The Challenge
Understanding the mechanical properties and behavior of bone helps researchers
develop replacement materials and for regenerative solutions to treat problems
such as osteoporosis. Test data on the mechanical behavior of bone under
combined loading patterns experienced in vivo also helps researchers create
accurate models for purposes such as predicting fracture in patients and
evaluating fracture treatment protocols.
Bone is a naturally anisotropic material, exhibiting different mechanical
properties in different directions. The composition and loading response of
hard cortical and spongy cancellous bone differ greatly and therefore require a
variety of testing solutions to accurately characterize the tissue in vivo.
There are several items of interest where testing bone is concerned: the
fracture line will differ depending on the type and combination of forces
applied; the rate of loading; and the moisture content, all of which influence
the mechanical properties of bone.
Our Solution
Instron's test systems provide the ability to perform variable speed tensile,
compressive, indentation, flexure, and fatigue testing on a variety of
different bone specimens, from small sections to intact long bones. With such a
diversity of sizes and geometries, fixturing is often unique to the objective
of the test. Instron offers a full line of test fixtures including potting,
tensile, bend, and indentation fixtures and compression platens for testing of
any bone specimen type.
Strain measurement is also dependent upon specimen size and geometry. For flat
or round bone specimens, a clip-on extensometer may be mounted directly. For
small, delicate specimens or those with irregular geometry, an LVDT may be
mounted to the test fixtures. In some cases, a non-contacting video
extensometer may also be an appropriate option.
An environmental bath is easily adapted to any of the test systems and is used
to ensure that both hard cortical bone and soft cancellous bone remain moist to
provide results indicative of the bone's behavior in the human body.
Instron software allows for versatility and simple modification of the loading
sequences to accurately simulate loading in vivo. In addition, calculations
such as elastic modulus, tensile strength and percent strain are simple to set
up and modify before or even after the tests have been conducted.
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