Tissue Expansion
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Direct answer
Expansion is the only reconstructive technique that creates new tissue rather than borrowing it: a silicone balloon implanted beside a defect is inflated with saline over weeks, and the overlying skin genuinely grows — through increased mitotic activity and collagen realignment, not mere stretching — to be advanced as a flap matching the missing skin in colour, texture, thickness, sensation and, on the scalp, hair. The price is two operations, weeks of visits and a visible deformity during inflation, with complications in perhaps a quarter of paediatric cases. Its strongest indications are post-burn scalp alopecia, facial resurfacing and staged breast reconstruction.
What you must remember
- Physiology is growth, not stretch: epidermis thickens through mitosis (the only layer that truly gains), dermis thins, fat atrophies, a fibrous capsule forms.
- Creep: mechanical (collagen realignment, viscoelastic lengthening under load) plus biological (new tissue from proliferation); stress relaxation lets tension fall at constant volume.
- The capsule is not the enemy: its vasculature gives the expanded flap a delay-like blood supply.
- Geometry: rectangular devices gain the most surface for a given base; a base two to three times the defect is the planning rule.
- Inflation begins two to three weeks after implantation, weekly or twice weekly to tolerance; the endpoint is discomfort or skin blanching, never a fixed volume.
- Ports integrated or remote; remote ports sit away from the shell, palpable, so misplaced injections are avoided.
- Complications in up to about a quarter of cases: exposure and extrusion (commonest), infection, deflation, pain, ischaemia.
- Relative contraindications: irradiated or heavily scarred beds, active infection, unstable burn scar, poor compliance, open malignancy.
- Breast use: two-stage expander-implant sequence after mastectomy, with autologous flaps preferred when radiotherapy has damaged the envelope.
Two balloons for a burnt scalp
An eight-year-old survives a flame burn leaving an alopec band over a quarter of the scalp. Two large rectangular expanders go in the subgaleal plane on either side of the scar, with remote ports tunneled away. Three weeks later, weekly injections begin — 30 to 50 mL at a sitting, advanced until the scalp is uncomfortably tight or the skin blanches. Over eight to ten weeks the expanders hold well beyond nominal volume, the family tolerating a misshapen head with the honest explanation that the bump is the factory where new scalp is made. At the second stage the capsules are opened, the scar excised, and the flaps advanced in opposing rotation, hair-bearing to hair-bearing over drains; expanded flaps behave like delayed flaps, so ratio rules are generous. A third of major alopecias need a second round months later; previously expanded tissue tolerates it again. The honest caveat: hair density per square centimetre falls slightly — follicles are not created — so the win is coverage where it matters, not more follicles.
Where candidates slip
First, they say skin "stretches": the examinable point is that mitotic activity increases and the epidermis thickens — growth, with creep as the mechanical complement. Second, they describe routine capsule removal — leaving or opening it is a considered decision, because its vessels are part of the delay effect. Third, they expand through unsuitable cover: unstable burn scar, irradiated skin or an infected field fails predictably, and saying so unprompted marks the trained candidate. Fourth, promising one operation when the technique costs two, plus weeks of an obvious deformity whose acceptance by child and family is itself a selection criterion. Finally, ports: injecting saline into the shell instead of the port bursts the device — hence remote ports placed unmistakably far.
Frequently asked questions
Does expanded skin stretch, or does it actually grow?
Both, but growth is the lasting part: increased epidermal mitosis thickens the epidermis permanently, while creep — viscoelastic lengthening and collagen realignment — contributes the immediate gain.
When does inflation begin, and how is the endpoint judged?
Two to three weeks after insertion, once healed; aliquots are injected weekly until the patient reports tightness or the skin blanches. Pain and blanching mean stop — and inject less next session — never chase a fixed volume.
Which expander shape gives the greatest surface gain?
Rectangular expanders convert base to surface most efficiently; round devices dome up and waste gain centrally, and the base should be two to three times the defect.
What is the commonest complication, and can it be salvaged?
Exposure or extrusion of the device, often through a thin incision line or after trauma in children. Minor exposure in a clean, expanding wound can sometimes be salvaged with antibiotics and accelerated advancement, but frank infection or major extrusion means removal and re-expansion later.
Why is the scalp the ideal site for tissue expansion?
Because it provides the only source of hair-bearing skin, the capsule and expanded flaps are robustly vascularised in the subgaleal plane, and the deformity during expansion is hidden by hair or headwear. Post-burn alopecia is its classic indication.