Tissue expansion

Biology

• Mechanical creep and biological creep: connective tissue remodelling, increased collagen synthesis, dermal fibroblast activation.
• Histological changes: epidermal thinning, increased mitotic activity, dermal compaction, neovascularisation, axial vessel realignment.
• Skin gain: ~50-100% of expander surface area available as flap; less elastic recoil after inflation reaches plateau.
• Optimum: rapid early inflation generates initial gain; slower late inflation maintains tissue viability.

Indications

• Scalp: alopecia (post-burn, post-RT, post-Mohs); scalp / forehead reconstruction.
• Face: cheek / forehead / neck reconstruction (often staged with subsequent flap advancement).
• Breast: post-mastectomy reconstruction (skin / soft-tissue) prior to definitive implant.
• Paediatric: giant congenital melanocytic naevus excision; burn scar / contracture.
• Trunk and limb: scar contracture, post-Mohs / sarcoma reconstruction.
• Bald scalp following large Mohs: hair-bearing tissue acquisition.

Expander types and design

• Shape: round, rectangular, crescent, custom; chosen to fit anatomy and target advancement.
• Volume: 50 mL to 1000+ mL; oversized to allow capacity for sustained inflation.
• Port:
  • Integrated (palpable on expander surface).
  • Remote (separate subcutaneous port connected by tubing).
• Material: silicone shell; saline filling.
• Textured surface: reduces capsular contracture, improves stability — caveat re ALCL association in breast contexts.

Technique

1. Planning: assess target defect size, available donor skin, anatomical constraints, vascular supply, scar planning.
2. Stage 1 insertion:
   • Sterile field; broad-spectrum antibiotic prophylaxis.
   • Incision parallel to subsequent flap design — ideally in inconspicuous site or eventual scar line.
   • Subgaleal / submuscular / subcutaneous pocket dissection.
   • Place expander; integrated or remote port.
   • Initial inflation 10-30% capacity intraoperatively if tissue permits.
   • Layered closure; drain where indicated.
3. Inflation phase (4-12 weeks):
   • Weekly / fortnightly saline injections via port; 10-15% of capacity per inflation.
   • Monitor skin perfusion, blanching, capillary refill.
   • Final volume often exceeds nominal capacity by 50-100%.
4. Stage 2 reconstruction:
   • Remove expander.
   • Advance / rotate / transpose expanded flap to cover defect.
   • Excise lesion (if not previously done) and inset flap.
   • Layered closure; appropriate drainage.

Complications

• Infection (most common; 5-10%) — may require expander removal.
• Exposure / extrusion: tissue thinning over expander; can lead to deflation / infection.
• Haematoma / seroma.
• Capsule formation: fibrous capsule contracture (especially textured) — caveat re BIA-ALCL in breast cases.
• Implant failure: deflation, port failure.
• Bone resorption: from sustained pressure; rare cosmetic concern; usually resolves.
• Neuropraxia: from pressure on adjacent nerves.
• Cellulitis over expanded skin.
• Tissue distortion / temporary cosmetic appearance during expansion — counsel patients.
• Patient-reported burden: time commitment, transport for inflation visits, psychological impact of visible expansion.

Practical points

• Counsel about cosmetic distortion during inflation phase — particularly facial expanders.
• Time the expansion to fit treatment plan: 6-12 weeks typical.
• Paediatric giant CMN: serial expansions of staged areas; meticulous oncological surveillance.
• Post-Mohs scalp / forehead: time tissue expansion after permanent paraffin clearance of margins.
• Multidisciplinary planning: plastic surgery, dermatology, oncology, psychology.
• Photograph through each phase.
• Patient education: avoid pressure / trauma to expander; report skin colour change / pain / fever immediately.