Download The Principles of Wound Healing

Abigail E. Chaffin, M.D.
Assistant Professor of Plastic Surgery
Division of Plastic Surgery
Tulane University School of Medicine
History of Wound Healing
 1700 BC Papyrus: Wound Healing
 100 BC Egypt: Wound Healing Methods
 1000 AD Gun Powder
 1500 AD Hot Oil
 20th Century Scientific Method
Wounds
 Customize
 Shotgun approach not
acceptable
 No two patients OR
wounds are identical
58y DM, Neuropathy: unaware
of R foot gangrene
Wounds
Wounds
 Reconstructive
Ladder
 Simple to Complex
Formal Debridement, Elevation/ABI’s
Appropriate IV ABX, Wound Vac, Skin Graft
Review of Wound Healing
 Three basic types of healing
 Primary
 Delayed Primary
 Secondary
Primary
 Wound surfaces opposed
 Healing without complications
 Minimal new tissue
 Results optional
Delayed Primary
 Left open initially
 Edges approximated 4-6 days later
Secondary
 Surfaces not approximated
 Defect filled by granulation
 Covered with epithelium
 Less functional
 More sensitive to thermal and mechanical injury
Secondary Wound Healing
Secondary Wound Healing
Secondary Wound Healing
Three Phases of Wound Healing
Inflammatory Phase
 Proliferative Phase
 Remodeling Phase

Three Phases of Wound Healing
 Inflammatory Phase
 Proliferative Phase
 Begins when wound is covered by epithelium
 Production of collagen is hallmark
 7 days to 6 weeks
 Remodeling Phase (Maturation Phase)
Inflammatory Phase
 Hemostasis and Inflammation
 Days 4 - 6
 Exposed collagen activates clotting cascade and
inflammatory phase
 Fibrin clot = scaffolding and concentrate
cytokines and growth factors
Inflammatory: Granulocytes
 First 48 hours
 Attracted by inflammatory mediators
 Oxygen-derived free radicals
 Non-specific
Inflammatory: Macrophages
 Monocytes
 attracted to area by complement
 Activated by:
fibrin
 foreign body material
 exposure to hypoxic and acidotic environment
 Reached maximum after 24 hours
 Remain for weeks

Inflammatory: Macrophages
 Activated Macrophage:
 Essential for progression onto Proliferative
Phase
 Mediate:
 Angiogenesis: FGF, PDGF, TGF-a&b and TNFa
 Fibroplasia: IL’s, EGF and TNF
 Synthesize NO
 Secrete collagenases
Inflammatory Phase
Inflammatory Phase
Inflammatory Phase
Three Phases of Wound Healing
 Inflammatory Phase
 Proliferative Phase
 Remodeling Phase
Proliferative Phase
 Epithelization, Angiogenesis and Provisional
Matrix Formation
 Begins when wound is covered by epithelium
 Day 4 through 14
 Production of collagen is hallmark
 7 days to 6 weeks
Epithelialization
Basal epithelial cells
at the wound margin
flatten (mobilize)
and migrate into the
open wound
 Basal cells at margin
multiply (mitosis) in
horizontal direction
 Basal cells behind
margin undergo
vertical growth
(differentiation)

Proliferative: Fibroblast
 Work horse of wound repair
 Produce Granulation Tissue:
 Main signals are PDGF and EGF
 Collagen type III
 Glycosaminoglycans
 Fibronectin
 Elastin fibers
 Tissue fibroblasts become myofibroblasts induced
by TGF-b1
Wound Contraction
 Actual contraction with pulling of edges toward
center making wounds smaller
 Myofibroblast: contractile properties
 Surrounding skin stretched, thinned
 Original dermal thickness maintained
 No hair follicles, sweat glands
Epithelialization/Contraction
Epithelialization
Collagen Homeostasis
 After Wounding (Optimal Healing)
 Days 3 - 7 week
 Collagen production begins
 Days 7 – 42
 Synthesis with a net GAIN of collagen
 Initial increase in tensile strength due to
increase amount of collagen
 Days 42+
 Remodeling with No net collagen gain
Collagen
 Normal Skin
 collagen ratio 4 : 1 Type I/III
 Hypertrophic Scar
 collagen ratio 2 : 1 Type I/III
Proliferative Phase
Three Phases of Wound Healing
 Inflammatory Phase
 Proliferative Phase
 Remodeling Phase
Maturation Phase
 Random to organized
fibrils
 Day 8 through years
 Type III replaced by type I
 Wound may increase in
strength for up to 2 years
after injury
 Collagen organization
 Cross linking of
collagen
Maturation Phase
Impaired Wound Healing
Wound Healing
 To treat the wound, you have to treat the
patient
 Optimize the patient
 Circulatory
 Pulmonary
 Nutrition
 Associated diseases or conditions
 Oxygen
 Fibroblasts are oxygen-sensitive
 PO2 < 40 mmHg collagen synthesis cannot
take place
 Decreased PO2: most common cause of
wound infection
 Healing is Energy Dependent
 Proliferative Phase has greatly increased
metabolism and protein synthesis
 Hypoxia:
 Endothelium responds with vasodilation
 Capillary leak
 Fibrin deposition
 TNF-a induction and apoptosis
 Edema
 Increased tissue pressure
 Compromise perfusion
 Cell death and tissue ulceration
 Infection
 Decreased tissue PO2 and prolongs the
inflammatory phase
 Impaired angiogenesis and epithelialization
 Increased collagenase activity
 Nutrition
 Low protein levels prolonged inflammatory
phase
 impaired fibroplasia
 Of the essential amino
 Methionine is critical
 Hydration
 A well hydrated wound will epithelialize
faster than a dry one
 Occlusive wound dressings hasten epithelial
repair and control the proliferation of
granulation tissue
 Temperature
 Wound healing is accelerated at
environmental temperatures of 30°C
 Tensile strength decreases by 20% in a cold
(12°C) wound environment
 Denervation
 Denervation has no effect on either wound
contraction or epithelialization
 Diabetes Mellitus
 Larger arteries, rather than the arterioles, are
typically affected
 Sorbitol accumulation
 Increased dermal vascular permeability and
pericapillary albumin deposition
 Impaired oxygen and nutrient delivery
 Stiffened red blood cells and increased blood
viscosity
 affinity of glycosylated hemoglobin for oxygen
contributing to low O2 delivery
 impaired phagocytosis and bacterial killing
 neuropathy
 Radiation Therapy
 Acute radiation injury






stasis and occlusion of small vessels
fibrosis and necrosis of capillaries
decrease in wound tensile strength
direct, permanent, adverse effect on fibroblast
may be progressive
fibroblast defects are the central problem in the
healing of chronic radiation injury
 Medications
 Steroids





Stabilize lysosomes and arrest of inflammation
response
inhibit both macrophages and neutrophils
interferes with fibrogenesis, angiogenesis, and wound
contraction
Also direct effect on Fibroblasts
 Minimal endoplasmic reticulum
vitamin A
 oral ingestion of 25,000 IU per day pre op and 3d
post op (not to pregnant women)
 Restores inflammatory response and promotes
epithelializaton
 Does not reverse detrimental effects on contraction
and infection
 Nutritional Supplements
 Vitamin C ( Ascorbic Acid)


is an essential cofactor in the synthesis of
collagen
excessive concentrations of ascorbic acid do
not promote supranormal healing
 Vitamin E



therapeutic efficacy and indications remain
to be defined
large doses of vitamin E inhibit healing
increase the breaking strength of wounds
exposed to preoperative irradiation
 Nutritional Supplements
 Glutamine
Enhance actions of lymphocytes, macrophages and
neutrophils
 Glycine
 Inhibitory effect on leukocytes, might reduce
inflammation related tissue injury
 Zinc
 common constituent of dozens of enzymes
 Influences B and T cell activity
 epithelial and fibroblastic proliferation is impaired
in patients with low serum zinc levels

Factors in Wound Healing
 Smoking
 1ppd = 3x freq of flap necrosis
 2ppd = 6x freq of flap necrosis
 Nicotine acts via the sympathetic system


vasoconstriction and limit distal perfusion
 1 cigarette = vasoconstriction > 90 min
Decrease proliferation of erythrocytes, macrophages and
fibroblasts
 Smoke contains high levels of carbon monoxide


shifts the oxygen-hemoglobin curve to the left
decreased tissue oxygen delivery
Syndromes Associated with Abnormal
Wound Healing
 Cutis Laxa
 Think defective elastin fibers
 Congenital
 AD, recessive or X-linked recessive
 Acquired
 Drug, neoplasms or inflammatory skin conditions
 Ehlers-Danlos Syndrome
 Think defective collagen metabolism
 AD and recessive patters
 10 phenotypes
Syndromes Associated with
Abnormal Wound Healing
 Ehlers-Danlos Syndrome
 Connective tissue abnormalities due to defects:




Inherent strength
Elasticity
Integrity
Healing properties
Syndromes Associated with
Abnormal Wound Healing
 Ehlers-Danlos Syndrome
 Four major clinical features




Skin hyper-extensibility
Joint hyper-mobility
Tissue fragility
Poor wound healing
Electrostimulation
 Electrical current applied to wounds
 Increases migration of cells
 109% increase in collagen
 40% increase in tensile strength
 1 to 50 mA direct or pulsed based on wound
Hyperbaric Oxygen
 Developed 1662 by Henshaw: Domicillium
 Atmospheric pressure at sea level = 1 ATA = 1.5ml
O2/dL
 Normal SubQ O2 tension is 30-50 mmHg.
 SubQ O2 tension < 30 mmHg = chronic wound
Excessive Healing
 Hypertrophic Scars
 Keloids
Hypertropic Scar
Keloids
 Extends beyond original bounds
 Raised and firm
 Rarely occur distal to wrist or knee
 Predilection for sternum, mandible and deltoid
 Rate of collagen synthesis increased
 Water content higher
 Increased glycosaminoglycans
Keloid Treatment
 Triamcinolone injections
 3-4 weeks
 Cross linking modulated
 Injections continued until no excess abnormal
collagen
 Excise
 Prevention during healing – pressure and injection
Keloid
Keloid
Keloid Scar
Keloid Scar
Questions
 The proliferative phase of wound healing occurs
how long after the injury?
1 day
B. 2 days
C. 7 days
D. 14 days
A.
 Which type of collagen is most important in wound
healing?
Type III
B. Type V
C. Type VII
D. Type XI
A.
 The tensile strength of a wound reaches normal
(pre-injury) levels:
10 days after injury
B. 3 months after injury
C. 1 year after injury
D. never
A.
 Which of the following is commonly seen in Ehlers-
Danlos syndrome?
A. Small bowel obstructions
B. Spontaneous thrombosis
C. Direct hernia in children
D. Abnormal scarring of the hands with contractures.
 Steroids impair wound healing by:
Decreasing angiogenesis and macrophage
migration
B. Decreasing platelet plug integrity
C. Increasing release of lysosomal enzymes
D. Increasing fibrinolysis
A.
 Supplementation of which of the following
micronutrients improves wound healing in patients
without micronutrient deficiency?
A. Vitamin C
B. Vitamin A
C. Selenium
D. Zinc
 Signs of malignant transformation in a chronic
wound include:
Persistent granulation tissue with bleeding
B. Overturned wound edges
C. Non-healing after 2 weeks of therapy
D. Distal edema
A.
 The treatment of choices for keloids is:
Excision alone
B. Excision with adjuvant therapy (e.g. radiation)
C. Pressure treatment
D. Intralesional injection of steroids
A.
 The major cause of impaired wound healing is:
Anemia
B. Diabetes mellitus
C. Local tissue infection
D. Malnutrition
A.
 Bradykinin, serotonin, and histamine in wounds
are released from:
Lymphocytes
B. Mast cells
C. Polymorphonuclear leukocytes
D. Platelets
A.
 Platelets in the wound form a hemostatic clot and
release clotting factors to produce:
Fibrin
B. Fibrinogen
C. Thrombin
D. Thromboplastin
A.
 In a healing wound, metalloproteinases are
responsible for:
Establishing collagen cross-link
B. Glycosylation of collagen molecules
C. Incorporation of hydroxyproline into the collagen chain
D. Initiating collagen degradation
A.
 Severe cases of hidradenitis suppurativa in the
groin area are best managed by excision of the
involved area and?
Closure by secondary intension
B. Delayed primary closure
C. Primary closure
D. Split thickness skin grafting
A.
 All of the following statements about keloids are true
except?
Keloids do not regress spontaneously
B. Keloids extend beyond the boundaries of the original
wound
C. Keloids or hypertrophic scars are best managed by excision
and careful reapproximation of the wound
D. Keloid tissue contains an abnormally large amount of
collagen.
A.
 Thank You