Factor of Risk for Fracture - Skeletal Aging and Osteoporosis: Biomechanics and Mechanobiology - page 140

almost always caused by a fall onto the hand [ 58 ]. Distal forearm fractures are
predictive of increased risk of subsequent hip or vertebral fractures in both men
and women [ 13 ].
Studies of factor of risk for distal forearm fracture have used a forward fall onto
the hand as the loading condition of interest. In all of these studies, loading has
been estimated as a damping coefficient times impact velocity [ 32 , 45 , 46 , 48 ]. The
damping coefficient was experimentally determined, and impact velocity estimated
from fall height [ 9 ]. The strength of the distal forearm in several recent studies of
factor for risk has been based on micro-finite element models [ 32 , 45 , 46 ]. This
approach is excellent for examinations of the distal forearm, as micro-finite ele-
ment models can be developed from HR-pQCT scans. An earlier study of distal
forearm factor of risk used mechanical testing of cadaveric radii to determine
distal forearm strength [ 48 ].

2.3.1 Age-, Sex- and Osteoporosis-Related Differences in the Factor
of Risk for Forearm Fractures

In a mechanical testing study, fracture strength was measured in cadaveric spec-
imens from nine female and 12 male donors [ 48 ] and factor of risk estimated for a
forward fall onto the hand. Mean factor of risk was 1.04 in females versus 0.79 in
males (p \ 0.01). Thus, this small study indicates that women are at greater risk of
fracturing the distal radius than men. The factor of risk was negatively correlated
with distal radius T-score (R 2 = 0.73), with a T-score below -1.5 indicating a

high risk of fracture.
Application of the factor-of-risk for wrist fracture in a population-based sample
of 700 women and men aged 20-97 years [ 63 ] showed that men had a higher
predicted forearm strength at all ages, largely due to their greater bone size.
In young adults, load to strength ratios at the distal radius were lower (better) in
men than in women, and increased (worsened) over life significantly more in
women than in men. These patterns are consistent with the higher rate of forearm
fractures in older women than men, and lack of marked age-related increase in wrist
fractures incidence in men.
Kazakia et al. [ 32 ] examined the variation of densitometric, geometric,
microstructural and biomechanical parameters with aBMD in one cohort of 58
post-menopausal women and another cohort of 142 men and women ages 20-78.
Factor of risk for distal forearm fracture was negatively correlated with aBMD
(R 2

= 0.80, p \ 0.0001), and was higher in osteoporotic individuals (p \ 0.01).

2.3.2 Association Between the Factor of Risk and Forearm Fractures

Factor of risk is increased in individuals with prevalent and incident forearm
fractures. In a cross-sectional, case-control study, 18 post-menopausal women
with a distal forearm fracture were compared with 18 age-matched controls [ 45 ].