Biomechanics of Tendon Bone Cartilage and Muscle Flashcards
torque =?
Force x distance
Stress =?
Force/ area
What is this:
a condition resulting from increased pressure within a confined body space, esp. of the leg or forearm.
compartment syndrome
What are the typical loading schemes on a bone?
bending, torsion, compression
How do you test a tendon/ligaments ability to handle a load?
applying tension and using a strain/stress curve
What happens if you stretch something to the point of the plastic region?
you have deformation
What is the amount of deformation?
What is the amount of loading?
strain
stress
What is the constant slope on the stress/strain curve?
elastic region
What happens after you hit the yield point/ yield stress point?
you get deformation
Yield stress indicates (blank) changes to the specimen
structural
What am I talking about:
All this is basically saying is you can stretch something to a certain point, after that point it will change from its previous abilities and work differently from this point on. I.e be too bendy or less elasticy
viscoelasticity
What is this:
from yield point to ultimate tensile stress, with structural irreversible changes in specimen
plastic region
What is this:
mechanical properties independent of direction of stress (such as a metal sphere)
isotropy
What is this:
mechanical properties different in all directions of loading
anisotropy
What is this:
mechanical properties symmetric within two planes (long bone, axial/transverse loading)
orthotropy
In successive cycles of loading and unloading, what happens to hysteresis?
Why?
it dissipates causes smaller differences between loading and unloading curves (i.e cyclic loading leads to less dissapated energy)
Due to internal friction
How do we keep cyclic loading from causing a problem with orthopedics?
by using pretensioning or cycling a graft to set tension
What is the failing point->
ultimate stress
If you have a ductile material what will your strain/stress curve look like?
long slope between yield point and ultimate stress
If you have a brittle material what will your stain/stress curve look like?
yield point and ultimate stress would be very close together
What is fatigue strength?
looks at how your construct will survive over time
If you continually apply cycles (i.e keep bending a paper clip) eventual it will fail. What is this?
fatigue strength and cycles
If you have a stress strain curve, what is the area under the curve of yield point and ultimate stress?
absorbed energy before break
strain=?
deformation/length
what kind of fracture does torsion give you?
spiral fracture
What kind of fracture does compression give you?
butterfly fracture
What is youngs modulus?
ratio of stress over strain
What is hooke’s law?
force needed to compress/extend spring by some distance is proportional to that distance. That is: F=kX ,where k is a constant factor characteristic of the spring, its stiffness.
what part of the stress/strain curve represents youngs modulus?
elastic region
What part of the femur is this: Trabecular bone force transmission Hematopoiesis Thin cortices
proximal/distal
What part of the femur is this:
Lamellar/cortical bone
Axial loading
bending
diaphyseal
(blank) can absorb significant energy with minimal mass.
trabecular bone
(blank) has a very high yield point (compared to trabecular bone), when this bone fails (cuz its more brittle) it fails catastrophically and thats it.
cortical bone (diaphysis)
As you continue to compress trabecular bone, the more you compress it, the more it (blank). Why does this happen?
resists compression. Because as its getting compressed it gets mroe dense which allows it to resist
Anisotropy describes what kind of bone?
cortical bone (meaning mechanical properties dependent on direction of loading)
Bone is strongest in (blank), weakest in (blank)
compression
tension
Bone resists loading (blank) rather than in a transverse mode.
axially (longitudinal)
So whats the strongest way a bone can resist force?
axially (longitudinal) and compressed
How is bone the weakest?
with hoop stress
(blank) are sensitive to strain rate and duration of applied load
mechanical properties
Bone is ductile with (blank) and brittle with (blank)
slow loading (walking up stairs) rapid loading (MVA)
What is creep?
it is applying a force for enough time that you get permanent deformation
(think like braces, you have them for a while and take them out and your teeth are straight)
What is cold flow?
the distortion of a solid under sustained pressure esp. with an accompanying inability to return to its original dimensions when the pressure is removed
What is stress relaxation?
When trying to creep you slowly need to apply less force to maintain the same amount of deformation
What is this:
Force necessary to maintain deformation decreases over time.
stress relaxation
What is this:
energy absorbed before ultimate failure
toughness
What is this:
ultimate strain substantially larger than yield strain
ductility
Because bone is a composite structure (mineral and non mineral component) the mineral component will (blank) but is brittle and the non mineral component does (blank)
resist compression
keeps cracks from propogating so adds to toughness.
What all contributes to fracture resistance?
work to fracture
post yield compliance
crack propagation
Aging and disuse respond to bone similarly which results in (blank)
bone resorption
T or F?
250,000 hip fractures/year USA
500,000 vertebral fractures
T
What are 2 forms of osteoporosis that occur in response to aging?
senile osteoporosis
postemenopausal osteoporosis
(blank) affects males and females
reduction in cortical and trabecular bone
senile osteoporosis
(blank) affects subset of females
Dis proportional loss of trabecular bone
postmenopausal osteoporosis
Do females lose more trabecular or cortical bone?
trabecular
What is this: Reduction in vertical trabecula disproportionally Reduction in thickness of trabeculae Increase in length of trabeculae “Triple Jeopardy”
response to aging
As you lose density, the modulus is reduced in a (blank) to (blank) ratio. So if you lose density it causes a LOT more loss in strength. AND as we get older we lose density :(
2 to 1
slope = 2
What is bones response to aging?
density
cortical thickness
diameter
In response to aging what happens to the following:
axial strength?
bending strength?
femoral shaft fractures?
same
increases (w/ diaphyseal expansion)
DOES NOT increase!
As your didasphyial bone expands, you maintain axial strength, but you get much greater movement of inertia which makes the bone stronger and more resistant to bending. This is why we see a lot more (blank) fractures in the elderly because as you get older your diasphyeal gets stronger
trabecular fractures
(blank) of the hip occur in single leg weight bearing as well as stair ascent
Spontaneous fractures
Single leg stance= (blank) times body weight 1600N
Stair ascent (blank) times body weight(4266)
Impact force with fall (blank) newtons
3
7-8
5-1500
Bone is strongest in (blank), weakest in (blank)
compression
tension
Bone volume increases with (blank) and decreases with (blanK)
use
disuse
With aging, what happens to trabeculae ?
become fewer, longer, less vertical
With aging what happens to diaphyseal bones?
they enlarge and increase bending resistance
What is the difference between the structure of a ligament and a tendon?
LIGAMENTS have a lower percentage of collagen BUT have more TYPE 3 collagen!
higher percentage of ground substance
less longitudinal organization of collagen
(blank) a flexible but inelastic cord of strong fibrous collagen tissue attaching a muscle to a bone.
tendon
(blank) a short band of tough, flexible, fibrous connective tissue that connects two bones or cartilages or holds together a joint.
ligament
(blank) human tendon 1,200-1800 MPa
(blank) human tendons 50-105 MPa
(blank) 9-35%
Elastic modulus
Ultimate tensile strength
Ultimate strain
What is the toe region of a tendon?
the uncrimping collagen fibers (they are wavy and straighten out with applied stress)
What are the regions of a stress strain curve of a tendon?
toe region, linear region, failure region
The slope of this region give you elastic modulus of tendon.
elastic region
When you have permanent stretching of the tendon you have what region?
failure region
What is a tendon dependent on (behaviorly?
rate, time, history dependent
What is this:
Time dependent elongation of tissue subject to constant force
creep
What is this:
time dependent decrease in load when deformation is held constant.
stress relaxation
First few cycles of loading and unloading create larger (blank).
With repetitive loading (blank) becomes minimal
hysteresis
hysteresis
What are the five zones of tendon insertion into bone.
What are the points of the zone?
Zone 1: parallel collagen fibers Zone 2: unmineralized fibrocartilage Zone 3: mineralized fibrocartilage Zone 4: cortical bone to transmit diff signals
(blank) strength increases to maturity than is rather constant
tendon
Where do adults get ligament failure?
mid substance (kids wont get this)
When you get old, what happens to your ligaments?
they get weaker
What happens with disuse of ligaments (i.e. to ligament substance and ligament bone interface)?
you get reduction in stength, even after rehab!!
WHat recovers first after disuse, the tendon or tendon/bone interface.
tendon
Corticosteroid are (blank) and (blank) dependent
time and dose
How long does it take for a change in strength to occur with steroid use?
6 wks
HOw long does it take for a change in failure load with steroids?
15 wks
Does a single does of steroids elicit a change?
no
What does estrogen due to ligaments and tendons?
reduces collagen production
In pregnancy, reduces pubic symphysis laxity
What is a bone fracture which occurs when a fragment of bone tears away from the main mass of bone as a result of physical trauma?
avulsion fracture
In diabetes what happens to your bone and tendons?
tendons can be normal, usually get a avulsion fracture
What does dialysis do to your tendons and ligaments?
weakens tendons-> leads to tendon rupture and hyperlaxity of ligaments
Are autografts effective?
yup
Tendon and ligaments are (blank)
viscoelastic
In vivo, (blank) rate is far below ultimate failure load
strain
Tendons and ligaments have severe negative (blank) effects with immobilization.
mechanical
Increase in mechanical strength with activity is (blank)
non linear
Reconstructed tendons/ligaments grafts (blank) reach native strength. Bone soft tissue interface remains weak link.
do not
What is this:
muscle shortens against a constant load, muscle tension remains constant.
isotonic
What is this:
muscle contracts at constant velocity.
isokinetic
What is this:
muscle length remains static as tension is generated.
isometric
What is this:
muscle contracture with decreasing muscle length.
concentric
What is this:
muscular contraction with increase in resting length. Resisting load is greater than muscle contraction force.
eccentric
What do you use eccentric excercises for?
treatment of tendinopathy
What are the three types of muscle training?
motor learning
endurance training
resistance training
What kind of muscle training is this:
increased oxidative capacity of Type I fibers
endurance trainin
What kind of muscle training is this:
increased cross sectional area type II fibers
resistance training
If you have immobilization of muscle what happens to the muscle fibers?
they get small
What kind of cartilage does this:
subject to high compressive loads applied statistically, cyclically, and repetitively over many years
articular cartilage
(blank) is a soft material that is fatigue resistant and tough, made up of water and is biphasic (allows it to transmit force without causing injury)
cartilage
What are the two phases of cartilage?
solid phase
fluid phase
There are three layers of cartilage, what are they and what is there fiber orientation?
superficial-> tangential fiber orientation
middle-> mixed
deep-> radial fiber orientation
The rate of (blank) is governed by rate fluid may be forced out of tissue
biphasic creep
What is this:
As you load the joint, the water becomes squished and a deformation and creep occurs which bares most of the weight.
biphasic creep
What is biphasic creep dependent on?
permeability of tissue and stiffness of porous material
What is this:
governed by rate fluid may be forced out of tissue
Dependent on permeability of tissue and stiffness of porous materiel
Primary mechanism 20/1 ratio
flow dependent rate of biphasic creep
What is this:
derived by friction of long chains molecules within the material
flow independent biphasic creep
Coefficient of friction inhuman joints is (blank to blank)
0.002 to 0.004
(blank) deal with load in a biphasic manner and utilizes primarily flow dependent creep
cartilage
