Chp 9: Mechanisms And Characteristics Of Musculoskeletal And Nerve Trauma Flashcards
What does the stress-strain curve represent?
The relationship between the stress placed on various tissues and the deformation that occurs
Load
An external force acting on tissues that causes internal reactions within the tissues
Stiffness
The relative ability of a tissue to resist a particular load (great stiffness means it can withstand a greater magnitude of load)
Stress
Internal resistance of the tissues to an external load
Strain
Extent of the deformation of tissue when its loaded
Deformation
The internal strain placed on the tissues from that stress results in deformation
Elasticity
A property that allows a tissue to return to normal following deformation
Yield point
Point where tissue is deformed to the extent where it no longer reacts elastically
Plastic changes
Beyond the yield point, deformation persists after the load is removed and results in permanent or plastic changes to the tissue
Creep
The deformation in the shape/properties of a tissue that occurs w/the application of a constant load over time
Mechanical failure
Ability of the tissue to withstand stress and strain is exceeded resulting ultimately in injury to the tissue
Difference between ductile and brittle tissues?
Ductile tissues can deform significantly before failing and consequently have a longer plastic area. Brittle tissues can deform very little before failure.
What are five types of tissue loading that can produce stress and strain?
Compression, tension, shearing, bending, and torsion
Compression produced by what forces?
Produced by external loads applied toward one another on opposite surfaces in opposite directions
What does compression do to a structure?
Shortens and widens a structure
What types of injuries are a result of compressive forces?
Arthritic changes in cartilage, fractures, and contusions
Tension forces
Forces that pull or stretch tissue apart. (Equal and opposite external loads that pull a structure apart)
Injuries that occur due to tension?
Muscle strains and ligament sprains
Shearing forces
Equal but not directly opposite loads are applied to opposing surfaces, forcing those surfaces to move in parallel directions relative to one another
Bending forces
Convex surface is elongated and subject to tension while the concave surface is shortened and subject to compression
Torsion forces
Caused by loads twisting in opposite directions from the opposite ends of a structure
Torsion forces usually result in what injury?
Spiral fractures at an oblique angle in long bones
Review Chart of Classification and Load Characteristics of In juries
Muscle strain
Muscle is overstretched by tension, or forced to contract against too much resistance a separation/tearing of the fibers occurs
Grade 1 muscle strain
Some muscle fibers stretched/torn. Some tenderness and pain on active motion. Movement is painful but full ROM possible
Grade 2 muscle strain
A number of muscle fibers have been torn, active contraction of the muscle is extremely painful. Depression/divet can be felt in the muscle belly at the place where muscle fibers have been torn. Bleeding causes ecchymosis and hematoma although not immediately. ROM decreased due to pain(Some swelling may occur bc of increased capillary permeability)
Grade 3 muscle strain
Complete rupture of a muscle occurred in the area of a muscle belly at the point at which the muscle becomes tendon or the tendinous attachment to the bone. Significant impairment/total loss of movement due to disruption of nerve fibers. Initially pains intense but then lessens due to unloading of the muscle
Healing timeframe for a hamstring strain is typically?
6-8 weeks
Muscle Cramps
Involuntary muscle contraction commonly occuring in calf, hamstrings, quads, etc.
Muscle guarding
After injury, the muscles that surround the injured area contract to, in effect, splint the area, thus minimizing pain by limiting movement.
Muscle spasm
Involuntary muscle contraction that results in increased tension and shortening of that muscle or a group of muscles which interferes w/voluntary movement.
Why do muscle spasms occur?
Consequence of neurological damage or disease
Why do muscle cramps occur?
Occur due to altered neuromuscular control bc of high demand activities that overload/fatigue muscles
Describe a clonic muscle spasm
Alternates quickly between involuntary muscle contraction and relaxation
Describe a tonic muscle spasm
Rigid muscle contraction that lasts a period of time