Microsurgery refers to a set of surgical techniques performed beyond the limits of human eyesight. These procedures require magnification by either surgical loupes or an operating microscope. Contemporary procedures that use microsurgical techniques include nerve and blood vessel repairs and grafts, free tissue transfers, limb replantation, and composite tissue allotransplantation. Technical expertise is essential for success, but preoperative planning and postoperative monitoring are also critical in achieving a successful microsurgical reconstruction.

The reconstructive “ladder” algorithm advocates repairing tissue defects with the least invasive option that will produce successful results. The simplest technique is direct closure, and the most complex technique—with the greatest potential morbidity—is free tissue transfer. Free tissue transfers, located at the “top” of the reconstructive ladder, are usually considered when local or regional tissues are insufficient or suboptimal for reconstruction. The unavailability of local or regional tissues may be a result of infection, inflammation, trauma, radiation, insufficient volume or surface area, insufficient vascular pedicle length, and/or the unacceptability of morbidity at that donor site. In these situations, free tissue transfer becomes the best option. Free tissue transfer is also the most suitable option when highly vascularized tissue is required, when specialized tissues (such as functional muscles) are not available locally, or when specialized components (such as vascularized bowel or bone) are required. Table 8.1 outlines common indications for free flap reconstruction.

A detailed discussion of the factors involved in choosing a specific free flap for a particular reconstruction is beyond the scope of this chapter but is covered elsewhere in this book. Generally speaking, the operating surgeon should ensure that the tissue chosen for free tissue transfer is of sufficient size to cover or fill the defect, is associated with acceptable donor site morbidity (i.e., the benefits of the reconstruction outweigh the disadvantages of the flap harvest), and replaces “like with like,” as with any reconstruction. Additionally, factors such as color, pedicle length, and vessel size similarity must be considered.

The reconstructive surgeon should establish that the patient is medically fit for the proposed procedure, which may be complex and lengthy. Microsurgical procedures are not specifically contraindicated by age, provided the patient is in reasonable health. However, the surgeon should rule out the presence of significant cardiovascular, respiratory, hepatic, or renal dysfunction and abnormal bleeding or clotting states.

The proposed procedure should be discussed at a level of detail suitable for the patient. This includes a discussion of the likely donor sites for the tissue transfer, anticipated morbidity at each site, expected intraoperative and postoperative course, possible donor and recipient site complications, expected level of discomfort and scarring, and expected postoperative recovery times needed to regain preoperative function and activity levels.

The correct instrumentation should be available for the operating team, along with additional sets in case of accidental damage or contamination of the instruments during the procedure. A microsurgical instrument set minimally includes fine jeweler’s forceps, vessel-dilating forceps, straight and curved microsurgical scissors, and microsurgical needle holders. Heparinized saline solution is frequently used for irrigation of the vessel lumen.

The choice of magnifying equipment depends on individual surgeon preference. Surgical loupes, which typically range from 2.5 × to 5.5 × magnification, can be used for fine dissection and the preparation of vessels. Some surgeons also prefer to use loupes rather than operating microscopes when performing the vascular anastomoses.4 The advantages of the operating microscope are that it provides wide-field adjustable magnification and allows significant depth-of-field perception. The microscope should have two sets of eyepieces to allow the surgeon and the assistant to operate simultaneously. The use of a video output device allows viewing of the operative field on a separate monitor and is helpful for the scrub team in following the anastomotic activity.

The free tissue transfer procedure should be outlined preoperatively to the anesthetic and nursing teams, as well as the ablative surgical team. This ensures that all parties are aware of the donor and recipient sites and helps to streamline operative activity. The need for (or avoidance of) anticoagulation, neuromuscular paralysis, vasopressors, and antibiotic prophylaxis should be discussed with the anesthesiologist. Patient positioning and preparation, the expected length of the procedure, and any resultant physiologic or anatomic risks should also be discussed. Intravenous and intra-arterial access should be planned in conjunction with the anesthetic and nursing teams to avoid interference with potential flap harvest and recipient sites.

The patient should be positioned for easy access to the flap donor and recipient sites. Dependent and pressured areas on the patient should be padded to avoid pressure damage, and the patient should be well secured on the operating table to allow limited change of position without the risk of a fall.

Careful preoperative planning is essential. This is particularly true in microsurgery, since the donor sites are limited and the consequences of flap failure are considerable. Often, the type of reconstruction needed is known prior to surgery (e.g., breast reconstruction). Other times, the extent of resection is altered based on intraoperative findings and pathologic examination (e.g., resection of head and neck tumors). In these latter situations, having discussed multiple possible flap options with the patient during consultation will allow for the most appropriate reconstruction to be performed without the need for delay or additional conversation. It is the responsibility of the microsurgeon to anticipate as many reconstructive variables as possible.

Multiple flap options are usually available and the microsurgeon must consider which to use. Donor site morbidity and replacing “like with like” are critical. Patient positioning is also important. Certain flaps may be harvested simultaneously with the ablative resection or wound preparation; this may decrease overall operative time and patient turning. Keeping ischemia time to a minimum is equally important, and timing flap harvest with recipient site preparation is key. In cases in which the flap may be rendered ischemic by the ablative team (e.g., when using a filet of extremity plap for a proximal defect), dissection of the flap prior to disease resection may maximize flap viability after reperfusion.

In the event of flap injury or flap failure, certain backup flap options may become important. Planned vein grafts may allow a short pedicle to reach the recipient vessels or bypass an area of vessel injury or disease. Ensuring potential vein graft harvest sites are appropriate for use and included in the sterile surgical field will facilitate their use during surgery, if needed. Furthermore, in the case of recurrent disease or late flap loss, backup options need to be considered for later use. Communication with the ablative team preoperatively is essential to understand the anticipated defect characteristics, optimize flap choice, and, consequentially, maximize the outcomes of the reconstruction.

Once the recipient site is available (e.g., after debridement or tumor resection), the defect is evaluated, and the final decision regarding the type of reconstruction is made. Surgical templates can be helpful in determining the exact dimensions and shape of the defect, particularly if it has a complex three-dimensional form.

Prior to free flap harvest, the recipient vessels are evaluated. Factors to evaluate include the presence of vessels; their distance from the defect (i.e., pedicle length required); their size, patency, and flow; and their condition (including previous radiation damage, atherosclerotic change, previous trauma, and/or infection). If the initially chosen vessels are inadequate, alternative recipient vessels are sought. Vein grafts may be required to bridge the distance between the donor and recipient vessels. Free tissue transfer requires a thorough understanding of the relevant donor and recipient site anatomy, including the main arterial and venous supply, major vessel variations, important associated structures, and associated nerve supply. The flap’s vascular pedicle is dissected under magnification, with care taken to avoid injury to the flap blood supply. The required pedicle length should be apparent from operative planning and intraoperative measurement. Ideally, the donor and recipient are vessels of similar diameter. The vessels are handled minimally and with care by holding the adventitial tissue on the outermost aspect of the vessel wall. It is equally important to avoid significant traction on the vessels. Manipulation of the lumen is avoided to minimize intimal injury.