# PREVENTION OF STRESS FRACTURES IN BONE

> **NIH NIH R01** · INDIANA UNIVERSITY INDIANAPOLIS · 1993 · $139,245

## Abstract

High shear stresses predicted by finite element analysis in the location
at which stress fractures occur in our rabbit model suggest that high
shear stresses contribute to the etiology of stress fractures.  We
propose to test the hypotheses that (1) large bending strains cause
locally high shear stress concentrations at sites where fractures occur
and (2) the fatigue life of bone subject to shear stress is shorter in
vivo and ex vivo.

The first experiment will test the hypothesis that stress fractures occur
at sites of high shear strain in the rabbit model.  Rosette strain gages
will be attached to the anterior cortex of the distal tibia, where stress
fractures occur, and to the midshaft of 20 rabbits.  The animals will be
loaded repetitively with the device we used to develop the model.  An FEM
of each rabbit tibia will be constructed and validated against the
midshaft strain state.  Measured shear strains in the distal tibia will
be compared to predicted shear strains at this site to determine whether
the magnitude and location of predicted and measured high shear strain
correspond.

The second experiment will test whether stress fractures occur at the
site of high shear stress if the point of high shear stress is moved from
the anterior tibial cortex to the posterior cortex.  This experiment has
five steps:  (1) Design, build and test a loading apparatus that alters
the location of high shear stress; (2) define the midshaft strain state
with the new apparatus; (3) construct an FEM of the rabbit tibia; (4)
verify the locations of high shear strain predicted by FEM; (5) apply
loads to 24 rabbits for 6 weeks to determine whether stress fractures
occur at the new location of high shear stress.  The third experiment
will determine whether shear stress rather than normal stress dictates
failure in the rabbit stress fracture model.  This will be accomplished
by performing shear fatigue tests.  Bovine mid-diaphyses will be machined
into shear test specimens.  Iosipescu shear specimens and Arcan shear
specimens will be used to induce pure shear in the transverse and
longitudinal directions respectively.  All tests will be conducted in an
environmental chamber under stress control at an initial strain range of
500, 1500 and 3000 microstrain using with an MTS Bionix testing machine.
If bone's fatigue life in shear is not significantly shorter than its
fatigue life in uniaxial compression or tension, then the hypothesis that
shear stress is the primary predisposing mechanical factor for stress
fractures must be rejected.

Results from this experiment will demonstrate the pathophysiological
mechanisms that underlie stress fractures.  If shear stresses cause
stress fractures, training programs that minimize the development of
shear stresses in locations at risk for stress fracture can be developed
for military training and sports medicine applications.

## Key facts

- **NIH application ID:** 3159918
- **Project number:** 2R01AR039708-05A1
- **Recipient organization:** INDIANA UNIVERSITY INDIANAPOLIS
- **SAM.gov UEI:** SHHBRBAPSM35
- **Principal Investigator:** David B Burr
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1993
- **Award amount:** $139,245
- **Award type:** 2
- **Project period:** 1990-01-01 → 1996-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/3159918

## Citation

> US National Institutes of Health, RePORTER application 3159918, PREVENTION OF STRESS FRACTURES IN BONE (2R01AR039708-05A1). Retrieved via MORVS 2026-10-24 from https://api.morvs.ai/grant/nih/3159918. Licensed CC0.

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