Ac. Courtney et al., AGE-RELATED REDUCTIONS IN THE STRENGTH OF THE FEMUR TESTED IN A FALL-LOADING CONFIGURATION, Journal of bone and joint surgery. American volume, 77A(3), 1995, pp. 387-395
To assess age-related changes in femoral strength as a component in th
e risk of fracture of the hip, we compared the loads at fracture of th
e proximal aspects of femora from the cadavera of older and younger in
dividuals, as tested in a fall-loading configuration. To provide a bas
is for non-invasive in vivo estimates of femoral strength, we also det
ermined the correlations between variables measured with dual-energy x
-ray absorptiometry and these loads. Femora from the cadavera of eight
older individuals (mean age, seventy-four years) and nine younger ind
ividuals (mean age, thirty-three years) were scanned with a Hologic QD
R-2000 densitometer to obtain densitometric and geometric information.
The femora were then tested mechanically in a loading configuration t
hat simulated a fall on the greater trochanter. The femora from the ol
der group were half as strong as those from the younger group (p < 0.0
01), and they absorbed one-third as much energy (p < 0.001). The areal
bone-mineral density of the femoral neck correlated strongly with the
load at fracture (r(2) = 0.92). CLINICAL RELEVANCE: The prevalence of
fracture of the hip increases exponentially with age. Ninety per cent
of fractures of the hip occur in individuals who are more than sevent
y years old, and more than 90 per cent of these fractures are the resu
lt of a simple fall from a standing height. Comparison of our data on
the load at fracture with estimates in the literature of impact forces
on the hip during falls from a standing height indicates that, on the
average, impact forces exceed the strength of the femora in older ind
ividuals by approximately 50 per cent but are approximately 20 per cen
t less than the strength of the femora in younger individuals. These f
indings help to explain the lower prevalence of fracture of the hip am
ong younger adults. However, since fewer than 5 per cent of all falls
result in a fracture of the hip, our data also emphasize that other fa
ctors, such as the direction of the fall, the site of impact, and the
use of passive and active energy-absorbing mechanisms, must be importa
nt determinants of the risk of such a fracture.