- See:
-
Elastic strain:
-
Biomechanics:
- Discussion:
- change in linear dimensions of a body resulting from the application of a force or load;
- strain energy is the energy a body is capable of absorbing by changing its shape under the
application of an external load;
- strain is a measure of deformation, or potential energy, or amount of work deformed body is
capable of doing in returning to its undeformed state;
- more rapidly a bone is loaded, the greater will be the energy absorption prior to failure;
- thus fractures associated with slow loading are generally linear, whereas rapid loading
infuses enormous strain energy so that an explosion of the bone takes place at failure;
- energy absorbed to produce frx of the femoral neck is approx 60 kg cm;
- in falls, kinetic energy is far in excess of this amount, however, this energy may be dissipated
by muscle action,
elastic strain and plastic strain of the soft tissues;
- load applied to a material produces stress within a material and thus invariably in deformation
(strain) of the material;
- analysis of mechanical conditions using the concept of strain allows one to understand why fractures w/
single, narrow gap are very intolerant of even minute amounts of displacement;
- such displacement may not be detected by vision but must be detected by intellect;
- instability is better tolerated by multifragmentary (comminuted) frxs because overall
displacement is shared between many fracture gaps;
- Critical Strain Levels of Repair Tissues:
(Elongation at rupture of different Sites)
Granulation Tissue:
100%
Dense Fibrous Tissue:
20%
Cartilage:
10%
Cancellous Bone:
2%
Lamellar Bone
2%
