Sexual dimorphism in cortical bone morphology during adolescent growth in Chinese

Ka-Yee Cheuk; Xiaofang Wang; Fiona W P Yu; Elisa M S Tam; Bobby K W Ng; Ali Ghasem-Zadeh; Roger Zebaze; Ego Seeman; Jack C Y Cheng; Tsz-Ping Lam

doi:10.1530/boneabs.6.P009

Objective: Previous study in Hong Kong reported boy-to-girl ratio of limb fracture was 5.5:1 in the adolescent group. Chinese children have increased risk for forearm fracture during puberty. This study aimed to investigate cortical growth in healthy Chinese adolescents during pubertal growth.

Methods: 214 boys and 219 girls aged between 7 and 17 years old with no bone diseases were recruited. Maturity was assessed by self-reported Tanner staging. Images of non-dominant distal radius were obtained using high-resolution peripheral quantitative computed tomography (HR-pQCT) at 5 mm proximal to growth plate. Proximal 40 slices of 110 slices were analysed by StrAx1.0. Cortical cross-sectional area (CSA), cortical porosity, volumetric bone mineral density (vBMD), trabecular bone volume fraction (BV/TV) and matrix mineral density were measured. ANCOVA was used to identify sex difference on bone parameters after adjustment for age, height and weight, dietary calcium intake (Ca) and physical activity level (PA).

Results: After adjusting for all confounders, boys had 11.1–12.8% larger total CSA than girls across puberty, but boys had 1–4% lower cortical CSA/total CSA in Tanner stage 2–5. In Tanner stage 1, cortical thickness was 6.1% greater in boys but cortical porosity did not differ from girls. From Tanner stage 2, cortical thickness did not differ by sex while boys had 8.4–12.6% higher cortical porosity. Boys had 0.7–1.6% lower matrix mineral density in Tanner stage 3–5 after adjusting for age, Ca intake and PA. In boys, 15.1–21.3% lower total vBMD and 14.3–23.8% lower cortical vBMD were found in Tanner stage 2–5 compared to girls. Boys had 13.8–15.2% greater trabecular vBMD after adjusting for age, Ca and PA.

Conclusion: Total and cortical CSA increase during pubertal growth in both sexes and are larger in boys. Cortical porosity was higher and matrix mineral density was lower in boys, perhaps because their skeletal maturing takes longer to complete. Transient physiologically changes of the cortical morphology, reduced bone density and higher cortical porosity in Tanner stage 2 boys might partly decrease bone mechanical strength and contribute to the increased risk of distal forearm fracture.

RGC of HKSAR (468809 & 468411).

Disclosure: The authors declared no competing interests.

Bone Abstracts

P009