Biomedical Engineering Reference
In-Depth Information
Factor of Risk for Fracture
Dennis E. Anderson and Mary L. Bouxsein
Abstract In considering the risk of fracture, both the loading applied to a bone
and strength of the bone are of importance. A conceptually simple approach for
considering both loading and strength is the factor of risk, U, which is the ratio of
applied load to failure load for a particular loading scenario. Theoretically a
fracture will occur if U C 1. The factor of risk may provide a better measure for
risk of fracture than current clinical measures such as bone mineral density.
However, the challenges of accurately determining both applied load and failure
load are significant. A number of studies have examined factor of risk for hip,
vertebral and distal forearm fractures. At all three locations, factor of risk has been
found to increase with age, and to be associated with incident or prevalent frac-
tures. While some studies show promising results, the factor of risk has not been
consistently better than bone mineral density alone in predicting the risk of frac-
ture. However, it should be noted that the approaches used to estimate applied load
and failure load in most studies have been relatively simple. Furthermore, only a
few loading conditions have been investigated, primarily fall impact to the side for
the hip, forward flexion/lifting for the vertebral body and forward fall onto the
hand for the distal forearm. Thus, in spite of its limitations and challenges, factor
of risk may still provide significant insight into the etiology of osteoporotic
fractures,
especially
as
methods
for
determining
bone
loading
and
strength
improve.
D. E. Anderson M. L. Bouxsein ( & )
Department of Orthopedic Surgery, Center for Advanced Orthopaedic Studies,
Beth Israel Deaconess Medical Center, Harvard Medical School,
330 Brookline Ave, Boston, MA 02215, USA
e-mail: mbouxsei@caregroup.org
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