Principles of Skin Grafts and Flaps

Principles of Skin Grafts and Flaps

CSA Espina, MD, DPBO

INTRODUCTION

The SKIN: a protective barrier

preventing internal tissues from exposure to trauma, radiation, temperature changes, and infection

thermoregulation, through sweating and vasoconstriction/vasodilatation

controls insensible fluid loss

Restoration of an intact barrier is of critical importance following wounding

Use of skin grafts and flaps provides: – accelerated healing of burns and other wounds– reduction of scar contracture– enhancement of cosmesis– reduction of insensible fluid loss– protection from bacterial invasion

INTRODUCTION

Principles of skin grafts and flaps

Simple primary closure– The most ideal approach to wound closure

Wounds too large to allow closure without tension results in poor scar formation– Tissue transplantation

Free tissues or GRAFTSTissues with their own blood supply

or FLAPS

GRAFTS

Grafts

General considerations– Potential healing abilities of the patient

Age – younger patients have better “take” General health – e.g., diabetics, immunocompromised

patients Nutrition

– Recipient bed Vascularity Contamination Contact between graft and bed – using bolus and

pressure dressings to prevent hematoma Nature of tissue loss

Grafts

Classification– According to biologic relationships

Autogenous grafts or autografts -

comes from the same individualHeterogenous – comes from sources

other than the patient himself

Grafts

– According to componentsSimple – includes only one component

like fascia graft, mucosa graft, etcCompound – includes more than one

component e.g., osseomyocutaneous (skin+bone+muscle) flaps or myocutaneous (skin+muscle) grafts

Full-thickness skin graft (FTSG)– Entire thickness of the dermis is included

Partial or split-thickness skin graft (STSG)– Less than the entire thickness of the dermis is included– Split-thickness skin grafts are further categorized based on

the thickness of graft harvested : Thin (0.005-0.012 inches), Intermediate (0.012-0.018 inches), or Thick (0.018-0.030 inches)

GRAFT SELECTION

Grafts

Advantages and disadvantages of

STSG vs FTSG:

1. Split thickness graft has better “take” under less optimal conditions

2. Full thickness graft contracts less and so remains eventually at its’ original size

Full-Thickness Skin Grafts (FTSG)

Ideal for visible areas of the face that are inaccessible to local flaps or when local flaps are not indicated.

Advantages:– retain more of the characteristics of normal skin

including color, texture, and thickness – undergo less contraction while healing– in children, are more likely to grow with the

individual

Full-Thickness Skin Grafts (FTSG)

Disadvantages: limited to relatively small, uncontaminated,

well-vascularized wounds do not have as wide a range of application as

split-thickness grafts donor sites must be closed primarily or, more

rarely, resurfaced with a split-thickness graft from another site

Full-Thickness Skin Graft (FTSG)

Two months post-op

Six months post-op

Split-Thickness Skin Grafts (STSG)

Uses:– resurface large wounds– line cavities– resurface mucosal deficits– close donor sites of flaps– resurface muscle flaps – for temporary closure of wounds created by the

removal of lesions that require pathologic examination prior to definitive reconstruction


Advantages:– can tolerate less ideal conditions for

survival and have a much broader range of application

– donor sites heal spontaneously with cells supplied by the remaining epidermal appendages

– donor sites may be re-harvested once healing is complete

Disadvantages:– more fragile– contract more during healing– do not grow with the individual– tend to be smoother and shinier than normal skin – they tend to be abnormally pigmented – when used to resurface large burns of the face, split-

thickness grafts may produce an undesirable mask-like appearance

– wound created at the donor site from which the graft is harvested is often more painful than the recipient site to which the graft is applied


DONOR SITE SELECTION

Selection of the donor site is usually based on the features wanted at the recipient site– more important in FTSG, because more of the

characteristics of the donor site skin will be retained by the grafted material in its new location.

Thickness, texture, pigmentation, and presence or absence of hair should be matched as closely as possible.


When grafting in children, consider that donor sites such as the groin, axillae, thigh, and chest will grow hair at puberty, and this hair growth may be undesirable at the new location.

Donor sites for full-thickness grafts also are chosen to be inconspicuous and easily closed primarily.

Full-thickness grafts may be harvested from– upper eyelid– nasolabial fold– pre- and postauricular regions– supraclavicular fossa


Split-thickness skin grafts may be harvested from any surface of the body, but sites should be chosen that are easily concealed in recreational clothing

Common sites include – upper anterior and lateral thigh– buttocks – scalp – upper inner arm


WOUND PREPARATION

The most critical component of successful skin grafting is preparation of the recipient site.

Physiologic conditions must be optimized to accept and nourish the graft.

Skin grafts will not survive on tissue without blood supply.

Wounds secondary to irradiation have a poor blood supply and are unlikely to support a graft.

Patients with wounds resulting from venous stasis or arterial insufficiency need to have the underlying condition treated prior to grafting to increase the likelihood of graft survival.

The wound also must be free of necrotic tissue and relatively uncontaminated by bacteria.

WOUND PREPARATION

Bacterial counts greater than 100,000 per square centimeter are associated with a high likelihood of graft failure.

To achieve an adequate wound bed, debridement, dressing changes, and topical or systemic antibiotics may be indicated prior to grafting.

WOUND PREPARATION

GRAFT SURVIVAL AND HEALING

Initial adherence:– initial adherence to the wound bed via a thin

fibrin network that temporarily anchors the graft until definitive circulation and connective tissue connections are established.

– begins immediately and is probably at its maximum by 8 hours postgrafting.


Plastic imbibition: – The period of time between grafting and revascularization of the

graft.– The graft imbibes wound exudate by capillary action through the

spongelike structure of the graft dermis and through the dermal blood vessels.

– This prevents graft desiccation, maintains graft vessel patency, and provides nourishment for the graft.

– This process is entirely responsible for graft survival for 2-3 days until circulation is reestablished.

– During this time, the graft typically becomes edematous and increases in weight by 30-50%.

Revascularization:– begins 2-3 days postgrafting– Theories

Inosculation is the establishment of direct anastomoses between graft and recipient blood vessels.

vascular ingrowth of recipient bed vessels into the graft along the channels of previous graft vessels

random new vascular ingrowth of recipient bed vessels into the graft without regard for previous graft vessels.

– full circulation to the graft is restored by 6-7 days postgrafting.


Without initial adherence, plasmatic imbibition, and revascularization,

the graft will not survive.


Wound contraction:– may produce serious functional and cosmetic problems

ectropion, retraction of the nasal ala, or distortion of the vermilion border.

– Contraction probably begins shortly after initial wounding and progresses slowly for 6-18 months following skin grafting.

– The wound bed is the locus of the contractile forces, and

the myofibroblasts in the wound bed is believed to be responsible for this contraction.


Reinnervation: – occurs from the recipient bed and the periphery along the empty

neurolemmal sheaths of the graft– sensibility returns to the periphery of the graft and proceeds

centrally– usually begins during the first month but is not complete for

several years following grafting– pain is usually the first perceived sensation followed later by

touch, heat, and cold– STSGs are reinnervated more quickly, but full-thickness grafts

are reinnervated more completely– reinnervation is always incomplete, and some degree of

derangement is permanent– usually the patient develops protective sensation but not normal

perception


Pigmentation: – returns gradually to full-thickness skin grafts, and they

maintain a pigment similar to the donor site much more predictably than split-thickness grafts.

– STSGs may remain pale or white or may become hyperpigmented with exposure to sunlight.

– it is generally recommended that the graft be protected from direct sunlight for at least 6 months after grafting or even longer.


GRAFT FAILURE

Poor graft contact or adherence to the recipient bed – most common reason for skin graft failure– Hematoma beneath the graft or seroma formation – Movement of the graft, or shear forces

Poor recipient site – The wound may have poor vascularity– surface contamination may have been too great to allow graft

survival. Technical error

– Applying the graft upside down – Applying excess pressure– Stretching the graft too tightly– traumatic handling of the graft

Differences of GRAFTS vs FLAPS

GRAFTS: Limited to transplantation of skin Depends on recipient site for nutrition Cosmetic – may discolor or contract Less adaptable to weight bearing Less able to survive on a bed with questionable

nutrition Requires pressure dressing Cannot bridge defects

Differences of FLAPS vs GRAFTS

FLAPS: Can carry other tissues Has own blood supply Better color take, less likely to contract More adaptable to weight bearing Can be used on a bed with questionable nutrition Requires no pressure dressing Can bridge defect

FLAPS

Flaps

Local and regional skin flaps provide the foundation for reconstructive surgery of the face.

Advantages:– Enable rapid reconstruction – Good color and texture match– Has a reliable and adequate blood supply

Uses – To reconstruct a large primary defect

Leaves a defect in the donor area which is closed primarily or with a skin graft

– To carry other structures such as bone

Flaps

Flaps

Classification– Based on distance in relation to the defect

Local flap– Raised from tissue immediately adjacent to or

very close to the primary defect

Distant flaps– Tissues moved at a distance from the primary

defect

Flaps

Classification– Based on composition

Simple– Skin and some subcutaneous tissue

Compound – Carries another tissue such as bone and

cartilage

Flaps

– Based on configuration

(ie, bilobed, rhombic, pinwheel)

Flaps

Classification– Based on blood supply

Random pattern flap– derives its nutrition from the dermal-subdermal

plexusAxial pattern flap

– With anatomically recognized arteriovenous circulation that follows the long axis of the flap and gives off branches to the dermal-subdermal plexus

– supplied by a named artery and vein

Flaps

Classification– Based on blood supply

Microvascular free flap– Taken free from other parts of the body

preserving its blood supply, and anastomosed to the available blood supply in the recipient area

LOCAL FLAPS

LOCAL FLAPS: ANATOMY AND PHYSIOLOGY

The microcirculatory system of the skin is composed of1. superficial plexus in the superficial dermal

papillae in the papillary dermis. supplies the more metabolically active epidermis by

means of diffusion

2. deep vascular plexus at the junction of the subcutaneous fat and reticular dermis

Physiologic factors affecting flap survival:1. blood supply to the flap through its base

2. formation of new vascular channels between the flap and the recipient bed

3. perfusion pressure of the supplying blood vessels


Neovascularization of the flap usually occurs 3-7 days after transfer.

– This vascularization occurs through 2 processes:

1. Direct ingrowth

2. Inosculationrefers to “anastomosing” of surrounding recipient capillaries into preexisting vessels in the flap.


REGIONAL FLAPS

As the distance of required flap transposition increases, the incorporation of a defined blood supply becomes critical.

Classified as axial, however most flaps have random pattern at their distal ends

Utilized to cover large defects which require bulk

Regional Flaps

Pectoralis Major Myocutaneous Flap (PMMF)– Major and most commonly used myocutaneous-

pedicled tissue transfer in head and neck reconstruction

– Based upon the pectoral branch of the thoracoacromial artery off the second portion of the axillary artery

– Able to handle 90% of virtually all head and neck defects that require a significant amount of soft tissue

Regional Flaps

PMMF– Advantages:

More durable blood supply Defect at the donor site can be closed primarily Provides tissue bulk to cover large defects

Regional Flaps

PMMF

PMMF

PMMF

Deltopectoral Flap (DP Flap)– Full thickness fasciocutaneous flap (including

the fascia of the pectoral muscles)– Medially based anterior chest wall skin without

muscle– Blood supply: 1st through 4th perforator

branches of the internal mammary artery– Used for large surface covering rather than thick

soft tissue replacement

Regional Flaps

DP Flap

Trapezius Flap – Utilizes the trapezius muscle with its overlying

skin– Blood supply: transverse cervical artery– Patient must be repositioned during harvesting of

the flap

Regional Flaps

Trapezius Flap

Trapezius Flap

Trapezius Flap

Trapezius Flap

Latissimus Dorsi Flap– another reliable and versatile flap– may be transferred as a muscle flap, a

myocutaneous flap, or even as a composite osteomyocutaneous cutaneous flap when harvested with underlying serratus muscle and rib

– can also be used as a free flap

Regional Flaps

Latissimus Dorsi Flap– The latissimus dorsi muscle is supplied by 2

separate vascular systems. – The dominant blood supply arises from the

thoracodorsal artery, which is the terminal branch of the subscapular artery.

– It also has a secondary blood supply, which arises from segmental perforating branches off of the intercostal and lumbar arteries.

Regional Flaps

Sternocleidomastoid Flap (SCM Flap)– Used to cover small defects in the head and

neck– Seldom used today because of

1. Limited tissue

2. Unreliable blood supply

3. Carries risk of nodal metastasis

Regional Flaps

Forehead Flap– A myocutaneous flap– Blood supply:

Superficial temporal artery Temporal artery Posterior auricular artery

– Versatile flap however, cosmetic problems may arise at the donor site especially for younger patients

Regional Flaps

Incision parallel to direction of hair follicle reduces likelihood of alopecia.

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Principles of Skin Grafts and Flaps