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ligaments
ligaments
111
Anatomy
Graduate
11/07/2013

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Term
the composition of ligament is similar to the composition of what other tissue?
Definition
tendon
Term
what are the 4 major components of ligament?
Definition
water, collagen, GAGs, elastin
Term
how much of the net weight of ligament is made up by water?
Definition
60-70% of wet weight
Term
what type of collagen is found in ligament?
Definition
Type I
Term
how much of the net weight of ligament is made up by collagen (list wet and dry percentage)
Definition
25% of wet weight and 75% of dry weight
Term
how much of the total weight of ligament is made up by GAGs?
Definition
<1% of dry weight
Term
how much of the total weight of ligament is made up by elastin in most ligaments?
Definition
<5%
Term
how much of the total weight of ligamentum nuchae is made up by elastin?
Definition
75.00000%
Term
why does the ligamentum nuchae have so much elastin?
Definition
ligamentum nuchae fibers go several hundred percent strain prior to failure to enable spinal flexion
Term
the structure of ligament is similar to the structure of what other tissue?
Definition
tendon
Term
describe unloaded ligament in one word
Definition
crimped
Term
how is the structure of ligament a bit different from the structure of tendon?
Definition
ligament has less of a purely parallel arrangement of fibers compared to tendon
Term
why is the arrangement of fibers in ligament not as parallel as the arrangement of fibers in tendon
Definition
ligaments usually have to restrain motion in more than one pure direction
Term
what do see, structure-wise, in the ligaments that control rotation?
Definition
bands of spirally oriented collagen fibers that tighten with rotation
Term
what are the functions of ligament?
Definition
joint stability, force attenuation, protective reflexes, positional sense
Term
explain how ligaments provide joint stability
Definition
ligaments protect joint structures such as articular cartilage, joint capsule, and meniscus from abrasive wear and tear
Term
how do ligaments attenuate force?
Definition
by deforming with load
Term
explain how ligaments provide protective reflexes
Definition
overstretching a ligament produces a protective spinal cord reflex to contract the muscle and pull you back into safety
Term
what happens to the protective reflex after a severe ankle sprain and how does this affect risk for future sprain
Definition
If you've had a really bad ankle sprain and you've torn the receptor organs, they can't mechanically stimulate the protective reflex, so you are 5x more likely to have another ankle sprain
Term
what is functional instability
Definition
the instability present after an ankle sprain secondary to loss of protective relfexes in the ligaments
Term
what part of joints enables them to have "position sense"
Definition
sensory end organs in the capsule and ligament
Term
what determines the frequency of signaling discharge of the sensory end organ?
Definition
joint angle
Term
how do the sensory end organs react when you move the joint to stretch the capsule/ligament
Definition
there is an increase in the frequency of discharge from the sensory end organs that goes up to the sensory cortex in the brain
Term
why is the risk for recurrent sprains so high
Definition
if you're jumping up and down and your sensory end organs have been disrupted, they don't signal up to the sensory cortex what position your foot is in, and you come down at a bad angle. When they're streched, the receptor rogans can't mechanically stimulate the protective reflex, so you just go down on it
Term
is the change in frequency of sensory receptors as a function of joint angle linear or curvilinear?
Definition
can be either!
Term
What are the 2 major determinants of functional joint stability?
Definition
the body's structural limits of stability + neuromuscular control
Term
what determines the body's structural outer limits of stability?
Definition
bony geometry, ligaments
Term
is everyone's body's limits of stability the same?
Definition
No, there is lots of variability of stability in terms of different geometry and different ligamentous/capsular stability
Term
describe how neuromuscular control can work for you and against you
Definition
neuromuscular control can provide stability, but it can be the force that puts the joint over the edge: muscle forces in the wrong direction can cause problems, such as subluxation of the humeral head
Term
what movement would give you a joint displacement curve for the ACL?
Definition
tibia moving anteriorly
Term
how many mm does the tibia move anteriorly during physiological loading?
Definition
1 -5 mm
Term
about how much joint displacement occurs with a typical clinical test
Definition
1 mm
Term
if you push/pull with 100N = 25 pounds of force on a stress test, what would happen
Definition
nothing. You are not even mimicking the physiological loading that occurs across a large jiont
Term
how many pounds of force are required on a stress test to get to the middle of the physiologic loading range
Definition
100 pounds
Term
what produces the physiologic loading range
Definition
the shearing and twisting forces of muscles
Term
what is on the y axis of a load-joint displacement curve?
Definition
load
Term
what is on the x axis of a load-joint displacement curve?
Definition
joint displacement
Term
how to have a good stress test?
Definition
stabilize, use force to attempt to approach the physiological loading force of the person's own muscles
Term
is the dependent variable on the x axis or the y axis
Definition
y axis
Term
is the independent variable on the x axis or the y axis
Definition
x axis
Term
when comparing joint laxity and forces of activity, which is the dependent variable
Definition
joint laxity
Term
when comparing joint laxity and forces of activity graphically, which is on the x axis
Definition
forces of activity
Term
what does a normal curve of joint laxity and forces of acitivity look like
Definition
when you have greater activity, there is increaed joint laxity allowing one bone to move on another
Term
when you have an injured curve, what does the curve look like
Definition
the curve for injured tissue is higher than the curve for normal tissue, meaning there is more joint laxity for the same force of movement
Term
what are you looking for when examining stress
Definition
is there more laxity on the involved side compared to the uninvolved side
Term
what will happen on a stress test if you don't push/pull vigorously enough
Definition
you may see no difference it is only when you push strenuously that are likely to see laxity in testing that exists under normal muscle forces
Term
what happens in stress testing when the primary restraint is torn but the secondary restraint is intact
Definition
you might see slight laxity, but you might get a false negative
Term
what will happen to the tissues if the primary restraint is torn
Definition
all of the stress is shifted to secondary restraitns which weren't really designed to deal with it. Over time, the secondary restraints become injured.
Term
what does it take to see large laxity on a clinical test when the primary restraint is torn + secondary restraint is stretched or torn?
Definition
patient must relax, technique must be good (strong force)
Term
what is a joint arthrometer
Definition
clinical testing with machine
Term
what are two joint arthrometers for shearing tibia on femur
Definition
rolimeter air cast, KT2000
Term
should you test the involved or uninvolved side first and why
Definition
test involved side first to surprise them and keep them from guarding.
Term
what are 2 biomechanical properties to help with ligaments that are too short because of contracture?
Definition
creep, stress relaxation
Term
if you're low on the stress-strain curve, and you just impose a little stress for a short period of time and then release the stress, what will happen t o the material
Definition
you are in the elastic range, so there will be no permanent deformation: the material will come right back to its original length or shape and you've done nothing
Term
how does creep work
Definition
if you take a low level load/stress within the elastic range and you impose it for a long period of time, it creates an increase in strain
Term
what is strain?
Definition
deformation
Term
what biomechanical property is used by the dynasplint pushing the elbow joint into extension with a constant moment
Definition
creep
Term
does creep really work
Definition
yes, but it depends on patient compliance
Term
how does stress relaxation work
Definition
push the joint until they feel increased stress to the point that they tell us to stop. Then hold them at that point and hold the strain constant.
Term
what is held constant in stress relaxation?
Definition
strain/elongation
Term
what changes in stress relaxation
Definition
stress is high initially. Over time, the stress relaxes and we can move into a new point of discomfort
Term
is serial casting an example of creep or of stress relaxation
Definition
stress relaxation
Term
what is held constant in creep?
Definition
load
Term
what changes in creep?
Definition
strain/elongation
Term
what is the joint active system
Definition
similar to serial casting but used 30 minutes, 3 times a day
Term
how often does stress relaxation occur in serial casting?
Definition
every 48 hours
Term
what is a potential problem with the joint active system?
Definition
straps are not wide, they would impose high contact pressure on the skin
Term
what is the effect of increasing strain rate on a ligament?
Definition
increase ultimate strength and energy at failure, make the ligament stiffer
Term
what part of the ligament is injured with higher strain rates?
Definition
mid-substance; the bone is stiffened, so the ligament is the weak link
Term
what part of ligament-bone interface is more likely to be injured with slower strain rates?
Definition
bone, avulsion fracture. Because bone and soft tissue are both weaker and less stiff, but moreso with bone
Term
what are the effects of immobilizaiton
Definition
better bone healing, but for other tissues: decreases ultimate strength and stiffness, increased strain at failure, causes adhesions, can cause contrature of ligament if immobilized in a shortened position
Term
what are the results of contracture of the ligament?
Definition
loss of functional ROM = alteration of normal movement patterns that places other tissues at risk for injury
Term
if you have an MCL injury, is it better to leave it alone or to repair + immobilize?
Definition
better to leave it alone
Term
what are the effects of immobilization on the dogs, considering laxity?
Definition
during immobilization, there is atrophy. When the immobilzer suddenly comes off, the poweruful muscle-tendon forces put tremendous stress on weakened tissues, making the joints lax.
Term
how is strength affected by immobilization?
Definition
normal strength returns faster in non-immobilized.
Term
what should you do if you ever strain your MCL?
Definition
don't get it repaired. Get a hinge brace so that you can move your knee but still be protected from valgus stress and IR.
Term
what are the ligament/capsule requirements for optimum healing?
Definition
good blood supply, controlled mobilization, protection from injurious stresses
Term
describe why controlled mobilization is needed in healing ligament
Definition
the tissue needs some loading to get an optimally healed result
Term
describe how to protect a healing ligament from injurious stresses
Definition
be sure that other ligaments are intact, provide external support such as a hinge brace, modify activities, redirect from dangerous activities like football
Term
how to protect ligaments from chronic irritation related to skeletal malalignment?
Definition
when someone has an acute injury to a ligament, look at alignment to be sure there are not malalignments that apply additional stress. For example, if someone has acute injury to MCL but also has forefoot varus, that will cause excessive prontation, which will cause dynamic genu valgus, which will increase MCL irritation at the knee. It will be difficult for this MCL to heal. it could become chronically injured and never heal. It needs some protection.
Term
what is one example of chronic irritation of a ligament related to dynamic overloading
Definition
repetitive overhead throwing
Term
why does repetitive overhead throwing cause MCL irritation at the elbow
Definition
it applies repetitive high magnitude valgus stress. ΣM=Iα. The sum of the moments is equal to the moment of inertia of the ball/lower arm times the angular velocity. The high velocity and the angle put a lot of stress through the MCL
Term
Explain ΣM=Iα at the elbow for repetitive overhead throwers
Definition
you get valgus overload at the elbow secondary to high magnitude angular accelration and moment of inertia.
Term
What creates the valgus moment?
Definition
the mass from what the thrower is holding
Term
how does valgus affect contact area and force in the elbow?
Definition
valgus stress drives the radial head and capitulum together with decreasd contact area and increased force. Puts a lot of tensile stress on the MCL and compressive stress on radius-capitulum
Term
what formula explains the tremendous valgus loading in overhead throwers
Definition
ΣM=Iα. Intertia is large and so is the angular acceleration. The resisting moment is huge.
Term
how do some pitchers get evengreater valgus stress at the elbow with the pick off attempt?
Definition
with the pick off attempt, the pitcher doesn't want to show early movement with his body. He uses his upper extremity to generate ball velocity. The moment ofinertia of the forearm, hand, and ball must be overcome during the acceleration phase of the throw. Acceleration with internal rotation pulls tensile stress through the ulnar collateral ligament to bring the forearm, hand, and ball along. the radial head feels increased compressive stress against the capitulum as the elbow moves into valgus
Term
what are some ways to decrease valgus loading of the throwing elbow?
Definition
more flexed elbow at ball release, plant foot first and then rotate trunk, pitch overhand
Term
how does a more flexed elbow at ball release reduce valgus loading of the trhowing elbow?
Definition
with a more extended elbow, the forearm and hand have a greater oment of inertia about the rotating trunk, creating more resistance to acceleration and causing it to lag behind more
Term
how does planting front foot prior to rotating as opposed to trunk rotation followed by planting the front foot release reduce valgus loading of the trhowing elbow?
Definition
trunk rotation can be fueled by having both feet on the ground.
Term
how does overhand pitching as opposed to side arm pitching reduce valgus loading of the trhowing elbow?
Definition
side arm pitching requires more ball velocity from UE motion and increases valugs stress imposed on the elbow
Term
describe the moving valgus stress test
Definition
start in flexion with some valgus. Extend elbow quickly as stressor is maintained.
Term
what is positive on the moving valgus stress test
Definition
pain reproduced 120-70 deg
Term
what to do if a patient reports instability with activity that you can't demonstrate on clinical exam
Definition
believe the patient! The patient is experiencing the influence of powerful joint forces.
Term
what is at risk for injury when ligaments are unstable
Definition
other ligaments, capsules, meniscus, articular cartilage
Term
what can you change to prevent more injury?
Definition
surgical repair, external support, activity modification, activity redirection.
Term
how to treat ligamentous contractures?
Definition
creep, stress relaxation
Term
whether or not to brace?
Definition
if folks are not doing high magnitude, forceful activities then braces are protective. They can be false protection for very vigorous and forceful activities.
Term
what modalities are good for ligaments
Definition
ultrasound, low level laser
Term
describe ultrasound for ligament
Definition
ultrasound early after surgical injury increases the ultimate strength and energy at failure. Pulsed, non-thermal.
Term
describe low laser level for ligamnts
Definition
low level laser shows increase in ultimate strength and stiffness after surgery.
Term
how do ultrasound and low level laser help ligaments?
Definition
mechanical stimulus making the reparative cells be more active.
Term
if someone has to have immobilization for some reason, what do you do?
Definition
be careful bringing them back. Don't stretch them because they are too weak to resist the stress initially.
Term
summarize the goal of interventions for ligament/capsular injuries
Definition
facilitate good blood supply, protect from too much stress, gentle mobility to optimize timely return of ligament mechanical properties, look for skeletal alignment and movement patterns that migh impose unwanted stress on healing tissues
Term
when is capsular shrinkage indicated?
Definition
in cases where capsular and ligamentous tissues are all stretched out, causing instability, and you want to shorten them.
Term
what is the most common locatin of capsular shrinkage
Definition
glenohumeral joint
Term
how does capsular shrinkage work?
Definition
laswer energy increases temperature, shrinks the collagen. Denatures the collagen
Term
what happens to shrinked tissue?
Definition
it becomes very weak
Term
what happens to tissue near the shrunken capsule?
Definition
can also be injured, which is bad
Term
what are the post-surgical protocols for capsular shrinkage
Definition
4 weeks of immobilization in sling and swath. No abduction and ER too early.
Term
is thermal shrinkage good?
Definition
good short term results, but not always good long term results. Low levels of physiologic loading can cause creep of the shrunken tissue.
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