Summary

A flap is a unit of tissue that is transferred from one site (donor) to another (recipient) while retaining its own blood supply. This distinguishes flaps from skin grafts, which rely on revascularisation from the wound bed. Flaps are used when the wound bed is avascular (exposed bone, tendon, implant), when bulk or padding is required, or when a high-quality tissue match is needed. Flaps are classified by their blood supply (Random vs Axial vs Free), tissue composition (Cutaneous, Fasciocutaneous, Muscle, Bone), and method of transfer (Local, Regional, Distant, Free). Free flaps require microsurgical anastomosis of vessels. Post-operative flap monitoring is critical for early detection of vascular compromise. [1,2]

Clinical Pearls

Reconstructive Ladder (Traditional): Secondary Intention → Primary Closure → Skin Graft → Local Flap → Regional Flap → Distant Flap → Free Flap. Simple before complex.

Reconstructive Elevator (Modern): Choose the best option for the defect, not necessarily the simplest. Sometimes a free flap is the best first choice.

Free Flap = Time-Critical Monitoring: Flap checks (colour, temperature, capillary refill, Doppler) every 1-2 hours in the first 24-48 hours. Early detection of vascular compromise = salvage possible.

Venous Congestion is More Common (and Salvageable): Dark, congested flap with rapid cap refill and dark blood oozing = venous outflow problem. Return to theatre urgently.

Common Indications

By Blood Supply

By Tissue Composition

By Method of Transfer

Traditional Reconstructive Ladder

                 FREE FLAP
                    ↑
              DISTANT FLAP
                    ↑
              REGIONAL FLAP
                    ↑
                LOCAL FLAP
                    ↑
                SKIN GRAFT
                    ↑
             PRIMARY CLOSURE
                    ↑
           SECONDARY INTENTION

• Principle: Start with the simplest option and escalate if needed.

Reconstructive Elevator (Modern Concept)

• Principle: Choose the best option for the defect and patient, not necessarily the simplest.
• Example: A large heel defect with exposed calcaneus may be best served by a free flap directly, rather than attempting and failing with simpler options.

Patient Factors

Recipient Site

• Adequacy of Recipient Vessels (For free flap): Often CT Angio or clinical assessment.
• Wound Bed: Debride to healthy tissue.

Donor Site

• Donor Site Morbidity: Consider functional and cosmetic impact.
• Vessel Assessment: Allen's Test for Radial Forearm.

Critical for Free Flaps (First 48-72 hours)

Frequency of Monitoring

• Hours 0-24: Every 1-2 hours.
• Hours 24-72: Every 2-4 hours.
• Days 3-7: 4-6 hourly (less frequent).

Adjuncts

• Implantable Doppler: Placed around anastomosis. Audible signal for continuous monitoring.
• LICOX / Tissue Oximetry: Measures tissue oxygen saturation.

Types of Vascular Compromise

Management of Compromised Flap

1. Clinical Assessment: Confirm vascular compromise. Check patient factors (BP, Hct, Temp).
2. Remove Dressings: Rule out external compression.
3. Urgent Theatre: Re-exploration. Identify and correct cause (Thrombus → Thrombectomy, Reanastomosis).
4. Time-Sensitive: Salvage rate decreases with delay. Best outcomes if explored within 6 hours.
5. Leeches: May be used for venous congestion as temporising measure (Hirudo medicinalis). Provide antibiotic cover.

Key Guidelines

What is a Flap?

A flap is a piece of tissue (skin, muscle, or bone) that is moved from one part of your body to another to repair a wound or defect. Unlike a skin graft, a flap carries its own blood supply, so it can cover areas where a graft would not survive, like exposed bone.

Why do I need a flap?

Your wound needs healthy tissue with a good blood supply to heal. The area cannot be closed simply and a graft cannot be used, so we need to bring tissue from another part of your body with its own blood vessels.

How is it done?

For a "free flap," we take the tissue, along with its blood vessels, from the donor site. We then connect (anastomose) these tiny vessels to blood vessels at the wound site using a microscope (microsurgery).

What is the recovery like?

You will be closely monitored after surgery because we need to check the flap has good blood supply. You may stay in bed initially to avoid disturbing the flap. The donor site will also need to heal.

Common Exam Questions

1. Definition: "What is the difference between a flap and a graft?"
   • Answer: A flap retains its own blood supply; a graft relies on revascularisation from the recipient bed.
2. Reconstructive Ladder: "Describe the Reconstructive Ladder."
   • Answer: Secondary Intention → Primary Closure → Skin Graft → Local Flap → Regional Flap → Distant Flap → Free Flap.
3. Flap Monitoring: "Signs of venous congestion in a flap?"
   • Answer: Purple/Blue colour, Brisk capillary refill (less than 1 sec), Tense/Swollen, Dark blood on scratch test.
4. Breast Reconstruction: "What is a DIEP flap?"
   • Answer: Deep Inferior Epigastric Perforator Flap – Free flap using abdominal skin and fat with perforating vessels, sparing the rectus abdominis muscle. Used for breast reconstruction.

Viva Points

• Free Flap Monitoring Protocol: Describe hourly checks for colour, temp, cap refill, Doppler.
• BOAST 4 Timings: Soft tissue coverage within 72 hours for open fractures.

Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.