Muscle Injury: Principles of Tissue Healing and Repair

Question 1

What are the 2 processes that occur to facilitate?

Answer 1

Regeneration and Repair

Question 2

What is regeneration?

Answer 2

tissue is replaced by the formation of surrounding undamaged cells in a ‘like for like’ basis.

Question 3

What is repair?

Answer 3

damaged tissue is replaced through granulation tissue to form mature scar tissue.

Question 4

What are the 4 main phases of muscle healing?

Answer 4

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

Question 5

What can affect muscle healing?

Answer 5

inadequate nutrition, persistent inflammation, excessive or insufficient movement and smoking can affect healing process and times

Question 6

What is the normal quoted time for bleeding in muscle injury?

Answer 6

normal quoted time 6-8 hours but depends on tissue type and mechanism of injury

Question 7

What type of injury would be more and less than the quoted time for bleeding?

Answer 7

-less vascular tissues such as ligaments will bleed less and for a shorter time
-crush injuriesto the highly vascular muscle tissue can bleed for up to 24 hours.

Question 8

In the inflammatory phase, what does cell damage cause the release of?

Answer 8

-Cytokines
-Kinins
-Histamines

Question 9

What are kinins important for?

Answer 9

Vasodilation (for more blood flow)
Stimulation of pain receptors

Question 10

What are histamines important for?

Answer 10

Vasodilator

Question 11

What is a consequence of the inflammatory phase due to the release of certain factors?

Answer 11

As a consequence we get redness and heat and hence increased nutrients and oxygen which increases metabolic rate of tissue cells and helps healing

Question 12

What happens to capillaries during inflammatory phase and what does this result in?

Answer 12

Also capillaries become more permeable hence
-Oedema – hence more pain and swelling (which cause temporary loss of function)
-And more fibrin hence stronger plug

Question 13

What happens to the level of white blood cells during the inflammation phase?

Answer 13

More white blood cell influx: neutrophils and monocytes (hence phagocytosis to clear cellular debris)

Question 14

What are the key signs of inflammation?

Answer 14

Redness
Heat
Swelling
Pain
Loss of function

Question 15

When does the proliferation phase start and how long may it last?

Answer 15

Starts as 24 hours post injury and can last 2-3 weeks or longer

Question 16

What occurs in the proliferation phase?

Answer 16

Deposition of healing material – and clean up of damaged tissue

Question 16

What are the 4 things that occur in proliferation phase?

Answer 16

1. Fibroplasia
2. Increase in extracellular collagen production
3. Myofibroblasts
4. Angiogenesis

Question 17

What is fibroplasia?

Answer 17

fibrous tissue formation to provide early scaffolding in tissue

Question 18

What happens when there’s an increase in extracellular collagen production?

Answer 18

Fibroblasts, cells which lay down early collagen (type 3 collagen) which is more elastic than type 1 (which is stronger). This provides strength and integrity and also the scaffolding for the next phase (remodelling phase).

Question 19

What happens with myofibroblasts?

Answer 19

Fibroblasts change to myofibroblast phenotype which are thick protrusions that extend to wound edges and extracellular matrix and contracts – approximating and contract wound edges together (minimise scarring)

Question 20

What is angiogenesis?

Answer 20

the formation of new blood vessels

Question 21

How long does the remodelling phase last for?

Answer 21

Last weeks, months or years

Question 22

What are the characteristics of remodelling phase?

Answer 22

maturation of collagen structure and arrangement occurs resulting in an organised and functional scar

Question 23

What are the steps involved in the remodelling phase of muscle healing?

Answer 23

1.Orientation of collagen fibres
-Re-orientation of collagen fibres due to pressure from contraction
-Forced alignment of fibres back to original formation
2.Collagen deposition: type 1 replaces type 3 collagen
-Once scaffolding is established and approximation of wound edges we have type 1 to give more tensile strength
3. Capillaries diminish in number
-Healing process diminishes, hence less capillarisation hence less redness
-This can be bad for chronic injuries when wound hasn’t healed yet
4. Tensile strength increases.
Rehabilitation – functionality and consequence of collagen type 1

Question 24

What is the assessment of soft tissue injury achieved by?

Answer 24

The assessment of soft tissue injury is achieved by many means and can involve radiological assessment such as MRI and Ultrasound.