The Chinese skeleton: insights into microstructure that help to explain the epidemiology of fracture

Abstract

Osteoporotic fractures are a major public health problem worldwide, but incidence varies greatly across racial groups and geographic regions. Recent work suggests that the incidence of osteoporotic fracture is rising among Asian populations. Studies comparing areal bone mineral density and fracture across races generally indicate lower bone mineral density in Asian individuals including the Chinese, but this does not reflect their relatively low risk of non-vertebral fractures. In contrast, the Chinese have relatively high vertebral fracture rates similar to that of Caucasians. The paradoxically low risk for some types of fractures among the Chinese despite their low areal bone mineral density has been elucidated in part by recent advances in skeletal imaging. New techniques for assessing bone quality non-invasively demonstrate that the Chinese compensate for smaller bone size by differences in hip geometry and microstructural skeletal organization. Studies evaluating factors influencing racial differences in bone remodeling, as well as bone acquisition and loss, may further elucidate racial variation in bone microstructure. Advances in understanding the microstructure of the Chinese skeleton have not only helped to explain the epidemiology of fracture in the Chinese, but may also provide insight into the epidemiology of fracture in other races as well.

Figure 1

Hip fracture incidence per 100 000 person-years in Asian and Caucasian women and men, in different populations.^,,,,,,,, Data from Refs. 7, 45, 47 and 50 standardized to US population.

Figure 2

Representative hip geometry images indicating (a) Hip Axis Length, defined as the distance from the base of the greater trochanter through the femoral neck to the inner pelvic brim (point B to A) and (b) Femoral Neck Axis Length, defined as the distance from the base of the greater trochanter to the apex of the femoral head (point B to C).

Figure 3

Representative HRpQCT images indicating smaller bone size but thicker cortices and more plate- (green) versus rod-like (red) trabeculae at the radius in premenopausal (a) Chinese American versus (b) white women; three-dimensional representations of lower cortical porosity in premenopausal (c) Chinese American versus (d) white women at the tibia