests that bone mineral accrual is mainly determined by the development in utero, and that prematurity induces a halt in the bone development process in the early postnatal period. QUS parameters are correlated with the severity of prematurity and might therefore have clinical applications when bone maturation in early life needs to be determined.

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