Wound Repair Flashcards
Anytime you perform SURGERY you create a WOUND
* Leaves underlying tissue vulnerable to —
* ~ — million surgeries per year in the US
* Wound healing remains problematic →why and what can we do to lessen this?
infection
50
CAUSES OF INJURY
physical (7)
compromised blood flow
crushing
desiccation
incision
irradiation
overcooling
overheating
CAUSES OF INJURY
chemical (5)
agents with unphysiologic pH
agents with unphysiologic tonicity
proteases
vasoconstrictors
thrombogenic agents
EPITHELIALIZATION
* Noted with —
* Renewal of epithelium occurs within — after injury
* Occurs faster with — substrate over wound
abrasions
hours
moisten
Renewal of epithelium occurs within hours after injury
(2)
- Completion occurs at 24 – 48 hours
- Free edge of epithelium migrate until it contacts the opposite edge
- Free edge of epithelium migrate until it contacts the opposite edge
(2)
- Signal is terminated in CONTACT INHIBITION
- Occurs over wound bed but under scabbing/superficial blood clot
- Occurs faster with moisten substrate over wound
- Epithelium does cross over
desiccated surface
PHASES OF WOUND HEALING
* Inflammatory phase
* Day
* Fibroplastic phase
* Days
* Maturation/remodeling phase
*
1-6
4- 3 weeks
3 weeks – 1 year
INFLAMMATORY PHASE: DAYS 1- 5ISH
Also called LAG PHASE:
(4)
- No increase in wound strength
- Due to little collagen deposition
- FIBRIN principle material holding wound together
- Has little tensile strength
2 phases of the Inflammatory Phase
- Vascular
- Cellular
VASCULAR PHASE
* Vasoconstriction of disrupted vessels
(2)
- Coagulation (platelets and fibrin)
- Clot formation 5-10 minutes
Vasodilation
(3)
- Increases permeability to site to allow healing factors and cells to
reach injury site - Mediated by histamine and prostaglandins (E1 and E2) from WBCs
- Causes EDEMA (leak of cells and fluid to site of injury)
CELLULAR PHASE
* PMN (neutrophils) arrive within 24 hrs of injury
(4)
- Margination:
- Diapedesis:
- Degranulation:
- Macrophages continue clearance of debris
- Margination:
- PMNs stick to side of blood vessels
- Diapedesis:
- PMNs migrate through vessel walls
- Degranulation:
- PMNS releasing lysosomal enzymes to destroy bacteria/foreign
materials/necrotic tissue
FIBROPLASTIC PHASE: DAY 4 – 3 WEEKS
* — are the dominant cell
Fibroblasts
Fibroblasts are the dominant cell
* Deposits
ground substance and TROPOCOLLAGEN over fibrin lattice
* Ground substance contains mucopolysaccharides →cement collagen fibers together
Fibroblasts are the dominant cell
* Secretes
FIBRONECTIN
FIBRONECTIN
(3)
- Stabilize fibrin
- Assists in recognizing foreign material
- Chemotactic factor to aid recruitment of fibroblasts and macrophages
FIBROPLASTIC PHASE: DAY 4 – 3 WEEKS
* Angiogenesis occurs:
(2)
- Increase vascularity (from wound edges inward)
- Causes raised and red color of wound
FIBROPLASTIC PHASE: DAY 4 – 3 WEEKS
Superfluous fibrin strands removed by —
plasmin
FIBROPLASTIC PHASE: DAY 4 – 3 WEEKS
* Excessive collagen deposited in haphazard manner
(2)
- Increases tensile strength (~ 5-7 days after injury →timing for suture removal)
- 70%-80% tensile strength compared to uninjured tissue
REMODELING PHASE: 3 WEEKS TO 1 YEAR/INDEFINITE
* Increase in collagen ORGANIZATION AND STRENGTH
(3)
- Collagen oriented in direction to better resist tension
- Type III collagen replaced by Type I
- Excess collagen removed →scar softens
Wound strength never reaches above
80% - 85% of
uninjured tissue
* Peak tensile strength at 60 days
REMODELING PHASE: 3 WEEKS TO 1 YEAR/INDEFINITE
* Wound erythema decreases as
* Wound contraction occurs by
vascularity decreases to site
migration of wound edges
toward each other
FACTORS THAT IMPAIR WOUND HEALING
* Foreign material
(4)
- Dirt, wood, glass, suture, bacteria
- “Non-self” material causes chronic inflammation
- Decreases fibroplasia
- Bacteria proliferation causing infection
- Destroys host tissue with bacteria byproducts
- Non-bacteria causes a harbor for bacteria
FACTORS THAT IMPAIR WOUND HEALING
Necrotic tissue
- Free bony fragment in extraction site is classic example
- Barrier to ingrowth of reparative cells
- Serves as a protected niche for bacteria
- Hematoma formation:
- Nidus for bacteria, as well as food source for bacteria
- Blood clot is small and functional, hematoma is large and of no use
FACTORS THAT IMPAIR WOUND HEALING
* Ischemia
(2)
- Decreased blood supply, resulting in poor oxygen delivery to needed site
- Increases wound infection by halting delivery of PMNs, WBCs, antibodies, ABX
- Ischemia
- Results from:
(4)
- Poorly designed flaps
- Tight sutures
- Internal pressure from edema/hematoma
- Hypotension during surgery
FACTORS THAT IMPAIR WOUND HEALING
* Tension
(2)
- Wounds closed under tension will cause ischemia at
margins with eventual opening (dehiscence) - If suture removed too early, the wound under tension will
reopen and heal with excessive scar formation
HYPERTROPHY
(5)
- Overgrowth of tissue within border of
wound edges - Any race
- Common in pediatrics
- Regresses with time
- Common on flexor surfaces
KELOID
(5)
- Overgrowth beyond border of wound
edges - Common in darker skin/hereditary
- Rare in pediatrics
- Grows for years
- Common on upper body, head/neck
KELOID/HYPERTROPHY TREATMENT
* Similar strategy for both findings
* — significantly more difficult to eradicate
* Triple therapy:
Keloid
- Surgical excision
- Corticosteroid injection
- 40 mg/cc injection intralesional
- 2-3 times per month for 6 months
- Silicone pressure dressing
- Worn 12-24 hours per day
- For 2-3 months
WOUND HEALING
(3)
- Primary intention
- Secondary intention
- Tertiary intention
- Delayed primary healing
PRIMARY INTENTION
(5)
- Edges of wound returned to anatomic position
- Wound edges directly next to each other
- Little loss of tissue
- Minimal scar
- Closure stabilized and accomplished with
sutures/staples/adhesives
PRIMARY INTENTION
ex (2)
- Lacerations
- Well reduced bone fractures
SECONDARY INTENTION
(4)
- Wound is allowed to granulate in
- May be packed by surgeon with gauze or drain
- Granulation results in broad scar
- Slower healing process
SECONDARY INTENTION
ex (3)
- Gingivectomy
- Tooth extraction
- Poorly reduced fracture
TERTIARY INTENTION
- Delayed primary closure
- Related to contaminated wounds
- Wound cleaned, debrided and observed
- Closure attempted after 4-5 days
- Purposely left open to observe for any signs and
symptoms of infection or further tissue necrosis - Skin grafting or flaps can be used to cover these type of
wounds
Primary intention
Epithelial migration
Amount of collagen
Contracture
Speed of healing
Remodeling necessary
Loss of function
none
minimal
minimal
rapid
little
little
Secondary intention
Epithelial migration
Amount of collagen
Contracture
Speed of healing
Remodeling necessary
Loss of function
considerable
large
considerable
delayed
considerable
potentially great
HEALING OF EXTRACTION SOCKETS
* Most cases healing is by
SECONDARY INTENTION
Immediately after extraction:
(3)
- Remnants of periodontal ligament remain attached to the lamina dura
- Gingival epithelial margin is separated at the crest
- Coagulated blood seals socket
HEALING OF EXTRACTION SOCKETS
* First week
(2)
- Inflammatory phase
- Fibroplasia begins
- Inflammatory phase
- WBCs break down and digest bacteria and debris
- Fibroplasia begins
(4)
- Fibroblast proliferate forming granulation tissue
- Neovascularization penetrates clot
- Clinical correlation: Localized osteitis, “dry socket,” occurs if this
phase fails - Epithelium begins to migrate down towards first granulation tissue
it comes into contact with
HEALING OF EXTRACTION SOCKETS
* Second week
(2)
- Granulation tissue increase and matures
- Small socket may close off at 14 days, molars by 3 weeks
- Third and Fourth week
(2)
- Almost all sockets will have epithelial closure by 21 days
- Deposition of early bone (osteoid) within the socket
HEALING OF EXTRACTION SOCKETS
* Four to six months
(3)
- Continued resorption and recontouring of alveolus
- Total resorption of lamina dura by 1 year
- Clinical correlation:
- What is time frame to wait before building a final prosthesis?
BONE HEALING
* Where do osteogenic cells responsible for bone repair come from?
(3)
- Periosteum
- Endosteum
- Circulating pluripotential mesenchymal cells
Primary Intent
Bone separation
Fibrous matrix
Callus
Speed of re-ossification
< 1 mm
Little between or
subperiosteal
Little
Fast
Secondary Intent
Bone separation
Fibrous matrix
Callus
Speed of re-ossification
> 1 mm
Large amounts extending past
bone ends
Large
Longer with replacement
process
BONE HEALING
* Factors most important to proper bone healing
(2)
- VASCULARITY
- IMMOBILITY
- VASCULARITY
- If low oxygenation →
- If severe →
cartilage will form instead of bone
fibrous tissue may never calcify →fibrous union
- IMMOBILITY
(2)
- Intermaxillary fixation (IMF), bone plates, direct wires
- Mobility prevents fibrous tissue from ossifying →fibrous union, non-union,
NERVE REPAIR
* OMS considerations with (2) nerves
inferior alveolar or lingual
Prognosis for return of sensory function is related to:
(3)
- How bad was the damage (severed, crushed, stretched, pinched)
- Condition of epineurium
- Amount of separation between nerve ends
NERVE REPAIR
* Two phases:
(2)
- Degeneration
- Regeneration
Degeneration
(2)
- Segmental demyelination
- Wallerian Degeneration
- Segmental demyelination
(2)
- Myelin sheath dissolved in isolated segments (slows nerve conduction)
- Symptoms: paresthesia, dysesthesia, hyperesthesia, hypoesthesia
- Wallerian Degeneration
(2)
- Axons and myelin sheath of nerve distal to site of interruption undergo disintegration in their
entirety - Axons proximal to the site of interruption undergo some degeneration generally a few Nodes of
Ranvier away
Regeneration
(4)
- Growth cone (growth of new nerve fibers from proximal nerve stump) starts growing down
remnant Schwann cell tube - Progresses 1 mm per day
- Continues until site innervated by the nerve is reached
- New myelin sheaths may form as axons increase in diameter
Abnormal nerve healing →
NEUROMA
* Mass of aimless nerve fibers
* Painful when disturbed (temperature, pressure, etc…)
Paresthesia
- Spontaneous and subjective altered sensation that IS NOT PAINFUL/UNCOMFORTABLE
Dysesthesia
- Spontaneous and subjective altered sensation that IS PAINFUL/UNCOMFORTABLE
- Hyperesthesia
- Excessive sensitivity of a nerve to stimulation
- Hypoesthesia
- Decreased sensitivity of a nerve to stimulation
- Anesthesia
- No sensation when stimulated
