X-ray Fundamentals
Biomechanics 1-9-2007
Stress – Force exerted over an area
Strain – What happens when you put stress on something
Creep – What happens when you put a force on a structure and leave it on it.
- Ex: when we wake up and are shorter because of constant gravity.
Stress Relaxation – When we stretch a ligament and then lock it in place.
- When we come back and measure the tension in a living tissue it will be zero.
- Ex: Braces on teeth
Stress Strain diagram
- Take 2 ligs and compare them
o 20 yr old and 40 yr old ACL
o Start stretching the ligaments and measure the force and see what happens
- The toe happens in ligaments and tendons that straighten out b4 they stretch
- Elastic region – when you put stress on the ligament it changes it size and when stress is taken off the ligament returns to normal size
- Plastic region – enough stress put on it and when we let go it remains longer than what is was
- Failure – at the very end
- This is how you make dx for injuries
- Grade 1 ligament injury – occurs in the elastic region but torn enough fibers that there are symptoms
o No real change in ligament
- Grade 2 – occurs in the plastic region
o Torn enough fibers that when you let it go it is permanently lengthened
- Grade 3 – all function is lost and there is no support
- In all the activity we do, we still have plenty of safety room before grade 1
Hysterisis
- Energy lost to the system due to the increased laxity
- Stronger is whichever one takes the most stress to break it
o So higher stress before strain is stronger
o It is also stiffer or less lax when its stronger
1-10-07
Levers
- What classifies a lever is where the fulcrum is
- SummationF1=Fxd=F2xd2 200
o Fd=Fd so ?(2)=100(10)
▪ 1000/2=500
▪ 500 +original 100 = 600
o If bend over plus 200 lb dumbbell
▪ 2000/2 = 1000
▪ 1000 +original 200 = 1200
- Whiplash
o C7 with 10lb head and the distance of neck
o Car makes head thrown forward 8 inches
▪ 10lb head x 10force of gravity = 100lb force
▪ 100 x 8 in distance = 800
▪ 800 + original 100 = 900
o Discs are type 1 levers – the fulcrum is situated towards one end
o Ankle is another lever where the fulcrum is between the force
When the fulcrum is at one end = type 3
- Ex: the elbow, or a wheel barrel
- Mechanical advantage
- The elbow has no mechanical advantage
- The advantage is the rate of motion and speed
1-16-06
Bones
- Protection
- Makes Marrow
- Flat bone makes blood when your older
- Mineral, such as calcium, if to high you die, to low you die
Bone pathologies
- Fracture
o Stress, compound
- Tumors
- Metastases
- Necrosis due to lack of blood supply
o Osteoporosis
o Leg caperthes = in a child
What is Bone?
- 3 Components of bone
o Collagen
▪ Type 1 long and skinny tough in tension
▪ Not good at resisting tension
o Mineral component i.e. concrete
▪ Good for compression, but breaks on stretch
o Fluid – Ca, Crystal, hydroxyl biphosphite
Bone Fracture
- How long to heal
o 3-6 weeks
- In order to heal
o Stabilization
o Blood supply
o Ends close together to recognize each other
o Time
- Bones that break and not heal in 3-6
o Patella gets to big of gap
o Rib fracture ( take a chest film see if punctured lung)
o Spondylolesthesis 7-10% of patients
▪ 90-95% at L5
▪ Won’t heal b/c it cant approximate to recognize itself
o Compression fracture – hard to heal b/c its hard to pull apart in the spine
o Clavicle fracture – hard to immobilize
▪ TOS may result due to insufficiency
o Skull fracture most likely kill you, 2nd is pelvic
o Neck of the femur
o Distal 1/3-1/4 of the tibia b/c of poor blood supply
o Dumerous b/c of the mm’s pulling it in different directions
Lost .9% of bone per week of immobilization
- repair rate when older is less than that
# practice fracture for orthopedic surgeons = wrist fractures
Stress fractures
- most common is spondylolistthesis
- bones is stronger in tension
- if you bend a bone it is stressed
- mm’s keep bone from bending
o get stress fractures when mm’s fatigue and stop preventing the bone from bending
o shin splints are often stress fractures
▪ Gluteus medius muscle
- Intrinsic muscles of the foot keep bones in foot from bending
o When these mm’s fatigue and quit firing strong enough the bones start to end and this can lead to cracks
- Treating
o Take the stress away…starts out as a lil crack and can turn into a full break
What have we learned about fractures?
- What bone
- How long to heal
- What ones not to have happen
1-17-06
Two different kinds of bone on every kind of bone you have
- Cortical
o Real dense bone that lines the rest
o Stiff and strong
o Gives bone strength
- Trabeculae
o That which is inside
o Weak and elastic
o Predominantly where there is bone loss
Bone Damage
- Intrinsic
- Extrinsic
- Bone remodeling
o Very active tissue w/ good blood supply
o Osteoclasts trying to take bone apart when there is stress on bone
o Some tumors put out hormones that remove osteoblasts increasing osteoclasts which puts holes in bones
Bone Density the highest at what age
- Man’s peak density is in 30’s
- Females max bone density 26-27, and rapidly decrease during menopause
- How do you prevent osteoporosis when it’s a normal process?
o Diet – Get rid of sodas and chips, TV
- How do you prevent hip fractures
o Hip pads
Osteoporosis in the spine
- Big white lines are the cortex
- Little white lines are the trabeculae
- When you push down on the endplate it will break or want to break
- How prevent long bone from bending
o Tie it in from the side
o You have horizontal and vertical lines that are hard to distinguish
o When you start to get osteo, decrease in estrogen, calcium, vit. D
▪ Body takes the calcium from the horizontal trabeculae first
▪ Osteoclasts have taken them out and now when compress endplates, tall vertical will bend and fracture ending in osteoporosis
Intrinsic
- Infection
- Chemical
o Cortical Steroids
o Radiation affects bone by killing the vasculature to the bone
- Mechanical
o Stress fractures
More bone at the bottom of the tibia
Area of MOI the amount of resistance to rotation of the area compared to the movement arm
- the farther away you get the bone away form the axis of rotation the stronger the bone will be
- tibia will always break at the bottom
- Same principle of an I beam
Moment area of Inertia
- Amount of resistance to rotation depends on area x moment arm
- The farther away from the axis of rotation, the stronger it will be
- Ex: tibia- more bone at bottom of tibia
1-27-07
Cartilage
2 Functions
- Fiscal elastic to decrease stress from bone to bone
- Painless frictionless surface for jts to move easily
Joints are cartilage surfaces
- Ex: synovial joints
What’s it made of?
- Water = 70%
o Not compressible
- Collagen
o Type II – Short and clumpy, resists tension when you squish something
- Proteoglycans (PG) Agrecan
o The kind of PG/Coll makes the difference, in cart; they bring in the water
- Cells
o What puts them together and tears them apart (the factory)
o Needs nutrition (water and food) and reason to exist
o Chondrocyte – make and tear down the collagen
▪ Stress tells these cells to build up or break down
▪ The cells have a covering that acts as a stress transducer to tell it what to do
▪ Not very active – they ave no innervation or blood supply
▪ Make Lubrican – That sits on the end of the cartilage and makes a barrier
Highest stress jt in body is in the back of the patella
Quickest way to study this is to cast/immobilize
- Only takes 2hrs to notice this breakdown process
- 8 weeks or longer the cartilage will be irreplaceably damaged
ELASTOhydrodynamic Lubrication
- When you put compression on cartilage, it conforms
- When you compress, water is forced out of tissue, and forms of wave
o Top cartilage surfs along the wave of water to keep the surface from touching
o This only happens when your moving
o When standing there is a boundary layer and lubicen (glycoprotein) sits on the cartilage surfaces keeping them apart
▪ This protein may trap a lot of molecules to help form a barrier like ball bearings
- In the joint we have close to non-newtonian friction = the faster you move a joint the less friction there is
Osteoarthritis
Over stressing a joint
- Decreasing a joint
o Cracking it (car accident, falling of high place)
▪ Little holes are normal, but if we get a big hole, its possible for PG to escape out along with water
▪ And we get a loss of cartilage
▪ Repair capacity all depends on the size
o Altered biomechanics
▪ Such as in the patella
o Disuse = no reason for it to exist
- Subchondral slerosis
o Even the joint is getting closer together, the bone is getting further apart and thicker cartilage (building up stress)
▪ No chance of reversing the process
- Osteophytes = Bone spurs
o One theory is that as one joint gets closer together, the capsule itself gets loser, so build these to keep the stability of the joint
o More popular theory = they form all around the surface area, increasing it, and decreasing the stress on the bone
- Geodes = Bone cysts (On X-ray their black)
o Form when osteophyts get more severe and painful
o These cysts expand in stormy weather which causes pain to people when the can tell its gonna rain
- Treatment
o Cartilage has no pain fibers, pain comes from periosteum = The most nerve sensitive area of the body. There is also pain nociceptors in the capsule
o Get them on program where their using the joint more then their using it now
o Water Walking – uses the same mm’s
o You can maybe rebuild cartilage (shown thru dogs and horses)
o Nutrition – Glucosamine condroytant (maybe)
1-30-07
Ligaments
- Fxn = To protect and limit/control (guide) motion of joints so they don’t go to far
o Sprain of Lig. = doesn’t resist tension anymore, and now the joint can go places that it shouldn’t go i.e. greater ROM
- Stress strain diagram
o Clinical test = 1-2 mm of motion
o @ 4 mm of displacement = Grade 1 tear
▪ Still in the elastic region @ the end
▪ Tx: return to normal activity ASAP, but not as strong as it was.
o In plastic region = Grade 2
o Grade 3 = ACL = 7-8 mm of tear
▪ Tx: Surgery to replace the ligament
Tendon
- from mm to bone
- stronger than mm, bone is stronger then tendon
- most injuries are traumatic separation of the joint or immobilization
o most tendons are 2-4 x’s stronger than the mm they attach to bone
o Tendonitis = golfer/tennis elbow
1-31-07
Muscles
- Type I = posture mm’s , made for endurance
o Subconsciously controlled
o Advantage of great endurance
o Large blood supply
- Fast twitch
o Disadvantage – mot much endurance
o Advantage – quicker and stronger
- Type III or type 2c pr satellite cells
o Responsible for repair of injuries
- The nerves are the first thing to change when you use mm’s more and more giving them more ability to contract
o E-stim can change the mm fibers
- Lose 20% mm strength per week w/o use
Concentric = mm tension is equal……blah
Isometric = mm contracts w/o anything happening = no work is being done
Eccentric = put wt in arm and tell it to contract, but weight is too heavy and the mm
Lengthens = negatives
Static work – no mechanical work performed
- It is the eccentric training that builds up the mm
Mm’s tear during eccentric motion
- they tear where the tendon and belly attach
When a mm is stretched there are 2 reflexes that will tell the mm to contract
- Fast twitch reflex
- Slow twitch reflex
- If you go slow enough you can stretch the mm w/o increasing firing in the mm
- You should hold a stretch 30 sec’s for optimum stretch
- This works to increase the ROM of a joint by stretching b/c it’s a neurological effect that allows that joint to go into a different ROM
o Gains no affect in the mm tendon mm
- THERE is NO known benefit to stretching
o May actually increase injuries
Pain with Exercise
- Not caused by lactic acid, it is all taken up within 30 min into the blood
- 1-2 days later your muscles are sore due to inflammation in the muscle
- Can it be reduced?
o Do the exercise before in a lighter manner which increases the rate of blood flow and whatever else is needed
Cramps
- Not do to dehydration cuz the whole body would be dehydrated
o Could be a factor, same with K levels
2-6-07
Nerve
- Blood supply
o Safety feature, they go both directions
o Only place that gets involved when pinched is the place that got pinched (spot injuries)
- Most injuries are not compressive, but stretching, causing a loss of ability to get blood supply in and out
- The bigger ones are affected first, the motor neurons
o Showing decrease in the reflex and mm strength
- Can stretch 10% before anything bad happens
- Inflammatory components hold these nerves in place and can’t stretch
- If you compress a sensory nerve there will be decreased pain, leg falling asleep
o Pain only when its been there for a while
- If you compress a motor nerve you will see decrease strength and reflex
The DRG is the only thing in the IVF that is pain sensitive
- everything else is from inflammatory process
Double Crush syndrome is from axoplasmic transmission
- Can’t measure axoplasmic flow – the messengers and raw materials that start in cell bodies and help maintain the nerve
- Fastest rate is 300 mm per day
- Slow ones are the repair
The disk
- Fcn = spinal movement
o 2* = shock absorption
- Parts of the disk
o Nucleus Pulposis – type II collagen, proteoglycans, water and cells
▪ Fcn – gives strength to resist force and absorb shock
o Annular fibers – type I collagen
▪ Resist tension and contain nucleus
o End plates – made of hyaline cartilage ½ mm thick
▪ Sumthin about blood
- Largest avascular structure of the body
- Movement is the key to disk health
2-7-07
GET FROM JEFF
2-13-07
Fxn of Spinal Facets
- Protect the disk
- Control the ROM and predict the ROM
- COMP DIED
2-14-07
The 3 ligaments that are important in the spine
- ALL – limits extension of C spine and L spine
o When were walking are head goes up and down, the spine is like a spring and compresses. This lig is being stretched by gravity and gets are head back up again through energy stored (so energy saver)
o Summary: Save E and protect Ext.
o Thoracic spine nuthin really
- PLL – Protect the disc?
- Ligamentum Flavum – Big rubber band
o Functions as attachment to the anterior capsule pulling it away to keep the joints congruent
o Normal motion of the spine
o As you age it gets less elastic and more thicker and doesn’t keep capsule from getting pinched
The facets really protect the spine from hyperextension
The multifidus
- Most related to back pain then anything else
- When fires, Biomechanicaly they extend the spine attached right underneath the SP and come lateral and extend the spine
- Makes up the posterior capsule wall
- The medial branch of dorsal rami innervates it and the capsule a wall
- A lot of mechanoreceptors in it
What is facet syndrome? Or Dorsal ramus loop syndrome
- Back pain with thighgroin pain (butt, legs)
- Well located paraspinal tenderness > Handout
- Reproduction of pain with extension
- Radiographic changes (signs of spasm)
- Pain below knee (no neurological signs of true root compression)
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