Flap reconstruction in the management of complex musculoskeletal injuries

Approach to wound evaluation

Evaluation of a traumatic musculoskeletal injury involves assessing not only the resultant wound but also the surrounding tissues. The soft tissue response to traumatic injuries is a challenge to define since the injury commonly extends beyond the region of highest force application. Consistent with other injury types characterized by an injury center of irreversible tissue damage and peripheral areas of variable salvageability, Arnez described the trauma “zone of injury” concept in the 1990s. This “zone” encompasses the wound in addition to the inflammatory response of the periwound soft tissues. It is characterized by perivascular derangements including increased blood vessel friability, perivascular scar tissue, and higher rate of microvascular thrombosis. The wound’s zone of injury presents clinically as an area of delayed necrosis, hindered wound healing, and vessels unsuitable for microvascular anastomosis.

Despite its description and recommendations to avoid reliance on tissues within it for reconstructive purposes, the true definition of the “zone of injury” remains elusive since there is no objective or reproducible manner to delineate it. Management options described to avoid use of tissues or recipient vessels in the zone of injury have included extensive proximal dissection of recipient vessels, use of vein grafts, and arteriovenous loops. Clinical evaluation of the tissues, including blood vessels supplying tissues to be transferred or recipient vessels for microvascular anastomosis, remains the standard for determination of the zone of injury. Tissues considered for salvage or reconstructive use are deemed viable/usable based on their color, turgor, bleeding from cut edges, and contractility in the case of musculature. In cases requiring microvascular surgery, recipient vessels for anastomosis should demonstrate lack of intimal hemorrhage, normal wall pliability, and pulsatile blood flow.

Adjuncts to assess soft tissue perfusion, tissue viability, and blood vessel status are available and used in the wound/periwound assessment. Use of indocyanine green fluorescent angiography in reconstructive surgery has ranged from vascular anastomosis interrogation to tissue perfusion assessment and flap planning. It is a simple technology based on light excitation of indocyanine green, a water-soluble tricarbocyanine dye excreted via the biliary system. Once stimulated by light, the dye fluoresces and allows real-time images/video of dye-containing vascular structures and the tissues they perfuse. Quantitative software accompanying commercial fluorescent angiography devices calculate both absolute and relative perfusion values indicative and predictive of soft tissue viability. Green et al performed a retrospective review of war-related traumatic injuries that employed indocyanine green fluorescent angiography in their management and found it effective in the guidance of removal of devitalized tissues in heavily contaminated wounds and tissue viability assessment of wounds with avulsion components.

In the absence of hard signs of a vascular injury requiring repair, formal angiography is not routinely needed in the assessment of the traumatized extremity. After clinical examination of extremity perfusion is completed, an arteriogram should be considered if the clinically identified zone of injury is large or if it involves a potential flap donor site or pedicle for planned microvascular anastomosis. Angiography provides data on the intraluminal characteristics of the vascular system as well as identifies clinically unidentifiable anatomic variations valuable in the planning of many forms of flap reconstruction of traumatic musculoskeletal injuries.

Due to cost and the invasive nature of angiography, it has been largely supplanted by computed tomography angiography (CTA) and magnetic resonance angiography (MRA) in preparation for traumatic wound reconstruction. The benefit of these imaging modalities is the capability of three-dimensional vessel evaluation in relation to surrounding structures. Comparatively, the vascular detail provided by CTA, particularly for small-caliber vessels, is better than that of MRA. Though more costly than CTA, the benefits of MRA over CTA are its use of magnetic resonance over radiation for image production in addition to the use of noniodine contrast medium.

Wound debridement/preparation

Debridement is the initial treatment of complex musculoskeletal injuries to allow for adequate assessment of the wound and to minimize infection risk. Dependent on the mechanism of injury, serial wound debridement procedures may be necessary to rid the traumatized area of dead, dying, and contaminated bone and soft tissues to achieve a stable and healthy wound bed. Irrigation of the wound is standard during debridement procedures and low-pressure irrigation systems are acceptable. Orthopedic involvement is critical during this process to provide provisional fracture stabilization as the wound evolves and the bony and soft tissue defect is defined.

Adjunct wound debridement tools are available to aid in the preparation of the traumatized area for reconstruction. These alternatives include high-frequency ultrasound, polyester fiber debriding pads, radiofrequency ablation, and hydrosurgery. These wound debridement modalities have been studied predominantly in chronic wounds with the exception of hydrosurgery. Hydrosurgery, which pressurizes sterile saline to produce a fine, high-velocity stream at the tip of a handpiece, has substantial support for its use alone or in combination with conventional sharp debridement in burn wounds and growing support for its use in traumatic open fracture wounds. Hydrosurgery benefits include the ease of control of the handpiece, multiple options in handpiece tips applicable to different wound types and geometry, and the high degree of tissue preservation combined with significant reduction in necrotic debris. Potential disadvantages to the use of hydrosurgery in the debridement of traumatic injury stems from the cost of the technology. Although there are data to suggest that use of hydrosurgery decreases duration of debridement interventions, whether this offsets equipment cost remains to be seen.

Timing of flap reconstruction

In his posthumously published thesis, Dr. Marko Godina recommended aggressive débridement of devitalized or contaminated bone and soft tissue followed by soft tissue coverage in the first 72 hours after injury. The “emergency free flap” concept was born since this management protocol resulted in increased flap success and reduced infection-related complications when compared with reconstruction in the subacute (72 hours to 3 months) or late (>3 months) time frames.

Significant advances in microsurgical techniques, flap types, and wound management have occurred since the publication of Godina’s thesis. Introduced in the mid-1990s, negative-pressure wound therapy (NPWT) is a groundbreaking development in wound care now commonly used in the management of traumatic musculoskeletal wounds. NPWT applies deformation and traction forces to the perimeter of a wound decreasing its size. In addition, it reduces edema, decreases bacterial counts, improves circulation, and increases the rate of granulation development. NPWT may be placed on both soft tissue and small areas of exposed bone and tendon safely to aid in the development of a healthy wound bed amenable to skin grafting, to simplify wound closure with local tissue transfer rather than free tissue transfer, or to achieve complete wound healing.

Artificial skin products, or dermal regeneration templates (DRTs), are another key addition to the technique armamentarium employed in the management of traumatic injuries. The design of artificial skin and its use in traumatic injuries, particularly burn wound reconstruction, began in the 1980s. Since that time, DRTs have been utilized in the management of other traumatic injury types in pediatric and adult patient populations. Their ease of application, high engraftment rate, use in clean and contaminated wounds, and use over exposed tendon, joints, and bones are the benefits of DRTs in traumatic wounds and have simplified wound closure techniques in certain cases as well as increased the safe interval between injury and definitive soft tissue reconstruction.

Although tremendous advancements, NPWTs and DRTs do not obviate the need for more advanced forms of soft tissue reconstruction particularly in wounds with large areas of bone stripped of periosteum, tendon denuded of paratenon, exposed orthopedic hardware and neurovascular structures. These wound care advancements, in conjunction with aggressive serial débridement and advanced microsurgical capabilities, have safely prolonged the time interval between injury and reconstruction completion outside of the 72-hour critical window advocated by Godina. Today, acceptable time frame to definitive reconstruction ranges from 1 to 4 weeks post injury, with a mean time frame of approximately 2 weeks.

Approach to reconstructive evaluation

The reconstructive approach to complex defects resulting from trauma is comparable to that of wounds resulting from other disease processes. Despite this similarity, an important distinction is the presence of concomitant injuries frequently influencing the reconstructive options available and the timing of their execution. The goal of reconstruction is to obtain adequate structural support and soft tissue coverage of any underlying critical structure (vasculature, tendon, bone, and hardware) while maintaining suitable contour and cosmetic appearance.

The reconstructive ladder describes the traditional wound closure algorithm that starts with the simplest closure option (the lowest ladder rung) and advances to more complex options (higher ladder rungs) when required. The simplest closure options include healing by secondary intention, primary closure, and delayed primary closure. Skin grafting, a higher ladder rung, is often sufficient to obtain healing in most traumatic injuries. More advanced reconstructive options include local tissue rearrangements, tissue expansion, regional flaps, and, at the top of the ladder, microvascular free tissue transfer. Special consideration should be given to more complex injuries whereby too simple of an approach to the injury may lead to a delay in wound care and coverage. As discussed earlier, more durable soft tissue coverage is necessary to cover large bone segments (devoid of periosteum), tendon (devoid of paratenon), exposed hardware, and neurovascular structures and satisfactory reconstructive solutions lie higher on the ladder.

Today, the reconstructive ladder has evolved into the reconstructive elevator concept. Instead of progressing “rung per rung” to achieve the optimal outcome, one simply skips rungs and executes the ideal reconstructive option, similar to elevator use to arrive at the correct floor. With the previously stated goal of restoring form and function, the sequential thought processes inherent in the ladder concept are replaced with more dynamic and creative processes characterizing the elevator concept that allows creation of reconstructive management plan individualized to the patient to provide optimal form and function in the scenario at hand.