Cartilage injury and Avascular necrosis Flashcards

1
Q

Cartilage

A

A non vascular dense supporting connective tissue composed of chondrocytes and various fibres or ground substance.

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2
Q

What are the three different types of cartilage?

A

Hyaline

Elastic

Fibro

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3
Q

Hyaline cartilage is found where?

A

Hyaline - most common, found in the ribs, nose, larynx, trachea. Is a precursor of bone.

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4
Q

Fibrocartilage is found where?

A

Found in invertebral discs, joint capsules, ligaments.

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5
Q

Elastic cartilage is found where?

A

Found in the external ear, epiglottis and larynx.

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6
Q

What is the tide mark?

A

The tide mark is the junction between the vascular and avascular tissue of the cartilage.

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7
Q

Why is articular cartilage unique?

A
  • Avascular
  • Aneural
  • Alymphatic
  • Non-immunogenic
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8
Q

What type of collagen makes up articular cartilage?

A

Collagen type 2

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9
Q

What makes up articular cartilage?

A
  • Chondrocytes - 5%
  • Extracellular matrix
  • Water - 75%
  • Proteoglycans - 10 - 15%
  • Collagen - type II; 10 - 20%
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10
Q

Function of articular cartilage:

A

Its principal function is to provide a smooth, lubricated surface for low friction articulation and to facilitate the transmission of loads to the underlying subchondral bone.

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11
Q

What is the function of hyaline cartilage?

A

Provides a stiff and flexible support - reduces friction between bony surfaces.

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12
Q

Function of elastic cartilage:

A

Provides support but allows deformation

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13
Q

Function of fibrocartilage:

A

Resists compression and limits movement.

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14
Q

What role does proteoglycan play in cartilage?

A

Very hydrophilic, takes water out of joint fluid and stores it in cartilage. Aggrecan most common.

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15
Q

Cartilage healing

A

Superficial can’t heal

Deep heals with fibrocartilage

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16
Q

What techniques are used to get cartilage to heal?

A
  1. Bone marrow stimulation techniques
  • Change superficial defect into deep defect (microfracture) (abrasion stimulation)
  • Stick something through tide mark, bleeds, forms plug, heals defect with fibrocartilage.
  1. Osteochondral grafting
    * Bone plug with bit of cartilage from non-weight bearing part and put it in
  2. Osteochondral scaffolds
    * Put something, hopefully chondrocytes will differentiate into articular cartilage
  3. Cell Therapy (Autologous Chondrocyte Implantation)
  4. Stem cell therapy
17
Q

What are joint alignment procedures?

A

Break leg, change weight bearing axis, offloading procedure.

18
Q

Hip avascular necrosis

A
19
Q

How does avascular necrosis of bone present on x-ray?

A

White area of thicker sclerotic bone.

20
Q

Avascular necrosis commonly affects where in the bone?

A

Epiphysis of long bones as most other areas have colateral blood supply.

21
Q

Classic joints of avascular necrosis:

A

Shoulder

Knee

Hip

22
Q

Classic sites of avascular necrosis?

A

Classical sites:

  • Head of femur, neck of talus and waist of scaphoid

Other common sites:

  • Humerus, knees, shoulder, ankles, lunate and jaw
23
Q

Causes of avascular necrosis?

A

Interruption of blood supply:

Smoking, drinking, deep sea diver, steroid use.

24
Q

Stages of avascular necrosis of bone:

A
  1. Necrotic
  • 1st week no histological changes
  • 2nd week, all cell types show evidence of necrosis
  • Increased water content visible on MRI
  1. Repair
  • Inflammatory response
  • Creeping substitution, dead bone resorption, new woven bone gets laid down. Woven = non structural
  • Cancellous bone
  • Cortical bone eventually after remodelling.
25
Q

AVN on x-ray

A
26
Q

What are investigation carried out in cases of suspected avascular necrosis?

A

MRI

Ischaemic marrow changes seen before other imaging.

27
Q

Sensitivity and specificity

A

Sensitivity and specificity

Sensitivity = true positive rate, if test says you have it you have it if its 100% sensitivity rate

Specificity true negative rate, if test says you don’t have it, you don’t have it %

28
Q

Ficat Staging:

A

Ficat Staging:

0 - preclinical

1 - seen on MRI

2 - sclerosis on plain film

3 - subchondral collapse

4 - degenerative change

29
Q

What is the treatment for AVN?

A

Supportive: painkillers, pain due to oedema, crutches, splint.

Surgical: drilling, decompress bone. So stretching that happens gets decompressed. Joint replacement.

Chemical: bisphosphonates! Can cause it but can help it too.

30
Q

Biphosphonates

A

Bisphosphonates are a class of drugs that prevent the loss of bone density, used to treat osteoporosis and similar diseases.