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Skin and Reconstruction > Skin grafts > Flashcards

Skin grafts Flashcards

1
Q

What are the classifications of free skin grafts based on the donor?

A

Autograft, allograft, xenograft, isograft

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2
Q

What are the classifications of graft based on thickness?

A

Full thickness (epidermis and dermis), split thickness (epidermis and part of dermis: thin, intermediate, or thick)

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3
Q

What are some examples of island grafts (or seed grafts)?

A

Punch, strip, pinch and stamp grafts

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4
Q

What is the most common donor site for graft procurement?

A

Cranial lower lateral thorax (thin skin which enhances graft survival, but also well haired which improves cosmesis)

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5
Q

What are the benefits/disadvantages of a donor site with a thicker dermis?

A

Thicker dermis may provide protection to abrasion, but may decrease graft survival initially due to greater distance for diffusion of oxygen and nutrients (lateral neck and dorsal lumbar regions have the thickest dermis)

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6
Q

What are the three most common causes of graft failure?

A

Movement, infection, separation

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7
Q

What are some methods to mitigate fluid accumulation under a graft?

A

Mesh graft and closed suction drainage

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8
Q

Why is infection detrimental to graft survival?

A

Bacterial products cause dissolution of fibrin attachments (i.e. pseudomonas and hemolytic strep produce plasmin and proteolytic enzymes that disrupt fibrin)

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9
Q

Why is it important to protect a free skin graft beyond the 14 days typically required for vascular ingrowth and engraftement?

A

Reinnervation of the graft can take several weeks. During this process there can be parasthesia or dysthesia that can result in self-trauma

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10
Q

Which types of graft result in the best hair regrowth and cosmetic appearance?

A

Full thickness sheet grafts or unexpanded mesh grafts

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11
Q

What are the characteristics of an appropriate recipient site for a free skin graft?

A

Should be vascular and free from infection, i.e. a healthy bed of granulation tissue or an acute wound surface that is vascular enough to provide granulation tissue and is free from infection and debris

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12
Q

What are generally considered poor graft recipient beds?

A

Fat, chronic/avascular granulation tissue, bone, tendon, cartilage, nerve, epithelium, irradiated surfaces

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13
Q

What are the stages of engraftement (or take)?

A
  1. Adherence
  2. Plasmatic imbibition
  3. Inosculation
  4. Vascular ingrowth
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14
Q

What are the two phases of graft adherence?

A

Phase 1: initial links between fibrin strands and collagen and elastin. Causes progressive increase in strength over first 8 hours

Phase 2: begins 72 hours after grafting. The fibrinous network is invaded by fibroblasts, leukocytes and phagocytes. Begins conversion into fibrous adhesion, which is normally complete by day 10.

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15
Q

What causes the purplish hue of a free skin graft during the first 48-72 hours after grafting?

A

Hemoglobin accumulation from plasmatic imbibition

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16
Q

At what rate does new capillary ingrowth occur during the phase of vascular ingrowth of engraftment?

A

0.5 mm/day

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17
Q

Describe the temporal changes in graft appearance

A

Initially pale
48 hours: red to dark purple due to congestion and hemoglobin accumulation
72-96 hours: reddish hue
7-8 days: red to pink if the graft has survived
Day 14: normal pale pink colour

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18
Q

What determines graft reinnervation?

A

Thickness of the graft, amount of scar tissue formation, innervation of the surrounding tissues

19
Q

Can split thickness grafts be performed in cats?

A

No because the skin of the cat is so thin

20
Q

What is the most common indication for a split thickness graft?

A

To cover a defect with extensive skin loss in the dog

21
Q

What are some hand knives that can be used to perform split thickness grafting in dogs?

A

Weck knife, Humby and Watson graft knives

22
Q

What is the ideal graft thickness for a split thickness graft in a dog?

A

0.35-0.38 mm

23
Q

What is the most commonly used dermatome?

A

Brown dermatome

24
Q

What are good donor graft sites?

A

Lateral thorax, thoracolumbar junction just lateral to dorsal midline, lateral thigh, proximolateral aspect of the forelimb.

25
Q

How long should split thickness grafts be immobilized for following surgery?

A

10-14 days

26
Q

What are the major disadvantages of split v full thickness grafts?

A

Thin/poor quality haircoat, thin dermis that may be prone to abrasion, lack sebaceous glands and may be dry and scaly.

27
Q

What are the major advantages of split v full thickness grafts?

A

Better survival (89 v 58% in one study). Proposed reasons include; less distance for nutrients to travel during imbibition, greater capillary plexus in exposed dermis compared to subdermal plexus (subcutaneous or deep vasculature) of full thickness grafts meaning more vessels available for inosculation. Also has more expansile capability.

28
Q

What are the three indications for full thickness meshed skin grafts?

A
  1. to allow drainage from exudative wound bed.
  2. to allow increased conformity to irregular surfaces (convex/concave)
  3. to allow coverage of larger wound surfaces through expansion of the graft
29
Q

What are ideal mesh expansion ratios for dogs and cats when using a mesh expansion unit?

A

3:1 to 4:1

30
Q

Is hyperbaric oxygen therapy recommended as an acute adjunctive therapy post-grafting?

A

No - there have been some reports with negative results. Additional research is required

31
Q

What are the advantages of meshed grafts (either split or full-thickness)?

A

Greater conformability, increased drainage, excellent viability (granulation tissue in meshes helps to stabilize and vascularize the graft)

32
Q

What are some disadvantages of meshed grafts (either split or full-thickness)?

A

Excessive granulation tissue may grow up and over the graft. Sparse hair growth in split thickness grafting

33
Q

What is the primary indication for a full thickness unmeshed graft?

A

To prevent contraction (should be limited to noninfected granulation beds with minimal to nil fluid production)

34
Q

What are the primary advantages of a unmeshed full thickness skin graft?

A

Cosmetic, no contraction during healing, thick and robust skin covering once healed, become moveable over subcutaneous tissues.

35
Q

What are the primary advantages of a unmeshed full thickness skin graft?

A

Decreased survival as compared to split thickness or meshed grafts

36
Q

What are the advantages of island grafts (pinch, punch, strip or stamp)?

A

Allow drainage, good conformability for irregular surfaces, easy to perform without specialized equipment, good viability, may withstand infection

37
Q

What are the disadvantages of island grafts (pinch, punch, strip or stamp)?

A

Poor cosmetic appearance, thin epithelium that may not be robust or suitable for areas that are prone to injury, excessive bleeding may float the graft out of the recipient bed (pinch and punch grafts), movement may disrupt stamp grafts that are overlaid on the surface of the granulation tissue without corresponding depressions (forming these depressions can create hemorrhage and is time consuming)

38
Q

Typically, how wide are strip-grafts?

A

5mm

39
Q

With paw pad grafting what typically lifts off the graft at around 10-14 days post-operatively?

A

A hard, darkened stratum corneum. A normal thick covering of pad skin will be restored with time.

40
Q

What are the two types of paw pad grafting that have been described?

A

Single stage (or segmental): requires harvesting paw pad tissues from other sites to fill a metacarpal or metatarsal wound.

Two-stage: use of existing viable pads on severely damaged foot (creation of new pad on stump following complete digital amputation). Pads are initially grafted to the cutaneous trunci muscle and then a pouch grafting technique is used to reapply them to the foot.

41
Q

What is a mucosal graft?

A

A free segment of mucosa removed from a donor site and placed in an area where mucosal coverage is needed.

42
Q

What are the different applications of a mucosal graft?

A

Conjunctival replacement, nasal mucosa replacement, preputial reconstruction.

43
Q

Where are mucosal grafts obtained from?

A

Either buccal or sublingual mucosa

Skin and Reconstruction (6 decks)

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