Sex- and Maturity-Related Differences in Cortical Bone at the Distal Radius and Midshaft Tibia Evaluated by Quantitative Ultrasonography.

Boys usually have higher values of bone mineral density measured by dual-energy X-ray absorptiometry than girls, but contradictorily also have a greater incidence of fractures during growth. The purpose of this study was to investigate sex- and maturity-related differences in bone speed of sound (SoS) at the radius and tibia in a sample of 625 healthy children aged 10-14 y and to analyze the contributions of physical activity (PA) to possible dissimilarities. Radial and tibial SoS was evaluated by quantitative ultrasound, maturity was estimated as the years of distance from the peak height velocity age, and PA was assessed by accelerometry. Comparisons between sexes and maturity groups (low: below average [<-2.5 y], high: average or above [≥-2.5 y]) were made by two-sample t-tests with unequal variances. Girls in the high-maturity group had higher SoS at the radius and tibia compared with girls in the low-maturity group (p < 0.001). There were no SoS differences at the radius or tibia between the high- and low-maturity groups in boys. Within high-maturity children, girls had higher SoS than boys at the radius and tibia (p < 0.001). There were no differences at the radius and tibia between girls and boys with low maturity. The results were not modified after controlling for PA. Regardless of PA, the results provide insight into sex- and maturity-related differences in bone SoS at the distal radius and midshaft tibia from maturity less than 2.5 y from the peak height velocity age, with boys having lower SoS.