Inflammation and Tissue Repair

What are the phases of tissue healing?

Inflammation - day 1-6 (0-3)

proliferation - day 3-20 (3 days - 6 weeks)

maturation - day 9 on (>6 weeks)

What happens at the inflammation phase of tissue healing?

prepares wound for healing - immediate protective response to destroy, dilute, or isolate the cells or agents that may be at fault

What happens if no inflammation occurs, what happens?

healing cannot take place!

What are the interventions for inflammation?

assist/don’t inhibit healing process

protection of injury site

pain and swelling control

What will you see with inflammation?

heat - increased vascularity/blood flow

redness - increased vascularity/blood flow

swelling - blockage of lymphatic drainage

pain - physical pressure or chemical irritation of pain (sensitive structures)

loss of function - pain/swelling

What is the vascular response to inflammation?

histamine released by mast cells, platelets, and basophils at the injury site

What is extravasation?

movement of cells from inside to outside of the vessel

What is the pathway for extravasation?

margination - cells/neutrophils go to the margin of the vessels

pavementing - go on the side of the vessels

diapedesis - sneak through damaged area of the vessel and go outside the cell

emigration - going to move towards the source of the injury by picking up mediators that are going to attach to the cell

What is chemotaxis?

ability of a chemical to attract cells

What is edema?

accumulation of fluid in extravascular space/interstitial tissues

What increases cause edema?

increased capillary hydrostatic pressure

increased interstitial osmotic pressure

increased venule permeability

overwhelmed lymph system

What is clinical swelling?

ecchymosis

What is effusion?

escape of fluid into a body cavity

What is a hematoma?

accumulation of blood in a tissue or organ

What is hemarthrosis?

bloody fluid in a joint

What is the hemostatic response to inflammation?

retraction and sealing off of blood vessels

What is the cellular response to inflammation?

plasma = erythrocytes, leukocytes, and platelets

leukocytes

neutrophils

monocytes

What are leukocytes?

polymorphonucleocytes - neutrophils, basophils, eosinophils

mononuclear - monocytes

both clean up, recruit, and promote repair

What are neutrophils?

highest concentration in blood so prominent in early phase of inflammation

active for 24 hours

What are monocytes?

converted to macrophages - active for 24-48 hours

considered MOST important cell in the inflammatory phase and is essential for wound healing

produce wide range of chemicals that attract other agents important for the healing process

phagocytosis

produce collagenase

When are macrophages most effective?

when O2 is present in affected tissues

Adequate O2…

assists in healing and minimizing risk of infection

What is the immune response to inflammation?

macrophage → T cells → B cells → plasma cells → antibodies

What happens at the proliferation phase of tissue healing?

cover wound/provide strength

rebuilds damaged structures

What are the interventions for the proliferation phase?

still protection

early to control the direction of the scar

prevent scar from limiting motions

progressive vigor as the strength of the tissues are adequately recovered to prevent scar adhesions, and to promote functional length

What is epithelialization?

keep what we want IN, what we don’t OUT

IN - fluid, electorlytes

OUT - foreign materials, bacteria

superficial - occurs within a few hours

deep - after collagen production and neovascularization

What starts and stops the process of epithelialization?

contact inhibition

What does collagen production do?

undifferentiated mesenchymal cells → fibroblasts +O2, ascorbic acid, zinc, iron, manganese, copper = fibroplasia

fibroblasts → procollagen → tropocollagen → microfibril → fibril → fiber

production of hyaluronic acid and GAG’s help to increase intracellular matrix and facilitate cellular migration

initial layer is very weak!!! - type III collagen

very limited tensile strength - as little as 15% of normal tissue

infection, edema, and/or excessive stress on tissue can further inflammation and scarring

What happens on day 12 of collagen production?

type III collagen being replaced by type I

What happens on day 21 of collagen production?

wound strength 20% of normal

What happens in 6 weeks of collagen production?

wound strength 80% of normal

What is wound contraction?

at ~5 days, myofibroblasts are primarily responsible for “shrinking of the wound” by pulling edges inward

uncontrolled wound contracture = tissue contracture

What are contractures?

conditions of fixed shortening of soft tissues that have high resistance to passive stretch - may result from adhesions, muscle shortening, or tissue damage

What is neovascularization?

development of a new blood supply to injured tissues - angiogenesis

necessary to bring O2 and nutrients to healing tissue

thought to be initiated by macrophages

immediate vascularization surrounds the injured area giving a red/pink hue

What happens at the maturation phase of tissue healing?

restoration of the prior function of the injured tissue

change in size, form, and strength of scar tissue

modifies scar tissue into its mature form

In hypertrophic scars:

pressure DECREASES O2 = decreased synthesis

What is the induction theory?

scar mimics the tissue it is healing

What is the tension theory?

scar responds to tension applied upon it

What are the forces thought to affect collagen structure?

muscle tension, joint movement, soft tissue loading and unloading, fascial gliding, temperature changes, mobilization

What are the two most impactful variables for successful remodeling?

phase of the repair process which mechanical forced were inducted

nature of the applied forces

Applying tension during healing…

increases tensile strength in healing tissue

What do immobilization and stress deprivation do?

decreased tensile strength and collagen structure

What are the interventions for the maturation phase?

tension to control direction of scar, greater than previous phase

preparing for return to previous level of function

What are the local factors that can affect tissue healing?

injury type, size, location

tissue type

infection

vascular supply

external forces

MOVEMENT!

What are the systemic factors that can affect tissue healing?

patient co-morbidities/disease

patient nutrition

patient age

time since injury

medications