Factor of Risk for Fracture - Skeletal Aging and Osteoporosis: Biomechanics and Mechanobiology - page 139

2.2.2 Association Between the Factor of Risk and Vertebral Fracture
Factor of risk is increased in individuals with vertebral fracture. In a cross-sectional
study of 81 patients with vertebral fractures [ 17 ] the mean factor of risk, using
forward flexion and vertebral strength estimated from spine BMD, was greater than
or equal to one for patients with vertebral fractures (men: 1.03; women: 1.35;
p \ 0.05) and was greater than the factor of risk for age-matched controls without
fracture (men: 0.76; women: 1.06; p \ 0.01). Moreover, in a study comparing 40
post-menopausal women with prevalent vertebral fracture to 40 without, the esti-
mated factor of risk for vertebral fracture (simulating 90 o forward flexion and using
QCT-based finite element analysis (FEA) to estimate vertebral strength) was
significantly higher in subjects with prevalent vertebral fractures than in those with
no fractures. The OR's for three different predictors of fracture were: factor of
risk = 3.2 (95% CI 1.4-7.5), FEA vertebral strength = 2.2 (95% CI 1.2-4.3) and
integral vBMD = 2.2 (95% CI 1.1-4.3) [ 44 ].
A more recent study examined the association between vBMD, vertebral
strength and the factor of risk in postmenopausal women with mild (n = 141) vs
moderate/severe (n = 52) prevalent vertebral deformities [ 47 ]. Vertebral strength
was estimated from QCT-based FEA, and activities included upright standing, plus
forward flexion with and without weights. Women with mild vertebral deformities
had lower vertebral strength and increased factor of risk compared to women with
no fractures, whereas women with moderate and severe fractures had even lower
vertebral strength and higher factor of risk values for several activities. Associa-
tions between vertebral fracture and vBMD, vertebral strength and factor of risk
were higher in women with moderate/severe fractures (OR = 2.9-3.5) than in
women with mild fractures (OR = 1.4-1.5), but were similar amongst different
predictors of fracture.
The use of factor of risk as a predictor for vertebral fracture was compared to
use of aBMD in both a cross-sectional case-control study with 89 postmenopausal
women with fractures and 306 controls, as well as a 10-year prospective study in
which 30 women with incident fractures were compared to 150 women without
[ 19 ]. In the case-control study, factor of risk was significantly associated with
prevalent fracture (OR 2.06; 95% CI 1.55-2.73), but was less sensitive and
specific than aBMD in distinguishing cases and controls. In the prospective study,
factor of risk was not predictive of fracture (HR 1.20; 95% CI 0.9-1.7), but aBMD
was (HR 2.4; 95% CI 1.5-3.8). This study concluded that factor of risk is not
better than aBMD in predicting the risk of fracture.
2.3 Studies of the Factor of Risk for Distal Forearm Fracture
Fractures of the distal forearm or wrist are the second most common osteoporotic
fracture after vertebral fractures, accounting for about 19% of fractures [ 7 ].
Excluding severe trauma, fractures of the distal forearm in adults over 50 are