Sex Differences in Bone Strength, Fracture Risk During Growth

Research from Canada published in the October 2016 edition of the Journal of Bone and Mineral Research has taken a look at the details of the differences in bone strength and fracture risk amongst boys and girls. The study was entitled, “Sex Differences and Growth-Related Adaptations in Bone Microarchitecture, Geometry, Density, and Strength From Childhood to Early Adulthood: A Mixed Longitudinal HR-pQCT Study”

Heather McKay, Ph.D. is with the Department of Orthopaedics at the University of British Columbia, and the Centre for Hip Health and Mobility at the Vancouver Coastal Health Research Institute.

Dr. McKay told OTW, “We have acquired the largest data set worldwide, of longitudinal measurements of bone strength and microarchitecture using high-resolution peripheral quantitative computed tomography (HR-pQCT) from early adolescence to young adulthood. As most studies of bone strength and microarchitecture in adolescents are cross-sectional, we wanted to examine actual changes in these important parameters in girls and boys while also accounting for the important influence of maturational status.

“One challenge of our dataset is that we were unable to acquire HR-pQCT on younger children so we could not identify at what point during early childhood and adolescent growth sex differences in bone strength and microarchitecture emerge. An inherent limitation of studies that use HR-pQCT is that we can only assess the distal radius and tibia. Thus, we aren’t sure whether the sex differences in bone strength, BMD [bone mineral density] and microarchitecture we observed are also present at other skeletal sites.”

“There were three key results of our study. First, consistent with previous cross-sectional and short-term longitudinal studies, we confirmed boys’ larger bone size and superior bone strength at the distal radius and tibia compared with girls’ across maturity. Second, unlike previous research, girls in our study did not have greater cortical BMD at the distal radius or tibia as compared with boys during the years surrounding peak growth. We believe this was due to the fact that we compared girls and boys on a common indicator of maturity, age at peak height velocity. Finally, we found that during adolescence, boys had consistently more porous cortices at the distal radius compared with girls, which may contribute to boys’ greater incidence of fractures during peak growth.”

“I would suggest that before undertaking a study in which bone outcomes are compared between adolescent boys and girls, researchers should consider incorporating a common maturational landmark, age at peak height velocity (APHV). APHV refers to the age when maximum linear growth in height occurs and generally occurs in boys and girls when approximately 90% of adult stature has been achieved. In cross-sectional studies, researchers can estimate APHV using validated prediction equations, or in longitudinal studies, APHV can be directly determined using serial measures of height.”