Surgery chapters
Skin grafts and flaps
Split-thickness and full-thickness skin grafts, how a graft takes and why it fails, and the types of flaps (random, axial, pedicled, microvascular), local flap designs, flap monitoring and the reconstructive ladder.
- A graft is moved without its blood supply and must gain a new one from the bed (imbibition, then inosculation and capillary ingrowth); a flap carries its own blood supply.
- Split-thickness grafts (epidermis plus part of the dermis) cover large areas and take easily but contract more and look worse; full-thickness grafts give better colour and texture and contract less, but only for small areas.
- Grafts fail mainly from haematoma or seroma, shear, infection (especially group A streptococcus) and a poor bed; they will not take on bare bone, tendon or cartilage, which need a flap.
On this page
Overview
Reconstructive plastic surgery replaces lost tissue to restore function and form. The two basic tools are:
- Grafts: tissue moved without its blood supply; it must be revascularised by the bed.
- Flaps: tissue moved with its own blood supply; it can survive on a poor bed and brings blood with it.
Choice depends on the wound bed, size, site, cosmetic needs and the patient.
The reconstructive ladder (toolbox)
From simplest to most complex:
- Healing by secondary intention (with dressings or negative pressure)
- Primary (direct) closure
- Delayed primary closure
- Split-thickness skin graft
- Full-thickness skin graft
- Tissue expansion
- Local flap
- Regional (pedicled) flap
- Microvascular tissue transfer (distant flap with vessels re-joined under the microscope)
Modern practice treats this as a toolbox: the surgeon chooses the method that gives the best result, not always the simplest first.
For the best cosmetic result on a clean facial laceration, the answer is primary closure with fine sutures placed along the relaxed skin tension lines, not a graft or flap.
Principles of plastic surgery
- Debride all dead tissue first.
- Good blood supply to the wound and the flap.
- Place scars along relaxed skin tension lines (Langer's lines approximately).
- Replace like with like (colour, texture, thickness, hair).
- Gentle handling of tissue, meticulous technique.
- Think of the donor site cost.
Skin grafts
Types
| Graft | What is taken | Other names |
|---|---|---|
| Split-thickness skin graft (STSG) | Epidermis plus part of the dermis (thin, intermediate or thick) | Thiersch graft, split-skin graft |
| Full-thickness skin graft (FTSG) | Epidermis plus the whole dermis (fat trimmed off) | Wolfe graft |
| Composite graft | Skin with fat or cartilage (e.g. from the ear rim) | Used for nasal ala, fingertips, eyelids |
| Other grafts | Nerve (sural nerve), tendon (palmaris longus, plantaris), bone, cartilage, fat | — |
By source:
- Autograft: from the same person (all definitive skin grafts).
- Allograft (homograft): from another human, e.g. cadaver skin; temporary cover in large burns.
- Xenograft: from another species (e.g. pig skin); temporary.
Split-thickness versus full-thickness grafts
| Feature | Split-thickness | Full-thickness |
|---|---|---|
| Dermis included | Part | All |
| Area that can be covered | Large; can be meshed to expand | Small only |
| Take | Easier (thin, less demand) | Needs an ideal bed and careful care |
| Primary contraction (on harvest) | Less | More |
| Secondary contraction (as it heals) | More | Less |
| Colour, texture, durability | Poorer; shiny, may be pigmented; less durable | Better match; more durable |
| Hair, sweat | No | May carry some |
| Donor site | Heals by itself in about 1–2 weeks from adnexal remnants; can be re-harvested | Closed directly |
| Common donor sites | Thigh (commonest), buttock (children), scalp, arm | Post-auricular, supraclavicular, upper eyelid, groin, inner arm |
| Typical uses | Large wounds, burns, temporary cover | Face, eyelids, fingers, flexor surfaces, small defects where contraction matters |
Thinner grafts take better but contract more; thicker grafts contract less and look better but take less easily. When a thicker split-skin graft is cut, the donor bed bleeds from fewer, larger points.
"Primary contraction" (immediate recoil on cutting) is greater in full-thickness grafts, but the clinically important secondary contraction during healing is greater in split-thickness grafts.
How a skin graft takes
| Stage | Time | What happens |
|---|---|---|
| Adherence | Immediately | Fibrin glues the graft to the bed |
| Plasmatic imbibition | First 48 hours | Graft soaks up plasma from the bed (nutrition by diffusion) |
| Inosculation | From about day 2–3 | Graft vessels link up with bed vessels |
| Capillary ingrowth / revascularisation | Days 4–7 onward | New vessels grow in; fibroblasts fix the graft |
A graft needs a vascular bed that can form granulation tissue: healthy granulation, muscle, fascia, fat, periosteum, paratenon or perichondrium.
Will not take on: bare cortical bone, bare tendon or cartilage (without their covering layers), heavily irradiated tissue, infected or sloughy wounds. These need a flap.
Causes of graft failure
- Haematoma or seroma under the graft (commonest): fluid lifts the graft off the bed.
- Shearing movement (poor immobilisation).
- Infection: especially group A β-haemolytic streptococcus, which can destroy a whole graft (and turn the donor site into a full-thickness wound). Pseudomonas also harms graft take.
- Poor bed: avascular, irradiated or dead tissue.
- Technical: graft upside down, too tight, too thick for the bed.
- Patient factors: smoking, malnutrition, diabetes, steroids.
How to prevent failure:
- Good haemostasis; meshing or "pie-crusting" the graft lets fluid escape.
- Tie-over (bolster) dressing or negative-pressure dressing to keep it still.
- Splint joints; elevate limbs.
- Culture the wound; delay grafting if β-haemolytic streptococcus is present.
β-haemolytic streptococcus (group A) on a wound swab is a contraindication to skin grafting until it is treated.
Meshed grafts
A split-thickness graft is passed through a mesher that cuts rows of slits, allowing it to expand (ratios from about 1:1.5 up to 1:6). Benefits: covers a larger area, lets blood and serum drain out, conforms to irregular beds. Downside: a permanent "string vest" pattern; avoid on the face and hands where possible.
Flaps
A flap is a unit of tissue moved from a donor site to a recipient site with an intact blood supply. Use a flap when:
- The bed cannot support a graft (exposed bone, tendon, joint, nerve, hardware, irradiated tissue).
- Bulk or padding is needed (pressure sores, heel).
- Better colour, texture or function is needed (face, hand).
Classification by blood supply
| Type | Blood supply | Key points |
|---|---|---|
| Random pattern flap | Subdermal plexus; no named vessel | Length to breadth about 1.5:1; longer flaps die at the tip (flap ischaemia); can be lengthened by a delay procedure |
| Axial pattern flap | A named artery running along the flap | Much longer flaps survive; e.g. forehead flap (supratrochlear), groin flap (superficial circumflex iliac), deltopectoral flap |
| Pedicled / island flap | Axial vessels kept attached as a stalk | Swung or tunnelled to the defect |
| Microvascular tissue transfer | Vessels divided and re-joined at the new site under the microscope | Any distant tissue can be moved; total loss if the anastomosis fails |
| Perforator flap | Small perforating vessels dissected out of the muscle | Less donor site damage |
The main limiting factor in designing a long random skin flap is ischaemia of its tip. The usual safe length to breadth ratio is about 1.5:1.
Classification by tissue
- Cutaneous: skin and fat.
- Fasciocutaneous: skin with deep fascia (e.g. radial forearm, anterolateral thigh).
- Myocutaneous (musculocutaneous): muscle with overlying skin (e.g. latissimus dorsi, pectoralis major, TRAM).
- Muscle only, later grafted (e.g. gastrocnemius for the knee).
- Osseous / osteocutaneous: bone with or without skin (e.g. fibula for jaw reconstruction).
- Special: jejunum for oesophageal or pharyngeal reconstruction, omentum.
Common named flaps
| Flap | Main vessel | Typical use |
|---|---|---|
| Pectoralis major (myocutaneous) | Thoracoacromial artery (pectoral branch) | Head and neck reconstruction after cancer surgery |
| Latissimus dorsi | Thoracodorsal artery | Breast reconstruction, chest wall, scalp, limb cover |
| TRAM (transverse rectus abdominis) | Superior epigastric (pedicled) or deep inferior epigastric (microvascular) | Breast reconstruction |
| Radial forearm | Radial artery | Intraoral and head and neck defects |
| Fibula | Peroneal artery | Mandible reconstruction |
| Gastrocnemius | Sural arteries | Knee and upper tibia cover |
| Forehead (paramedian) | Supratrochlear artery | Nasal reconstruction |
Local flaps (by movement)
| Flap | How it moves | Typical use |
|---|---|---|
| Advancement | Slides straight forward | Flexor surfaces; may need Burow's triangles excised at the base |
| V-Y advancement | V-shaped flap advanced and closed as a Y | Fingertip injuries, extremities |
| Rotation | Semicircular flap rotated about a pivot | Convex surfaces (scalp, cheek, buttock pressure sores) |
| Transposition | Moved sideways over intact skin; donor site closed or grafted | Many sites |
| Rhomboid (Limberg) | Parallelogram-shaped transposition flap | Cheek, temple, back, pilonidal sinus |
| Bilobed | Two lobes: the second closes the first's donor site | Nose, convex surfaces |
| Bipedicle | Attached at both ends ("bucket handle") | Lower eyelid |
| Z-plasty | Two triangular flaps swapped | Lengthening a contracted scar band, changing scar direction |
| W-plasty, multiple Y-V plasty | Series of small flaps | Breaking up straight scars; release of burn contractures |
Z-plasty = Zig-Zag to lengthen: swapping two triangles turns a tight straight band into a longer, zig-zag line across the contracture.
Monitoring a flap
Check colour, temperature, turgor and capillary refill frequently (hand-held Doppler for microvascular flaps).
| Feature | Arterial insufficiency | Venous congestion |
|---|---|---|
| Colour | Pale, white | Blue, purple, dusky |
| Temperature | Cold | Warm at first |
| Turgor | Flaccid | Swollen, tense |
| Capillary refill | Slow or absent | Brisk |
| Pinprick bleeding | Little or none | Dark blood, fast |
Treatment of a failing flap: release tight sutures or dressings, reposition to relieve pedicle kinking or tension, drain haematoma, urgent re-exploration of a microvascular anastomosis; medicinal leeches as a last resort for venous congestion.
Causes of flap failure
- Poor flap design or anatomy (inadequate blood supply from the start).
- Too much tension or kinking of the pedicle.
- Tight dressings around the pedicle; haematoma.
- Infection, sepsis.
- Failure of microvascular anastomosis (thrombosis).
- Smoking, hypotension, hypothermia, vasoconstrictors.
A flap that is blue, swollen and bleeds dark blood briskly has venous trouble, not arterial. A pale, cold flap with no refill has lost its arterial inflow.
Other reconstructive tools
- Tissue expansion: a silicone balloon placed under nearby skin is gradually filled with saline through a port, stretching the skin for later use. Good colour and texture match (e.g. scalp after burn alopecia, giant naevi). Problems: many visits, cost, infection and extrusion. Never under irradiated skin.
- Negative-pressure wound therapy (vacuum-assisted closure): foam dressing under suction removes exudate, reduces oedema and promotes granulation; used to prepare wounds or secure grafts.
- Skin substitutes and dermal templates (e.g. Integra): artificial dermis later covered with a thin split-skin graft.
- Fat grafting (lipofilling): small volumes of fat injected to fill contour defects and scars.
Expect: definition of graft versus flap, split-thickness versus full-thickness grafts (donor sites, contraction, cosmetic result, uses), graft take by imbibition then inosculation, haematoma as the commonest cause of graft failure, β-haemolytic streptococcus as a contraindication to grafting, beds that will not take a graft, meshing, the 1.5:1 ratio and tip ischaemia of random flaps, axial and myocutaneous flaps and their vessels (pectoralis major on the thoracoacromial artery), local flap types including Z-plasty for contractures, signs of arterial versus venous flap failure, and primary closure for the best cosmetic result on the face.
Quick revision
- Graft: no blood supply. Flap: own blood supply.
- Take: imbibition (48 h) → inosculation → capillary ingrowth.
- Failure: haematoma/seroma (commonest), shear, infection (group A strep), poor bed.
- No graft on bare bone, tendon or cartilage: use a flap.
- STSG: large areas, easy take, more secondary contraction; donor thigh.
- FTSG: small areas, face/eyelids/fingers, less contraction; donor post-auricular, supraclavicular, groin.
- Random flap 1.5:1; axial flap on a named artery.
- Z-plasty lengthens a scar band.
- Pale cold flap = arterial; blue swollen flap = venous.
Written by The House Job from standard surgical references (Bailey & Love).
FAQ
What is the difference between a skin graft and a flap?
A graft is detached completely and depends on the wound bed to regain a blood supply, while a flap keeps or brings its own blood vessels and can survive on a poor bed.
Why do split-thickness skin grafts contract more than full-thickness grafts?
They carry less dermis, and it is the dermis that resists the contraction of the healing wound, so thinner grafts shrink more over time.
Why does a skin graft fail?
Most often because blood or serum collects under it and stops it sticking to the bed. Movement, infection (especially group A streptococcus) and a poorly vascularised bed are the other main causes.
When is a flap needed instead of a graft?
When the bed cannot nourish a graft, such as bare bone, tendon, cartilage, joints, metalwork or irradiated tissue, or when bulk, padding or a better cosmetic match is required.