Michael J. Morykwas

Vacuum-assisted Closure: A New Method for Wound Control and Treatment: Clinical Experience

Despite numerous advances, chronic and other difficult-to-man-age wounds continue to be a treatment challenge. Presented is a new subatmospheric pressure technique: vacuum-assisted closure (The V.A.C.). The V.A.C. technique entails placing an open-cell foam dressing into the wound cavity and applying a controlled subatmospheric pressure (125 mmHg below ambient pressure). Three hundred wounds were treated: 175 chronic wounds, 94 subacute wounds, and 31 acute wounds. Two hundred ninety-six wounds responded favorably to subatmospheric pressure treatment, with an increased rate of granulation tissue formation. Wounds were treated until completely closed, were covered with a split-thickness skin graft, or a flap was rotated into the healthy, granulating wound bed. The technique removes chronic edema, leading to increased localized blood flow, and the applied forces result in the enhanced formation of granulation tissue. Vacuum-assisted closure is an extremely efficacious modality for treating chronic and difficult wounds.

Vacuum-assisted closure: a new method for wound control and treatment: animal studies and basic foundation.

A series of basic animal studies using a new subatmospheric pressure technique (The V.A.C.) to expedite wound healing are presented. The technique entails placing an open-cell foam into the wound, sealing the site with an adhesive drape, and applying subatmospheric pressure (125 mmHg below ambient) that is transmitted to the wound in a controlled manner. Utilizing a pig model, four studies were undertaken to determine the effect of subatmospheric pressure on laser Doppler-measured blood flow in the wound and adjacent tissue (N = 5), rate of granulation tissue formation (N = 10), clearance of bacteria from infected wounds (N = 5), and measurement of nutrient flow by random-pattern flap survival (N = 5). Blood flow levels increased fourfold when 125 mmHg subatmospheric pressure was applied. Significantly increased rates of granulation tissue formation (p ≤ 0.05) occurred with both continuous (63.3% ± 26.1%) and intermittent (103% ± 35.3%) application. Tissue bacterial counts significantly decreased (p ≤ 0.05) after 4 days of application. Random-pattern flap survival significantly increased (p ≤ 0.05) by 21% compared to controls. We determined that the application of controlled subatmospheric pressure creates an environment that promotes wound healing.

Effects of varying levels of subatmospheric pressure on the rate of granulation tissue formation in experimental wounds in swine.

The use of subatmospheric pressure to promote wound healing has increased in popularity during the last several years. The original studies on granulation tissue formation used a 125-mmHg vacuum. The use of alternative sources of subatmospheric pressure has led to many questions regarding efficacy or risk. In this report a swine model is used to quantify and compare the effects of low vacuum suction (25 mmHg) and high vacuum suction (500 mmHg) produced by various vacuum pumps and wall suction systems with the standard 125-mmHg vacuum. Additionally, the effects of an unregulated air leak in the sealing system were examined. All four wound treatments were examined on each of 4 pigs. Wounds were treated until one of the wounds had granulated to a level flush with the surrounding tissue. Wounds treated with the standard 125-mmHg vacuum had filled with granulation tissue by day 8. At this time wounds treated with 25 mmHg had filled 21.2% with new granulation tissue, and wounds treated with 500 mmHg had filled 5.9% with new tissue. Wounds treated with 125 mmHg with a hole in the sealing drape had increased in size 197% because of the debridement of necrotic tissue. In conclusion, wounds treated with a 125-mmHg vacuum exhibited a significant (p < 0.0001) increase in the rate of granulation tissue formation compared with treatment at 25 mmHg or 500 mmHg. The presence of an unregulated air leak in the sealing drape results in significant progression (p < 0.0001) of the wound secondary to dehydration and progressive necrosis.

Vacuum-assisted closure: state of basic research and physiologic foundation.

Summary: A tremendous amount of research has been conducted in recent years investigating the mechanisms of action by which the application of subatmospheric pressure to wounds increases the rate of healing. Similarly, numerous studies have also been conducted examining the physiologic response of wounds to the applied subatmospheric pressure. However, many more need to be conducted. A series of basic studies examining the use of subatmospheric pressure to treat wounds is presented, including the original studies upon which the vacuum-assisted closure device was based (on blood flow, granulation tissue formation, bacterial clearance, and survival of random-pattern pedicle flaps). Subsequent studies analyzing removed fluids, envenomation/extravasation, burns, grafts, and in vitro tissue culture studies are also reviewed. Two broad mechanisms of action are proposed: removal of fluid and mechanical deformation. Fluid removal both decreases edema–-thus decreasing interstitial pressure and shortening distances of diffusion–-and removes soluble factors that may affect the healing process (both positively and negatively). The relationship of mechanical deformation to increased growth is well known to plastic surgeons, as it is the basis of tissue expansion. While much has been done, a great deal more needs to be done to elucidate the mechanisms of action responsible for the dramatic response seen clinically.

Vacuum-assisted closure: state of clinic art.

Summary: Treatment of wounds has been the cornerstone of plastic surgery since its inception. Vacuum-assisted closure provides a new paradigm that can be used in concert with a wide variety of standard existing plastic surgery techniques. It was originally developed as an alternative treatment for debilitated patients with chronic wounds. It has rapidly evolved into a widely accepted treatment of chronic and acute wounds, contaminated wounds, burns, envenomations, infiltrations, and wound complications from failed operations. The ease of technique and a high rate of success have encouraged its adaptation by thoracic, general, trauma, burn, orthopedic, urologic, as well as plastic surgeons. This article discusses multidisciplinary advances in the use of the vacuum-assisted closure technique over the past 10 years and its status as of 2006. Creative surgeons continue to regularly adapt the system to difficult problems. This technique in trained surgical hands greatly enhances the scope and safety of wound treatment.

A controlled subatmospheric pressure dressing increases the rate of skin graft donor site reepithelialization

The ability to increase the rate of skin graft donor site reepithelialization significantly in a cost-effective manner has important implications for the patient undergoing major reconstructive procedures. In this study the effect of externally applied reduced pressure (the V.A.C.) on the rate of healing of donor site wounds was initially investigated using a porcine model (N = 4), then repeated on humans (N = 10). Spirt-thickness skin grafts were harvested from the backs of pigs using standard technique. Half of the donor sites were treated with subatmospheric pressure (125 mmHg) and half were treated with an OpSite dressing. Biopsies taken every 48 hours demonstrated that sites exposed to reduced pressure healed at a much faster rate than sites treated with a standard occlusive dressing. Similarly, donor sites in humans reepithelialized faster in 7 of 10 patients, the rate was. the same in 2 of 10 patients, and Opsite was faster in 1 of 10 patients. We believe this technology has the potential to be a relatively simple and cost-efficient method for increasing the rate of donor site healing.

The use of negative-pressure wound therapy (NPWT) in the temporary treatment of soft-tissue injuries associated with high-energy open tibial shaft fractures.

Objectives: To evaluate the utility of negative-pressure wound therapy (NPWT) in the setting of high-energy open tibial shaft fractures. Design, Setting, and Patients/Participants: This was a retrospective consecutive series in a level 1 university-based trauma center. Forty-nine consecutive patients presenting to a level 1 trauma center between 1996 and 2004 with 50 grade/type III open tibial shaft fractures were assessed. Intervention: The open wounds associated with each fracture were each treated with NPWT before definitive wound closure or coverage. Main Outcome Measurements: Infection rate, need for amputation after attempted definitive coverage, problems with bony healing requiring surgical intervention, reoperation rate after definitive coverage, and the type of definitive coverage required. Results: The overall infection rate for all grade/type III open fractures was 15 of 50 fractures (30%), with 11 of 50 (22%) requiring repeated surgery for infection. The infection rate was 12.5% for grade/type IIIA open fractures, 45.8% for grade/type IIIB, and 50% for grade/type IIIC. Twenty-four of 50 fractures (48%) required subsequent surgery to facilitate fracture healing. Five fractures required amputation after attempted coverage. Seven of 24 fractures initially classified as grade/type IIIA and 10 of 24 fractures initially classified as grade/type IIIB ultimately required free tissue transfer or rotational muscle flap coverage. Conclusions: Infection and nonunion rates with the use of NPWT for temporary coverage of wounds associated with grade/type III open tibial shaft fractures are similar to those of historical controls, but this technique may be beneficial in decreasing the need for free tissue transfer or rotational muscle flap coverage.

Use of subatmospheric pressure to prevent doxorubicin extravasation ulcers in a swine model

Application of subatmospheric pressure to sites injected with doxorubicin prevented ulcer formation in treated sites (0 ulcers/16 sites) compared to control wounds (10 ulcers/16 sites) in a pig model.

Analysis of silicon in human breast and capsular tissue surrounding prostheses and expanders

Diffusion of polydimethylsiloxane from silicone breast prostheses and soft-tissue expanders has been associated with capsular contraction. We used electron dispersive x-ray analysis and scanning electron microscopy to assess the presence of silicon in capsular tissue surrounding three categories of breast prostheses and expanders. Breast and subcutaneous tissues external to the capsules were used as control specimens. Semiquantitative results allowed capsules to be ranked according to implant type. Silicon was localized within the inner 2.0 mm of capsular tissue. The analyses of tissues from 2 patients exhibiting unilateral, Baker grade IV contraction after bilateral placement of prostheses showed less silicon present in the severely contracted capsule than in the less-contracted capsule. Results from this study diminish the importance of silicon as the initiator of capsular contraction.

Swelling and pressure-volume relationships in the dermis measured by osmotic-stress technique

Water transfer across the extracellular matrix (ECM) involves interstitial osmotic forces in as yet unclear ways. In particular, the traditional values of Starling forces cannot adequately explain fluid transfer rates. Here, we reassess these forces by analyzing fluid transfer in live pig and human dermal explants. Pressure potentials were controlled with inert polymers adjusted by membrane osmometry (range = 3-219 mmHg), and fluid transfer in and out of the explants was followed by sequential precision weighing. Water motional freedom in the dermis was examined by NMR. In pigs, mean hydration pressure (HP; the pressure at which volume did not change) was 107 +/- 22 and 47 +/- 12 (SE) mmHg at 4 degrees C and 37 degrees C (P = 0.012, paired t-test, n = 7). Volume changes observed in response to pressure potential were reversible. The equation, Volume change = V(max)/[1+(time/T(1/2))(d)], where V(max) is maximal volume change; T(1/2), time at volume = 1/2 V(max); and d, a rate parameter, was fitted to experimental progression curves (r(2) > 0.9), yielding V(max) values linearly related to pressure, with mean slopes -3.5 +/- 0.28 and -2.6 +/- 0.21(SE) mul.g(-1).mmHg(-1) at 4 degrees C and 37 degrees C. NMR spin-spin relaxation times (T(2)) varied within 200- to 400-mum distances in directions perpendicular to the epidermis, with slopes reaching 0.03 ms/mum. Results support a mechanism in which fluid transport across the ECM is locally regulated at micrometer scales by cell- and fiber-gel-dependent osmomechanical forces. The large HP helps to explain the fast interstitial in/out flow rates observed clinically.