S1: Muscle Injury: Principles of Tissue Healing and Repair Flashcards

1
Q

What is the rationale for understanding the healing process of muscle injury?

A

It is vital to developing safe and effective practice and not understanding can result in advice and intervention that impedes healing and causes additional injury

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2
Q

What is tissue healing?

A

The body’s replacement of destroyed tissue by living tissue

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3
Q

What are the two different types of tissue healing?

A

Repair= where the damaged tissue is covered up –> Scar tissue

Regeneration= where tissue regrows –> new muscle fibres

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4
Q

What are the 4 stages of tissue healing?

A
  1. Bleeding
  2. Inflammation
  3. Proliferation
  4. Remodelling

(Big Igloos Parties Rock)

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5
Q

Describe the timeline of tissue repair phases

A

Bleeding –> within hours
Inflammation –> days
Proliferation –> weeks
Remodelling –> weeks to months

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6
Q

Describe the bleeding phase

A
  • Occurs following a soft tissue injury
  • Relatively short lived phase
  • The bleeding will generally take place over a few hours (this varies over nature of tissue and the nature of injury)
  • Bleeding is also an inflammatory mediator –> initiates inflammation which is the next stage in tissue healing
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7
Q

Describe inflammation

A
  • It is an helpful reaction to injury

- There are several outcomes: resolve, tissue repair, remove infected tissue and pathogens

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8
Q

What do chemical cascades cause in inflammation?

A

i) Complex vascular interactions (e.g. blood vessels dilate and capillaries become leaky)
ii) Complex cellular interactions and reactions (e.g. neutrophils and monocytes accumulate)
iii) Complex chemical (released from cells) interactions and reactions

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9
Q

What are the signs of inflammation?

A
Swelling
Heat
Loss of function 
Redness
Pain
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10
Q

Describe proliferation

A
  • Generation and deposition of granulation (repair) tissue
  • Rapid onset and peaks later on
  • The peak in activity represent the time phase during which the bulk of scar tissue is being formed
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11
Q

Name the 4 key events that occur during proliferation

A

1) Fibroplasia
2) Angiogenesis
3) Increase in extracellular collagen (type 3 which is relatively weak). Collagen is synthesised by fibroblasts and they provide strength and intergrity to the healing tissue
4) Myofibroblasts cause wound contraction to minimise scarring.

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12
Q

What is fibroplasia?

A

It is the laying down fibrous material.

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13
Q

What is angiogenesis?

A

Changes in blood vessels, repair and replacement

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14
Q

How do Myofibroblasts (and fibroblasts) help minimise scarring?

A

Fibroblasts turn to myofibrioblast phenotype and thick actin protrusions extend to wound edges and extracellular matrix - this contracts- approximating the wound edges.

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15
Q

What are the signs of proliferation?

A
  • Redness as a result of formation of increased number of capillaries
  • Swelling from increased number of capillaries (leaky)
  • Pain from pressure-sensitive nerve endings (more sensitive, lowered threshold)
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16
Q

Describe remodelling

A
  • Essential component of tissue repair
  • There is maturation of wounds collagen structure and arrangement
  • Not swift or highly reactive
  • Results in an organised and functional scar (allows stretching)
17
Q

What are the key events in remodelling?

A

1) Orientation of collagen fibres
2) Collagen transition: type 1 collagen replaces type 3 collagen
3) Capillaries diminish in number: less needed as healing is completed
4) Tensile strength increases

18
Q

What is the difference between type 1 and type 3 collagen?

A
  • Type 3 collagen is thought to play a role in fibroblast diffrentiation
    Type 1 collagen is mechanically stronger
19
Q

Signs of remodelling

A
  • Decreased redness from reduced capillaries
  • Decreased oedema from reduced extracellular matrix substances
  • Decreased pain from lessened nerve sensitivity
20
Q

Risk factors that lead to reduced ability to withstand normal tensile stresses

A
  • Injury history,
    • Fatigue/overuse
    • Weak muscles
    • Muscle tightness/decreased flexibility
    • Failure to stretch/improper warmup
    • Disease
    • High risk sports and activities
    • Mechanical problems
    • Age
    • Medication use, NSAID abuse and steroids
  • Lower temperature
21
Q

What factors delay tissue healing?

A
  • Inadequate nutrition
    • Ongoing inflammation
    • Drying of the wound
    • Excessive movement (or lack of movement, can lead to collagen not lining up properly)
      Smoking
22
Q

What is direct and indirect cause of muscle injury?

A

Direct - which would be trauma
Indirect - e.g. Fatigue/overuse can result in repetitive microdamage that exceeds the body’s ability to repair
e.g. infection

23
Q

List some methods that can be used to investigate muscle injury

A
  • Magnetic Resonance Imaging
  • Diagnostic Ultrasound (to see how muscle works under ultrasound and movement so better than MRI)
  • Clinical Examination = Interview/Questions and Physical Examination
  • Subjective Assessment = Thinking about how it occurred
  • Objective assessment = Thinking about rehabilitation
24
Q

What is PRICE?

A

protection, rest, ice, compression and elevation

25
Q

What is POLICE?

A

protection, optimal loading, ice, compression and elevation

26
Q

Which is favourable: POLICE or PRICE?

A

POLICE

27
Q

Why is optimal loading better than rest?

A

Optimal loading is better, because long periods of inactivity after trauma have been shown to have an adverse effect (collagen will not form properly and in the correct direction to stress) and that progressive mechanical loading is important in repair of tissue.