Indications and Selection of Free Flaps for Soft Tissue Coverage of the Upper Extremity

Michel Saint-Cyr, MD, FRCS(C)a'*, Amit Gupta, MD, MS, MCh(Ortho), FRCSb aDepartment of Plastic Surgery, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390-9132, USA hHand Surgery Division, Department of Surgery, University of Louisville, 315 E. Broadway, Suite 195,

Louisville, KY 40202, USA

Meaningful interaction with our environment is predicated on the highly coordinated actions of a mobile and sensate hand. Trauma or tumor resection can gravely disrupt this fine balance. Therefore, it behooves the hand microsurgeon to make every attempt to restore form, function, and sensation to the injured hand. There are several options for soft tissue reconstruction of the upper extremity including skin grafting, local flaps, regional flaps, and free flaps. Because of the structural complexity and importance of the hand in total body function, a graded approach using the reconstructive ladder is not always desirable. Free flap soft tissue reconstruction should always be selected early in the treatment algorithm if a better end result can be anticipated.

The advantages of free flap coverage of the upper extremity following trauma or tumor resection have been acknowledged by several authors. Most importantly, these benefits include the ability to provide early coverage with composite reconstruction of all damaged or missing tissues and early mobilization to restore function.

The purpose of this article is to review the indications and options for selection of free flaps for soft tissue coverage of the upper extremity.

* Corresponding author.

E-mail address: [email protected] (M. Saint-Cyr).

Initial requirements

Early aggressive debridement of all nonviable and necrotic tissue is pivotal before any attempt at free flap soft tissue reconstruction [1-13]. This critical step cannot be overstated. It serves to significantly decrease the bacterial load of the wound and permits a clear evaluation of all injured and missing structures [11-13]. We strongly favor early aggressive debridement in favor of traditional serial debridement whenever possible. Serial debride-ments can delay final wound closure and trigger a cascade of additional tissue loss from desiccation [8]. The accumulated edema and granulation tissue makes tissue planes less clear and requires any microsurgery to be performed farther away from the zone of injury. Also the ultimate goal of early mobilization and return to function is delayed. Tissue viability and infection can also be difficult to evaluate when extensive granulation tissue is present. Unlike the lower extremity where delayed reconstruction is much better tolerated, early mobilization of the hand is crucial to restore function. Joint stiffness, tendon adhesions, and soft tissue contracture can seriously impede the final outcome and are more easily avoided with earlier coverage [12]. Nevertheless, serial debridement should only be considered when conversion of a contaminated wound to a clean wound is impossible. Examples include severe crush injuries with tissues of indeterminate viability, massive wound contamination, electrical burn injuries, and unstable patients.

During aggressive debridement, the wound should be excised leaving only tissue that is clearly

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viable. Tourniquet control is used to provide better visualization of viable and nonviable tissue [1,8-13]. Debridement is begun at the periphery of the wound, out of the zone of injury, to identify a clear plane between injured and noninjured tissue. This approach is likened to the extirpation of a tumor where the wound is excised en bloc leaving behind only healthy uncontaminated tissue [1,9,10] (Figs. 1-3). Radical debridement also allows better identification of the extent of injury. Crushed and contaminated skin should be excised back to viable bleeding skin edges. Avulsed, soiled, and devascularized muscle, fascia, and subcutaneous tissue should all be excised. Small bony fragments providing no structural support are de-brided, whereas bony fragments with viable periosteum or attached articular cartilage are left in place. The critical step involves debridement of all marginally and questionably viable tissue to convert a contaminated wound into a clean wound and thus minimize the risks of infection [1,7-17]. Longitudinal structures showing anatomical continuity, such as vessels with flow, nerves, and tendons are spared. Once debridement is considered complete, the tourniquet is released and all areas that are not vascularized are reex-cised under tourniquet control. Normal tissue should be encountered at all levels when definitive debridement is completed. Ringer's lactate and a bacitracin solution are then used for wound irrigation using a bulb syringe. Pulsed lavage should be used with caution to not damage the vital structures of the hand and should never be a substitute for adequate debridement.

Following radical debridement, the wound is thoroughly examined to evaluate what anatomical parts are missing and what needs to be replaced.

Fig. 1. Appearance of a contaminated wound before radical debridement.
Fig. 2. Conversion of a contaminated wound into a clean wound following radical debridement.

Goals of reconstruction are not only to provide soft tissue coverage but most importantly to restore function. In deficits requiring coverage only, the size and depth of the wound are assessed. Muscle flaps provide well-vascularized tissue [1822] and are used for deep space obliteration, while fasciocutaneous flaps are used for flat superficial wounds. Adequate debridement should obliterate dead spaces and produce the flattest wound surface possible. After assessing the length of vascular pedicle needed, other factors that are important include the amount of missing bone, the length of the tendon defects, the need for vein grafting, and the length of nerve gaps. Other key requirements for soft tissue reconstruction include provision of a stable bony framework, adequate recipient vessels outside the zone of injury, adequate blood supply of tissues adjacent to the recipient site, a stable patient, and a surgeon experienced in microvascular surgery.

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