Soft Tissue Reconstruction

Introduction

The optimal soft tissue characteristics required for coverage of defects involving the upper and lower extremity vary according to the site and location of the defect. Characteristics of interest include pliability, durability, sensibility, the ability to cover large surface areas with minimal thickness, and cosmetic appearance. These features allow the best functional outcome, maximally protect the vital structures of the extremity, and optimize the esthetic result. Consideration of donor-site morbidity and minimal disruption of local vasculature becomes more critical when considering the functional restoration of the extremity. Although soft tissue defects can occur from a variety of conditions (trauma, tumor, or infection), soft tissue coverage remains a vital operative intervention that protects underlying vital structures, such as nerves, tendons, blood vessels, and bone; preserves the integrity and continuity of musculoskeletal structures; prevents functional disability; and promotes an acceptable esthetic result. Techniques include primary wound closure, delayed primary wound closure, skin grafting, local random flaps, axial pattern flaps, island adipofascial and fasciocutaneous flaps, muscle or myocutaneous pedicled flaps, and microvascular free-tissue transfer, or free flaps. Optimal choices depend on the extent of the defect and available soft tissue donor sites.

Reconstructive Ladder and Elevator

The concept of the “reconstructive ladder,” or choosing the simplest closure or coverage option available, has been at the forefront of soft tissue reconstruction since its description by Mathes and Nahai in 1982 and assists the surgeon in choosing the best coverage option. However, this approach assumes the coverage technique as the important outcome of interest and may not optimize the reconstruction plan or the functional result in more complex cases. When this is the case, it may be prudent to choose the more complex option to facilitate the reconstruction plan and functional outcome. This paradigm has been described as the “reconstructive elevator.”

Initial Evaluation

The detailed patient assessment is critical to the success of any soft tissue repair or reconstruction. The general condition of the patient and the ability to withstand reconstruction must be carefully determined. Included in this analysis is the causative aspect of the defect. In cases of trauma, the antecedent injuries need to be factored; the mechanism of injury, the degree of energy imparted to the soft tissues, and the presence of contamination will significantly affect the surgical plan. A quick analysis of the clinical problem with a template of reconstructive choices is an important and essential step at this point. Ensuring treatment will occur in the correct facility, with the appropriate resources and expertise emphasizing a multidisciplinary approach to care, will ensure the optimum outcome.

The typical approach used by plastic and reconstructive surgeons is to devise a patient-specific surgical plan that includes contingencies for every possible extent or type of defect. This is particularly important in extensive trauma, wherein the final defect after required tissue débridement may be quite different than anticipated. An algorithm, or list of options, for soft tissue reconstruction is often useful and will help the surgeon organize the surgical plan, but in the end, all plans must take a customized approach to the patient. A reconstructive management strategy is based on the evaluation of the defect and the patient's specific functional needs. The mechanism of injury, the location and extent of the wound, tissue viability, contamination, and exposure of vital structures are all critical considerations. A plan for concurrent acute and definitive fracture care must be coordinated with the trauma team and within the scope of wound care.

Most reconstructive surgeons favor immediate reconstruction, except when the defect demands a delay. In high-energy injury patterns, in cases of infection, or in heavily contaminated wounds, it may be necessary to delay definitive wound closure or coverage until an adequate, multistaged evaluation and débridement may be performed. Vacuum-assisted closure (VAC) dressings have improved the treatment of open wounds and may allow some additional delay in flap reconstruction without expectation of further morbidity. However, the general trend supported by the literature remains to cover tissue as soon as the injured patient and limb are optimized, even if this extends past the 72-hour window proposed by Godina.

Skin Grafts

Dermal Substitutes

The past several decades have seen significant research and interest in dermal substitutes for a variety of applications, including burns, nail bed reconstruction, complex wounds, coverage of donor-site defects of flaps, degloving injuries, after oncologic resection, in congenital correction, and in heavily contaminated war wounds after staged débridements. Perhaps the most commonly reported dermal substitute for wound coverage is Integra (Integra Life Sciences, Plainsboro, NJ), an acellular bilaminate membrane composed of cross-linked bovine tendon collagen and chondroitin-6-sulfate. Integra is most commonly used in a meshed bilayer construct with the addition of a silicone layer to prevent desiccation. Dermal substitutes such as Integra are easy to use or apply, limit donor-site morbidity, are readily available, and have a proven track record in burn patients and complex extremity wounds ( Box 19.1 ). One prospective trial analyzed 18 patients with bilateral dorsal hand wounds; one hand received STSG alone, and the other received one-stage dermal substitute and STSG. Although there was no difference in graft survival, the dermal substitute cohort had improved range of motion and superior skin quality (Vancouver Burn Skin Score). In addition, in a retrospective review of patients with severe burns, those treated with Integra had an average length of stay 40% shorter than those treated with skin grafting alone.

In many cases, use of Integra has eliminated the need for complex flap reconstruction and its associated morbidity. Coupled with a split-thickness or full-thickness skin graft, usually performed 14 to 21 days after initial application, Integra has provided reliable coverage of complex wounds with exposed muscle, tendon, and even bone. However, successful coverage has not been proven with application directly over the fracture. The disadvantages of dermal substitutes are the financial cost of the implant and the inherent lack of antimicrobial properties, prompting the use of additional antimicrobial dressings that may increase cost. NPWT is now commonly used with Integra application and may accelerate healing and time to skin graft placement. In addition to primary coverage of complex wounds, Integra has been used to decrease donor-site morbidity in flap surgery by providing a more supple, durable coverage. Integra has also been used effectively to provide durable coverage of amputation stumps that allow functional prosthetic usage.

Random-Pattern Flaps

By definition, random skin flaps have no named blood vessels and rely on the subdermal vascular plexus for perfusion. This limits the geometry of the flap, requiring that the length of the flap be no more than twice the base of the flap to ensure flap blood flow. Longer flap geometries have been described, but flap viability may be compromised, and when this occurs, it will be at the distal extent of the flap. This type of flap requires mobile skin, and the donor defect can usually be closed, although the addition of a Z-plasty may be required.

Axial-Pattern Flaps

Axial-pattern flaps are fasciocutaneous flaps designed around a named artery and vein. The groin flap is a classic example of this flap, designed around the circumflex scapular artery and vein. Axial-pattern flaps have the advantage of supplying a much larger flap than random-pattern flaps, and due to a larger, more robust vascular system, they can be converted to free flaps if required.

Island-Pattern Flaps

Island-pattern flaps are similar to axial-pattern flaps, in that the flap is supplied by a named artery and venous outflow. However, as the name would imply, island flaps can be separated completely from the harvest site and transposed somewhat distantly on its named arteriovenous pedicle. The advantage is usually ease of flap harvest and inset. The disadvantage is the potential loss of a named artery supplying distant structures. Common examples include the radial forearm flap in the upper extremity and the reverse sural artery flap in the lower extremity. Island-pattern flaps may be fasciocutaneous, involving the skin and fascia, or adipofascial flaps, preserving the skin at the donor site.

Perforator Flap

Perforator flaps are fasciocutaneous flaps that derive their blood supply from intramuscular and intermuscular septal perforators from the deep vascular arterial system. The most common example of this type of flap is the anterolateral thigh flap. Perforator flaps can be pedicled or used as free flaps. Propeller flaps are a subgroup of perforator flaps, defined as perforator flaps that are islanded and rotated into a defect. These flaps have seen increased popularity in the reconstruction of small soft tissue defects in the upper and lower extremity.

Free Flap

By definition, a free flap is harvested, its blood supply is divided, and then it is reanastomosed to an arteriovenous supply at the flap recipient site, usually requiring microsurgical techniques. A free flap, or free tissue, is usually classified by its blood supply. A free flap can include skin, fascial and subcutaneous fat, muscle, bone, or combinations of any tissue type based on its blood supply. Muscle flaps, such as the latissimus dorsi muscle flap, continue to be commonly employed in reconstructive surgery. Muscle flaps have the advantage of covering large defects and filling three-dimensional volume defects, but they may not be the best coverage option when staged reconstructive procedures, such as tendon or nerve reconstruction procedures, are anticipated. Because of these limitations, fasciocutaneous and adipofascial flaps based on large named arteriovenous pedicles, or even smaller flaps based on smaller perforator vessels, have recently gained popularity among reconstructive surgeons.

Surgical Planning

Selecting the optimal reconstructive option depends heavily on the location of the defect. For simplification, the following algorithmic approach divides the upper extremity into five anatomic zones: shoulder, arm (within 6 to 8 cm from elbow), elbow (including lower 6 to 8 cm of arm), forearm, and hand. Specific flaps, as shown in Table 19.1 , can effectively reconstruct each anatomic region.

A defect that involves bone, blood vessels, and/or nerves will need a careful assessment and stepwise treatment plan. Reconstruction typically involves skeletal fixation as the starting point. All vascular repairs typically require autologous grafts. Determination for acute repair versus delayed reconstruction of any nerve or tendon injuries must be determined before definitive wound closure or coverage.

Intuitively, the lack of local available soft tissue generally precludes a simple reconstruction method. However, certain anatomic areas are easier to reconstruct with fasciocutaneous flaps, which provide durable coverage. These areas include the shoulder, limited defects on the dorsal elbow, or even in the cubital fossa. In certain situations when there is a healthy, well-vascularized soft tissue bed comprising healthy muscle or even paratenon, a simple skin graft may be an easy reconstructive strategy. Of course, the long-term problems with graft contractures and lack of durability, usually due to thin, insensate coverage, adversely affect the outcome.

Understanding the vascular roadmap becomes essential to upper extremity reconstruction in two critical ways: (1) identification of donor vessels and (2) understanding the impact of sacrificing a vessel for flap anastomoses. Methods of assessing vascular integrity include a simple physical examination of the pulses, an Allen test (using Doppler ultrasound confirmation both preoperative and intraoperatively), and, when needed, an angiogram or a magnetic resonance angiogram (MRA) if available. More recently, indocyanine green fluorescence angiography used in the SPY imaging system has gained increasing interest and use for flap design and intraoperative and postoperative flap assessment. Further work is ongoing to define its role as a reliable tool for the surgeon.