4- Ligaments

Question 1

What is “anisotrophic”?

Answer 1

having unlike mechanical properties in different dictions; that is, the mechanical properties depend on the orientation of the applied force

Question 2

How do ligaments work in pairs?

Answer 2

work in pairs to stabilize the joint, a ligament on the lateral side is stabilized by a ligament on the medial side (ex in book was lateral talofibular ligament is balanced by deltoid ligament on medial side of the ankle)

Question 3

What is the relationship between load and elongation on a curve?

Answer 3

a) Ligaments have built in laxity to allow small deformation in joints, but when stretched become stiff to stabilize joints.
b) At low loads the ligament is lax and not stiff, as load increases so does elongation and with it stiffness. Once load is too large the ligament will tear

Question 4

How can a joint be stabilized if a ligament is torn?

Answer 4

ligament is torn, a pt may use muscles to actively stabilize the joint (ex if ankle ligament is torn they can use the fibularis longus and brevis)

Question 5

What is the histological organization of ligaments?

Answer 5

display band-like connective tissue, they are intricate amalgams (combining or uniting multiple entities into one form) of extraceulluar matrix proteins

Question 6

What are fascicles?

Answer 6

densely organized fiber bundles in muscle and ligament. Ligaments are composed of longitudinally oriented fascicles, that take the form of organized sinusoidal waveform when viewed from longitudinal axis called the crimp.

Question 7

What is a crimp?

Answer 7

the crimp is when the fibers bunch into a wavy pattern (think of a hair crimper) under no stretch, this allows room for stretching when the ligament is stretched

They are also in a gang rivalry with the bloods.

Question 8

What are the 3 basic types of cells in a ligament?

Answer 8

a) Fusiform: spindle-shaped, related to crimped collagen fibers
b) Ovoid: found in columns, w/ amorphous ECM in periceullular space
c) Spheroid: found in columns, w/ amorphous ECM in periceullular space

Question 9

How does a ligament get its blood supply?

Answer 9

a) The supply originates in the blood vessels near the joint surfaces
b) The cells of ligaments depend on diffusion of nutrients from vascularized tissues

Question 10

What is an engoligament?

Answer 10

the vascularized layer of loose connective tissue that surrounds bundles of individual collagen fibrils w/in a ligament

Question 11

What is the epiligament?

Answer 11

the vascularized layer that covers the surface of the entire ligament

Question 12

Where are the nerve fibers located that supply a ligament?

Answer 12

located near the vessels, predominantly in the epiligament

Question 13

What are the types of receptors that supply the nerve?

Answer 13

Ruffini receptors, Pacinian Receptors, Golgi Receptors, Free Unmyelinated nerve endings.

Question 14

What is the role of the mechanoreceptors in the ligament?

Answer 14

play a role in proprioception by helping to provide the sense of where the body is in space.

Question 15

What would happen if the mechanoreceptors in the ligament are injured?

Answer 15

if an ankle ligament is damaged and healed, but the mechanoreceptor nerve pathway has not been reestablished, a pt may have a poor sense of where the foot is relative to the ground if not staring at the foot, they “do not trust the ankle”. This leads to clumsiness. Nerve pathway may return faster with PT.

Question 16

What are the 4 zones of the direct attachment of a ligament to a bone?

Answer 16

(1) Ligament
(2) Nonmineralized fibrocartilage
(3) Mineralized fibrocartilage
(4) Bone

Question 17

What is the indirect attachment of a ligament to bone?

Answer 17

fibers pass directly into bone w/o intervening layer of fibrocartilage. The fibers of the ligament blend with the periosteal layer.

Question 18

What is the molecular stucture of collagen?

Answer 18

a macromolecular triple helix composed of 3 AA alpha chains, which are composed of repeating triplets of polypeptides. Usually the chain starts with glycine then proline. The proline causes the alpha chains to wind into a left-handed triple helix. The 3 alpha chains then wind together into a right-handed triple helix. It is the helix’s spiral shape that gives collagen the ability to resist tensile forces.

Question 19

What type of collagen makes up 90% of a ligament’s collagen?

Answer 19

Type I

Question 20

What type of collagen makes up the remaining 10% of a ligaments collagen?

Answer 20

Type III

Question 21

How is collagen produced?

Answer 21

type I collagen is produced intracellularly and modified extracellularly by cleavage which then aggregate into microfibrils which takes on a staggered pattern. The staggered pattern allows oppositely charged AA to align and bond giving the fibril extra tensile strength.

Question 22

What is the size of a collagen molecule?

Answer 22

300nm

Question 23

What are the 2 other components of ligaments besides collagen?

Answer 23

a) Proteoglycans: such as chondroitin 4-sulfate and dermatan sulfate
b) Glycoproteins: such as elastin and fibronectin

Question 24

What is a sprain?

Answer 24

damage to ligament, and are graded to amount of gross displace of the joint. This is caused by anything that causes a large amount of tension in ligament

Question 25

What is a grade 1 sprain?

Answer 25

pain but no joint instability, intrafibrous injury to ligament

Question 26

What is a grade 2 sprain?

Answer 26

some but not all fibers are torn, minimal joint instability

Question 27

What is a grade 3 sprain?

Answer 27

you’re screwed, complete tear of ligament and great instability

Question 28

What occurs during the 7-10 days of the inflammatory stage of ligament healing?

Answer 28

(1) Begins w/in hours and extends through 7 to 10 days. It is characterized by presence of necrosis, inflammatory cells, and growth of neovascular tissue on surface of ligament remnant.
(2) Hematoma forms from capillary damage, signaling continuation of migration of inflammatory cells
(3) Do not want to impede inflammation, so no anti-inflammatories

Question 29

What occurs during the 10-21 days of the proliferation stage of ligament healing?

Answer 29

(1) Characterized by an increase in cell density in the ligament remnants with ovoid cells and gradual neovascularization of the entire ligament remnant.
(2) New collagen forms and so does a scar
(3) Cells migrate from torn ligament ends into granulation tissue. So the space between torn ends is filled with matrix of disorganized proteins and many cells

Question 30

What occurs during the 21 days-years of the remodeling stage of ligament healing?

Answer 30

(1) This phase starts when fibroblast response slows down and matrix alignment starts to happen, collagen condenses w/in scar.
(2) Over time the collagen becomes more aligned, it is similar to original but not perfect

Question 31

How long do you need to complete ligament healing?

Answer 31

minimum of 1 year but may extend to several

Question 32

Do ACL tears heal?

Answer 32

no

Question 33

What is the Tx for ACL tears?

Answer 33

Tx is ligament reconstruction, which is removal of torn ligament and replacement with a tendon graft. The graft is never as good b/c of the complex geometry of the native ACL, also proprioception is usually lost with an ACL tear.

Question 34

Why can immobilization during healing of a joint lead to stiffness?

Answer 34

can cause stiffness b/c, w/o appropriate signals from normal mechanical stress, the healing tissue fails to orient itself in the correct direction. The tissue takes on a haphazard orientation causing adhesions.

Question 35

What does immobilization of intact ligaments do?

Answer 35

can weaken them and their attachments to bone

Question 36

What is characteristic of Ehlers-Danlos syndrome?

Answer 36

characterized by weakness/laxity in ligaments, skin and blood vessels.

Question 37

What is the etiology of Ehlers-Danlos?

Answer 37

mutation in fibrillar collagen genes, and genes that modify fibrillar collagen

Question 38

What is Ehlers-Danlos Syndrome Type I?

Answer 38

an autosomal dom disorder caused by mutation in the gene that codes for collagen type V which is required for forming collagen type I fibrils, this leads to decreased ligament stiffness and joint laxity

Question 39

What is the etiology of Marfan’s syndrome?

Answer 39

an autosomal dom disorder caused by mutation in fibrillin gene.

Question 40

What is the role of fibrillin?

Answer 40

a glycoprotein and is a component in elastin-containing microfibrils.
i) So if you have a mutated fibrillin gene and decreased fibrillin, you have structurally weak elastin (which is important to structure of ligaments)

Question 41

What are the clinical manifestations of Marfan’s syndrome?

Answer 41

ligament laxity, loose joints, aortic dilation, and other connective tissue problems.