Different Poissons ratios

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• Different Poissons ratios
• Shear stress at interface-bonding problems

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• Less stress concentration when placed centrally

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Load-Transfer

• Affected by bonding characteristics at interface
• Frictional/adhesive characteristics
• Orientation of interface relative to loading
  direction
• Surface microstructure/texture

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• True only when bonded surface is perpendicular to
  loading direction

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• Bonded case, both compressive and shear at
  interface, shear gt compressive for small angles
• Press-fit, get a tensile hoop stress in bone to
  prevent expansion, and maintain
  equilibrium-abnormal loading

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• Rigidity of stem affects
• Bone stresses (may cause resorption)
• Interface stresses (may cause loosening)
• Non-cemented stems tend to be canal filling and
  thicker---hence.(more stiff, more stress
  shielding)
• Bone stiffness-VERY IMPORTANT

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SENIOR DESIGN??