Microsurgical Techniques

Intro & Armamentarium - Tiny Titans' Tools

• Microsurgery: Surgery under magnification (loupes/microscope) for fine structures.
  • Key uses: Free tissue transfer, replantation, nerve repair, lymphatic reconstruction.
• Magnification:
  • Loupes: 2x-8x.
  • Operating Microscope: 4x-40x; provides illumination, depth.
• Core Instruments:
  • Needle holders (e.g., Castroviejo).
  • Forceps (e.g., Jeweler's, DeBakey micro).
  • Scissors (e.g., Vannas).
  • Vessel dilators.
  • Microvascular clamps (e.g., Acland).
  • Contrast background (e.g., blue/green).
  • Fine-tip bipolar cautery.
• Microsutures:
  • Sizes: 8-0 to 12-0 (typically 9-0, 10-0).
  • Material: Nylon (common), Polypropylene.
  • Needles: Fine, tapered, 3/8 or 1/2 circle.
• Essentials:
  • Irrigation: Heparinized saline/Ringer's lactate.
  • Good ergonomics & tremor control.

⭐ For microvascular anastomosis, suture sizes 9-0 and 10-0 are most commonly used.

Vascular Choreography - Stitching Lifelines

• Vessel Prep: Gentle handling, adventitial stripping (~2mm), heparinized saline irrigation, Acland clamps.
• Anastomosis Types:
  • E-E (End-to-End): Standard, similar diameters.
  • E-S (End-to-Side): Size mismatch, bypass, flow-through.
• Suturing (Interrupted):
  • Suture: 8-0 to 12-0 Nylon. Needle: Tapered, 50-150µm.
  • Stay Sutures: 2-3 (bi-/triangulation).
  • Bites: Full thickness, equidistant, evert intima.
  • Knots: 6-10 per 1mm vessel; 2-1-1 or 3-1-1 throws.
• Patency Check: Acland "milking" test, Doppler ("whoosh").
• Avoid: Tension, torsion, kinking, backwalling, intimal trauma.

⭐ The "Acland" or "empty-and-refill" test (milking test) is a simple, reliable intraoperative method to confirm microvascular anastomosis patency by observing blood flow dynamics.

Neural Networks & Tissue Travels - Wiring & Wrapping

• Nerve Repair (Neurorrhaphy): Aim for tension-free coaptation.
  • Types: Epineurial (common), Perineurial (fascicular), Group fascicular.
  • Suture: 8-0 to 11-0 monofilament.
  • Nerve Grafts: For gaps > 2-3 cm. Donors: Sural, medial antebrachial cutaneous nerve.
  • Axonal Regeneration: ~1 mm/day. 📌 "A Millimeter A Day"
• Nerve Conduits: Short gaps (< 3 cm); e.g., vein, collagen.
• Free Tissue Transfer (Free Flaps):
  • Vascularized tissue (skin, muscle, bone) transferred & re-anastomosed.
  • Indications: Large/complex defects, avascular beds.
  • Monitoring: Clinical (color, temp, CRT), Doppler.

⭐ The radial forearm free flap is a workhorse for intraoral reconstruction due to its thin, pliable skin paddle and reliable vascular pedicle.

Flap Vigilance - Watching & Woes

• Clinical Monitoring (📌 5 C's):
  • Color: Pink (normal); Pale (arterial↓); Dusky/Blue (venous↑)
  • Capillary Refill: 1-2s; ↓/absent (arterial); brisk then absent (venous)
  • Cold/Warmth: Cool (arterial↓); Warm then cool (venous↑)
  • Consistency: Normal turgor; Doughy (venous↑)
  • Cut (Pinprick): Bright red; No blood (arterial↓); Dark (venous↑)
• Adjuncts: Doppler (handheld/implantable), Tissue pO₂ (>30 mmHg), temperature probes.
• ⚠️ Compromise:
  • Arterial: Pale, cool, no bleed.
  • Venous: Swollen, dusky, dark bleed.
  • Urgent re-exploration: <4-6 hours.

⭐ Venous thrombosis: most common cause of early free flap failure.

• Woes: Hematoma, seroma, thrombosis (A/V), kinking, infection, partial/total loss.

High‑Yield Points - ⚡ Biggest Takeaways

• Microsurgery utilizes magnification (loupes/microscope) for structures typically < 2-3 mm.
• Vessel anastomosis (end-to-end, end-to-side) is fundamental for free tissue transfer.
• The "no-touch" technique minimizes intimal trauma, preventing thrombosis.
• Suture materials are typically 8-0 to 11-0 monofilament nylon.
• Warm ischemia time is critical; prolonged duration risks flap necrosis.
• Key applications: free flaps, replantation (digits, limbs), nerve repair, lymphatic surgery.
• Common complications: vasospasm, thrombosis (arterial/venous), flap failure.