Better skeletal microstructure confers greater mechanical advantages in Chinese‐American women versus white women

Despite lower areal bone mineral density (aBMD), Chinese‐American women have fewer fractures than white women. We hypothesized that better skeletal microstructure in Chinese‐American women in part could account for this paradox. Individual trabecula segmentation (ITS), a novel image‐analysis technique, and micro–finite‐element analysis (µFEA) were applied to high‐resolution peripheral quantitative computed tomography (HR‐pQCT) images to determine bone microarchitecture and strength in premenopausal Chinese‐American and white women. Chinese‐American women had 95% and 80% higher plate bone volume fraction at the distal radius and tibia, respectively, as well as 20% and 18% higher plate number density compared with white women ( p  < .001). With similar rodlike characteristics, the plate‐to‐rod ratio was twice as high in the Chinese‐American than in white trabecular bone ( p  < .001). Plate‐rod junction density, a parameter indicating trabecular network connections, was 37% and 29% greater at the distal radius and tibia, respectively, in Chinese‐American women ( p  < .002). Moreover, the orientation of the trabecular bone network was more axially aligned in Chinese‐American women because axial bone volume fraction was 51% and 32% higher at the distal radius and tibia, respectively, than in white women ( p  < .001). These striking differences in trabecular bone microstructure translated into 55% to 68% (distal radius, p  < .001) and 29% to 43% (distal tibia, p  < .01) greater trabecular bone strength, as assessed by Young's moduli, in the Chinese‐American versus the white group. The observation that Chinese‐American women have a major microstructural advantage over white women may help to explain why their risk of fracture is lower despite their lower BMD. © 2011 American Society for Bone and Mineral Research