Principles of Plastic Surgery and Surgical Techniques
What this domain tests
Technique judged as a set of principles: tissue handling, tension-free closure, geometry of rearrangement, suture choice, and safe local anaesthesia. Stems frequently ask you to choose the correct flap geometry or to spot a technical error.
Core principles
- Replace like with like; follow the reconstructive ladder but do not climb it for its own sake - a free flap may be the simplest single-stage answer.
- Incise along RSTL, cross them at right angles where possible, and place scars in aesthetic subunit borders.
- Handle tissue with skin hooks, keep tissues moist, achieve meticulous haemostasis, and close with minimal tension; undermining in the correct plane distributes tension.
Flap geometry and lengthening
- Transposition moves tissue over a pivot point; a Burow triangle or back-cut closes the secondary defect.
- Rotation redistributes adjacent tissue; a rotation flap needs a back-cut or Burow triangle to avoid a standing cone.
- Advancement (V-Y, island) moves tissue in a straight line.
- Z-plasty: each limb equals the central limb. A 30-degree Z lengthens by about 25%, 45 degrees by 50%, 60 degrees by 75%. Larger angles gain length but produce more tension and dog-ears. Multiple small Z-plasties (five-flap) give better contour on long bands.
- Rhomboid (Limberg) flap uses 60/120-degree angles; the bilobed flap uses two lobes of roughly 45–50 degrees each.
Sutures and local anaesthesia
- Monofilament sutures carry less infection risk; braided sutures handle better but harbour bacteria.
- Absorbable: polyglactin, poliglecaprone, polydioxanone. Non-absorbable: nylon, polypropylene, silk.
- Lidocaine maximum 4.5 mg/kg plain and 7 mg/kg with adrenaline; bupivacaine 2–3 mg/kg. Tumescent dilute lidocaine permits higher totals but demands weight-based calculation.
- Upper-limb tourniquet 250 mmHg or 100 mmHg above systolic, released by 2 hours.
Worked example
A 3 cm burn band crosses the antecubital fossa. A single 60-degree Z-plasty lengthens by 75% of the central limb - 2.25 cm gained - but each limb must also be 3 cm, which may not fit the available skin and produces bulky dog-ears in a visible area. Reasoning: if the surrounding skin cannot accommodate 3 cm limbs without tension, use three smaller 60-degree Z-plasties along the band, achieving the same lengthening with better contour and less tension per flap.
Traps
- Believing a Z-plasty adds tissue; it only redistributes it.
- Constructing limbs unequal to the central limb.
- Cutting perpendicular to RSTL for a cosmetic excision.
- Exceeding lidocaine limits by ignoring adrenaline-containing solutions.
- Choosing a complex flap where a graft or secondary-intention healing would serve better.