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DXA-derived section modulus and bone mineral content predict long-bone torsional strength.
V K Sarin1, E G Loboa Polefka, G S Beaupré
1Rehabilitation Research & Development Center, VA Palo Alto Health Care System, CA 94304, USA. sarin@bones.stanford.edu
Acta Orthopaedica Scandinavica
|April 7, 1999
Summary
Dual energy x-ray absorptiometry (DXA) scans can predict bone strength using section modulus (Z). However, bone mineral content (BMCL) showed similar predictive accuracy for bone strength in this study.
Area of Science:
- Orthopedics
- Biomechanical Engineering
- Medical Imaging
Background:
- Dual energy x-ray absorptiometry (DXA) is used to estimate bone strength via section modulus (Z).
- Previous research assumed DXA-derived Z values correlate with bone strength in bending and torsion.
Purpose of the Study:
- To assess the validity of DXA-derived section modulus (Z) as an indicator of bone strength.
- To compare the predictive power of Z and bone mineral content (BMCL) for torsional bone strength.
Main Methods:
- DXA scans were performed on dog, pig, and human femurs (n=22).
- Ex vivo torsional strength tests and torsional finite element models were utilized.
- Section modulus (Z) and bone mineral content (BMCL) were calculated from DXA scans.
Main Results:
- A strong correlation was found between BMCL and torsional strength (r² = 0.87).
- A strong correlation was also observed between DXA-derived Z and torsional strength (r² = 0.86).
- Adjusting Z values for cross-sectional shape and bone tissue properties did not improve the correlation with strength.
Conclusions:
- DXA-derived section modulus (Z) can predict bone strength across a wide range of bone sizes.
- No significant advantage of using DXA-derived Z over BMCL was found for predicting bone strength.