Soft Tissue Surgery Equine Principles of Wound Healing 1 and 2 Flashcards
What is one of the first considerations when an animal presents with a wound?
Whether vital structures may be penetrated or traumatises- failure can result in death
Pay particular attention to head, thorax, abdomen, joints, tendon sheaths
How much does skin thickness vary?
Where on the body does skin have the highest chance of injury?
1-6mm
Thickest where there is the greatest chance of injury, thinnest at least
Epidermis- stratum corneum, stratum granulosum, stratum spinosum, stratum basale
Dermis- superficial papillary layer, deep reticular layer
Contains- sweat glands, hair, sebaceous gland, subcutis/cutaneous muscles, arteries, veins, lymphatic nerves
What are tension lines?
What are the skin cellular mediators?
Tension lines- normal tension exists due to elastic fibres in dermic- langers lines of tension
Skin edges retract when an incision is made across these lines- less retraction when made parallel
Cellular mediators-
Growth factors- proteins that bind to cell surface receptors and result in activation of cellular proliferation and/or differentiation- may involve
Cytokines and chemokines- small signalling proteins secreted by cells, cytokines cause growth, differentiation and activation functions, chemokines- cytokines with specific chemotactic function
What are the phases of wound healing?
Inflammtory phase/lag phase
Proliferative phase
Remodelling phase
What is the function of the inflammatory phase and what happens?
How is it characterised?
How long does it last?
Haemostasis, protects against infection, substrate and cellular signals for next steps, removal of wound contamination, d
- Tissue disruption initiates hemostasis and inflammation
- Transient vasoconstriction- occlusion of injured vessels
- Vasodilation after several minutes- heat, redness, swelling
- Fibrin seal creates- acts as meshwork
- Platelets aggregate and release chemoattractant, growth factors and proteases
- Haemostasis
- Attracts other cells needed for wound healing
- Provided a temporary scaffold for the migration of fibroblasts and epithelial cells
- Removal of wound contamination, damaged and dead tissue
Characterised by erythema and oedema of wound edges
96 hours
What cells are involved in the inflammatory phase and what is the function?
Neutrophils-
stimulated by various factors and arrive within 24-48 hours
kill bacteria
require high pp of O2
usually short lived
Monocytes-
mature to macrophages (TGF-B)
Debrine the wound of devitalised collagen and fibrin clots
Essential for further secretion of signalling molecules
Primary leukocyte in the wound at 48-96 hours
What happens during the proliferative phase of wound recovery?
Overview- angiogenesis, fibroplasia and granulation tissue formation, epithelisation, contraction
- 4-12 hours following injury
- Aims- permanent closure of the wound replacement of lost tissue
- Duration depends- wound size, location, age and hwalth
- Capillary ingrowth, collagen production, wound contraction and coverage
- Microvascular network within wound- provides oxygen and nutrients to cells
- Fibroblasts start to synthesise collagen, glycosaminoglycans and fibronectin
- Fibroblasts transformed into myofibroblasts and start to cause wound contraction
- Clinically characterised by development of granulation tissue
- Epithelial cells begin to proliferate (EGF, TGF-a)
- Move into the wound- minimise fluid loss and invasion
- Migration into wound until contact inhibition occurs
- Attempts to recreate normal epidermal thickness
What happens during the remodelling stage of wound healing?
Tissue strength- 20% of original at 3 weeks, 50% and 3 months, 70-80% final
- Remodelling and strengthening of collagen
- Increased stiffness of tissues and matrix more rigid
- Mechanical loading import- fibroblasts stimulated by TBF-b to differentiate into myofibroblasts
- Net collagen synthesis complete 4-5 weeks post wounding
What local and systemic factors slow wound healing?
Local factors-
wound perfusion, tissue variability, wound fluid accumulation, infection- foreign body, mechanical factors- movement
Systemic factors-
Immunology
Oncology
Systemic conditions- obesity, malnutrition, diabetes
Thermal injuries
External agents
Excessive scarring
What are the different types of open wounds?
- Surgical incision
- Laceration- combination of tissue damage and loss extending to any depth beneath the epithelium
- Abrasion- superficial loss of surface epithelium without exposure of underlying dermis and submucosa
- Degloving
- Shearing
- Puncture- minimal tissue loss- damage can occur to underlying tissues
- Burn- thermal, chemical, electrical, radiation
- Pressure sores
- Cast and bandage related sores
What are examples of closed wounds?
- Contusion (bruise)- damage occurs primarily to sub-epithelial tissues- produces a characteristic bruise
- Haematoma
- Crush injury
- Hygroma
- Ulcers- complete loss of surface epithelium with exposure and damage to underlying tissue
After open and closed what are the additional classifications of wounds?
Clean- elective surgical wounds, not entering the resp, urogenital or GI with no break in asepsis
Clean contaminated- surgical wounds involving the respiratory, urogenital or GI tracts without significant contamination or minor break-in asepsis and primary closure
Contaminated- fresh traumatic wound less than 4-6 hours old, surgical wounds involving the organ tracts with significant contamination, surgery in the presence of inflammation, major breaks in asepsis
Dirty- traumatic wounds greater than 4-6 hours, contain foreign material/significant devitalised tissue, perforation of a hollow viscus, surgery in the presence of abscessation
What history and first aid with wounds?
Initial history-
full medical history- concurrent diseases, medical treatment
When the injury occurred/when the animal was last seen to be normal
Dis the owner see the animal sustain the injury
How did it occur
Initial first aid:
apply pressure if there is a haemorrhage
clinical examination to ensure no other injuries have been missed
check cardiovascular status
sedation may be requires in LA to perform safety
Describe an initial wound assessment and what needs to be noted?
- In most wounds- appropriate to clip the areas to assess the wound fully- apply- sterile gel to the wound first
- Clip around the site of the wound
- Remove the gel gently and surgically prepare the surrounding skin with aseptic
- Lavage with sterile saline or another appropriate solution
- Location- region in the thorax, abdomen, joint, tendon/sheath
- Depth superficial
- Direction- probe
- Severity- amount of contamination
- Injury to other structures
After the wound is assessed what decisions need to be made?
Does the wound involve other structures- bones, joints, tendon sheath, cavities
Further assessment required?- X-ray, ultrasound, MRI
Sedation or GA
How should it be managed- suitable for primary closure etc
How does infection affect wounds?
How can it be reduced?
Bacteria inhibit all phases of wound healing
Time is critical
Flushing and debridement reduce the quantity of bacteria
Systemic antibiotics are important where contamination and infection is present
Tetanus- a horse can be given tetanus antitoxin
Surgical management-
Lavage- dilution
Debridement- remove dead tissue
Wound closure- primary/secondary
What is first intention wound healing?
What needs to be considered and what conditions are required?
What is second and third intention?
First- The wound is closed immediately and completely using a strict aseptic technique
Consider- suture material selection, needle, knots
Conditions- minimal bacteria contamination, devitalised tissues, no dead space, foreign bodies and blood clots removed
Second- occurs when wound cannot heal by first intention- infection, severe soft tissue damage, regular wound care required- dressing bandages, debridement
Third intention- treat as an open wound initially, allows tissue debridement
Wound then closed by primary intention
Briefly outline how wounds should be managed?
Wound protection and immobilisation
Aftercare-
antibiotics- may or may not be required
NSAIDs
± application of devices to prevent self-trauma
Patients may require rest
Skin sutures are generally removed 10-14 days post-surgery
Surgical site infections- can occur, can be sensitive
Prevention- wash hands, wear gloves, swab persistently infected
