Negative Pressure Dressings: An Alternative to Free Tissue Transfers?

F ree flap reconstruction is a well established technique for the closure of large, complex wounds of the extremities with exposed functional structures.¹ The management of wounds in which there are large areas of exposed bone or tendons or in wounds that are located in functionally active areas can become a formidable task when free flap coverage is contraindicated. Such circumstances include extensive crush or burn injuries in which the condition of the recipient vessels eliminates free tissue transfer as an option. Other situations that may necessitate an alternative to free flap transfer include patients with significant comorbidities, patients who are unable to tolerate extended periods of general anesthesia, and patients who have had free flap failure at the wound site. The only viable alternatives to free tissue transfer for the management of large, complex wounds of the extremities with exposed bone and other functional structures are pedicled flaps (eg, cross-legged flaps). However, these methods have a wide range of complications and are not always feasible. Skin grafting is not a treatment of choice for coverage of wounds with exposed bone or hardware, especially over disrupted periosteum. In 1995, a new method utilizing negative pressure was used by Argenta et al.² at the Bowman School of Medicine in Winston-Salem, NC, and approved by the US Food and Drug Administration (FDA) for the management of wounds in a wide variety of clinical settings. Negative pressure wound therapy (NPWT, V.A.C.® Therapy™ System, KCI, San Antonio, Tex) has been reported to serve dependably and superiorly to conventional dressings in the management of large complex wounds.³ Myers et al.⁴ concluded that NPWT may serve as an effective adjunct to definitive treatment to delay free tissue transfer when it is appropriate but should not be used in place of free tissue transfer. Recently, DeFranzo et al.⁵ and Heugel et al.⁶ have reported successful management of wounds with small areas of exposed bone, tendon, and orthopedic hardware using NPWT. The authors’ experience supports these previous reports and further suggests that NPWT might have a significant role in the management of wounds with large areas of exposed bone and tendon in cases where free tissue transfer is contraindicated. Methods and Patients Between July 2001 and March 2004, the authors performed 26 free tissue transfers to large complex wounds of the upper (5) and lower (21) extremities with exposed bone, tendon, and orthopedic hardware using established techniques.^7,8 During the same time period, the authors managed 4 patients with large, complex wounds of the extremities, which would require free flap reconstruction under routine circumstances. However, various contraindications precluded free flap transfer in 3 cases. In 1 case, free flap transfer failed. In 3 of these cases, the wounds contained large areas of exposed bone, devoid of periosteum, and tendon, and in 1 case, the wound was located over a functionally active area (elbow). Those 4 patients were managed with NPWT and subsequent split-thickness skin grafts. Successful closure of all wounds was achieved with satisfactory aesthetic and functional results. Negative pressure wound therapy foams were applied in a standard manner after the wounds had been completely debrided of all nonviable tissues. The foams were cut to fit the dimensions of the wounds and were covered with transparent, adhesive plastic film to form an airtight seal; the dressing was then connected to either wall suction or a suction device through a hose maintaining continuous negative pressure in a range of 100–125 mmHg. Throughout the course of wound management and before the application of the skin graft, 1 patient (Case 1) was discharged from the hospital, and NPWT treatment was continued on an ambulatory basis. Negative pressure wound therapy dressings were changed at the bedside or in the operating room every 2 to 3 days. Split-thickness skin grafts were applied to the wounds after they had been completely “filled” with granulation tissue. Two of 4 patients in this series had very similar wounds and a similar clinical course; thus, the authors are restricting this article to 3 case reports. Case Reports Case 1. A 46-year-old man with a history of noninsulin-dependent diabetes mellitus, hypertension, chronic tobacco use, and a recent attack of acute pancreatitis presented for evaluation of a large, open, complex wound in the antecubital fossa of the left arm. The wound developed secondarily to incision and drainage of a large abscess at that area performed by a general surgeon. The authors’ initial assessment revealed an open, cross-shaped wound with an irregular surface extending from the distal anterior arm to the antecubital fossa and further distally to the upper forearm. The wound had 2 components, 1 lying parallel to the axis of the arm and the other lying across the antecubital fossa. The wound was 18 cm x 14 cm in size, relatively clean, with neurovascular structures of the antecubital fossa lying just beneath the wound bed (Figure 1). At the time of evaluation, it was noted that the patient had severe contracture of his left elbow joint. Because of the location of the wound over a functionally active area (elbow joint) and the close proximity of vital structures to the wound surface, free tissue transfer was initially considered for coverage of the wound. However, the ultimate decision was made to treat the patient with NPWT with subsequent skin grafting and to forgo free microvascular tissue reconstruction of the wound. This decision was based on the patient’s past medical history as well as detailed evaluation of his current general condition, which precluded extended general anesthesia. While being managed with NPWT, the patient was placed on simultaneous rehabilitation therapy to restore mobility in his elbow joint. The occupational therapy was successful with satisfactory restoration of the range of motion in the elbow joint. Subsequently, the patient was discharged from the hospital and NPWT treatment was continued on an ambulatory basis until the wound was completely filled with granulation tissue and the range of motion in the elbow joint became normal. The overall length of NPWT treatment before the application of a split skin graft was 14 days. After the skin grafting of the wound, the left upper extremity was immobilized in a splint for 1 week. Postoperatively, there were no complications, skin graft take was 100%, and range of motion in the elbow joint remained normal (Figure 2A and B). Case 2. A 33-year-old man had been involved in a motor-vehicle accident as a pedestrian, pinned between a slow moving van and a guardrail. Upon the accident, the patient sustained a severe crush injury to the right lower leg consisting of open grade IIIB tibial and fibular fractures with development of compartment syndrome. Initially, the patient was managed by the orthopedic trauma service. First, multiple decompressing fasciotomies were performed to relieve the compartment syndrome. After serial debridements over the next 5 days, an open reduction and internal fixation of the tibial fracture with an intramedullary nail was done. Subsequently, the plastic surgery service was consulted for evaluation and management of the open wound at the site of the injury. The wound measured 25 cm x 15 cm and was located at the antero-lateral aspect on the right lower leg. The tibia was exposed in the wound at the extent of 16 cm, including the fracture site (Figure 3).Upon the patient’s evaluation, the decision was made to close the wound with a latissimus dorsi muscle free flap and cover it with a split skin graft. Angiography revealed patency of all 3 vessels of the right leg. The posterior tibial vessels were not suitable as recipient vessels due to the proximal and lateral location of the wound. The proximal portions of the anterior tibial vessels were within the zone of the injury (contusion), and the use of popliteal vessels would necessitate long vein grafts and repositioning of the patient during the surgery. Therefore, the decision was made to perform the so-called reversed free flap transfer using a distal portion of the anterior tibial vessels (ie, below the distal edge of the wound) for the anastomoses. The operation was performed 2 weeks after the initial injury. On the first postoperative day, the free muscle flap showed signs of venous congestion. The patient was immediately taken to the operating room. Thrombus was found in the vein despite the patent anastomosis and absence of any mechanical problems. Thrombectomy was performed with concomitant revision of venous anastomosis. However, venous congestion of the flap was not relieved, and the flap eventually failed. In the authors’ opinion, the probable cause of this failure was the contusion and insufficiency of the vena commitantae at its proximal extent within the zone of the injury. After removal of the flap, the wound was managed with NPWT. In 19 days of NPWT treatment, the wound developed a bed of fine granulation tissue completely covering the exposed tibia including the fracture site (Figure 4). At this time, the wound was covered with a split-thickness skin graft. There was complete graft take over the granulation tissue with satisfactory contouring (Figure 5). Subsequent functional rehabilitation of the patient was also successful, and there were no wound complications in the long-term period. Case 3. A 34-year-old man presented with an open grade IIIB right tibial and fibular fracture resulting from a high-speed motorcycle accident. Following reduction and fixation of the fracture, the wound was closed primarily by the orthopedic service. The stress on the skin surrounding the primary closure caused a widespread full-thickness skin necrosis. Serial debridements of the necrotic tissues created 2 large complex wounds over the right leg. The superior wound measured 20 cm x 12 cm and contained exposed tibia devoid of periosteum and the fracture site (Figure 6A). The distal wound measured 10 cm x 7 cm and contained exposed tendons (Figure 6B). Initially, a large latissimus dorsi muscle free flap was planned for coverage of these right lower leg wounds. Unfortunately, exploration of the posterior tibial vessels, which were the only suitable recipient vessels for the free flap, revealed posttraumatic inflammation and fibrosis of the vessels and surrounding tissues to such degree and extent that the reconstructive surgery was excluded as an option. It was decided to proceed with NPWT management of the wounds. Over the course of 40 days, the wounds were completely filled with fine granulation tissue, and subsequently, they were covered with 2 split-thickness skin grafts. A piece of acellular dermal matrix (AlloDerm®, LifeCell Corporation, Branchburg, NJ) was used over the small area of the exposed Achilles tendon underneath the skin graft. The skin graft take was 100%, and the patient completely recovered and became fully ambulatory (Figure 7A and B). Discussion Currently, free flap transfer is a widely accepted standard in the management of large, complex wounds of the extremities, particularly those with exposed bone.^1,9 Despite the high success rate of this technique, there still exist cases in which flaps fail. Additionally, clinical circumstance can sometimes preclude the use of free flap transfer altogether.¹⁰ Previously, in such cases, attainment of adequate wound closure presented a formidable task, as no viable alternatives to free tissue transfer existed.⁹ Negative pressure wound therapy has emerged as a powerful tool in the treatment of open wounds.² However, there have been only limited reports of the successful use of this method in the management of wounds with exposed bone.^11,12 There have also been no reports in the literature describing the effects of granulation tissue formed by NPWT over functionally active areas, such as joints. The NPWT dressing converts an open wound into a closed wound without the need for frequent dressing changes. It is believed to exert its effect through several mechanisms: the removal of edematous fluids that contain inflammatory mediators inhibiting wound healing via a unidirectional flow; increasing blood flow to the wound by decompressing the capillary bed; decreasing the bacterial inoculation; decreasing oxygen tension in the wound thus promoting angiogenesis via the creation of a hypoxic gradient; and decreasing the dimensions of the wound by providing a tensile force on the tissue via the suction the negative pressure generates. All of these factors are thought to contribute to wound healing.¹³ A study by Morykwas et al.¹⁴ showed that granulation tissue formation in experimental wounds in swine increased over controls by 63.3% with continuous suction and 103.4% with intermittent suction. However, for patient comfort, continuous suction is generally preferred to intermittent suction.¹⁴ The quality of the granulation bed formed under the NPWT dressing allows for better take of skin grafts. In a study by Scherer et al.¹⁵ comparing wounds prepared for split-thickness skin graft by NPWT to those prepared by conventional dressings, only 3% of wounds receiving the NPWT required a second skin grafting compared to 19% of wounds prepared by conventional dressings. The authors of the study suggest that this difference might be accounted for by the NPWT decreasing the size of the wound at a greater rate than conventional dressings and thus decreasing the size of the skin graft necessary to cover the wound resulting in a greater likelihood of graft survival.¹⁵ The authors’ experience with the NPWT has shown it to be effective in the achievement of adequate closure of large, open wounds of the extremities, including those with exposed bone devoid of periosteum (Cases 1 and 2). Additionally, the NPWT dressing has served as an effective alternative to free tissue transfer for a wound located at a functionally active area, such as the elbow, allowing the patient to fully restore the active function of the joint. In the authors’ opinion, the mechanism of effectiveness of NPWT treatment in the closure of wounds with exposed bone devoid of periosteum might be attributable to the mechanical force provided by the negative pressure allowing the granulation tissue to expand over the exposed bone from the adjacent areas of the wound. In addition, as demonstrated in Case 3, it seems that the biomechanical properties and texture of the granulation tissue formed by NPWT treatment differ from those created by conventional dressing management in a way that prevents formation of contractures. This may allow satisfactory restoration of joint function of the involved areas. The validity of free tissue transfer for the management of large, complex wounds of the extremities with exposed functional structures, particularly bone, is well established.^1,16 Free flap reconstruction represents a standard approach in the management of these wounds in the authors’ practice as well. The authors believe that this method remains the first choice in the treatment of large, complex wounds of the extremities as it provides immediate closure of the wound with well vascularized, durable tissues. However, free tissue transfer is not always possible. The cases presented in this report illustrate that NPWT may serve as a valuable alternative to free flap transfer where the reconstructive option is contraindicated or when the free flap fails. Further experience will establish the value of the NPWT as a definitive alternative to free tissue transfer. Conclusion Negative pressure wound therapy dressings have a well established niche in the current philosophy of wound management. However, as clinical experience with the usage of this device grows, so does the spectrum of its utility. The authors’ limited experience shows that in certain cases in the management of complex open wounds of the extremities, particularly those with exposed bone, even devoid of periosteum, the NPWT dressing can serve as an effective substitute when free tissue transfer is contraindicated.