Rib fractures are associated with high rates of morbidity and mortality. Improved
methods to assess rib bone quality are needed to identify at-risk populations.
Quantitative computed tomography (QCT) can be used to calculate volumetric bone
mineral density (vBMD) and bone mineral content (BMC), which may be related to
rib fracture risk. The objective of this study was to determine if vBMD and BMC
from QCT predict human rib structural properties. 127 mid-level (5th–7th) ribs
were obtained from adult female (n = 67) and male
(n = 60) postmortem human subjects (PMHS). Isolated rib QCT
scans were performed to calculate vBMD and BMC. Each rib was subsequently tested
to failure in a dynamic simulated frontal impact and structural properties, peak
force (FPeak), percent displacement
(δPeak), linear structural stiffness
(K), and total energy (UTot)
were calculated. vBMD demonstrated no significant differences between sexes
(p > 0.05); however, males had a higher BMC than females
(p < 0.001). Further, sex-specific differences were
observed in all rib structural properties except for
δPeak (p > 0.05). Age had a
significant relationship with both vBMD and BMC (p < 0.001)
but only in females when separated by sex (p < 0.001). vBMD
predicted FPeak, δPeak,
K, and UTot
(R2 = 9.2%–30.9%, p < 0.05)
but was not able to predict δPeak in males.
Similarly, BMC also predicted all rib structural properties, except for
δPeak in males, but explained more meaningful
amounts of variation (R2 = 22.2%–67.7%,
p < 0.001). When predicting rib structural properties,
BMC captures sex-specific variations in bone size that are obfuscated by vBMD
and contribute to the biomechanical response of the rib during mechanical
loading. Incorporating BMC into assessments of injury risk may therefore provide
additional insight into the multifaceted nature of rib bone quality and
differential fracture resistance.
