Biomechanics
4-30-99

Glossary in Nordin and Frankel is important to read and know

•	Looking at stresses upon the body
•	Stress = force / area   (area of application)
•	Osteophytes grow to increase surface area to decrease stress
•	Strain—what happens to body due to stress—how much is the change when under compression
•	Ligamentum flavum—only one in double digit values
•	Most ligaments have 3-4mm give
•	Creep—lengthening of something due to stretch tension    ex:  disc height  --does not continue; it stops at a point
•	Stress relaxation—put stress on and anchor it at a certain point   ex:  braces on teeth               ex:  club feet—cast that holds feet in place

Strength of Materials
•	Weaknesses and strengths of materials that make up systems (bones, muscles, nerves, ligaments)

Stress/Strain Diagram
Ex:  sprained ankle

•	Elastic area—remove stress, goes back to normal, typically only work in a small area w/a lot to spare
•	Plastic area—let go, it doesn't go back all the way, leads to weakening
•	Fails—ligament tear—completely gone
•	Hysteresis—energy loss going back

Bone

•	The faster you had it, the more resistance it has
•	Top graph is slow applied pressure

Low velocity fracture—Collie's fracture—wrist to prevent fall

Medium velocity, some fragments—more swelling

High velocity—lots of damage