Influence of three different preservative techniques on the mechanical properties of the ovine cortical bone.

Purpose: Preservative treatments are necessary for disinfection and long term storage when dealing with biological tissue. Freezing is a gold standard but infectious risk can only be eliminated by using chemical fluids that may alter the mechanical properties, depending on their composition. Therefore, we experimentally evaluated the influence of freezing and of two commonly used preservative fluids (formalin and alcohol) on the intrinsic mechanical properties of ovine cortical bone samples, compared to purely fresh samples.

Methods: Prismatic specimens were prepared from the sheep's metacarpal bones and were divided into four groups (fresh, fresh-frozen, formalin and alcohol). All samples underwent four-point-bending; fresh samples were tested immediately, preserved samples were tested after 14 days. Bending modulus, bending strength, yield strength and energy absorption for the elastic and plastic region were determined.

Results: Significant differences were found for the plastic energy absorption for formalin (-41%) and alcohol (+37%) preservation com- pared to fresh samples. Formalin preservation revealed embrittlement of the cortical bone samples and alcohol preservation revealed higher ability of plastic energy absorption.

Conclusions: Our results indicate that freezing has no influence on the mechanical properties of the ovine cortical bone. Preservation with chemical fluids (formalin and alcohol) showed no influence on the elastic properties but it was observed for the ability of plastic energy absorption. Therefore, these methods seem to be suitable for preservation without evident altering of the elastic mechanical properties.