Influence of different preservation methods on the mechanical in vitro stability of bones: a comparative study using porcine metatarsals.

INTRODUCTION: Large quantities of bone specimens are required for the mechanical testing of orthopedic and trauma implants. Currently, fresh-frozen or chemically preserved bones—such as formalin-fixed—are commonly used. This study aimed to evaluate the effects of different conservation methods on mechanical bone stability under standardized conditions. MATERIALS AND METHODS: Porcine metatarsals were divided into seven groups based on the preservation technique: fresh, fresh-frozen (− 18 °C), frozen with repeated freeze-thaw cycles, vacuum-sealed and refrigerated (4 °C), and chemically fixed using formalin, Thiel-fixation, or glycerol-based methods. All specimens underwent three-point bending tests to assess mechanical stability. Following induced fractures, bones were stabilized with a plate osteosynthesis (DCP® small fragment set, Synthes®, Germany) and retested. Bone mineral density (BMD) was also measured via dual-energy X-ray absorptiometry (DXA). RESULTS: Results revealed no significant differences in BMD, maximum load, or breaking strength between groups. However, chemically fixed bones—especially formalin and glycerol—showed significantly reduced deformation, indicating increased stiffness. Additionally, chemically fixed specimens exhibited more consistent fracture patterns compared to fresh or physically preserved bones. After osteosynthesis, bones preserved with glycerol showed a significant increase in both maximum load and breaking strength. CONCLUSIONS: While physical preservation methods had no notable effect on mechanical stability, chemically fixed bones exhibited altered deformation characteristics and should therefore be used selectively, depending on the research question.