Feasibility of quantitative ultrasound measurements on the humerus of newborn infants for the assessment of the skeletal status.

Quantitative ultrasound (QUS), although widely used in adults has, so far, been scarcely employed in newborn infants and children. This study aimed to evaluate the feasibility of the use of QUS in newborn children and the factors influencing QUS parameters. In 140 consecutive healthy full-term newborn babies (76 male and 64 female; gestational age: 39.5 +/- 1.5 weeks) QUS parameters were assessed within 3 days of the child's birth at the distal diaphysis of the humerus by use of Bone Profiler, after an appropriate modification of caliper and software. In all subjects we evaluated the amplitude-dependent speed of sound (AD-SoS) (meters per second), the characterizing graphic trace parameters [signal dynamic (SDy), fast wave amplitude (FWA) and bone transmission time (BTT)], SoS (meters per second), that is, the speed of sound calculated on the first peak, and hBTT, that is, the interval time between the first peak of the ultrasound and when this reaches the speed of 1,570 m/s, which is the velocity of ultrasound in the soft tissue. This latter parameter allows one to measure bone tissue independently of soft tissue. QUS measurements were also performed at the phalanges on all mothers (age range 24-38 years), who also completed a self-report questionnaire on their obstetric history, smoking and dietary habits and family history of osteoporosis. In 73 mothers and their children QUS was repeated after 12 months. All QUS parameters were slightly higher in male than in female newborn infants but the difference was not significant. BTT and hBTT of neonates showed a significant relationship with birth weight (r = 0.20; P < 0.05 and r = 0.37; P < 0.01, respectively) and with cranial circumference (r = 0.22; P < 0.05 and r = 0.36; P < 0.01, respectively). In newborn infants none of the QUS parameters was significantly influenced by maternal QUS or by maternal smoking and calcium intake. In a model of multiple regression analysis the cranial circumference was the only parameter entered into the model, explaining approximately 15% of hBTT value. At month 12 AD-SoS and SoS were slightly lower than at birth (-11% and -0.1%, respectively), whereas both BTT and hBTT showed a significant (P < 0001) increase. The present study demonstrated the feasibility of the use of QUS, as assessed by a new measurement approach at the humerus, in the evaluation of skeletal status in neonates. BTT and, above all, hBTT, appears to be the best parameter for both evaluation of skeletal status at birth and monitoring of bone growth in the first year of life.