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Medicine 2.1 > Physiology of Cartilage and Fracture Healing > Flashcards

Physiology of Cartilage and Fracture Healing Flashcards

1
Q

What are the types of cartilage and where are they found?

A
  • Hyaline/articular: found in skeletal system, growth plate, trachea, larynx, nose
  • Elastic: found in ear, epiglottis
  • Fibrocartilage: found in meniscus and IVD’s
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2
Q

What is the function of articular cartilage?

A
  • Smooth lubricated surface for articulation

- Facilitate load transmission and create low friction environment

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3
Q

What are the features of articular cartilage?

A
  • Avascular
  • Aneural
  • Non-immunogenic
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4
Q

What is the composition of articular cartilage?

A
  • Cells: chondrocytes

- ECM: collagen, water, proteoglycans/proteins

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5
Q

What zones exist in articular cartilage before subchondral bone?

A
  • STZ (10-20%)
  • Middle Zone (40-60%)
  • Deep zone (30-40%)
  • Calcified zone
  • Tidemark
  • Subchondral bone
  • Cancellous bone
  • More chondrocytes as we go down
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6
Q

What are chondrocytes (what are they formed from and what do they do)?

A
  • From mesenchymal stem cells

- Synthesise and maintain ECM

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7
Q

Describe the composition of articular cartilage?

A

-Cells 5%
-Matrix 95% (water, mineral (70%)
(organic component 30% (collagen (60%), proteoglycan (25%), protein (15%))

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8
Q

What are the features of the ECM in articular cartilage?

A
  • Mainly type II collagen embedded in gel of negatively charged proteoglycans
  • Hyaluronan and aggrecan
  • Protects chondrocytes from loading forces
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9
Q

How is cartilage synthesised and what stimulates and inhibits this?

A
  • Synthesis by chondrocytes
  • Collagen, proteoglycan, protein synthesised
  • Stimulated by growth factors eg. IGF-1, TGFB
  • Inhibited by cytokines eg. IL-1
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10
Q

How is cartilage degraded and what stimulates and inhibits this?

A
  • Chnodrocytes also involved
  • MMP’s degrade proteoglycans/collagen
  • TIMPS’s inhibit degradation by MMP’s (could potentially be therapeutic target in future).
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11
Q

Describe healing of cartilage?

A
  • Has poor healing as is avascular
  • To heal properly injury must penetrate the subchondral bone and even then wont be the smooth hyaline cartilage like before
  • Heals by inflammation, repair/proliferation, remodelling.
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12
Q

What is the composition of fibrocartilage?

A
  • Cells: fibrochondrocytes

- ECM: collagen type 1, water, proteoglycans, glycoproteins, elastin

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13
Q

What are possible injury causes to fibrocartilage?

A
  • eg. meniscus tears
  • Acute: trauma, sports, infection
  • Chronic: osteoarthritis, previous injury
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14
Q

How may cartilage damage be diagnosed?

A
  • X-ray but not ideal
  • MRI
  • Arthroscopy as it allows scan and something to be done
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15
Q

What are treatment options for cartilage damage?

A
  • Physio
  • Medical
  • Surgical (arthroscopy)
  • Cartilage transplant
  • Joint replacement surgery
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16
Q

Describe physio treatment for cartilage damage?

A

-Range of motion exercises, muscle strengthening, aerobic conditioning, weight loss

17
Q

Describe medical treatment for cartilage damage?

A
  • NSAID’s (ibuprofen, dicloferac)
  • Oral glucosamine (to inhibit proteoglycan degradation, effectiveness debatable but very low risk)
  • Chondroitin sulfate
  • Steroid injections
  • Viscosupplementation (of things like hyaluronan and aggrecan).
18
Q

Describe arthroscopic treatment for cartilage damage?

A
  • Either microfracture (stimulate healing by putting holes to penetrate bone)
  • Meniscal repair
  • Menisectomy
19
Q

Describe cartilage transplant options for cartilage damage?

A
  • OAT (make chondrocytes from stem cells)
  • ACI (autologous chondrocyte implantaion)
  • Cadaver allografts
  • Osteomy
20
Q

Describe joint replacement surgerty options for cartilage damage?

A
  • Remove worn cartilage and replace with synthetic material

- Key objective is pain relief and range of motion

21
Q

What is mature (lamellar) bone?

A
  • All cortical and cancelluos bone
  • Osteoblasts lay down matrix in sheets (lamellae)
  • Paralell, organised collagen fibres
22
Q

What is immature (woven) bone?

A
  • Randomly alligned collagen fibres

- In adults (bone healing callus)

23
Q

What is cortical bone?

A
  • Mature bone laid down in concentric rings
  • Most of skeleton
  • Slow turnover rate/metabolic activity
24
Q

What is cancellous bone?

A
  • Spongy or trabecular bone

- Higher turnover rate and undergoes greater remodelling

25
Q

What is the composition of bone?

A
  • Cells
  • Matrix :
  • organic (type 1 collagen, non collagenous proteins)
  • inorganic (hydroxyapatite crystals)
26
Q

What are the parts of the long bone?

A
  • Diaphysiss
  • Epiphysis
  • Metaphysis (transition between above 2)
27
Q

What types of fracture healing may occur?

A
  • Indirect (secondary)

- Direct (primary)

28
Q

What is standard blood supply to bone?

A
  • Nutrient artery and vein
  • Vessels that enter around epiphysis and diaphysis
  • In kids also periosteal blood supply
29
Q

What is indirect fracture healing?

A
  • Formation of bone via a process of differential tissue formation until skeletal continuity is restored.
  • Via a callus
30
Q

What are the stages of indirect fracture healing and briefly describe each one?

A
  • Haematoma forms
  • Soft callus formation (1 week to 1 month), bone is disorganised and woven
  • Hard callus formation, bone still disorganised but begins to mineralise
  • Remodelling; osteoclasts degrade woven bone, then osteoblasts lay down organised lamellar bone
31
Q

Describe direct fracture healing?

A
  • Direct formation of bone, withut process of callus formation to restore skeletal continuity
  • Relies upon compression of bone ends
  • No callus
  • Direct bone formation via osteoclastic absorption and osteoblast formation
32
Q

What is the importance of blood supply to bone and what may affect this supply?

A
  • Bone needs blood supply to heal

- Supply can be compromised due to surgical factors (iatrogenous) or anatomical factors

33
Q

Describe the anatomic factors that may disrupt blood supply?

A
  • Certain fractures are prone to problems with union or necrossis (bone death) due to potential problems with blood supply
    eg. proximal pole of scaphoid fractures, surgical neck of humerus fractures, talar neck fractures, intracapsular hip fractures
34
Q

What patient factors may inhibit fracture helaing?

A
  • Increasing age
  • Smoking
  • Diabetes
  • Anaemia
  • Malnutrition
  • PVD
  • Hypothyroidism
  • Alcohol

Medicine 2.1 (29 decks)

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