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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