The response of pediatric ribs to quasi-static loading: mechanical properties and microstructure

Traumatic injury is a major cause of death in the child population. Motor vehicle crashes account for a large portion of these deaths, and a considerable effort is put forth by the safety community to identify injury mechanisms and methods of injury prevention. However, construction of biofidelic anthropomorphic test devices and computational models for this purpose requires knowledge of bone properties that is difficult to obtain. The objective of this study is to characterize the relationship between mechanical properties and measures of skeletal development in the growing rib. Anterolateral segments of 44 ribs from 12 pediatric individuals (age range: 5 months to 9 years) were experimentally tested in three-point bending. Univariate mixed models were used to assess the predictive abilities of development-related variables (e.g., age, stature, histomorphometry, cross-sectional geometry) on mechanical variables (material and structural properties). Results show that stature, in addition to age, may be a reliable predictor of bone strength, and that histomorphometry has potential to explain bone properties and to further our understanding of fracture mechanisms. For example, percent secondary lamellar bone (%Sd.Ar) successfully predicts peak force (F P) and Young's modulus (E). Application of these findings is not restricted to injury biomechanics, but can also be referenced in forensic and anthropological contexts.