Premenopausal Chinese-American women have “far
greater”
bone strength than Caucasian-American women, according to a
study from Columbia University.
The findings were presented at the
2011 Orthopaedic Research Society Annual Meeting in Long
Beach, Calif.
“This is a breakthrough finding in ethnic and
racial differences in bone microstructure, and the difference between
Chinese-Americans and Caucasians is striking,” study co-author X. Edward
Guo, PhD, professor of biomedical engineering at Columbia University’s
School of Engineering and Applied Science, told Orthopedics Today. “It
will have significant clinical, basic science and anthropological implications
as we begin to explore the genetic and environmental causes of these remarkable
differences.”
The Columbia team was led by Guo, John P. Bilezikian,
MD, Marcella Walker, and X. Sherry Liu.
In the study,
high-resolution peripheral quantitative CT (HR-pQCT) was
utilized to quantify the microstructures of the distal radius and the tibia.
Bilezikian told Orthopedics Today that the HR-pQCT instrument, theirs’
being one of only a handful currently in use in the United States, permits
high-resolution scans of the skeleton noninvasively.
Using the images obtained by the HR-pQCT, the
investigators used a novel technique called individual trabeculae segmentation
to analyze the structure and strength of the trabecular bone. Individual
trabeculae segmentation is different from more traditional techniques because
it automatically recognizes each plate and rod in the bone — precisely
determining the thickness and orientation of each.
Analyses based on individual trabeculae segmentation
were applied to subvolumes of the distal radii and tibias. The authors noted
that the most important factor when determining bone strength is the ratio of
plate-to-rod in trabecular bone.
Bilezikian and Walker led the clinical aspect of the
study and quantified microstructures in the distal radius and tibia.
“We believe the data from these sites can be
applied to other sites such as the hip,” Bilezikian said.
Ninety-five premenopausal women (49 Caucasian and 46
Chinese-American) underwent HR-pQCT scans, as well as dual-energy X-ray
absorptiometry (DXA) scans of the lumbar spine, total hip and femoral neck.
Despite a lack of difference in age, BMI and a real
bone mineral density between Chinese-American and Caucasian
women — as well as a cross-sectional bone area 9% lower at the radius and
6% lower at the tibia in Chinese-American women than in Caucasian women —
the authors found Chinese-American women had 18% and 10% more cortical
thickness in the distal radius and tibia respectively than Caucasian women.
In a finding the authors noted as
“remarkable,” when compared to Caucasian women, Chinese-American
women were found to have a 95% and 80% higher plate bone volume fraction at the
distal radius and tibia respectively. Furthermore, Chinese-American women
exhibited 20% and 18% higher plate number density.
In contrast to all of these findings, however, the
rod-like characteristics measured were all similar. This means the plate-to-rod
ratio was two-times higher in Chinese-American women than it was in Caucasian
women. Additionally, the trabecular plates were found to be “significantly
greater” in size in Chinese-American women.
“Although [Chinese-American women] have smaller
bone size than [Caucasian] women, thicker cortices and more plate-like
trabecular bone led to 14% and 8% greater whole bone stiffness at the radius
and tibia, respectively,” the authors wrote in their discussion.
“Chinese-American women have fundamentally
different bone microstructure from Caucasians,” Guo said. “This
dramatic difference in bone microstructure may explain the low fracture risk in
Chinese-Americans.”
Bilezikian noted that the paradox of why
Chinese-American women have reduced bone density but do not have the expected
high risk of fractures can now be explained by these findings. – by
Robert Press
Reference:
- Liu XS, et al. Better skeletal microstructure confers greater
mechanical advantages in Chinese-American women then Caucasian women. Paper
#329. Presented at the 2011 Orthopaedic Research Society Annual Meeting.
January 13-16. Long Beach, Calif.
- John P. Bilezikian, MD, can be reached at
jpb2@columbia.edu.
- X. Edward Guo, PhD, can be reached at
exg1@columbia.edu.
Disclosure:
This study was supported by NIH grants R01 AR051376 and K23 AR053507, a
National Osteoporosis Foundation grant, and the Mary and David Hoar Fellowship
Program of the New York Community Trust and the New York Academy of Medicine.
Guo and a co-author of this study hold the copyright of the ITS software used
in this study and may or may not benefit financially.