Scanning electron microscopy of human cortical bone failure surfaces

Area of Science:

• Biomaterials Science
• Materials Science
• Orthopedic Research

Background:

• Human cortical bone's complex structure influences its mechanical properties.
• Understanding bone's fracture behavior is crucial for treating skeletal diseases and injuries.
• Previous studies have explored bone's mechanical response, but its composite nature under varying hydration requires further investigation.

Purpose of the Study:

• To investigate the fracture mechanisms of human cortical bone under different hydration conditions.
• To compare the fracture behavior of bone to synthetic composite materials.
• To propose a model for cortical bone based on composite material principles.

Main Methods:

• Undecalcified human femoral bone samples were subjected to bending-induced fracture.
• Fracture surfaces were analyzed using scanning electron microscopy (SEM).
• Specimens were tested in both dry and hydrated (saline solution) states.

Main Results:

• SEM analysis revealed fracture patterns analogous to those in fiber-reinforced synthetic composites.
• Dry bone samples exhibited brittle fracture characteristics, similar to brittle matrix laminates.
• Wet (hydrated) bone samples displayed ductile fracture behavior, akin to ductile matrix laminates.

Conclusions:

• Cortical bone can be effectively modeled as a laminated composite material.
• The extracellular matrix of calcified proteins acts as the matrix, and the calcified collagen fiber system serves as the reinforcement.
• Bone's hydration state significantly influences its fracture behavior, mimicking synthetic composite responses.