biomech.final Flashcards
A slow deformation of cartilage occurs with what?
Creep.
What is the syringe effect with cartilage?
High speed loading insufficient time to squeeze water out of tissue and the cartilage is very stiff, and little deformation occurs.
What will happen to cartilage after you unload a slow load?
Immediate restoration to 90% original thickness via elastic recoil. The last 10% comes back slowly.
Synovial fluid acts as what?
A lubricant between articular surfaces.
What are the 2 types of lubricant?
Fluid film- thick film of lubricant. Boundary- last resort for cartilage.
What is the friction of fluid film?
Almost zero.
When will hydrodynamic lubrication be used?
Non-parallel surfaces with tangential movements.
What will hydrodynamic lubrications create?
A lifting action keeping surfaces apart and reducing friction.
What is squeeze lubricant like and what will it be used for?
Surfaces are kept apart and there is a perpendicular force. The viscosity keeps the lubricant toegether. Good for high loads with short durations.
What type of lubrication is important in severe loading?
Boundary lubrication.
How will unwanted material from solid surfaces be removed (in cartilage)?
Mechanical action (movement).
What are the 2 ways cartilage can wear?
interfacial and fatigue.
What can cause interfacial wear of cartilage?
Interaction of articular surfaces causing adhesions or abrasions.
What can cause fatigue wear?
With repetitive cyclic loading so reloading before the cartilage has time to fully re-imbibe.
What will immobility do to synovial fluid?
Decreases the circulation.
Degeneration of cartilage promotes what?
Further degeneration.
What type of failure occurs easily with cartilage?
Tensile.
What is the repair capacity of cartilage like?
Limited.
What is the function of muscles?
1) Produce motion 2) Support and stability (posture and joint stability) 3) shock absorption 4) proprioception
What muscle is continuously active in standing posture?
Quadratus lumborum.
What would happen to the spine without muscle support?
A force of 5 lbs at T1 would permanently displace the spine
Tension from muscles is produced where?
In the elastic components.
What are the two tensions?
Active and passive
What is active tension?
Contractile elements
What is passive tension?
The passive element (elastic properties of muscle fiber and fascia)
What is contained in a musculotendinous unit?
1) The contractile component (actin and myosin) 2)A primary eleastic component (the tendons) 3) Second elastic component (connective tissue made up of epi, peri and endomysium and sarcolemma in parallel with contractive components
What produces tension?
Produced in the elastic components leading to active contraction and passive stretch
How is tension released?
When the muscle returns to its resting length
What are the parts involved in touching your toes?
Intial muscle stretch is elastic and the further elongation results from viscosity of the muscle-tendon sturcture.
What are the benefits of elasticity/distensibility?
1) Allows the contractile element to return to resting postitions after completed contraction 2) Protects the contractile components from passive overstretching and injury 3) Good shock absorber for the muscle
What is the force actively caused by a contaction on the bony lever?***
Muscle tension.
What is the external force exerted in the muscle?***
The resistance or load.
Muscle contraction causes what?***
Rotational force vector at the joint called torque or bending force vector called moment.
What are the different types of contraction?
1) Isometric 2) Concentric 3) Eccentric
What is the first type of rehab exercise?***
isometric contraction.
What is isometric contraction like?
Little or no joint movement and no change in muscle length.
What is isometric contraction used for?
Stabilize joints, hold posture against gravity
What type of contraction will the muscle shorten and length?
Shorten- concentric. Lengthen- eccentric.
What happens to the muscle in a concentric contraction?
Muscle shortens (overcomes resistance)
What happens to the joint in a concentric contraction?
Joint moves (ie: quadriceps shorten while walking up stairs)
What are some concentric exercises used for?
With the use of machines, tubing, dead weights are used for strength and endurance
What happens to the muscle in an eccentric contraction?
Muscle lengthens while contracting (the resistance overcomes the contraction)
What is the purpose of an eccentric contraction
To decelerate the motion of the joint to control the movement and dampen any sudden shock on the joint
What type of contraction creates the most tension?
Eccentric contraction
When should eccentric exercises be introduced in rehab?
Better performed in the later stages of rehab of an injured muscle
Rank the relative tension from most to least for muscle contractions
Eccentric > Isometric > concentric
When is the maximum tension of a muscle produced?
At its rest length
What happens to production as the muscle shortens or lengthens?
It decreases
Is the tension production in a muscle variable or the same for an isometric tension
It is variable for different muscle lengths
What is the resting length of a muscle where the most tension found?
Optimal overlap between thick and thin filaments and all cross bridges are available to particpate in the contraction
Why is the the tension decreased when the muscle is elongated?
There is littler tension developed by the contractile componenet because there is only a slight overlap of thick and thin filaments and the passive is a result of the connective tissue
Why is the the tension decreased when the muscle is shortened?
There is a weak contraction, the thick and thin filaments are overlapped too much and restricts productive cross bridle cyclins.
The whole muscle tension is what?
A combination of the tension caused by the active contraction of the sarcomere and the passive elastic tension on the other components.
Does passive tension in muscles play an important role in everyday activities?
No most muscles only cross one joint and are normally not stretched enough for passive tension to plan an important role
What types of muscles does passive tension have an effect on?
Two-joint muscles
The total force that a muscle can produce is influenced by what?
The velocity it can attain.
For concentric contractions, with a greater load what happens to the velocity of the muscle shortening?
slower
For eccentric contractions, type of load causes a faster velocity of the muscle shortening?
Greater load (resistance)
What is the force or tension that a muscle can produce promortional to?
Contraction time
If the contraction time increases what happens to the force or tension developed?
The greater the force developed
What are the mechanical properties for force production of a muscle based on?
1) Length-tension relationship 2) Load- velocity relationship 3) force-time relationship
Will a long skinny muscle or a short fat muscle be able to generate more force?
Short fat.
Why will short fat muscles be able to generate more force?
More sacromeres lie in parallel and the greater the physiological cross sectional area.
The Longer skinny muscles are good at what?
Excursion (lengthening).
Why are longer skinny muscles good at excursion?
More sacromeres lie in series and the smaller physiological cross sectional area.
How can cross sectional areas be increased?
Physical training.
Does a muscle perform more work with concentric contraction starting from a pre-stretched or a resting length?
A pre-stretched state (reason is unknown)
What is the concept behind plyometric exercises?
Starting a concentric contraction from a pre-stretched position
What is the effects of increased temperature in muscle?
1) Increased enzymatic activity of muscle metabolism leading to increased efficiency of the contraction 2) Increased elasticity (of collagen) leading to a greater pre-stretch effect 3) Increase blood flow to the muscle
What are the effects of increased temperature caused by warming up?
1) Increased blood flow to the muscle 2) Release of heat energy from uscle contraction, increased metaboli rate, and friction of contractile elements sliding over each other
What are the effects of physical training?
1) Activation of motor pathways 2) increase in cross sectional area of muscle fibers (cells) 3) Relative percentage of fiber types may also change
Resting muscles have no EMG activity so what is the muscle tone due to?
Viscoelastic properties.
What causes EMG activity?
The degree of activation of the contractile component of the muscle cells
What is thixotropy?
The reduction in viscosity of a fluid following movements. Like shaking a bottle of ketchup.
What happens to a thixotropic material when moved?
The more motion introduced to a thixotropic material, the less stiff it becomes.
Lake and robinson found what related to thixotropy?***
A 3X increase in thixotropic stiffening within 10 minutes of rest.
What causes thixotropy?
Change of viscosity between the sliding actin and myosin filaments they have a tendency to stick together.
What are some examples of thixotropy in muscle?
1) Warming up makes muscles less stiff 2) the high viscosity of resting muscle can help maintain posture without expending energy
What can cause hypertonic resting tones?
Shortening of elastic elements and can be due to increased EMG activity (spasm).
How is a digital pressure evaluation of muscle tone done and why?***
to see how easy it is to indent and how springy it is.
How should muscels be tested for muscle tone using range of motion test with end feel?***
Should be done at a constant rate to prevent a stretch reflex and to negate the thixotropic effect.
What is another test to test for muscle tone?***
Flapping test. (check if tissue is able to shake and move)
What is a primary disease of muscle? (3)
1) Muscular dystrophy 2) Fibromyositis 3) Primary fibromyalgia
What can cause DOMS (delayed onset muscle soreness)?***
Trauma leading to microtears)
What are different issues that can occur from trauma in muscles?
1) DOMS 2) Contusion/laceration pain 3) Strain pain (torn fibers)
What can cause muscle hypertonia?
Spasms, harbor trigger pints, contracture/scar tissue, fascial shortening, spastic UMN lesion.
What is the only thing that causes muscle hypertonia that is not painful?***
Fascial shortening.
What can cause muscle hypotonia?
Inhibited muscles, weak, neurological deficit.
What happens with loss of motor memory?
Loss of coordination/ speed of contraction.
What are hematoma and myositis ossificans?
Bony formation in a spot that was bruised.
What should not be done with bruises to prevent hematoma and myositis ossificans?
No trigger point therapy, no ultrasound, no heat, no aggressive stretchin.
What is a major site for muscle strains?
Musculotendinous junctions.
What is a grade 1 strain?
1) Minimal pain and splinting 2) minimal palpatory pain 3) Pain with muscle test, 4)some loss of range of motion
What is a grade 2 strain?
(partial tearing of the muscle, hemorrhage, marked pain, splinting) 1) same symptoms as grade 1 but more severe 2) pain and weakness with muscle teast 3) sometimes palpable defect
What is a grade 3 strain?
Severe strain (complete rupture) 1) marked loss of function 2) marked weakness with muscle test (often NO PAIN) 3) palpate torn muscle
What is the progression of fibrotic repair?
Fibrinous slurry > myofibrinosis (fiber formation in all directions) > to adhesions > contracture
What happens during fibrotic repair? (5)
1) Loss of elasticity, flexibility 2) Pain with contration and stretching 3) Decreased contractile strength 4) Decreased range of motion 4) Joint fixation
What type of occurance are muscle spasms?
Transient.
Are all muscle spasms painful?
No.
What causes pain with muscle spasms?
Local ischemia, increase load, possible shear effect between spasmed and non spasmed fibers.
Can contracture/ fascial shortening be painful?
May or may not be painful.
What happens to a muscle that is stretched for a long period of time?
It will relax and become weak.
What is a trigger point or myofascial pain syndrome?
A focus of hyperirritability in a tissue that, when compressed is locally tender and can give rise to referred pain
What causes trigger points?
1) Can be the result of injury 2) Can be due to muscle weakness
What is a contracture / fascial shortening?
Fixed shortening of a muscle due to fascial fibrosis or muscle fiber shortening
How is the resistance of contractures to stretching when relaxed?
There is a fixed high resistance and increased stiffness
Are contractures painful?
They can be both painful or non painful
What type of exercise will build stength, bulk, endurance, and enhance motion?
Isotonic.
What can cause inhibition weakness?
1) Injured joint/muscle 2) subluxation syndrome 3) MFTP 4) Overative antagonist (reciprical inhibition)
What does immobility/disuse of a muscle do? (3)
1) May atrophy (loss of width and length to some degree) 2) Sports-specific fibers are lost 3) Loss of strength or indurance
What happens to a muscle stretched for a long period of time?
It will relax and become weak.
What is a major cause of stretch weakness?
Postural strain
What is a lower motor neuron lesion?
one that affects the nerve root and/or peripheral nerve damage
What can accompany muscle weakness?
1) radiating pain into an extremity 2) sensory loss 3) decreased stretch reflex
Why does a loss of motor memory occur? (4)
1) To cope with injury for synergist substition (ie: shoulder hiking with rotator cuff strain) 2) new motor program 3) some muscles become relatively inactive (not necessarily weak) 4) coordination and speed of contraction is impaired
What are the 3 types of rehabilitation exercises?
Isometric exercise, isotonic exercise and isokinetic exercise
What is an isometric exercise used for?
For early activation of muscle (but will not reverse atrophy)
What is isotonic exercise used for?
Strength, bulk, endurance, enhance motion
What is isokinetic exercise used for?
stamina, maximum exercise throughout ROM.
What are the rehabilitative effects of adjusting? (3)
1) Trust may cause relaxation of segmental muscles 2) Re-establish segmental nerve supply 3) Adjust adjacenet extremity joints
Where is the nucleus pulposus located?
Centrally located ( a little posterior in lumbars)
How much water content is in the Nucleus pulposus and when is it the highest in a person’s life?
Water content is 80-90% and highest at birth
Where in the spine is the size and ability to swell greatest in the Nucleus pulposus?
In the cervicals and lumbars
What is the IVD cross section like in the lumbars?
30-50%.
What is always happening to the Nucleus pulposus?***
There is always pre-stress.
What causes intradiscal pressure and why is this needed?
The ligamentum flavum (under elastic tension) and all the longitudinal ligaments create intradiscal pressure and stiffness to help support the spine
What are some characteristics caused the by the hydrostatic features of the nucleus pulposus?
1) allows uniform distribution of pressure throughout the disc 2) the disc stores energy (acts as a shock absorber 3) distributes load
What is the purpose of the nucleus pulposus?
Allows uniform distribution of pressure throughout the disc and stores enery and distributes loads.
IVD works kind of like what?
Cartilage in the hydraulic system.
What is the IVD made of?
Fibrocartilage.
What happens with compression of the IVD?
Expels the water and dampens the and re-distributes the load
Where are the annular fibers of the annulus fibrosis attached to?
Attached to the end plates of the inner zones by Sharpey Fiber’s
Where are the adjacent lamina fibers of the annulus fibrosis situated?
Opposite directions to the annular fibers orientated at 120 degrees
What are the fiber orientation of the IVD compared to the disc plane? ***
They are angular degrees. (30 degrees)
Pessure in the nucleus puplosis is directed where?
Radially outward in all directions.
What load are IVDs best able to handle?
Compressive loads
What causes the stiffness in compression for IVDs?
High stiffness due to fluid pressure
Is the IVD more flexible at low or high loads?
Low loads
What is the function of the IVD being stiffer at high loads?
To shock absorb, dampen and stabilize
What is pressure in the nucleus pulposis due to?
Fluid pressure
With a compressive force directed on the nucleus pulposis where does the pressure and force become directed?
Directed radially outward in all directions
What is a Schmorl’s node?
A bulging endplate that is due to a herniating nucleus pulposis into the vertebral body
Compression forces place what type of load on the annulus fibers? ***
Tensile.
What happens with the IVD with a compression load?
NP- bears most of the load and distrubutes the force as a tensile load to the annulus fibers.
In the morning the annular fibers have increased tensile loads from what?
The NP is full of fluid and creates a type of tensile stress on annular fibers.
Since the annular fibers have increased tensile loads in the morning they will be more susceptible to what type of injury?
Lifting injuries.
When will compression loads cause disc herniations?***
They wont not even if the load is enough to cause deformation because compression is harder on bone.
What actions create tensile and compressive stresses on the disk?
Flexion, extension and lateral bending
What stress does rotation produce on the disc?
Shear stress (and tensile stress on the disk)
What type of motion creates tensile stress on the posterior aspect of the IVD and why is this significant?
Flexion and this is the common place for disc herniations. (endplates have been found, not the disc)
What type of stretching should not be done in the mornings?
Flexion stretching.
Direction of herniation is in the same or opposite direction of the load? **
Opposite.
Forward flexion to the left can cause what type of disc herniation?
Posterior and to the right.
How common are anterior disc herniations?
Rare.
What type of loads cause the most injury to the disc?
Torsion.
What is torsion?
Shear, compression, tension.
What is the major cause of injury to the disc?
Torsion and flexion (even greater when combined)
Are shear injuries to the disc common?
No they are rare because a large load is needed for injury and the disc is stiff to these loads
What causes shear loads?
Torsion or rotation, flexion, improper lifting
Will there be more pressure on the discs with standing or sitting? ***
More with sitting, besides there was one study that says that sitting will create less pressure than standing.
Is there more load on the spine with supported sitting or unsupported sitting?
Unsupported sitting
What will increase disc pressure while sitting?
Slumping and even worse would be lifting something under your chair.
What will decrease disc pressure while sitting?
Backward inclination of the backrest.
What will create lower disc pressure laying down or the 90 90?
Laying down is 25 and 90 90 is 35.
How many times more load are dynamic loads than sitting static loads?
2 times
Where is shock absorption the greatest?
In the lumbars
What does the disc display when it absorbs shock?
It desplays histeresis
How does hysteresis increase?
With a larger load
What are the 2 general mechanisms for injuring a disc?
- short duration HIGH AMPLITUDE. 2. LONG DURATION low magnitude. (failure is due to fatigue)
What plays a larger factor for injury of the disc, environmental loading or genetics?
Genetics probably plays a much larger factor than environmental loading.
What are the 2 most common problems seen with discs?
internal derangement, degeneration.
What part of the disc is innervated?
Outer anulus and not the nucleus pulposis.
What happens with tears in the disc?
New nerves and blood vessels grow in and now pain can be felt.
Tears in the disc first occur where?
In inner laminae.
Tears in the inner laminae of the disc are commonly a cause of what?
Low back pain and referred pain into the leg. **No nerve damage
Why will the tearing in the disc begin near the center?***
Peripheral attachment to vertebra is stronger than central.
With disc tearing where will damage be more likely to start near? ***
Near the nucleus pulposis.
Nucleus pulposis will migrate into fissures where?
Usually in a posterior direction.
What happens with a contained disc herniation? (3)
1) Disc material herniates into spinal 2) The nerve root is irritated/compressed 3) The NP material is NOT exposed
What happens with a non-noncontained disc herniation?
The NP material is exposed triggerin autoimmune response and increased severity
A 35 year old and a 65 year old would each probably have what disc problems?
35- disc herniation. 65- disc degeneration.
What occurs with disc degeneration? (5)
1) Proteoglycan is reduced in disc 2) Disc becomes less hydrated 3) disc is less elastic 4) cannot absorb shock or distribute loads as effectively 5) the disc is more susceptible to stress and injury
What happens with compression of a degenerated disc? (4)
1) disc dries out and losses hydrastatic “spring” 2) endplates have less pressure in center 3) outer annulus gets much more compression because the NP flattens out 4) annular fibers may bulge symmetrically into the canal because they are bearing more of the axial load
What are characteristics of the self sealing phenomenon?
1) 1st post injury loading curves differs from pre-injury curve 2) 3rd post-injury loading curve is similar to pre-injury curve 3) implies the presence of a mechanical reapir system
Spinal stability is provided by what 3 things?
- Structural integrity of discs and ligaments. 2. Co-contraction of the stabilizing muscles. 3. Proper functioning motor contol system.
The motor control system is ____ dependent?
Loop.
What is the motor control loop system dependent on?
1) Uncorrupted information from transducers (mechanoreceptors in disc and liagaments and spindles in golgi tendon organs in muscles 2) Proper functioning software in the NS 3) Muscles that respond with proper timing, strength and endurance
What damage can lead to structural instability?
Damage to ligaments and disk
Muscles protect joints when?
When they are not at end range. They protect joints in the neutral zone.
The neutral zone is protected by what?
Fluctuating tone of low back and abdominal muscles.
Name the important lumbar stability muscle?
Transverse abdominus. (less important is the inernal obliques and mutlifidi)
When will the multifidus atrophy?
With chronic pain.
What is the multifidus impotant in?
Segmental stabilization.
When do the multifidi atrophy?
Atrophies post surgery, lumbar disc herniations and standard exercises may not reverse atrophy
Rotatoes primarily provide what?
Proprioceptive information.
What are 2 stabilizing strategies?
1) Muscle activity helps to stabilize the whole torso 2) Muscle activity directly helps to stabilize the spinal column itself
How is intra-abdominal pressure created?
By coordinated contraction of the diaphragm, abdominal and pelvic floor muscles
Intra-abdominal pressure converts the abdomen into what?***
Rigid cylinder that helps stabilize the spine.
What 2 things will contribute to the intra-abdominal pressure?***
Co-contaction of the trunk flexors and extensors.
When will the Intra-abdominal pressure increase?
lifting, lowering, running, jumping, unexpected perturbations.
What happens due to co contraction of intra abdominal muscles?
Co-contraction directly stabilizes the spinal column itself making it more rigid and less likely to buckle
What would happen if no co-contraction of the abdominal muscles occured?
The spine would be unstable when upright
The higher the load on the spine in a standing position the more active the ______.***
QL’s.
The QL’s are direct _____.
Low back stabilizers.
What activity will precede any sudden movement of the arm?
Transversus abdominis and diaphragm activity.
The first 50-60 degrees of flexion occurs where?***
In the lumbar spine.
Where will the last few degrees of flexion come from?***
By tilting of the pelvis and rotating forward at the hip.
How can tight hamstrings effect flexion?
It can make the flexion come from lumbars and the lumbar spine to bear more of the load.
Weak or inhibited G. max can cause what?
Increased load to lumbar spine during bending and lifting, shift of stress up to TFL during gait, and instability of the SI joint.
What are some causes of tight hamstings? ***
Overuse, sustained postures, weak rectus abdominus and inhibited gluteus maximus leading to instability in lumbar spine
What happens at full flexion?***
The superficial erector spinae become inactive, but the deep extensors and QL remain activated as we hang on our posterior ligaments.
What will protect the joints at end range?
Ligaments.
What happens with sustained flexion for 10 minutes?***
- Superficial erector spinae relax. 2. Creep occurs in the viscoelastic tissues. 3. Random spasms in the multifidi. 4. effects of hystersis. 5. 50% of tissue recovery in about 10 minutes. 6. Hyperexcitability in the multifidus after standing up.
What is the problem with repetitive loading?
1)Muscles tire and spine lose some of its core stability 2) Repetitive end range loading creates elastic deformation (which does not recover immediately) and hysteresis (temporary loss of shock absorption with each cycle of loading)
What kind of stress does flexion create on posterior fibers?
Tensile stress
During flexion load on the ligaments what do the ligaments resist?
Shear load
How does maintaining lumbar lordosis is during bending protective?
Extensor muscles resist shear load
How long could it take to have full recovery of sustained flexion?
up to 48 hours.
What is the most common risk for disc injury?
Repetitive flexion.
During high or low cycles of end range can cause damage even in the elastic range.
High.
What activity modifications of flexion should be done?
avoid sustained flexion postures and avoid high repetitions (especially near end range).
When are loads on the facets greatest?
When the spine is hyperextended and stress on facet increases up to 30% of total load
Where can pain be coming from with hyperextension?
Not necessarily due to facet injury it could be coming from the disc.
Extension causes what type of load on the anterior fibers of the disc?
Tensile.
are anterior herniations common?
No they’re rare
How are the the erector spinae muscles intensely activated?
by arching the back in prone position
What is recommended for early exercise in rehab cases to make the vertebrae more parallel?
Putting a cushion under the abdomen in a prone position
What is the order of stress from least to most with rotation?
- Full range twisting. 2. High rotational torque in neutral. 3. High rotational torque through a full range of rotation.
Right hand vacuuming promotes what?
Left torsion.
The compressive load on the spine is the result of a combination of what? (4)
1) body weight, 2)the external load you are lifting, 3)how you are lifting it, 4) compression caused by the muscle contraction of the low back muscles.
What are the factors that affect how a person is lifting? (3)
1) The position of the object relative to the center of motion of the spine 2) the degree of flexion or rotation of the spine 3) the rate of loading
Holding an object close to the body reduces what?
The bending moment.
How does lever arm affect the load on the spine?***
The shorter the lever arm, the lower the load on the spine.
A higher lever moment means what?
More Newtons of force on the spine
What is the most important lifting advice?***
Keep the object close to the body.
What is harder to do lower or raise a load?
Lowering the stress involved can approach spinal tolerance.
What will create sacroiliac stability?***
The oblique dorsal muscle-fascia-tendon sling.
What is the oblique dorsal muscle-fascia-tendon sling made of?***
Latissimus dorsi, thoracolumbar fascia, and the contralateral gluteus maximus.
What type of stabilization will the oblique dorsal muscle-fascia-tendon sling provide for the SI joint?***
Force couple.
Conscious contraction of what muscle can help to stabilize the SI joint?***
Transverse abdominis.
What are peripheral nerves composed of?
1) Nerve fibers 2) connective tissue 3) blood vessels
What is the most direct impact to nerves?***
Blood loss it is even more than direct damage.
Where is epineurium found and what is its function?
Superficial and between fasciales and used to protect the nerve from external trauma, contains blood supply
Where is perineuriumfound and what is its function?
encases each fascicle and provides mechanical strength and a biochemical barrier
Where is endoneurium found and what is it made of?
Inside the fascicles and made up of fibroblasts and collagen
Is endoneural fluid pressure higher in the nerve or in the surround subcutaneous tissue?
Slightly higher in the nerve than the surround tissue
what causes the increase in fluid pressure? (3)
1) trauma and local edema 2)external compression 3) increased fluid pressure
Vessels pierce through the perineurium how?
At an oblique angle.
What does swelling do to the vessels in the perineurium?
It closes down the obliquely running vessel
What can injury a nerve?
Stretch (traction), compression, chemical (inflammation) or mechanical irritation
What type of injury can cause a stinger/ burner?
Stretch (traction).
What kind of deformation is plasticity?
Permanent.
At what % of strain on nerves does the plastic region begin?
Plastic range begins at about 20% strain
What are some characteristics of a nerve?
1) considerable tensile strength 2) can be lengthened with very little load 3) they are very elastic
What is a tensile load like on the microcirculation? (3)
impaired venular flow at 8% of strain and all intraneual microcirculation ceased at 15%.
Where does tearing being in nerves?
In the endoneurial tubes
At what percentage does complete failure of the nerve occur?
25-30%
What happens to the mechanical strength of previously injured nerves?
They may lose some of this mechanical strength
In the rabbit tibial nerve at what happened when 15% of strain was placed on it?
All intraneural microcirculation ceased
In the rabbit tibial nerve at what happened when 8% of strain was placed on it?
impaired venular flow at 8% of strain and all intraneual microcirculation ceased at 15%.
In the rabbit what % of tensile load is needed to block neural flow?
12% followed by minimal recovery.
What is the ultimate tensile load on a human nerve root?
13-19%.
A SLR test will cause the nerve roots in the lumbar spine to move how much in the IVF?
2-5mm.
What is the purpose of orthopedic testing?
Testing the peripheral nerves by stretching them to reproduce symptoms and the reduction of tension on peripheral nerves or nerve roots may relieve symptoms
What is very susceptible to effects of compression especially in the bony window of the IVF?***
DRG.
What ganglion may be in the IVF?
Sensory DRG.
What part of a nerve will have less tissue protection?
The nerve root.
Since the nerve root has less tissue for protection what will this mean?
More sensitive to compression and irritation and more sensitive to ischemic changes than compression.
How was the pressure increased in the porcine model by Rydevik and Olmarker?***
pressure increased5mm Hg every 20 seconds.
What happened with 5-10 mm Hg on the nerve root?
Venous flow was stopped in some venules, retrograde stasis.
What happened with 10 mm Hg pressure on the nerve root?
Transport of methylglucose to roots reduced 20-30%.
What happened with 20-30 mm Hg pressure on PERIPHERAL NERVES?
axonal transport blocked.
What happened with 50 mm Hg pressure on nerve roots for 2 minutes?
Causes entraneural edema, increased endoneurial fluid pressure, impaired capillary blood flow.
How long did the edema last with the 50 mm Hg pressure on the nerve roots for 2 minutes?
Lasts even after the comressive force is removed.
if the edema caused by the compression on nerve roots leads to fibrosis what happens?
A longer lasting effect
What does Fibrosis leads to within nerves?
Scars, and can cause increase endoneural fluid pressure and ischemia.
How does scarring due to fibrosis affect nerves?
Impair NR glide through IVF and can cause deformation and degeneration.
What happened with 50-75 mm Hg pressure on nerve roots for 2 hours?
Affects nerve conduction and incomplete recovery.
What happened with 100-200 mm Hg pressure on nerve roots for 2 minutes?
Pronounced nerve block and had a greater effect on recovery.
What does Compression do to nerves?
affects the ability of nerve function.
What is more damaging to nerve roots fast or slow onset of compression?***
Rapid onset is more damaging.
What will cause a more permanent change to nerves velocity or amplitude?***
Velocity is temporary and amplitude is permanent.
What happens at a site of injury in a nerve?
Action potential velocity and amplitude is reduced.
What is the pain like with acute nerve root compression?
Does not usually cause pain.
What will acute nerve root compression cause?
numbness, paresthesia and weakness.
What type of fibers are most susceptible to compression?
Larger fibers are more susceptible than smaller ones.
What causes radicular pain?
Minimal compression and irritation
What will make a nerve less likely to recover from damage?
The longer the duration of the pressure the more likely there will be irreversible damage.
What is the critical pressure level for peripheral nerves when functional changes occur?***
30 mm Hg. Due to vascular changes
Low levels of pressure for long periods can lead to what with peripheral nerves?
Scar formation.
what occurs at 80 mm Hg of pressure on a peripheral nerve?
axonal transport blocked.
what occurs at 30 mm Hg of pressure on a peripheral nerve?
complete ischemia
what occurs at 200-400 mm Hg of pressure on a peripheral nerve?
nerve fiber damage and rapid loss of function
When do radicular syndromes occur?
When the nerve root is compressed or irritated.
Is it damaging for 10 mm Hg at 2 sites than 50 mmHg at one site for the same amount of time?
Yes, two sites is more damaging
What takes up 35-50% of the IVF space?
The nerve root and its sheaths
what fills the rest of the IVF?
Connective and adipose tissue
What can reduce the IVF space? (5)
Scar tissue, osteophytes, stenosis, disc herniation or instability
What do motion of the neck affect?
The IVF and the central canal.
What happens to the IVF size with flexion, extension, ipsilateral rotation, contralateral rotation?***
Flexion- 31% increase. Extension- 20% decrease. Ipsi rotation- decrease. Contralateral rotation- increase.
What does cervical flexion do to the IVF size and nerve root?
It increases the IVF size but increases tension on the nerve root
What is a spinal cord injury known as?
Myelopathy.
What does cervical extension do to the IVF size spinal cord?
makes the cord shorter and fatter but also makes the canal smaller
What are some causes of central canal stenosis? (6)
1) Tumor (SOL) 2) Fracture 3) Instability 4) Instability 5) Adhesions/scar tissue 6) Infection
At what speeds do 80% of motor vehicle accidents occur?
At less than 25mph
In a typical rear end collision what are the common injuries in the cervical spine?
Hyperextension and hyperflexion
With a rear end impact what happens in the first 60 msecs?
The “S”curve = 1) the lower cervical spine is pushed forward by car seat momentum 2) the head momentarily remains behind 3) The spine assumes an S curve with the lower spine in segmental extension and upper spine in flexion
Is the “S” curve a physiologic motion?
No, not at all
In addition to the S curve what happens to the longitudinal aspect of the cervical spine?***
It causes axial compression
What does axial compression do to the stiffness of the spine?
Results in 50% decrease in stiffness of the cervical spine making it less able to resist flexion and extension forces
What is the “s” shaped curve?
1) Bending moment in flexion in upper cervicals 2) Bending moment in extension in the lower cervicals
At what segment is maximum extension found in the S shaped curve?
maxium extension is in c5-C6 motion unit
What happens due to the compressive load and shifting IAR at the bendming moment in relation to joints?
It is much more damaging to the joints (disc and facets)
in a rear end impact, what happens in the first 100 msecs?
1) The head catches up with the lower spine and there is 5x the force of gravity depending on the speed of the car and then ramping occurs as well
in a rear end impact, what happens in the first 150 msecs?
The entire spine goes into extension
What is ramping?
The head rolls backward over the head restraint
what is the muscle response for a rear end impact?
80, 125-215 msecs at which S curve load has already occurred but occurs before head hits the head restraint
What is an absolute contraindication to cervical manipulation after a whiplash accident?
Any signs of cerical cord trauma
With a rear impact what occurs with the occiput, C1 and C2?
They are loaded in flexion often resulting in joint restriction
What occurs in upper cervical injury (more common in high speed impacts)?
Injury to noci and mechanoreceptors that may account for balance disorders, dizziness, and perhaps mild traumatic brain injuries
What happens to musculature with a rear end impact? ***
Post structures are compressed and the anterior structures are torn (SCM, Scalenes, Longus Colli)
Can tensile loads tear the smooth muscle of the esophagus?
Yes, but these patients usually go to the ER
What can cause dysphagia after a MVA?
Mostly due to swelling in the anterior neck
can TMJ be an issue after MVA?
Yes, because it can drop the mandible and strain the anterior TMJ capsure although tmj symptoms are controversial
can the sympathetic chain be damaged from a MVA?
Yes
What happens if the deep flexors are damaged in a rear end impact MVA?
Results in instability (structural)
What happens if the superficial flexor muscles of the neck are damaged but the deep flexors are intact but weak?***
It causes a functional instability that can either causes persistent pain or increase susceptibility to future injury
What happens if there are sprains in the ALL?
If severe it can lead to structural instability
Which injury is the most common according to a cadaver study?
Disc and ALL tears
What is the typical lesion that occurs from the ALL injury?***
Avulsion of the disc from the end plate and tears of the annular fibers
What injury was found to be the most common at C4-C5 and C6-C7 in the cadaver study?***
Disc injuries
When are anterior fiber tears more common?
In rear end collisions
Are posterior disc herniations with nerve root compression common in MVA?
No they are not common.
What are rim lesions?
Linear clefts that run close and parallel to the end paltes in the peripheral part of the disc, near the rim get damaged
Where are rim lesions more common?
In the upper cervical region
where does healing of rim lesions occur?
Only in the outer 1/3
With which cervical motion can avulsion fractures occur and where do they occur?
Avulsion fractures may occur in lower corner of vertebral body
How does a facet capsular sprain occur?
Shear force and hyperextension places tensile load on the facet capsule
Why do facet capsular sprains affect people so much?
Facet joints are rich in nocireceptors
Where does facet compression occur more often?
Posteriorly in middle and lower cervicals
What can become intra-articular inclusion with facetal compression?
Meniscoids or synovial folds can become impinged
What causes 60% of the chronic pain in late whiplash?
Facet joints
What is not common in a rear-end collison?
Disc herniation
Can the nerve root be directly traumatized by the IVF?
Yes and it causes a radicular syndrome into the arm
What follows the phase of hyperextension in a rear end collision and what is it caused by??
Rebound hyperflexion follows hyperextension and it is caused by deceleration of the auto, impact of the seat and muscle stretch reflex
What nerve may be tractioned by hyperflexion and what does it lead to?
The greater occipital nerve may be tractioned causing a neurapraxis injury that contributes to headaches
What can hyperflexion do to the upper cervical nerve roots?
It can increase the tension on these nerve roots
Can MVA stretch the facet capsules leading to strain?
Yes , 29-35% have strains occur
What causes a deceleration injury?
Front end collisions
What happens in a deceleration injury? (4 steps)
1) The head rotates forward, forcibly flexing the neck 2) Followed by a degree of recoil resulting in hyperextension 3) The deceleration is first applied at CO-C1 then at C6 4) The neck will under go shear force
What are multiple plane injuries caused by? (4)
1) multiple impacts 2) postion of patient 3) tangential impacts 4) Patient’s structural health
What are important details to find out about an acident in the history? (4)
1) Magnitude and direction of forces 2) postion and attitude of the body 3) force dampeners and augmenters 4) detailed list of symptoms and when they occurred including LOC
What are important to know about the magnitude and direction of the forces?
1) direction of impact 2) make and model of vehicles 3) vehicle speed 4) estimate of damage (body damage, drive away or tow, glove compartment fly open, objects fly from the back
What are important to know about the position and attitude of the body?
Which way is the body turned/ which way is the head turned?
What head position is the primary feature related to symptom persistence after a MVA
Rotated or laterally flexed head at time of impact
What happens to musclature if the head is rotated in a MVA?
More load on facets on facing side and more tearing in the opposite SCM
What are important to know about the force dampeners and accelerators?
1) Use of seat belt = dampener for body but augmenter for head and neck (3x more likely to cause injury) 2) Airbag (dampener) 3) brakes applied (augmenter for head and neck 4) damage to seat (dampener) 5) state of preparedness (unaware -> 15x higher risk for symptoms
What is the proper positioning of a head rest to decrease the amount of hyperextension?
Aligned with the EOP
Do head rests prevent the S curve ? **
No because they can occur becore any of the muscle compensatory mechanisms occur.
Rank the immediate symptoms from most to least
Neck pain, headache, shoulder pain, back pain
What are the most injury resistant tissues in the neck ?
The muscles
Do muscles high frequency of healing?
They heal with high resiliency
What are the long term effects of chronic whiplast?
1) persistent facet syndromes (c5-C6, C2-3) 2) subluxations 3) joint instability (xrays may be negative for weeks)
How does one protect themselves in a rear end collison? (5) **
1) Put your head and back against the seat 2) straight arm the steering well and get a good grip 3) If stopped, put your foot on the brake as hard as possible 4) look straight ahead and slightly up at the top of the windshield 5) scrunch your shoulders towards your ears to brace for impact
