Effect of Preservative Solution on Fracture Characteristics of Bovine Femoral Cortical Bone

Abstract

Accurate determination of the mechanical properties of bone requires a preservation method that has minimal effects on these properties. It is conceivable that long-term exposure of bone to formalin and/or saline may have some effect on its mechanical properties. We examined the effect of fixation with neutral buffered formalin on the fracture toughness of bovine femoral cortical bone (Haversian or laminar), and we also analyzed the elution of bone minerals in the preservative solution. Formalin-preservation periods were 30 days and 150 days. To test the anisotropy of the bone, two different specimens in which we had introduced an initial crack in a circumferential or radial direction were used as specimens. Fracture toughness testing was performed on three-point bend specimens and with 1 mm/min or 20 mm/min cross-head speed. A 30% maximum decrease in fracture toughness was observed. The rate of decline in fracture toughness was relatively high in the laminar bone specimen under 20 mm/min cross-head speed. Calcium elution into saline was higher than into formalin preservative, confirming that bone minerals elute markedly into aqueous solutions such as saline.