Download Stress – force applied / surface area

Biomechanics
1 of 16
Summer 05
Stress – force applied / surface area
 10,000 lb elephant or 100lb woman?
 You would want the 10,000 lb elephant
 Woman had high heels on ( 400lb/sq. inch)
Strain – the change in an object when a force is put on it
 a rubber band, if you pull on the rubber band the change in its length is the
strain
 a desk with weight on it also has strain
 strain muscle
In a chart, stress is in the Y axis and Strain is in the X axis there is a linear line going
between them and that area is called the elastic range. As the line starts to drift more
toward the strain side it becomes the plastic range. At the plastic range you can release
the stress, but you will never go back to the way things were.
 So, if referring to bone you would have more plasticity in a child, yet an
adult is able to handle more stress. Geriatrics would have about the same
as an adult, but less plasticity.
Ligament



Grade (type) 1 – torn fibers, still in the elastic region, so when the stress is
taken away the ligament is still the same length (Drawer test, Lockmans
test) – it hurts when you pull, but there is no extra movement
 Deal with it, no real treatment
Grade (type) 2 – everywhere in between grade 1 and grade 3 (went into
plastic range)
 Rehab muscles around it, do not immobilize, there is really no
perfect fix to shorten the ligament
Grade (type) 3 – gone, extra movement, ripped apart
 New one or try to tie old one together, or leave it alone (Surgery)
Tibia elasticity – there is some bending going on every time you walk. So under the curve
on the stress / strain chart you have an area where this energy is stored.
Hysteresis – energy lost in a living thing
Creep – the change in length when a constant load is placed on something over time.
What happens to living tissue that has a constant load placed on it…ex. Getting up in the
morning, you get the initial compression, then throughout the day you get shorter. There
is a limit.
Stress-relax – a measure of stress put on something upon loading it. The stress reduces
over time, …ex. Braces on your teeth, the wire is tightened, and then the teeth move
closer together to take off the stress.
IN CLASS EXERCISE WITH PHYSICS AND LEVERS
Biomechanics
2 of 16
Summer 05
a vertebra is an example, this is where the fulcrum is not exactly in the
middle, but is not on the very end. The ankle is another one.
When you stand normally with perfect posture, the only muscles firing are your soleus or
gastronemius, since you are built in with a forward lean
Weight A X distance to fulcrum A = weight B X distance to fulcrum B
Weight on fulcrum = weight A + weight B
Whiplash
A typical whiplash is a force of 8Gs. (G-force)
Facets
If put into an equation with distances at the C2 fulcrum, It is shown to have 400
lbs on the fulcrum.
Disc
If you have 100 lbs of compression when standing straight up, with no muscles firing.
Now you lean forward to pick something up. And use a 10 inch length and 2 inch length,
you end up applying 600 lbs to the disc.
Now you lean all the way over and pick up a 100lb dumbbell. Using the 10in + 10in and
2in measures again. You get 2700 lbs on the disc.
The biceps is another type of lever, which is not really efficient.
* What is the advantage of this? Speed and ROM, but give up brute strength.
We have NO wheel barrel type joints. The ones that are really efficient. These types offer
less speed and ROM.
The shorter the moment arm the more the force needed. The longer the moment arm the
less force needed.
The secret is the moment arm.
Name four properties of bone?
1. Mineral storage
2. Support - for muscle
3. Protection - ribs, vertebra, skull
4. Hematopoesis
5. Absorbs shock
What are the 2 most common bone pathologies you expect to see in practice?
 Osteoporosis
 Fractures - spondylolesthesis (L5 pars) 5-7% have this in US
o For healing? - close together, blood supply, immobilize
Biomechanics
o
o
3 of 16
Summer 05
Time? - (6-8 weeks)
Don't heal?
 Ribs - because of movement do not heal as fast
 Scaphoid - blood supply is unique
 Neck of femur - circumflex artery is broken in fracture and is
within the joint capsule
 People would die from this before because they would get
pneumonia because of having to lay in bed
 Clavicle - due to immobilization, then you get a bigger callous and
ossification around the bone fracture
 Vertebra - compression fracture (surgery can fix this…cement)
 Tibia - (6-8 months if broken on the distal end) known as a boot
top fracture, also there is not a lot of blood supply
 Humerus - due to all the muscle attachments it is hard to
immobilize
A
B
The faster you load the bone the stronger the bone becomes
A - is the fast one
Energy is released into the soft tissue, and you can get muscle and soft tissue damage.
The energy is located under the line.
Biphasic material makes bone up
 Calcium phosphate - concrete portion
 Type 1 collagen - elastic portion
When we bend bone it can crack, so we always try to keep the bone from bending. Using
muscles we keep our bones from getting stress fractures. When fractures occur they are
usually do to muscle fatigue.
For stress fractures, you must stop stressing the bone for it to go away. If you do not then
you will get a fracture that is not just a stress fracture.
Osteoporosis - Imbalance between osteoblasts and osteoclasts activity
 It appears in the hip and vertebra vertical lines. Once you start seeing a
white line appearance you can tell they have osteoporosis.
 Your body pulls from the least amount of stress areas
Biomechanics


4 of 16
Summer 05
After the vertical supports are gone bending occurs
THIS IS A CHILDHOOD DISEASE since your greatest bone density is in
childhood.
Describe your treatment plan to treat/prevent/improve osteoporosis in
a. 78 y woman - vit D and calcium supplements, avoid trippers in the
hallway in their home, trochanteric belts=>50% reduction in hip
replacement, depressed ability to put on bone mass
b. 12 y woman-just starting to increase bone mass, proper nutrition and
antigravity exercise to start at appropriate density
Review from book
o Bone is a highly active tissue, always turning over and repairing. Doesn't
form scar tissue when damaged.
o Strength and Properties of cortical bone vs. trabecular bone
o Strain Sprain diagram
o Load bone in different direction, acts differently. Bone likes compression,
designed to prevent bending.
o Evulsion fracture-muscle tendon pulls bone from bone, only happens to
young people and bone disease. Look for bone problems when this
occurs. Old fractures will look like a separate bone, not just fragment.
o Compression fracture-bone is supposed to be white, when grey there is
osteoporosis. Cannot tell how old the fracture is.
o Bilateral femoral neck fractures-electric shock therapy, lightning
o Bending-break at the weakest point, not necessarily where the bend is
occurring. Altered stress distribution occurs. Rare to see high
compression fractures, more commonly a high tension-fast failure fracture
like in running.
o Callus-used to stabilize fracture site not necessarily strong, be sure callus
has started to dissolve.
o Stresses on Ant tibia-no muscle to prevent from going into tension. Fig 232 walking vs jogging 3x the stress on the tibia with jogging than walking
o Rate of loading fig 2-35
o Surface Area of bone Fig 2-39, Flat bones break when hit from 90 degrees
because that is the weakness
o Inertia-farther you get from the mid-point less resistance, stronger at the
metaphysis than the diaphysis
o Fig 2-45 putting a small hole in bone changes the stress loading on the
bone
o If bone does not have stress on it then it will go away
o Once you get metal in a bone, you will always be more susceptible to bone
infections
o Figure 2-50 - vertebra that has slight osteoporosis and increased
osteoporosis
Biomechanics
o
5 of 16
Summer 05
Approximately 1% of bone mass loss will give you about 2% strength loss
of the bone.
 Every week inside a cast you loose 1% for some time
 Sometimes the bone strength or mass will not come back
 Usually after 8 weeks of being in a cast
Ends of Bones








Hyaline cartilage - Cartilage - allows for the movement between bones so
that they can move with little resistance
Osteoarthritis - a cartilage disease, can get this from disuse
Cartilage - made up of collagen (mostly type 1), water (by weight is the
most), proteoglycans (GAG), cells
 Collagen - allows for some give
 Water - not compressible
 GAG - a big ball of barb wire…attachment points for water and
they attach and fall off with decompression and compression.
 Cells - make matrix, collagen, and GAGs. They put out the
enzymes that take out the proteoglycans.
 One makes lubricin and cartilage
 The other is like a dam allowing fluid in or out
Immobilization - this will cause cartilage to go away (same as bone)
 Immobilized longer than 8 weeks - causes irreparable damage
Elastohydrodynamic - this is what lets us move with almost no friction
 What's going on is that you are technically surfing across the
joints. This prevents wear and tear.
 The human joint has .01 to .001 compared to a car engine that has
a coefficient friction of .1
 The faster you move the joint the less friction you have, which is
the opposite of what normally happens comparing to other moving
objects
Lubricin - coats the surfaces of the cartilage
 There is just enough fluid in the joint to cover the cartilage
ROM, Nerve supply, blood supply, nutrition all make up the quality of the
joint
Sympathetic nervous system controls how much fluid goes in each joint
KNEE
With joint DJD, osteophytes (spurs occur), subchondral sclerosis, joint narrowing, cyst
formation
HAND
Heberden nodes, bouchard nodes, joint-space narrowing, subchondral sclerosis
Risk Factors for OA
Biomechanics

6 of 16
Summer 05
Age (trauma), smoking (lack of O2), immobilization or sedentary lifestyle,
hard lifestyle, nutrition, bone hardening diseases, injury,
Subchondral Bone - when you lose chondrocytes you lose the ability to repair or replace
the cartilage
GAG - chondroitin (holds twice as much water)
Figure 3-20 in book. Talking about lubricin. Cartilage is really not smooth when
magnified.
Degenerated cartilage pictures - p89
If you know charts on pgs 98-100 you will understand the joint degeneration.
With a femur you usually get degeneration on the superior part of the head.
OsteoArthritis - THIS WAS PUSHED or Exaggerated
 Decreased joint space, osteophytes, cysts, subchondral sclerosis
 Knee is on of the most prevalent areas that this disease occurs. Can also
occur in the spine and as the uncinate processes deteriorate and get
osteophytes they can move into the IVF
 Treatment? - non for it currently
 Can't get to the joint since decreased blood supply,
What is the difference between Ligaments and Tendons
Difference and similarities
Table 4.1
Ligament of Flava - is the only tendon with elastin
Ligament - to control or restrict motion
 Cellular Material: Fibroblasts 20%
 Extracellular Matrix: 80% (water 60-80%)
 Solids: 20-40%
 Collagen: 70-80%
 Type 1: 90%
 Type 3: 10%
 Ground Substance: 20-30%
Achilles tendon does tear more often than any other, and usually the tendon has
decreased stability due from continued injury
Biomechanics
7 of 16
Summer 05
Tendon - allows for the attachment of muscles to bone so movement can take place
(2-3 times stronger than the muscle)
 Cellular Matrix: Fibroblasts 20%
 Extracellular matrix: 80%
 Water: 60-80%
 Solids: 20-40%
 Collagen: slightly higher ?(75 - 85%)?
 Type 1: 95-99%
 Type 2 : 1-5%
 Ground Substance: slightly less ?(15-25%)?
ACL - lockmans test to see if problem is present. Tibia should not move forward.
Grade 1 - there is really nothing to do with this one as it just needs to heal
Grade 2 - there is no way to make it shorter, once a ligament is stretched it will not go
back without surgery
Grade 3 - ACL can move about 7 inches (surgery or no repair at all)
Drugs, steroids, cortico steroids, and so on can destroy the tendon.
Pregnancy - this can affect the ligaments and tendons too
Diabetes - bad on for tendons because it causes biomechanical change in them
Genetic component Muscles






Three types of muscle
 Type 1 slow twitch
 Type 2A fast twitch oxidative glycolytic
 Type 2B fast twitch glycolytic
What is the ratio? It depends on each person individually
Fibers get bigger, more do not develop
Eccentric is negative work
 This is the only way muscle injuries occur
 This is also the way to build muscle
Isometric is no movement
Concentric is positive
Cramps

What causes cramps - lactic acid, chemical imbalance
 Combination overall things
( THE NOTES ON CRAMPING ARE LACKING DETAILS - READ THE BOOK)
What is the primary function of the disk?
Biomechanics







8 of 16
Summer 05
Movement
Protects, barrier to spinal cord
The disk should be how big?
 Cervical 1/3rd of the vertebra
 Thoracic 1/10th of the vertebra
 Lumbar 1/3 to 1/4 of the vertebra
When you are first born the disk ratio is 1/1. This is why babies are more
limber than a 30 year old person.
Cervical gets the most flexion and extension
 Lumbar is next and thoracic is the least amount of F/E
What vertebra has the largest ROM besides C1/C2?
 C5
Where is the most degeneration? - Cervical spine
Growth of Disc
 Grows vertical
 Grows early, fast
 Water content - high (92% when born and 80% when you die)
Composition






Water, collagen, GAGs, cells
Water - cannot be compressed
Collagen - depends on the type of disc
Gag's or proteoglycans - chondroitin sulfate
Cells - fibrocytes
Avascular - this is the largest tissue in the body that is
As you age your disc gets bigger by about 10% as you go from 20 to 80 years old. So
disc narrowing is not a normal aging process. There is a billing code for this
How does it work?
 Vertebral end plate - made of cartilage and is like a doilie
 Nucleus gets its nutrition from the end plate.
 Shear rotation decreases integrity by half, however with traction or
compression the fibers work well together
 Disc height narrowing is common, but abnormal
Shrinking is usually due to osteoporosis or end plate degeneration.
DJD




Herniation
End plate fracture can cause this
Smoking, since it changes the o2 levels
Atherosclerosis
Loss of the nucleus
Biomechanics









9 of 16
Summer 05
Some type of load disrupts the end plate, this then disrupts the
environment and then there is a self destruction of the disc's cells
Lab test will help find inflammation (sed rate)
After the annular fibers torn , herniation is a lot easier to occur.
look at size and symptomology to determine where it is at.
Removing the disc really does not help either
Blood can pool in thecal sac
Caughing, sneezing, bearing down, laughing
Consider orthopedic tests fro sciatica or herniation
Conservative care is the treatment of choice
5 essay questions for test
What your body is made out of
Strength and weaknesses
Muscle, bone, ligament, tendons, disc,
Levers
Chapters 1-6
No complicated physics problems
osteoarthritis
Whats the most common bone disease - osteoporosis
Most common tendon ds - overuse syndrome
Nerve - compression / tension injuries
Disc - DJD and herniated
Second Half of Classes
NEW MATERIAL TEST 2 - Make sure you read the book too
Carpal tunnel can be caused by RA and pregnancy
 Truly any disease that causes swelling
Double crush syndrome
 Two subclinical create a clinical problem
Axoplasmic pull
 Goes both ways in the nerve, but different transport systems
 1mm a day is the repair time
 Not much pressure needed to stop axoplasmic flow
Biomechanics

10 of 16
Summer 05
Subluxated guinea pig, and watched kidneys deteriorate. This is one of the
first studies that showed what we were effecting
Facets - what do they do or provide
 Protect the disc, to not allow to much rotation
 Cervical Spine Facets  Vertically - slope at 45 degrees and protects from moving forward
in translation
 Horizontally - no degree - so it gives shear force to the disc
 Thoracic spine facets  Vertically - slope at 60 degrees
 Horizontally - 20 degrees of movement
 Lumbar spine
 Vertically - 90 degrees - supports no weight
 Horizontally - 45 degrees
Joints of lushka - keep us from sliding all around

Facet tropism - L5
Law of springs - the more turns you have the more efficiency or strength you have
Relative strength curve = 2n + 1
 This gives you strength, reliability,
small thoracic disc, little rom, flat and decrease to change over time
When a curve is flat or reduced then a disc is abnormal.
Lumbar spine varies a lot
Sacral Base angle = 41.1 +/- 7.7
 Pregnant - sacral base angle changes
4 ligaments
ALL



More effect on cervical and lumbar spine, not much effect in the thoracics
Lordosis - stretches to store energy
Kyphosis - really no known fxn yet

Biomechanically not a lot of stuff
PLL
Ligamentum Flavum
Biomechanics




11 of 16
Summer 05
Made of elastin fibers
Runs up central canal
Embeds and help forms the joint capsule in vertebrae
This losses elasticity and thickens with age
Supra Spinous

Limit flexion
3 important muscles in practice
Erector spinae (multifida)
 Erects the spine
Psoas Muscle



Can compress the bodies and disc
Milgrims test
Quadratous lumborum
Quadratous lumborum

Nerves


Sympathetic Chains Medial branch of the Dorasl Rami
 Innervates capsule and multifida
 Seen reltaed to facet syndrome


Ligamentum flava
Capsule
Multifida
Muscular Dysfunction to facet dysfunction
How do you diagnosis facet syndrome
 Back pain associated with groin or thigh pain (-30)
 Well localized paraspinal tenderness (-30)
 Reproduction of pain with extension rotation (-30)
 Significant corresponding radiographic changes (-20)
 Pain below the knee (-10)
 Out of 100 total points where is the patient
Muscle when you are born, then to ligament as adult, then bone when you get really old
Biomechanics
12 of 16
Summer 05
Bone is stronger than lig, and a lig is stronger than a muscle
Men's pelvis is higher than females
 L5 is buried more and if there are strong ligaments then it will not move
much
Lumbar multifida pull straight down
The set point of the spine is when the ligaments and fascia of the back take off the stress
on the muscles
Psoas muscle - attach to the disk
When lifting keep object close to your body
Pictures of joints looking at the cavitation sounds.
The joint has a vacuum on it to keep it together and is strong in keeping it
together. So the popping sound is when the joint can no longer stay together and
surface tension breaks, as the Joint space opens.
Paraphysiological space when broken is where you get the effects of the
adjustment. This helps the mechanoreceptors to fire. And then after the
adjustment it takes some time to get back to where it was.
The faster you try to separate the joint the easier things will go and less pressure
will occur.
What controls the amount of fluid in the joint (sympathetics)
Reasons why there might be capsular swelling
DJD, muscle spasm, entrapment, extrapment
Entrapment - meniscoid
Extrapment - limited ROM on both sides, but not totally fixated
Joints
Shrinks joint capsules (125 -127)
Increases compressice loading (128)
Contraction / contracture (129,130)
Glycosaminoglycans (131,132)
Fibrosis (124,125)
Ligaments (136, 137)
143-154
Eburnation 128
141 - 170
Table 7
Biomechanics
13 of 16
Summer 05
Unmarried male - minus 10 years
Cigarette smoking male - minus 7
30% overweight
Top 3 deaths in men
Accidents, Homicides, suicide
Shoulder - this is the 2nd most freely moveable joint
 Soft tissue is what contains and keeps this joint stable
 It is not really easy to dislocate, but can happen to anybody
 It is almost all muscle control,
 Shoulder impingement syndrome
 Many people have a muscle tear, and do not even know it is present

Surgery and chiropractic can help tears
 Surgeons and chiropractors

4 reasons why a person could not raise there arm out
 Adhesions
 Muscle injury (deltoid)
 Biceps tendon destruction
 Joint problem or decreased rom

4 joints of the shoulder
Glenohumeral
Acromioclavicular
Sternoclavicular
Scapulothoracic

What unique about the AC joint?
The acromian process cuts the supraspinatous when deformed. This is not
an uncommon finding though. If someone has a normal acromian, the
person might actually develop an osteophyte
 If arm is over the head of the person for sometime the body cannot
get blood to the arm
 Swimmers, baseball, sleeping
Lymphatic Drainage
 Diaphragm, 1st rib,
7-21-05


Fractures of the knee are uncommon because the other tissues tear first.
Dislocated knees are not common but can occur. Tearing of tissues happen, so
some rehab might be needed.
Biomechanics











14 of 16
Summer 05
Fractured Patellas are not common either.
Tibial plateau fracture - these happen when the elderly slip of some stairs or jam
the leg. Even repeated stress can cause this.
Evulsion fracture of the tibial eminence along with tearing.
Child abuse has fractures (evulsion fractures)
Osteochondritis dissicans - evulsion fracture at the knee shown
RHA causes a lot of periartcular osteopenia. The RHA causes the meniscus to
degenerate
Calcification in the meniscus is caused by CPPD
Hemophelia got aids from transfusions
No cortex - either infection or tumor
Multiple myeloma - punched out lesions in the patella
Padgett’s of the patella
Ankle






Talus, tibia, fibula
Stable
Ap view, plane is parallel to the earth when standing (toes pointed at the X-ray
machine
Most common clinical complaint - sprained ankle
o Grade 1 - 3
o They do fracture when fully dorsi flexed, otherwise there will be a
ligament sprain.
 Either medial or lateral malleolus gets broke off
Osteochondritis dissicans - #2 spot for this,
o A young kid that has an ankle that swell up is a sign that it might be
present.
In a grade 3 ankle sprain the tib fib could lead to osteo arthritis later on in life.
FOOT





Bones work almost as a screw action. The main axis goes through the big toe too.
Plantar fascia - is a spring/energy absorber
o Helps maintain arch of foot
o Everyone gets this at one point in there life
o Plantar fascitis can be debilitating
Shoes - make sure both bend at the same area
Lisfranc's joint - at the base of the meta tarsals
o Surgeon for Napolean who amputated people with gang green
Bunion ectomy (11 billion a year)
o 1% of al halux valgus is congenital
 Caused by pointed toe, high heal shoes
Every time you divert from a straight line it takes more energy to get back
Biomechanics
15 of 16
Summer 05
With the pelvis moving back and forth it smooths out the transition of the gait. The
shoulder goes opposite of the legs, however this twists the spine.
So the transition is at the T12, L1 junction
L5-S1 and T12-L1 are the most common areas for tropism
The joint will also go up and down
This helps to limit the amount of up and downward movement
The highest stressed areas of the spine is where tropism occurs
 Ankylosing Spondylitis - this is a disease that limits movement as the
spine fuses
In order for the swinging leg to get by you have to bend the knee
The ankle must also be working properly, otherwise you could end up with peg leg.
Sloppage gait, you can hear them coming. L5 nerve root used to be the cause (syphillus)
and would cause people to step harder.
A shoulder problem could throw your gait off.
The Gluteus maximus is not always firing, yet there is always some muscle firing
throughout the gait.
All that the muscles do is get the foot out in front. The gait is very efficient. You are
actually burning the same amount of energy standing as you do walking. People can walk
for days as they do not use a lot of energy in walking.
50 questions MC
50% Spine 





basic anatomy, facets how they differ from cervical to lumbar, body
shapes, curves of the spine and significance,
Disc – normal bulging young to old, herniations
Ligaments of the spine, what's the function
Certain muscles of the pine
Orthopedics and how they work
Scoliosis as an example of biomechanics put into a pathological




What is unique biomechnically
Strengths, weakness, what is a common injury
Muscular problems are most common in shoulder (supraspinatus tear)
Shoulder is very unstable

Ball and socket, most common problem is OA, due to high stress
Shoulder
Hip -
Biomechanics
16 of 16



Know angle #s
Fractures - do not focus on this
OA








Another unstable joint
Internal ligaments
Meniscus
ACL, MCL
Orthopedic tests specific for the knee ***BOARDS***
Arthritis at knee, more than any other joint except the spine
Acute injuries are not always seen due to instability
Mainly ligamentous and meniscus tear
Summer 05
Knee
Ankle/foot




How it is a stable joint and little changes can effect it
Inversion sprains (lateral lig injured)
Know prognosis and possible treatment
2 functions - what has to happen for things to work
GAIT

pelvis works? Muscles work?
 3 concepts about the muscles when you walk
 Stretch eccentrically first
 Don't fire that much
 Antagonistic muscles fire at the same time, so we are not
really propelling ourselves with our muscles
KNOW DEFINITIONS
Know anatomy
READ question carefully