KIN 3160 - Ch.9 Mechanisms and Characteristics of MSK and NERVE Trauma

Define Trauma

a physical injury or wound that is produced by an external or internal force.

When does a “mechanical injury,” occur?

A mechanical injury occurs when an external force applied to any part of the body causes a harmful disturbance in functionality or structure to an internal anatomical structure or tissue. The magnitude of the force is often times enough to damage or destruction to said tissues and structures

What is meant by “Elastic properties,” or “Elasticity” with regards to tissues?

Elasticity is a property which allows a tissue to return to normal after deformation.

What is “Stiffness” and is it an elastic or plastic property?

Stiffness is the relative ability of a tissue to resist a particular load. the greater the stiffness, the greater the load it can withstand before reaching its yield point.

Stiffness is an elastic property of tissues (b.c. it will return to normal after load)

What is the difference between “Stress,” & “Strain,” in tissues?

Stress: the internal resistance of the tissues to an external load.

Strain: the extend of deformation of a tissue under a load

An Internal strain placed on tissues by stress results in deformation of the tissue.

what is meant by a “yield point,” with regards to tissue stress-strain curves?

a yield point is the point where a tissue becomes too deformed to return to its normal shape due to a load exceeding a tissue’s stiffness (no longer reacts elastically). After a load is removed, deformation persists and causes “plastic changes.” *see plastic changes cue card*

what is a “plastic change,” with regards to a tissue’s stress-strain curve?

plastic changes are permanent changes to a tissues due to the excessive deformation of that tissue.

what is meant by “Creep,” in a tissue’s stress-strain curve

Creep is the deformation in the shape and or properties of a tissue that occurs with a constant load over time.

what is meant by “mechanical failure” ?

Mechanical Failure is when the ability of a tissue withstand stress and strain is exceeded, resulting in injury to a tissue.

What is the difference between “ductile” and “brittle” tissues?

ductile tissues: can deform significantly before mechanical failure and therefore have a much larger elastic area under a stress-strain curve.

brittle tissues: can deform very little before mechanical failure. Therefore have a much smaller elastic area under a stress-strain curve.

what is a stress-strain curve?

a stress-strain curve is a graphical representation of the relationship between stresses & strains, elastic & plastic properties interact when a tissue is out under a load. (See Fig 9-1, page 261)

what is “compression” ?

what injuries are most commonly caused by compressive forces

compression is a form of tissue loading produces stress and strain via external loads applied toward one another on opposite surfaces. compression results in the shortening and widening of a structure.

Arthritic changes in cartilage, fractures, and contusions are most commonly caused by compression.

What is Tension?

what injuries can be caused by tension?

tension is the force that pulls or stretches a tissue. Tension is generated in response to equal and opposite external loads that pull a structure apart.

Tension can cause muscle strains and ligament sprains.

What is “shearing” ?

what injuries may result from shearing?

Shearing occurs when equal, but not directly opposite forces/loads are applied to opposing surfaces. Injury results when shearing has exceed the strength of a tissue.

Shearing can result in skin injuries such as blisters or abrasions (scrape or partial skin tear) and injuries to intervertebral discs.

What is “Bending” and how can it occur?

Bending is when external forces/loads

Bending occurs in 1 of 3 ways:

1.) (4-point bending) when 2 force pairs are applied at opposite ends of a structure or

2.) (3-point bending) when 3 forces cause bending or

3.) when an already bowed (bending) structure is given an axial load (longitudinal).