Bone microarchitecture and stiffness in premenopausal women with idiopathic osteoporosis.
BACKGROUND
Idiopathic osteoporosis (IOP) is an uncommon disorder in which low areal bone mineral density (aBMD) and/or fractures occur in otherwise healthy premenopausal women.


OBJECTIVE
Our objectives were to characterize bone mass, microarchitecture, and trabecular bone stiffness in premenopausal IOP and to determine whether women with low aBMD who have never fractured have abnormal microarchitecture and stiffness.


METHODS
We conducted a prospective cohort study of 27 normal controls and 31 women with IOP defined by low trauma fracture (n = 21) or low BMD (Z score <or=-2.0; n = 10).


METHODS
We assessed aBMD by dual-energy x-ray absorptiometry; volumetric BMD and cortical and trabecular microarchitecture of the radius and tibia by high-resolution (82 microm) peripheral quantitative computed tomography; and trabecular bone stiffness (elastic moduli), estimated by micro-finite element analysis.


RESULTS
Fracture subjects did not differ from controls by age or body mass index, which was lower in low-BMD subjects than controls. Fracture subjects also had lower aBMD than controls at all sites (P < 0.05-0.0001). Bone size was similar in controls and fracture subjects but 10.6% smaller in low-BMD subjects (P < 0.05). Every trabecular parameter in both fracture and low-BMD groups was markedly worse than controls (P < 0.01-0.0001). Cortical thickness was significantly lower in both fracture and low-BMD groups at the tibia but not radius. Bone stiffness estimated by micro-finite element analysis was comparably reduced in low-BMD and fracture groups.


CONCLUSIONS
Premenopausal women with IOP had marked trabecular microarchitectural deterioration at the radius and tibia. Cortical parameters were affected only at the tibia. Although they had not fractured, microarchitectural deterioration was similar in IOP women with low BMD and those with fractures.
Cohen
Adi
A
Department of Medicine, Columbia University, New York, New York 10032, USA. ac1044@columbia.edu
Liu
X Sherry
XS
Stein
Emily M
EM
McMahon
Donald J
DJ
Rogers
Halley F
HF
Lemaster
Jeanette
J
Recker
Robert R
RR
Lappe
Joan M
JM
Guo
X Edward
XE
Shane
Elizabeth
E
D000293:Adolescent; D000328:Adult; D000465:Algorithms; D015519:Bone Density; D001842:Bone and Bones / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008875:Middle Aged; D010024:Osteoporosis / Q000473:pathology / Q000503:physiopathology*; D017697:Premenopause; D011446:Prospective Studies; D011884:Radius / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D012016:Reference Values; D013977:Tibia / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed; D055815:Young Adult