| Introduction |
- Charateristics of orthopaedic implants depend
- structural properties (this topic)
- material properties
- Structural characteristic differs from strength characteristic
- not only depends on the material, but also the structural configuation of the object (cylinder, rectangle)
- the stuctural properties can also be demonstrated in a stress vs. strain curve
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| Bending Rigidity (stiffness) |
 Definitions
- defined as the slope of the curve in the elastic range on a structure stress-strain curve
- stress shielding of proximal bone in THA is related to implant stem stiffness
- Solid Cylinder
- proportional to the radius to 4th power for a solid cylinder
- cylinder A has great rigidity than cyliner B on illustration above (and thus has greater radius)
- Hollow Cylinder
- proportional to the radius to the 3rd power for a hollow cylinder
- Rectangular Object
- proportional to the (base x height) to the 3rd power
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| Area Moment of Inertia (I) |
- Closely related to bending rigidity
- area moment of inertia is a function of: structure width, thickness, and polar moment of inertia (J)
- polar moment of inertia represents an object resistance to torsion
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| Deflection |
- Proportional to: (applied force/elastic modulus)(area moment of inertia)
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