1. Wound Healing Orlando Canizares, MD
Tulane University Health Science Center
Division of Plastic & Reconstructive Surgery

2. Overview Wound Healing Phases Factors Influencing
Adjuncts to Wound Healing
Fetal wound healing
Wound Care
Principles
Dressings
Abnormal Scarring

3. Phases of Wound Healing
Tissue Injury and Coagulation
Inflammation
Remove devitalized tissue and prevent infection
Early
Late
Fibroproliferative
Balance between scar formation and tissue regeneration
Fibroblast migration
Collagen synthesis
Angiogenesis
Epithelialization
Maturation/Remodeling
Maximize strength and structural integrity
Contraction
Collagen Remodeling

4. Tissue Injury and Coagulation
INJURY (Physical, antigen-antibody reaction, or infection)
Transient (5-10 minute) vasoconstriction
Slows blood flow, aid in hemostasis
Histamine mediated vasodilation and permeability changes
Vessels become lined with leukocytes, platelets and erythrocytes
Leukocyte migration into the wound
Endothelial cells swell and pull away from each other -> allowing serum to enter the wound
Hemostatic factors from platelets, kinins, complement, and prostaglandins send signals to initiate the inflammatory phase
Fibrin, Fibronectin, and plasma help form a clot and stop bleeding

6. Early Inflammation Complement Cascade Activation PMN infiltration
24-48 hours
Stimulated by:
Complement components (C5a)
Formyl-methionyl peptide products from bacteria
Transforming Growth Factor (TGF)-b

7. Early Inflammation PMNS
Predominant cell type from hours
Phagocytosis and debridement
Removal of PMNS does not alter wound healing

8. Late Inflammation Macrophage
Most critical cell type
Predominates after hours
Attracted by:
Growth factors (PDGF, TGF-b)
Complement
Clotting components
IgG
Collagen and elastin breakdown products
Leukotriene B4
Platelet factor IV

9. Late Inflammation Macrophage Functions
Phagocytosis
Primary producer of Growth Factors (PDGF, TGF-b)
Recruitment of fibroblasts (proliferative phase)
Proliferation of extracellular matrix by fibroblasts
Proliferation of endothelial cells (angiogenesis)
Proliferation of smooth muscle cells
This leads to the Fibroproliferative phase

10. Late Inflammation Lymphocyte
Appears at 72 hours
Attracted by:
Interleukins
IgG
Complement products
Role yet to be determined

12. Fibroproliferative Fibroblasts Collagen synthesis Angiogenesis
Migrate into the wound via ECM
Predominant cell type by day 7
Collagen synthesis
Begins on days 5-7
Increases in linear fashion for 2 to 3 weeks
Angiogenesis
Promoted by macrophages (TNF-alpha, FGF, VEGF)
Epithelialization
Mitosis of epithelial cells after hours
Modulated by growth factors (EGF, FGF, KGF)

13. Fibroproliferative Extracellular Matrix
Forms a scaffold for cell migration and growth factor sequestration (fibronectin, proteoglycans, collagen, etc.)
Proteoglycans and Glycosaminoglycans
chondroitin sulfate
heparan sulfate
keratan sulfate
hyaluronic acid (1st to appear)

14. Collagen Principle building block of connective tissue
1/3 of total body protein content

15. Collagen Types
Type 1
Bones, skin, and tendons
90% of total body collagen
Found in all connective tissues except hyaline cartilage and basement membranes
Type 2
Hyaline cartilage, cartilage-like tissues, and eye tissue

16. Collagen Types Type 4 Type 3 Type 5 Skin
Skin, arteries, uterus, abdominal wall, fetal tissue
Association with Type I collagen in varying ratios (remodeling phase)
Type 4
Basement membranes only
Type 5
Basement membranes, cornea
Skin
Type 1 : Type 3 ratio is 4:1
Hypertrophic scars/immature scars ratio maybe as high as 2:1

17. Collagen Metabolism Dynamic equilibrium Healing wound
Synthesis (Fibrosis) vs. Degradation (collagenases)
Collagenase activity
Stimulated: PTH, Adrenal corticosteroids, colchicine
Inhibited: Alpha 2-macroglobulin, cysteine, progesterone
Healing wound
3-5 weeks equilibrium is reached between synthesis and degradation (no net change in quantity)

18. Angiogenesis
Formation of new blood vessels throughout inflammatory and proliferative phase of wound healing
Initiated by platelets
TGF-b and PDGF
PMN
Macrophages
TNF-alpha, FGF, VEGF
Endothelial Cell
Forms new blood vessels

19. Epithelialization Repithelialization begins within hours of injury
Stimulated by
Loss of contact-inhibition
Growth factors
EGF (mitogenesis and chemotaxis)
KGF, FGF (proliferation)

20. Epithelialization
Epithelium advances across wound with leading edge cells becoming phagocytic
Collagenase (MMP)
Degrades ECM proteins and collagen
Enables migration between dermis and fibrin eschar
Mitosis of epithelial cells hours after injury behind leading edge

22. Maturation/Remodeling
Longest phase: 3 weeks – 1 year
Least understood phase
Wound Contraction and Collagen Remodeling
Wound Contraction
Myofibroblast
Fibroblasts with intracellular actin microfilaments

23. Maturation/Remodeling
Collagen Remodeling
Type 3 Collagen degraded and replaced with Type 1
Collagen degradation achieved by Matrix Metalloproteinase (MMP) activity (fibroblasts, PMNs, macrophages)
Collagen reorientation
Larger bundles
Increased intermolecular crosslinks

24. Tensile Strength Collagen is the main contributing factor
Load capacity per unit area
(Breaking capacity- force required to break a wound regardless of its dimensions)
Rate of tensile strength increases in wounds vary greatly amongst species, tissues and individuals
All wounds begin to gain strength during the first days (~20% strength), variable then after
Strength 60 days
NEVER reaches pre-injury levels
Most optimal conditions  may reach up to 80%

25. Predominant Cell Types

26. Special Characteristics of Fetal Wound Healing
Lack of inflammation
Absence of FGF and TGF-b
Regenerative process with minimal or no scar formation
Collagen deposition is more organized and rapid
Type 3 Collagen (No Type 1)
High in hyaluronic acid
Area of ongoing research

27. Factors That Influence Wound Healing
Oxygen
Fibroblasts are oxygen-sensitive
Collagen synthesis cannot occur unless the PO2 >40mmHg
Deficiency is the most common cause for wound infection and breakdown
Hematocrit
Mild to moderate anemia does not appear to have a negative influence wound healing (given sufficient oxygenation)
>50% decrease in HCT
some studies report a significant decrease in wound tensile strength
while other studies find no change

28. Factors That Influence Wound Healing
Smoking
Multifactorial in limiting wound healing
Nicotine
Vasoconstrictive -> decreases proliferation of erythrocytes, macrophages, and fibroblasts CO
Decreases the oxygen carrying capacity of Hgb
Hydrogen Cyanide
Inhibits oxidative enzymes
Increases blood viscosity, decrease collagen deposition and prostacyclin formation
A single cigarette may cause cutaneous vasoconstriction for up to 90 minutes

29. Factors That Influence Wound Healing
Mechanical Stress
Affects the quantity, aggregation, and orientation of collagen fibers
Abnormal tension -> blanching, necrosis, dermal rupture, and permanent stretching
Hydration
Well hydrated wounds epithelialize faster
Environmental Temperature
Healing is accelerated at temperatures of 30 C
Tensile strength decrease by 20% in 12C environment

30. Factors That Influence Wound Healing
Denervation
No direct effect on epithialization or contraction
Loss of sensation and high collagenase activities in skin -> prone to ulcerations
Foreign Bodies (including necrotic tissue)
Delay healing and prolong the inflammatory phase
Nutrition
Delays increases in tensile strength
Edema
May compromise tissue perfusion

31. Factors That Influence Wound Healing
Oxygen Derived Free Radicals
Degrade Hyaluronic acid and collagen
Destroy cell and organelle membranes
Interfere with enzymatic functions
Age
Tensile strength and wound closure rates decrease with age

32. Factors That Influence Wound Healing
Infection
Prolongs inflammatory phase, impairs epithiliazation and angiogenesis
Increased collagenolytic activity -> decreased wound strength and contracture
Bacterial counts > 105, b-hemolytic strep
Chemotherapy
Decreases fibroblast production and wound contraction
If started days after injury, no significant long term problems, but short term decreased tensile strength
Radiation
Stasis and occlusion of small blood vessels
Decreased tensile strength and collagen deposition
Systemic Diseases DM
Glycosylated RBCs  Stiffened RBCs & Increased blood viscosity
Glycosylated WBCs  impaired immune function
Renal Dz

33. Factors That Influence Wound Healing
Steroids
Inhibit wound macrophages
Interfere with fibrogenesis, angiogenesis, and wound contraction
Vitamin A and Anabolic steroids can reverse the effects
Vitamin A
Stimulates collagen deposition and increase wound breaking strength
Topical Vitamin A has been found to accelerate wound reepithealization

34. Factors That Influence Wound Healing
Vitamin C
Essential cofactor in the synthesis of collagen
Deficiency is associated with immune dysfunction and failed wound healing (Scurvy)
Immature fibroblasts and extracellular material
High concentrations do not accelerate healing

35. Factors That Influence Wound Healing
Vitamin E
Large doses inhibit wound healing
Decreased tensile strength
Less collagen accumulation
HOWEVER
Antioxidant that neutralizes lipid peroxidation caused by radiation  Decreasing levels of free radicals and peroxidases  increases the breaking strength of wounds exposed to preoperative radiation

36. Factors That Influence Wound Healing
Zinc
Deficiency:
Impairs epithelial and fibroblast proliferation
Decreases B and T cell activity
Only accelerates healing when there is a preexisting deficiency

37. Factors That Influence Wound Healing
NSAIDs
Decrease collagen synthesis an average of 45% (ordinary therapeutic doses)
Dose-dependent effect mediated through prostaglandins

38. Adjuncts to Wound Healing
Fibrin-based tissue adhesives
Increase breaking strength, energy absorption, and elasticity in healing wounds

39. Adjuncts to Wound Healing
Hydrotherapy
Whirlpool
Pulsed Lavage
Stimulates formation of granulation tissue
Clean non draining wounds with healthy granulation tissue should NEVER be subjected to hydrotherapy
Water agitation damages fragile cells

40. Adjuncts to Wound Healing
Hyperbaric Oxygen
Increases levels of O2 and NO to the wound
Benefit: Amputations, osteoradionecrosis, surgical flaps, skin grafts
None to minimal benefit with necrotizing soft-tissue infections
Wounds require adequate perfusion
Many off-label uses (Benefit? Financial?)
Acne, Migraines, Lupus, Stroke, MS, and many more
Medicare Coverage
14 Covered Areas (next slide)

41. Medicare Coverage of HBO
(1)  Acute carbon monoxide intoxication
(2)  Decompression illness
(3)  Gas embolism
(4)  Gas gangrene
(5)  Acute traumatic peripheral ischemia
(6)  Crush injuries
(7)  Progressive necrotizing infections
(8)  Acute peripheral arterial insufficiency
(9)  Preparation and preservation of compromised skin grafts
(10)  Chronic refractory osteomyelitis
(11)  Osteoradionecrosis (ORN)
(12)  Soft tissue radionecrosis (STRN)
(13)  Cyanide poisoning
(14)  Actinomycosis

42. Adjuncts to Wound Healing

43. Wound Care General Principles
Cleaning and Irrigation
Need at least 7psi to flush bacteria out of a wound
High pressure can damage wounds and should be reserved only for heavily contaminated wounds
Debridement
Most critical step to produce a wound that will heal rapidly without infection
Non-selective: Dakin solution, Hydrogen Peroxide, etc.
Useful in wounds with heavy contamination
When starts to granulate, start selective
Selective: sharp, enzymatic, autolytic, or biologic

44. Selective Debridement
Enzymatic
Naturally occurring enzymes that selectively digest devitalized tissue
Collagenase (Santyl), Papain-Urea (Accuzyme), etc.
Autolytic
Uses the body’s own enzymes and moisture to breakdown necrotic tissue
7-10 days under semi occlusive and occlusive dressings
Ineffective in malnourished patients
Biologic
Maggots
Calcium salts and bactericidal peptides
Separate necrotic from living tissue making surgical debridement easier

45. Wound Care General Principles
Fundamentals of Surgical Wound Closure
Incision should follow tension lines and natural folds in the skin
Gentle tissue handling
Complete hemostasis
Eliminate tension
Fine sutures and early removal
Evert wound edges
Allow scars to mature before repeat intervention (2 weeks to 2 months scar appearance is the worst)
Scar appearance depends more on type of injury than method of closure
Technical factors of suture placement and removal are more critical than type of suture used
Immobilization of wounds to prevent disruptions and excessive scarring (Adhesive strips after suture removal)

46. Wound Dressings Over 2,000 commercially available
Red-Yellow-Black Classification
Created to help choose appropriate dressings in wounds healing by secondary intention
Treat worse colors first
Black -> Yellow -> Red

48. Dressing Types Alginates (Aquacel) Creams (Silvadene cream)
Wounds with heavy exudates (dry the wound)
Converts in a sodium salt -> hydrophilic gel occlusive environment
Change when begins to weep exudate
Creams (Silvadene cream)
Opaque, soft solid or thick liquids with a slight drying effect
Wounds with moist weeping lesions
Ointments (bacitracin)
Semisolids that melt at body temperature
Aid in rehydration and topical application of drugs

49. Dressing Types Foams (Mepilex) Films (Tegaderm)
Hydrophobic polyurethane sheets with a non absorbent adhesive occlusive cover (very absorbent and nonadherent)
Absorb environmental water and slow epitheliaztion
Films (Tegaderm)
Transparent polyurethane membranes with water-resistant adhesives
Conform well, semipermeable to moisture and oxygen, impermeable to bacteria
Promote autolytic debridement
Good for wound monitoring
Can lead to maceration in wounds with a heavy exudate and can tear skin

50. Dressing Types Gauze Hydrocolloids Hydrogels
Highly permeable to air and allow rapid moisture evaporation
Stick to granulation tissue and damage the wound with removal
Painful removal
Lint can harbor bacteria
Hydrocolloids
Completely impermeable
Avoid in anaerobic infections
Comfortable and adhere well (good for high-friction areas)
Good at absorbing exudate
Hydrogels
Starch and water polymers in gels, sheets, or impregnated gauze
Rehydrate wounds (poor for absorbing exudate)

51. Dressing Types VAC Dressing
Sub atmospheric pressure dressing to convert an open wound to a controlled closed wound
Decreases interstitial fluid/edema
Improves tissue oxygenation
Removes inflammatory mediators
Increase speed of granulation tissue formation
Reduces bacterial counts
Silver-impregnated (Acticoat, Arglaes, Silveron)
Antibacterial (effective against MRSA, VRE, yeast, and fungi)
Moist environment
Wound Matrix (Alloderm, Oasis, Apligraft, Dermagraft, Integra)

52. Alloderm Acellular dermal matrix derived from donated human skin
Epidermis and all dermal cellular components are removed

53. Oasis
Thin (0.15mm), translucent layer of porcine small intestinal submucosa (SIS)
Primarily made of a collagen-based ECM
Biologically important components of the ECM remain active
Glycosaminoglycans (hyaluronic acid), proteoglycans, fibronectin, and growth factors such as FGF and TGF
Application:
Clean wound base
Cut to size slightly larger than wound, apply directly, moisten with saline
Dress with standard dressings: moist, compressive, etc.
Change dressings with standard frequency

54. Apligraf Living bilayered skin substitute (epidermis and dermis)
Dermis is devoid of Langerhans cells, melanocytes, macrophages, lymphocytes, hair or blood vessels
Includes: PDGF, TNF, VEGF, FGF
Has shown improved healing in Diabetic and Venous stasis ulcers

55. Dermagraft Derived from newborn foreskin tissue
Cryopreserved human fibroblast-derived dermal substitute
Composed of fibroblasts, ECM, and a bioabsorbable scaffold
Fibroblast are seeded into the scaffold and secrete collagen, matrix proteins, growth factors and cytokines to create a human dermal substitute containing living cells
Multiple studies showing higher percentage of healed diabetic foot ulcers versus controls

56. Integra Outer layer of a semi-permeable silicone membrane
Inner layer is a porous matrix of fibers of cross-linked bovine tendon and glycosaminoglycans, that allows dermal ingrowth
After dermal ingrowth the silicone film is removed and a STSG is placed (~3 weeks)

57. Abnormal Scarring
Hypertrophic Scars
Keloids
Widespread Scar

58. Comparison of Abnormal Scars
Keloid
Hypertrophic Scar
Widespread Scar
Borders
Outgrows wound borders
Remains within wound borders
Wide, flat, depressed
Natural History
Appears months after injury, rarely regresses
Appears soon after injury, regresses with time
Appears within 6 months of injury
Location
Mostly face, earlobes, chest
(Never eyelids or mucosa)
Flexor surfaces
Arms, legs, abdomen
Etiologic Factors
Possible autoimmune, endocrine (puberty, pregnancy)
Tension
Tension and mobility of wound edges
Treatment
Intralesional steroids, compression therapy, silicone gel sheeting, radiation therapy
Often worse after surgery alone
Same as Keloids but outcome usually more successful
Scar excision/layered closure

59. Comparison of Abnormal Scars
Keloid
Hypertrophic Scar
Widespread Scar
Genetics
Significant familial predilection
Low familial incidence
No inheritance pattern
Race
African > Caucasian
Low racial incidence
Not related to race
Sex
Females > Males
(Equal)
Equal
Unknown
Age
Most commonly years
Any age, mostly less than 20 years
Any Age

60. Hypertrophic Scar

61. Keloids

62. Keloid: Treatments
No universally effective treatment, usually a combination of treatment types
Case by Case basis
Prevention (the best therapy)
Avoid non essential surgery, minimal tension, use cuticular monofilament synthetic sutures, avoid wound-lengthening techniques, and avoid incisions across joints

63. Keloids: Treatments Surgery: Alone 50-80% reoccurrence rate
Excision with early postoperative radiation (~25% reoccurrence rate)
Excision with corticosteroids (50-70% reoccurrence rate)
Pressure- increase collagenase activity
24-30mm Hg, 18-24h/day for 4-6 months
Silicone gel sheeting- mechanism unclear (decrease movement/tension)
80-100% -improvement in hypertrophic scars
35%- improvement in keloids
Corticosteroids- intralesional
Decreases collagen synthesis- unclear mechanism
Maybe used in conjunction with surgical excision
Complications- hypopigmentation, skin atrophy, telangiectasias
Lack of randomized control trials to determine site specific dosages
Cryotherapy
Found to be helpful in early vascularized lesions

64. Keloid Treatment Radiation
Most effective when given post operatively
No advantage if given preoperatively
~25% reoccurrence rate when combined with excision
15-20 Gy administered over several doses (5-6)

65. Keloid Treatments Antitumor/Immunosuppressive Agents
5-FU
Reports of effectiveness
Uppal et al.: 50% improvement in Keloid Score
Haurani et al.: 19% reoccurrence rate after intralesion injection after surgery at 1 year
Literature still in debate over appropriate dosage
Bleomycin
Limited studies to date suggesting effectiveness
Interferon
Some reports showing effectiveness others showing none
Ongoing study needed

66. Thank You