S1: Muscle Injury: Principles of Tissue Healing and Repair

Question 1

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

Answer 1

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

Question 2

What is tissue healing?

Answer 2

The body’s replacement of destroyed tissue by living tissue

Question 3

What are the two different types of tissue healing?

Answer 3

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

Regeneration= where tissue regrows –> new muscle fibres

Question 4

What are the 4 stages of tissue healing?

Answer 4

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

(Big Igloos Parties Rock)

Question 5

Describe the timeline of tissue repair phases

Answer 5

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

Question 6

Describe the bleeding phase

Answer 6

• 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

Question 7

Describe inflammation

Answer 7

• It is an helpful reaction to injury

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

Question 8

What do chemical cascades cause in inflammation?

Answer 8

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

Question 9

What are the signs of inflammation?

Answer 9

Swelling
Heat
Loss of function 
Redness
Pain

Question 10

Describe proliferation

Answer 10

• 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

Question 11

Name the 4 key events that occur during proliferation

Answer 11

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.

Question 12

What is fibroplasia?

Answer 12

It is the laying down fibrous material.

Question 13

What is angiogenesis?

Answer 13

Changes in blood vessels, repair and replacement

Question 14

How do Myofibroblasts (and fibroblasts) help minimise scarring?

Answer 14

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

Question 15

What are the signs of proliferation?

Answer 15

• 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)

Question 16

Describe remodelling

Answer 16

• 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)

Question 17

What are the key events in remodelling?

Answer 17

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

Question 18

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

Answer 18

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

Question 19

Signs of remodelling

Answer 19

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

Question 20

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

Answer 20

• 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

Question 21

What factors delay tissue healing?

Answer 21

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

Question 22

What is direct and indirect cause of muscle injury?

Answer 22

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

Question 23

List some methods that can be used to investigate muscle injury

Answer 23

• 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

Question 24

What is PRICE?

Answer 24

protection, rest, ice, compression and elevation

Question 25

What is POLICE?

Answer 25

protection, optimal loading, ice, compression and elevation

Question 26

Which is favourable: POLICE or PRICE?

Answer 26

POLICE

Question 27

Why is optimal loading better than rest?

Answer 27

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.