Reconstructive Surgery (Flaps, Grafts, Microsurgery)
What this domain tests
Selection of graft versus flap and pedicled versus free tissue transfer, plus microsurgical physiology and failure management. Stems usually describe a defect and a bed - the bed determines the answer.
Grafts
- Split-thickness grafts (0.2–0.3 mm) take on muscle, periosteum, perichondrium, paratenon and healthy granulation; they fail on bare bone, bare tendon without paratenon, bare cartilage and infected beds.
- Survival sequence: plasmatic imbibition (first 24–48 hours), inosculation, then true revascularisation by day 4–7.
- Full-thickness grafts contract less secondarily, match colour better, and are reserved for small defects such as the face and hands.
- Failure causes: haematoma, seroma, shear, infection (beta-haemolytic streptococcus), and inadequate bed.
Flaps
- Classification by blood supply: random versus axial. Mathes–Nahai muscle types I–V: type III has two dominant pedicles (rectus abdominis, gluteus maximus), type V has one dominant plus segmental pedicles (latissimus dorsi, pectoralis major). Cormack–Lamberty classifies fasciocutaneous flaps as A–D.
- Perforator flaps (ALT, DIEP, SCIP) spare muscle; musculocutaneous flaps carry bulk and reliable perforators.
- Bone flaps: fibula (up to 25 cm, peroneal artery, requires adequate run-off), scapula, iliac crest, radial forearm.
Microsurgery
- Arterial thrombosis typically presents within 24 hours; venous thrombosis may present up to a week later with a congested, purple flap and brisk dark bleeding.
- Monitoring: clinical colour and capillary refill, handheld or implantable Doppler, near-infrared spectroscopy, microdialysis.
- Salvage is highest with re-exploration within a few hours; reported salvage rates are around 50–70%.
- Manage vasospasm with warm room, adequate hydration, topical papaverine or lidocaine; reserve systemic anticoagulation for specific indications.
Worked example
After resection, a 9 × 6 cm scalp defect exposes bare skull without periosteum. Reasoning: a skin graft cannot vascularise on bare cortical bone, so the ladder starts higher. Options are burring the outer table to diploe to create a granulating bed for a split graft (small defects, unfit patients) or a free flap - ALT or radial forearm - for a defect of this size, providing durable single-stage cover that tolerates radiotherapy.
Traps
- Calling a full-thickness skin graft a flap.
- Grafting onto bare tendon without paratenon.
- Attributing a pale, cool flap to venous occlusion (venous shows congestion; arterial shows pallor and slow refill).
- Planning a fibula before confirming three-vessel run-off in the leg.
- Leaving a congested flap to "settle" instead of returning to theatre.