DXA-derived section modulus and bone mineral content predict long-bone torsional strength.
Previous studies have used dual energy x-ray absorptiometry (DXA) scans to calculate the section modulus (Z) of adolescent and adult human femurs. The DXA-derived values of Z were assumed to be proportional to bone strength in bending and torsion. In this study we used dog (n 5), pig (n 4), and human (n 13) femurs covering a linear bone mineral content (BMCL) range of 0.91-6.1 g/cm. Using DXA scans, ex vivo torsional strength tests, and torsional finite element models, we assessed the validity of using the DXA-derived Z value as an indicator of strength. The correlation between BMCL and strength was r2 = 0.87 and the correlation between Z and strength was r2 = 0.86. Based on finite element results, the dog and pig section moduli were adjusted to be comparable to the human data based on cross-sectional shape and bone tissue shear strength differences. With these adjustments, the correlation between adjusted section modulus and measured strength did not improve (r2 = 0.87). These data indicate that DXA-derived section modulus can be used to predict strength over a wide range of bone sizes. However, a clear advantage of using DXA-derived section modulus rather than BMCL could not be found.
Sarin
V K
VK
Rehabilitation Research & Development Center, VA Palo Alto Health Care System, CA 94304, USA. sarin@bones.stanford.edu
Loboa Polefka
E G
EG
Beaupré
G S
GS
Kiratli
B J
BJ
Carter
D R
DR
van der Meulen
M C
MC
D015502:Absorptiometry, Photon; D000328:Adult; D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density; D002102:Cadaver; D004285:Dogs; D005269:Femur / Q000000981:diagnostic imaging* / Q000503:physiopathology; D020342:Finite Element Analysis; D006801:Humans; D016014:Linear Models; D011237:Predictive Value of Tests; D011877:Radionuclide Imaging; D015203:Reproducibility of Results; D013552:Swine; D013718:Tensile Strength; D014102:Torsion Abnormality / Q000503:physiopathology