Researchers have developed a mathematic formula
to predict a woman's risk of osteoporotic
fracture. The equation has proved 75 percent
accurate and will allow physicians to tailor
their treatment strategies to help women prevent
fractures of fragile bones. The study appears
in the October issue of Radiology.
"Approximately 45 percent of women have different
levels of bone mineral density between their
hip and their spine, leading to uncertainty
as to how physicians should assess their future
fracture risk," said the study's lead author,
Margaret Joy Henry, B.Sc(Hons)., Ph.D., statistician
in the Department of Clinical and Biomedical
Sciences at The University of Melbourne, Australia.
"We have derived an equation that successfully
predicted 75 percent of fractures in women,
two years after their initial measurements
were taken."
Women with osteoporosis have brittle bones
that are more likely to break as a result
of a minor bump or fall. Bones affected by
osteoporosis are less dense than normal bones,
due to larger pores in the bone, reduced calcium
levels and fewer blood vessels.
The equation developed by Dr. Henry and colleagues
takes into account a variety of risk factors,
not just bone mineral density. A patient's
likelihood of falling, low bone mass, excess
or low body weight and additional factors
are combined into a single formula that can
indicate to a physician how serious a woman's
fracture risk may be. Treatment strategies
may then be targeted on the basis of a woman's
predicted outcome.
A total of 231 elderly women who had sustained
a low-trauma fracture of the hip, spine, humerus
or forearm during a two-year period were recruited,
as well as 448 elderly women who were selected
randomly and had not sustained a fracture
during the same two-year period.
The equation was developed based on measurements
obtained in this study population. It was
then tested in a third group of women from
the community, who were randomly selected
to be followed for a six-year period to determine
the success of the formula for predicting
fractures.
By using the formula, 75 percent of fractures
were successfully predicted two years after
the baseline measurements were obtained. The
authors also discovered that heavier body
weight seemed to increase the force applied
to the skeleton during a fall. Findings of
most previous studies indicated that lighter
body weight led to increased risk of fracture,
due to lower bone mass.
Development of this formula to predict future
fracture risk is important because it will
allow physicians to better adapt treatment
strategies for women with osteoporosis, especially
by taking into consideration different bone
density measurements throughout the body.
A variety of treatment regimens can be used,
including hormone replacement therapy, non-hormonal
medicines, vitamin D and calcium supplements,
and additional therapies such as calcitriol--an
active form of vitamin D that improves the
absorption of calcium from the digestive process.
"As the average age of the population increases,
the number of fractures attributable to osteoporosis
is set to increase dramatically," said Dr.
Henry. "The ability to predict fracture risk,
based on simple clinical measurements, will
assist in targeting treatment for people at
highest risk, thus helping reduce the burden
of this disease."
Dr. Henry and colleagues are currently assessing
risk factors in a large cohort of men to develop
a similar formula for use in the male population.
