DIAGNOSIS

Upon evaluation of a traumatic wound for reconstruction, many factors are considered. Assuming that the overall condition of the patient permits reconstructive surgery, the plastic surgeon must evaluate the nature and location of the wound. The wound bed needs to be clean and free of devitalized tissues. High-energy wounds and electrical burns produce extensive soft tissue damage, far beyond the zone of injury. All necrotic material needs to be aggressively debrided prior to embarking on reconstruction.

The concept of the “reconstructive ladder” recommends the use of the least invasive repair that will satisfactorily close a wound. The methods begin with secondary healing and progress through skin grafting to microvascular free-tissue transfer. This paradigm has been largely supplanted by the “reconstructive elevator” concept.¹ With this approach, the surgeon evaluates the wound and decides on the best option, not necessarily the least complicated one (Figure 1).

Figure 1 The “reconstructive elevator” evolved from the “reconstructive ladder” as the paradigm for approaching complex musculoskeletal reconstruction.

The ultimate goal for involvement of the plastic surgeon is to provide a reconstructive plan that gives special consideration to body symmetry and contouring and minimizes donor site defect and deformity.

ANATOMY

Split-thickness skin grafts (STSG) consist of the entire epidermis and a portion of the dermis, with an average thickness of 0.012–0.015 inches. STSGs require a vascularized wound bed, free of necrosis, with minimal bacterial burden. Healed grafts shrink considerably, bear abnormal pigmentation, and leave underlying tissues highly susceptible to trauma. Full-thickness grafts include the entire thickness of the skin, resist contraction, have potential for growth, and have texture and pigment more similar to normal skin. However, they require an even better vascularized wound bed.

The most important anatomical aspect of muscle flaps is their vascularity. Because blood supply is usually the limiting factor in flap success, flaps are most often categorized by the vascular system on which they are based. McGregor proposed the concept of “random” and “axial” pattern flaps based on the importance of the presence or absence of a major vessel running along the axis of the flaps.² Random pattern flaps do not incorporate a dominant vascular supply, relying on the networks of small-diameter vessels to sustain the transferred tissue. They are limited in size and may require delay for successful transfer. Axial pattern flaps incorporate an anatomically recognized arteriovenous system running along the long axis of the tissue which permits successful transfer of vascularized flaps with high length-to-breadth ratios. They obtain their vascular supply from the musculocutaneous and fasciocutaneous systems, both of which rely on multiple “perforator” arteries. Knowledge of muscle vascular anatomy is helpful in predicting the viability of overlying skin territories based on such perforating vessels.

The now classic schema of Nahai and Mathes has divided muscles into groups according to their principal means of blood supply.² A type I muscle, such as the gastrocnemius or tensor fascia lata (TFL), is supplied by a single pedicle. A type II muscle, such as the trapezius or gracilis, has a dominant pedicle, with one or more minor pedicles. A type III, the serratus anterior (SA) or gluteus maximus (GM), for example, has dual dominant pedicles. A type IV, such as the tibialis anterior (TA) or sartorius, has segmental pedicles. The type V, such as the internal oblique muscle or latissimus dorsi (LD), has a dominant pedicle, with secondary segmental pedicles. Most muscles fall into the type II group. Types I, III, and V are the most reliable because complete muscle viability can be sustained by a single vessel. Sometimes the muscle territory of a minor pedicle is poorly captured by the dominant pedicle in a type II muscle. Owing to their segmental means of perfusion, type IV muscles would potentially only allow small flaps that have limited application.

Certain muscle flaps can be raised on a simple pedicle. Due to musculocutaneous vascular perforators, an island of skin can be carried with the muscle (myocutaneous/musculocutaneous flaps). When the perforator is traced through the muscle to the pedicle, thereby preserving the muscle, a cutaneous perforator flap results. Blood vessels also travel from major arteries and veins through intermuscular septae to the skin. When the skin and fascia are raised on septal perforators, a fasciocutaneous flap is created. Any flap with a dominant pedicle can become a free flap by division and subsequent reanastomosis of the vascular pedicle artery and vein into the recipient bed. Free flaps may be muscle only, musculocutaneous, fasciocutaneous, or osteomyocutaneous.

SURGICAL MANAGEMENT: PRIMARY FLAPS

Musculoskeletal trauma will be grouped into five soft tissue coverage regions: head and neck, upper extremity, chest and trunk, abdomen, and the lower extremity (Table 1).

Upper Extremity

Injuries involving the tactile surface of the hand with disruption of its sensory supply represent the most difficult reconstructive problems. The reconstructive goal must include restoration of sensibility if maximal function is to be achieved. A skin graft requires a suitable recipient bed such as muscle, fascia, paratenon, or periosteum. In the absence of structures capable of sustaining a graft, as in cases of exposed bone without periosteum or exposed tendon without paratendon, a well-vascularized flap is necessary to provide durable soft tissue coverage.

The groin flap (GF), reported by McGregor and Jackson in 1972, revolutionized the reconstruction of upper extremity wounds.² It is a versatile flap with a reliable vascular supply that is capable of covering large defects of the hand and wrist and provides an excellent tissue bed for subsequent procedures such as tendon reconstruction.

The radial forearm (RF) flap is designed to include the radial artery when raised as a pedicle fasciocutaneous flap. It can be raised proximally to cover defects involving the proximal forearm and elbow or distally (reversed) to cover defects involving the forearm, wrist, and hand. The main contraindication to its use is related to its dependence on the hand having adequate perfusion by the ulnar artery as demonstrated by a normal Allen’s test.

Various situations preclude the use of local, regional, or distant pedicle flaps. Involvement of the hand and forearm in an injury may eliminate all potential local or regional flap options. Although distant pedicle flaps, such as the GF, are useful for coverage of large defects, defects resulting from circumferential injuries are extremely difficult to cover with such a flap. Occasionally, defects involving the volar and dorsal aspects of the hand or more proximal circumferential defects can be covered by a combined groin and epigastric flap. However, free flaps offer far greater versatility and availability of donor sites for coverage of extensive defects. Additionally, tailoring of the free flap to suit the reconstructive needs of the wound is more easily accomplished because of the diversity of available flaps. Limb elevation, early mobilization, and the ability to cover even extensive circumferential defects are additional advantages to the use of free-tissue transfer (Figure 2).

Figure 2 (A) View of an upper extremity after a severe crushing injury; preliminary application of external fixator for fractures of radius and ulna. (B) Appearance after serial debridements and internal fixation of fractures; note exposed vessels, nerves, and tendons. (C) Latissimus dorsi muscle free flap to be used for coverage of the wound. (D) Appearance after inset of flap. (E) Coverage of flap with meshed split-thickness skin graft. (F) Appearance at 3 months postoperative.

The most commonly used free flap in soft tissue coverage of the dorsum of the hand is the RF free flap. Thicker coverage for a palmar or forearm defect can be provided by a medial plantar, scapular, parascapular, or lateral arm flap. Coverage of an extensive circumferential defect can be provided by RA, SA, or LD flaps.

Lower Extremity

Thigh

Lower extremity trauma wounds benefit from plastic surgical consultation and intervention because of large soft tissue defects and combined vascularized bone graft and soft tissue requirements. Common coverage methods for the thigh are: (1) flaps based on the thigh muscles, with or without skin grafts—in particular, the gracilis, sartorius, vastus lateralis, gluteal, and TFL flaps; (2) fasciocutaneous flaps such as the medial and posterior thigh; and (3) more distant flaps such as the RA, based on the deep inferior epigastric pedicle.

Knee

The alternatives for soft tissue coverage of the knee are muscle flaps, fasciocutaneous flaps, and free-tissue transfer. The gastrocnemius muscle flap is readily available for knee coverage; however, it does not reliably cross the midline to the contralateral aspect of the knee or to the superior aspect of the knee. The distally based muscle flaps are unreliable. The saphenous fasciocutaneous flap, as described by Walton and Bunkis, is useful if available.² For extensive defects covering the entire surface of the knee, free-tissue transfer of a large fasciocutaneous flap or muscle flap is the most reliable.

Proximal Third

For soft tissue coverage of the proximal tibia, local muscle flap options include the medial and lateral gastrocnemius. The lateral is usually the shorter muscle and is compromised by the position of the peroneal nerve. Fasciocutaneous flaps include the saphenous flap, or a distally based medial or lateral fasciocutaneous flap. Free flaps are indicated when the local soft tissue injury contraindicates the use of local muscle or fasciocutaneous flaps or when the deficit is extensive (Figure 3).

Figure 3 (A) View of a lower extremity after a severe crushing injury. Note fragments of fractured tibia and fibula exposed in the wound; preliminary appearance after debridement. (B) Appearance after inset of latissimus dorsi muscle free flap. (C) Coverage of flap with meshed split-thickness skin graft.

Middle Third

Choices for coverage of the mid-tibial region include the soleus muscle, which is readily available and transposes well over this area. Fasciocutaneous flaps from the lateral or medial leg, based distally or proximally, are useful. Of course, free flaps are appropriate when local soft tissue coverage is not available or the defect is extensive.

Distal Third

The distal portion of the leg has poor skin elasticity, frequent severe edema, and osseous structures that lie in the subcutaneous tissue and are quite vulnerable. Such wounds also have a high rate of osteomyelitis, which often results in amputation. The distal third of the leg has significant tendinous structures that take skin grafts poorly. Finally, the foot and ankle require good flap durability because they are so frequently exposed to friction and shear by walking and footwear. Small ankle or distal tibial defects less than 4 cm² may be covered by the extensor brevis muscle flap, slightly larger defects by the supramalleolar flap, and somewhat larger defects by the dorsalis pedis fasciocutaneous flap. These flaps require a blood supply not compromised by the injury. The distally based muscle flaps are unreliable. Distally based fasciocutaneous flaps (based laterally or medially), including the sural neurocutaneous flap, may be safely used when perforators can be identified at the respective base of the flap.

Foot

Several small muscle flaps, such as the flexor hallucis, flexor digitorum brevis, and abductor hallucis brevis, are available for coverage of wounds of the foot but are rarely of practical use, given the frequent global injury to the foot and ankle area. The sural artery flap may be of benefit for small or moderate-sized wounds of the ankle and proximal foot as well as the heel area. Medial plantar flaps and dorsalis pedis flaps are examples of reliable local fasciocutaneous flaps. Island pedicle flaps of interdigital skin are useful for small defects. Most of these wounds, however, require some type of free-tissue transfer for satisfactory closure.

Indications for flap coverage of the foot are exposed bypass grafts, chronic osteomyelitis, open fractures, and tendon and nerve exposure. Indications for free-tissue transfer include large or circumferential defects exposing fractures, open joints, or the Achilles tendon; incisions or soft tissue trauma that compromise the lateral or medial fasciocutaneous areas; and compromise of the distal arterial flow, which may prevent the use of lateral supramalleolar or dorsalis pedis flaps.

COMPLICATIONS MANAGEMENT

In general, microvascular tissue transfers are a large metabolic challenge for patients; all of the complications common to major surgery are possible. Specifically, flap necrosis is the only serious complication. Loss of a few millimeters, or even 1–2 cm, at a margin of the flap usually has no deleterious effect. Loss of the major portion of the flap occurs in about 4% of the cases and is almost always explained by an obvious precipitating cause. A major flap loss may require the performance of a second flap, though most compromised free flaps can be salvaged. Venous congestion owing to insufficient venous outflow is the most common complication which, with early recognition, may be rectified by flap revision or the use of medicinal leech therapy. Godina demonstrated the benefits of achieving healthy, soft tissue wound coverage over open lower extremity fracture within 5 days after injury.² This approach minimizes the risk of acute and chronic infection and maximizes flap survival.