Cortical Bone Mechanics and Composition: Effects of Age and Gender - Skeletal Aging and Osteoporosis: Biomechanics and Mechanobiology - page 61

Table 1 Elastic modulus of human cortical bone measured in monotonic tests
Orientation Bone Test Modulus (GPa) References

Longitudinal Femur Tension 15.6-19.4 [ 59 , 60 , 62 , 148 ]

Compression 15.2-18.1 [ 60 , 62 , 149 ]

Torsion 3.3-5.0 [ 51 , 54 ]

3pt-Bending 10.8-15.8 [ 63 - 66 ]

4pt-Bending 12.1 [ 150 ]

Tibia Tension 18.0-29.2 [ 59 , 60 ]

Compression 25.9-35.3 [ 60 ]

Cantilever bending 10.6 [ 151 ]

Fibula Tension 18.5 [ 59 ]

Humerus Tension 17.2 [ 59 ]

Radius Tension 18.5 [ 59 , 152 ]

Ulna Tension 18.4 [ 59 ]

Compression 14.2 [ 55 ]

Radial Ulna Compression 3.8 [ 55 ]

Lateral Compression 4.2 [ 55 ]

The elastic modulus of cortical bone depends strongly on its porosity [ 56 ].
Porosity also strongly influences the apparent, volumetric bone mineral density of
cortical bone, so measures of density strongly correlate with elastic modulus
[ 57 , 58 ]. In addition, modulus may vary with anatomic location, loading mode,
orientation, degree of mineralization, and specimen size. As shown in Table 1 ,
samples from human tibias tend to have a higher elastic modulus than samples
from other sites including the femur; samples from the fibula, humerus, radius and
ulna were reported to have similar tensile elastic moduli [ 59 , 60 ]. The elastic
properties may also change with anatomic locations within long bones [ 53 ]. For
instance, the elastic modulus of human cortical bone from male donors is greater
for femoral diaphysis than metaphysis [ 61 ].
Although some data suggest a difference between tensile and compressive
moduli, Reilly et al. [ 62 ] concluded that there was no significant difference
between these two loading modes based on paired comparisons from *200
samples of human femoral cortical bone. On the other hand, the flexural moduli
obtained from three-point and four-point bending tests are significantly different
(lower) from those of axial (tension or compression) tests [ 63 - 66 ]. It should be
noted that unlike a uniaxial test, the elastic modulus value obtained from bending
tests is based upon linear elastic beam theory, which may not fully reflect the true
elastic behavior of bone in bending.
Due to spatial heterogeneity and hierarchical features, the elastic behavior of
bone depends on specimen size (Table 2 ). Micro-specimens taken from osteons
and interstitial tissues of human femurs have revealed significantly different
properties when compared to those of macro-specimens. The tensile [ 67 ] and
compressive [ 68 ] moduli at the microscopic level are much lower than those
obtained at the macroscopic level. In contrast, torsion tests at the microscopic level
have obtained modulus values significantly higher than those obtained at the