The Impact of Developmental Age and Loading Rate on the Patterns of Bone Fracture Under Torsion and Bending Using Either Immature Porcine or Ovine Femurs

摘要

The determination of whether pediatric long bone fracture is based on accidental trauma or an abusive act is a major question in forensics. A recent clinical study has suggested that the mechanisms of long bone fracture can be determined based on the fracture pattern. While human pediatric bone is difficult to obtain, immature animal models, like porcine and ovine models, can act as adequate surrogates for scientific studies. The first research topic explored in this thesis is the influence of specimen age and loading rate on whole-bone fracture patterns. Under femoral torsion, the spiral fracture pattern (fracture ratio) was shown to increase with porcine age and rate of twist, bringing into question results of the clinical study. The second research topic explored direction-specific tensile and shear test data versus specimen age and loading rate in the immature porcine model. Results showed that both porcine age and loading rate can affect transverse and longitudinal shear stress components, altering the torsional fracture pattern. In another study the immature ovine femur was used in concentrated four-point bending tests, and was shown to produce transverse fractures, while mature specimens produced compressive wedge fractures. Preliminary evidence suggested that at higher test rates, a tensile wedge pattern is produced for mature specimens. As impact direction is currently cited by tensile wedges, consistent generation of compression wedges muddle this practice. The compilation of this work demonstrates that loading rate and developmental age affect fracture patterns in immature femora, highlighting that caution needs to be taken when analyzing pediatric long-bone fractures.