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Back to Orthopedics Articles
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The risk of hip fracture rises exponentially with age, and may
result from fragility of the femoral neck.
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Certain types of exercise could protect against the steep
increase in risk of hip fracture with age, suggests research
in this week's issue of The Lancet.
The risk of hip fracture rises exponentially with age,
and may result from fragility of the femoral neck. Dr Paul M Mayhew
(University of Cambridge, UK) and colleagues used computed
tomography to scan sections of femurs from 81 adults who died
suddenly. They created three-dimensional reconstructions of the
bone, then obtained a cross-sectional image of the mid-femoral neck.
From these cross sections, they estimated the amount of stress that
each region could tolerate before becoming unstable.
The thin cortical zone of the upper femoral neck became
substantially thinner with age. In women, cortical thickness fell by
6?4% per decade, and critical stress by 13?2% per decade in the
region most compressed by a sideways fall. Similar, but
significantly smaller results were evident for men. This thinning
reduced the amount of energy that the femur could absorb before
buckling.
The authors suggest that the reason for this thinning is that
bipedal walking does not transmit much load to this region. By
contrast, the cortex of arboreal apes is almost symmetrically thick,
since tree-climbing loads this region more than walking. As people
age, their amount and variety of exercise is reduced, and walking
becomes the main source of load on the femur.
The authors state: "Several popular forms of exercise also
involve extension of the flexed femur under load (cycling, sculling,
gymnastics, weights). Some should be investigated for their
potential to protect, as part of our society's drive to increase
physical activity for health."
In an accompanying Comment, Charles H Turner questions whether
this new theory about buckling failure is too simplistic, but
welcomes the potential for more detailed assessment of the regional
pattern of bone loss and targeted interventions to strengthen
underused bone regions.
###
Dr J Reeve, Box 157, Department of Medicine, Addenbrooke's
Hospital, Cambridge CB2 2QQ, UK. T) +44 (0)1223 741617
Dr Charles H Turner, Departments of Biomedical Engineering and
Orthopedic Surgery, Indiana University Purdue University
Indianapolis, USA; T) +1 317 274 3226
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