# Microvascular Surgery Fundamentals for OMFS

## Introduction

Microvascular free tissue transfer has revolutionized reconstructive surgery in the head and neck. The ability to transfer vascularized bone, soft tissue, and skin from distant donor sites to complex maxillofacial defects has dramatically improved functional and aesthetic outcomes. Proficiency in microvascular technique is an essential skill for the contemporary OMFS surgeon involved in ablative and reconstructive surgery.

## Principles of Microvascular Surgery

### Fundamentals

Free tissue transfer involves harvesting a composite tissue flap with its vascular pedicle, transferring it to a distant recipient site, and restoring blood flow via microvascular anastomosis. Success depends on meticulous surgical technique, appropriate vessel selection, and vigilant postoperative monitoring. Overall free flap success rates in experienced centers exceed 95%.

### Essential Equipment

The operating microscope or surgical loupes (3.5-6x magnification minimum, with a microscope preferred for vessels under 2 mm) is the primary visualization tool. A microvascular instrument set includes jeweler's forceps, microscissors, vessel dilators, approximating clamps, and background material. Microsutures of 8-0 to 10-0 nylon on tapered needles are used. Microvascular coupling devices provide mechanical anastomosis for venous connections. Irrigating solutions consist of heparinized saline at 100 units per mL.

## Microvascular Anastomosis Techniques

### End-to-End Anastomosis

This is the standard technique when donor and recipient vessels are of similar caliber. The vessel ends are prepared by removing adventitia and irrigating with heparinized saline, ensuring clean cuts without intimal damage. An approximating clamp is placed and background material applied. Two stay sutures are positioned 120 to 180 degrees apart, and the front wall is completed with evenly spaced interrupted sutures. The clamp is rotated 180 degrees and the back wall completed. Clamps are removed (venous first, then arterial) and the anastomosis is observed for patency and leaks. Gentle dilation of vessel ends with vessel dilators is performed prior to anastomosis. Tension, twisting, and kinking of the pedicle must be avoided.

### End-to-Side Anastomosis

This technique is used when the recipient vessel caliber is much larger than the donor or when preservation of antegrade flow in the recipient vessel is important. An arteriotomy is created in the recipient vessel wall matching the donor vessel diameter. It is commonly used when anastomosing to the external carotid or internal jugular vein.

### Mechanical Coupling Device

The mechanical coupling device is a ring-pin device that everts the vessel walls for rapid anastomosis. It reduces anastomosis time significantly and is most commonly used for venous anastomosis, less commonly for arteries. It requires vessels of appropriate size and compliance.

![Intraoperative photograph showing microvascular arterial anastomosis under the operating microscope using 9-0 nylon sutures](/images/residency/omfs/microvascular-anastomosis.jpg)

## Recipient Vessels in the Head and Neck

### Arterial Options

The facial artery is the most commonly used recipient artery due to its reliability, accessibility, and appropriate caliber. The superior thyroid artery is a good alternative with consistent anatomy. The lingual artery is useful for floor-of-mouth reconstruction. The external carotid artery (end-to-side) is employed for large-caliber pedicles or when branch vessels are unavailable.

### Venous Options

The facial vein or common facial vein is the first choice. The internal jugular vein (end-to-side) provides reliable, high-flow drainage. The external jugular vein is useful but may contain valves. The retromandibular vein is another option. Two venous anastomoses may improve venous drainage and reduce congestion.

## Common Free Flaps in OMFS

| Flap | Type | Pedicle | Primary Use in OMFS | Key Advantage |
|---|---|---|---|---|
| Fibula | Osteocutaneous | Peroneal artery + venae comitantes | Mandibular reconstruction | Multiple osteotomies, implant placement |
| Radial forearm (RFFF) | Fasciocutaneous | Radial artery + cephalic vein | Tongue, floor of mouth, buccal | Thin, pliable, long pedicle |
| Anterolateral thigh (ALT) | Fasciocutaneous/myocutaneous | Descending branch LCFA | Large soft-tissue defects | Large volume, primary donor closure |
| Scapula | Osteocutaneous | Circumflex scapular artery | Maxillary/midface reconstruction | Bone + large soft-tissue paddle |

### Fibula Free Flap

The fibula free flap provides vascularized bone for mandibular reconstruction, with the peroneal artery and venae comitantes as the pedicle. It allows multiple osteotomies and dental implant placement.

### Radial Forearm Free Flap (RFFF)

The RFFF is a thin, pliable fasciocutaneous flap ideal for intraoral soft-tissue reconstruction. Its pedicle consists of the radial artery and cephalic vein or venae comitantes. It is excellent for tongue, floor of mouth, and buccal mucosal defects. Donor site morbidity includes the need for a skin graft and potential radial bone fracture if bone is harvested.

### Anterolateral Thigh Flap (ALT)

The ALT is a versatile fasciocutaneous or myocutaneous flap with the descending branch of the lateral circumflex femoral artery as its pedicle. It provides larger soft-tissue volume than the RFFF, and the donor site can often be closed primarily. It is ideal for large soft-tissue defects of the head and neck.

### Scapula Free Flap

The scapula free flap provides bone from the lateral scapular border and a large soft-tissue paddle. The pedicle is the circumflex scapular artery. It is useful for composite maxillary and midface reconstruction.

![Diagram illustrating common recipient vessels in the neck for microvascular free flap anastomosis](/images/residency/omfs/recipient-vessels-neck.jpg)

## Postoperative Flap Monitoring

### Clinical Monitoring

Hourly assessments are performed for the first 48 to 72 hours by trained nursing staff. Parameters include skin paddle color (pink versus pale versus dusky), capillary refill (1 to 2 seconds is normal), turgor, and temperature. The pin-prick test is useful: bright red bleeding indicates arterial inflow, while dark rapid bleeding suggests venous congestion.

### Adjunctive Monitoring

An implantable Doppler probe placed on the pedicle artery or vein provides a continuous audible signal. An external handheld Doppler confirms flow at marked skin paddle locations. Near-infrared spectroscopy monitors tissue oxygenation. Loss of Doppler signal mandates immediate surgical exploration.

### Flap Compromise

Arterial insufficiency presents as a pale, cool flap with absent capillary refill and no Doppler signal. Venous congestion presents as a dusky or purple, swollen, tense flap with rapid dark bleeding on pin-prick and brisk capillary refill. Venous thrombosis is the most common cause of flap failure. The salvage rate decreases significantly after 6 to 8 hours of ischemia, making early re-exploration critical.

![Clinical photograph demonstrating assessment of a skin paddle for color, capillary refill, and turgor during postoperative free flap monitoring](/images/residency/omfs/flap-monitoring.jpg)

## Clinical Pearls

Microvascular success depends on atraumatic vessel handling, meticulous technique, and tension-free anastomosis. Two venous anastomoses improve drainage reliability and reduce venous congestion risk. The first 48 to 72 hours are the critical window for flap monitoring, and early exploration for compromise is essential. Venous thrombosis is more common than arterial and accounts for the majority of flap failures. A structured flap monitoring protocol with trained staff is indispensable for any microvascular program.

## References

1. Wei FC, Mardini S. *Flaps and Reconstructive Surgery*. 2nd ed. Elsevier; 2017.
2. Bui DT, Cordeiro PG, Hu QY, et al. Free flap reexploration: indications, treatment, and outcomes in 1193 free flaps. *Plast Reconstr Surg*. 2007;119(7):2092-2100.
3. Disa JJ, Cordeiro PG. Mandible reconstruction with microvascular surgery. *Semin Surg Oncol*. 2000;19(3):226-234.
4. Kruse AL, Zwahlen RA, Gratz KW. Free flap monitoring with the implantable Doppler probe. *Int J Oral Maxillofac Surg*. 2010;39(2):182-183.