Debridement of Chronic Wounds: A Review of Past & Present Treatment Strategies

  Chronic wounds clearly represent a healthcare burden of tremendous magnitude as they afflict hundreds of thousands of patients while costing on the order of billions of dollars annually in the US alone. The difficulties posed to those living with and caring for nonhealing wounds are not new; rather, they have plagued human civilizations for thousands of years. Archaeologists have found evidence through tablets unearthed from Babylonia that prove people were concerned with the proper treatment of wounds as early as 2100 B.C. These tablets spell out in the Sumerian language a sort of “primitive” wound care prescription. Recommendations included “to pound together dried wine dregs, juniper, and prunes,” adding beer to the mixture in order to create a salve that would harden over the oiled wound.¹ Similarly, ancient Egyptian physicians were well known in the Near East for their unique healing skills. Acute wounds were covered with raw meat and swabs soaked with honey to prevent infection and bandaged with pads, linen, and nets.² Burn dressings used the milk from mothers of male babies as well as moldy bread, honey, and copper salts.³ While ancient Greek physician Hippocrates advocated the “dry” treatment of wounds,⁴ several hundred years later Galen, the ancient Roman physician and surgeon to the gladiators, proposed and wrote prolifically on the theory of “laudable pus,” which held that suppuration of wounds should be encouraged as a part of the natural healing process. This latter theory was adopted by much of ancient civilization and became a tradition that precluded aseptic treatment of wounds up to the 19th century.⁵ As such, little progress was made in wound management during this time.

  In 2000, Vincent Falanga, MD, FACP, professor of dermatology and biochemistry at the Boston University School of Medicine, and Gary Sibbald, FRCPC, ABIM, DABD, Med, professor of public health sciences and medicine at the University of Toronto, formally introduced the concept of wound bed preparation.^6,7 Separately, but similarly, their focus was initially on the management of bacterial and moisture balance as well as debridement of devitalized tissue. Three years later, at a meeting of the International Wound Bed Preparation Advisory Board, an algorithmic approach to wound bed preparation was delineated with the development of the T.I.M.E. acronym — tissue debridement, infection or inflammation control, moisture balance, and attention to edge effect.^8,9 The concept was updated by Sibbald in 2006 to emphasize treatment of patient-specific factors that impair wound healing and was made more comprehensive in 2011 with links to evidence-based literature, expert opinions, and clinical practice-based strategies.^10,11 Taken together, this framework encompasses globally applicable strategies for wounds of differing types that aim to aid clinicians in maximizing wound healing potential.

Role of Debridement

  Arguably, debridement is the most fundamental principle and effective technique of achieving wound bed preparation. Pierre-Joseph Desault introduced the term “debridement” in the late 1700s as he described the significance of freshening the edges of war wounds prior to closure. He was referring to sharp debridement specifically, but the term refers generally to attempts to clear devitalized wound tissue including necrotic and senescent cells, inflammatory enzymes, and biofilms of bacterial colonies in order to restore a healthy wound base with a viable extracellular matrix. When utilizing this technique, Desault recognized a notable increase in wound healing and overall patient survival.¹² Throughout the 20th century, debridement practices have progressed periodically. The World Wars and other conflicts presented surgeons with complex injuries from diverse weapons leading to sporadic bursts of innovation. As the discovery and evolution of antibiotics continues to increase survival, there has also arisen a corresponding increased need for creative and practical patient care management. Accordingly, progress in the care of diseases associated with chronic wounds, such as diabetes and venous insufficiency, has increased the demand for innovations in wound care.¹³

  Operative wound debridement must be meticulous and methodical. As the wound is explored, it is critical to determine tissue viability through examination of the tissue’s color, temperature, and bleeding capability so that unviable tissue may be removed. If bony involvement is suspected, preoperative radiographs should be considered. If abscessed cavities are found, these should be drained adequately. The end point for most tissue types would be debridement to bleeding tissue, but specialized tissues such as cartilage, tendon, and irradiated wounds require careful consideration. A key guiding principle to follow would be that upon completion of the debridement, ‘‘no stone should be left unturned,” ie, no crevice left unexplored.¹⁴

  The removal of necrotic tissue overlying the wound base is important for a number of reasons. First, this nonviable tissue makes accurate assessment of the depth and condition of the wound difficult. Additionally, necrotic tissue represents a near-perfect nidus for bacterial growth and, as it obscures the wound in general, it also may hide early signs of local wound infection. In addition to removing tissue, various debridement techniques have been shown to significantly reduce bacterial burden.¹⁵ Finally, debridement clearly promotes healing through the conversion of a chronic wound environment to a more active and responsive acute healing environment.¹⁶ It is important to recognize that multiple debridements are most often necessary to achieve wound stability with chronic wounds.

  Relying on past experience and advances in technology, new types of debridement continue to develop. The current methods of debridement can be divided into several categories including autolytic, biologic, enzymatic, mechanical, and surgical. These categories can be further broken down and will be outlined here. Debridement of varying techniques has subsequently become ingrained as a surgical standard of care and will most certainly continue to evolve to more fully meet the needs of patients living with wounds.

Review of Current Techniques

  Autolytic Debridement

  This type of debridement relies on the inherent ability of the body, through its own enzymes, immune cells, and moisture, to liquefy and eliminate necrotic tissue. To perform autolytic debridement, the wound is covered with a moist-retention dressing to create an environment that allows for the digestion of devitalized tissues by endogenous enzymes and/or phagocytic cells. Hydrocolloids, hydrogels and transparent films are utilized as dressings, all of which maintain wound fluid in contact with the necrotic tissue. Autolysis necessitates limited technical skills and is comparatively easier to perform. It is selective in that only necrotic tissue is liquefied and is virtually painless for the patient; however, this method is time-consuming and risks include wound edge maceration and infection. As such, it is essential that wounds be cleared of any remaining debris at each dressing change. Autolytic debridement is indicated for wounds with minimal necrosis, as an adjunct after more aggressive debridement, and in patients who are unable to tolerate pain or surgical procedures.¹⁶ Studies examining autolytic debridement have been limited and have typically compared different dressing types in the treatment of chronic wounds. Two separate studies found no significant difference in healing rate of pressure ulcers between groups treated with polymer hydrogel dressings versus hydrocolloid dressings and transparent absorbent acrylic dressings versus hydrocolloid dressings.^17,18 Further, a study performed in 2010 also found no significant reduction in wound area for pressure or venous leg ulcers (VLUs) when comparing charcoal dressings with hydrocolloid dressings.¹⁹

  Biologic Debridement

  Sterilized maggots, specifically larvae of the green bottle fly (Lucilia sericata), are the workhorses of biologic debridement, which is accordingly also known as maggot debridement therapy (MDT). The maggots work selectively and fairly rapidly to digest necrotic tissue and secrete bactericidal enzymes, which make them effective against methicillin-resistant Staphylococcus aureus and beta haemolytic streptococcus. Currently, MDT is viewed as a secondary strategy for patients after surgical debridement or for those who are not candidates for surgical procedures.16 In the mid-1990s only a handful of physicians were using medical maggots. In 2004, the US Food and Drug Administration approved larval therapy for debridement of chronic wounds including pressure ulcers, venous stasis ulcers, neuropathic foot ulcers, and nonhealing traumatic or postsurgical wounds. Today, any licensed physician in the US can prescribe this therapy; however, likely due to patient and physician aversion, biologic debridement has still not gained widespread acceptance. In Europe, however, MDT is widely practiced and approximately 50,000 treatments were applied to wounds in 2011 worldwide.²⁰

  In 2002, a cohort-controlled study examined the difference between pressure ulcers treated with conventional therapy and those treated with larval therapy.²¹ Results demonstrated an increased number of completely debrided wounds, a greater reduction of necrotic tissue, and a greater increase in granulation tissue in patients treated with maggot therapy. Also, there was a significant reduction in mean surface area of wounds at three weeks of maggot use. An additional cohort study examined standard debridement therapy versus maggot therapy for diabetic foot ulcers (DFUs) and found similar results. Specifically, during the first two weeks of conventional therapy, there was no significant debridement of necrotic tissue, while during the same period with maggot therapy there was an average 4.1 cm reduction of necrotic tissue. After four weeks of therapy, maggot-treated wounds were completely debrided, whereas conventionally treated wounds remained covered over 33% of their surface area by necrotic tissue at five weeks.²² Thus, maggot therapy was more effective and efficient in debriding nonhealing foot and leg ulcers than continued traditional care. A similar study examined hydrogel debridement versus maggot therapy for necrotic leg ulcers and found that while maggot therapy led to quicker debridement there was no significant difference in overall healing time or health-related quality of life.²³ Additionally, a related study using the same set of patients found no significant difference in the cost of maggot therapy compared with hydrogel debridement.²⁴

  Enzymatic Debridement

  Manufactured enzymes, namely collagenase and papain-urea, serve as the debriding agents in enzymatic debridement. For bulk debridement, papain has historically been preferable as it is a broad-spectrum enzyme, whereas collagenase is less traumatic for viable cells.¹⁶ In 2008, however, papain-urea ointment was taken off the market. Thus, collagenase is currently one of the few remaining options for both inpatient and outpatient use. Collagenase is derived from fermentation by Clostridium histolyticum. The ointment form contains 250 collagenase units per gram of white petrolatum. It is recommended that the ointment be applied daily and discontinued when healthy granulation occurs; however, there is evidence in burn literature to support continuation for the duration of healing due to reduced scar formation and maintenance debridement. Overall, enzymatic debridement is suitable for nonsurgical patients and is effective in removal of moist, flimsy eschar and tissue debris. Unfortunately, it lacks the ability to penetrate thick eschar and enzyme application can be painful for the patient. Some, including the authors, may find it to be expensive.

  A study performed in 2005 compared the use of collagenase with an autolytic dressing in the treatment of chronic leg ulcers. The research group concluded that although there was no significant difference calculated, there seemed to be better appearance of the re-epithelialized area, granulation tissue, and remaining eschar with the autolytic dressing.²⁵ Two earlier studies examined the use of a fibrinolysin-desoxyribonuclease solution versus saline and a krill enzyme solution versus saline for the debridement of chronic leg ulcers.²⁶ The first study found that the fibrinolysin-desoxyribonuclease preparation was significantly more effective in debriding the wound and allowing for formation of granulation tissue than saline alone. The second study accordingly concluded that the enzymatic preparation taken from the digestive system of the Antarctic krill (Euphausia superba) was found through computer imaging to be significantly more effective than saline in debriding VLUs.²⁷

  Mechanical Debridement

  As the name implies, mechanical debridement involves the physical removal of necrotic tissue from a wound using one of several different methods including wet-to-dry dressing changes, hydrotherapy, wound irrigation, and negative pressure wound therapy (NPWT). Generally, these methods don’t necessitate a trip to the operating room. In the first form of mechanical debridement — wet-to-dry dressing changes — a moist dressing (such as gauze) is placed in direct contact with the wound bed and allowed to dry. The dressing is then manually removed and, in the process, brings with it adherent necrotic and slough tissue. This type of mechanical debridement is indicated for decontaminating wounds with moderate amounts of necrotic debris and specifically can be used for contaminated or infected laparotomy wounds, perianal/groin wounds, and foot wounds.²⁸ The advantage to this technique is that the cost of the actual material (ie, gauze and saline) is minimal. Disadvantages include that wet-to-dry dressing changes remove tissue in a non-selective manner and may traumatize healthy or healing tissue including the removal of new epithelium each time the dressing is changed. Thus, it may be preferable to reconsider the strategy once the wound is granulating. Additionally, this method can be time-consuming and can cause excessive pain as well as bleeding.

  Hydrotherapy consists essentially of wound soaks in a water bath or whirlpool. The water temperature in the bath should range from 33.5 °C-35.5 °C for most patients. In patients living with peripheral vascular disease, the temperature should not exceed 1 °C above skin temperature. In patients living with cardiopulmonary disease, the temperature should not exceed 38 °C. This technique is effective and relatively easy to perform; however, over-soaking can lead to tissue maceration, waterborne pathogens may cause contamination or infection, and disinfecting additives may be cytotoxic.

  Wound irrigation is often recommended for acute wounds with a presumed high bacterial load. In fact, wound irrigation is a basic component of standard open fracture care.²⁹ In this form of mechanical debridement, irrigating systems cleanse the wound non-surgically with saline or antibiotic solutions. When used intraoperatively, irrigating systems remove loose, devitalized tissue and control bacterial load with high pressure (typically from 2-10 psi, whereas pre- and postoperative debridement of this type cleanses more gently at lower pressure). High-pressure irrigation when compared with low-pressure irrigation has been shown to more effectively remove bacteria and debris, leading to lower rates of wound infection. Also important is the volume of irrigation fluid used as increasing volume yields decreasing bacterial counts.³⁰ Additionally, pulse lavage has been shown to more effectively reduce bacterial burden than continuous flow. There has been some concern regarding bacterial spread and contamination possibly resulting from wound irrigation systems. As such, irrigation is most often utilized as an adjunct to surgical sharp debridement and should not be used when the fluid is likely to collect in dead space.¹⁴

  NPWT addresses simultaneously many of the issues associated with wound healing. In particular, the negative pressure environment decreases swelling, which increases wound blood flow and allows for improved oxygen and nutrient delivery to the wound area. The continuous removal of exudate also yields reduced bacterial counts as well as decreased inflammation in general. Finally, the bulk of the NPWT device may prevent patients from putting pressure on the area, thereby preventing cycles of ischemia and reperfusion that impede wound healing.³¹ Contraindications to this therapy include inadequate wound bed preparation such as remaining eschar, devitalized tissue, and desiccated wound; inadequate hemostasis or exposed vessel; fistula; and cancer with positive margins. If the wound develops odor or infection while using NPWT, it is advisable to switch therapy to wet-to-dry dressing changes with Dakin’s solution.

  Multiple studies have been performed to examine the techniques of mechanical debridement against one another and mechanical debridement along with other types of debridement.

  A few of the key studies are highlighted as follows: In 2003, a randomized controlled crossover study looked at wound depth and volume of primarily surgically debrided DFUs treated with NPWT versus conventional dressings. Results of this study confirmed NPWT significantly decreased wound dimensions compared with wet-to-dry dressing changes.³² Also in 2003, another group aimed to determine the amount of time for wound size reduction of 50% in patients with surgically debrided pelvic pressure sores managed post-procedurally with NPWT or saline moistened gauze. Researchers found both groups effectively formed granulation tissue and there was no difference noted between the groups in time to 50% wound size reduction.³³

  A further study performed in 2004 again compared the effect of NPWT or conventional moist-gauze therapy on wound surface area and bacterial load. Results indicated NPWT significantly reduced wound surface area and the quantity of non-fermentative gram-negative bacilli. There was, however, a significant increase in staph in the NPWT group. Thus, the study concluded that while NPWT positively affected wound healing, this effect could not be explained by lessening of the bacterial burden.³⁴ The same authors published a follow up in 2007 that showed a shorter duration of therapy for NPWT-treated patients versus those treated with wet-to-dry dressing changes.³⁵ A multicenter randomized controlled trial published in 2008 examined treatment of DFUs using NPWT compared with advanced moist wound therapy (defined as predominantly hydrogels and alginates). The authors found a larger proportion of wounds treated with NPWT reached closure and the NPWT group required fewer secondary amputations.³⁶ Lastly, traditional dressing changes were evaluated against hydrotherapy with conventional treatment for management of pressure ulcers. Results showed the group assigned to whirlpool therapy plus conventional treatment experienced wound healing, measured by wound dimensions, at a faster rate.³⁷

  Surgical Debridement (Sharp and Hydrocision)

  Although numerous techniques of debridement are utilized in practice, surgical debridement has become the standard of care in many cases and is most commonly the standard against which other techniques are judged. The surgical method involves direct removal of necrotic and dessicated tissues as well as a subsequent reduction in microbial load, providing the most efficient method of wound bed preparation. This type of debridement makes possible the most accurate assessment of wound depth and severity, making it essential in life- and limb-threatening infections. Wounds with extensive, adherent eschar clearly benefit from and often require surgical debridement. A limitation of surgical debridement: It’s non-selective in that, more often than not, some healthy tissue is removed during the procedure. Additionally, not all patients are surgical candidates, and those who tolerate the procedure may be limited by bleeding tendency and pain tolerance.¹⁶

  Classically, sharp debridement has been performed with a scalpel blade or scissors to excise tissue in segments. The Weck knife is a specialized scalpel that can be used to excise tissue tangentially. Tissue is frequently removed to just beyond the interface between the wound margin and healthy tissue so that slight margin of normal tissue is excised. Curettes or a metal ruler can contribute to sharp debridement when scraped across the surface and edges of the wound. Osteotomes and rongeurs may be needed to remove tougher tissues like bone.¹⁴

  Developed rather recently, hydrocision uses tangential hydrodissection to accomplish surgical debridement. Specifically, the high-pressure saline beam from the Versajet (Smith & Nephew) device can be used to excise wound tissue with precision in a tangential manner, causing minimal damage to surrounding tissue. It has been proven in a recent randomized controlled trial to be as effective in reducing bacterial burden as high-powered irrigating systems and has been shown to decrease the number of surgeries required for wound bed preparation for both acute and chronic wounds.^38,39 Tangential hydrosurgery seems to be particularly helpful in concavities, tight spaces, and in burn wound excision.⁴⁰

  The efficacy of surgical debridement has been demonstrated by three recent randomized controlled trials. Published in 1996, the first study examined DFUs healing with use of recombinant human platelet-derived growth factor. The results clearly show higher rates of healing at centers that performed debridement more often.⁴¹ The second multicenter randomized controlled trial examined treatment of VLUs and DFUs using a phase III bioengineered dermal matrix.⁴² As a part of the protocol, if indicated, sharp debridement was to be performed at each clinic visit. Similar to the prior study, this trial showed that centers where debridement was performed more frequently exhibited higher rates of wound closure. In 2008, a prospective randomized controlled trial compared tangential hydrosurgery with conventional surgical debridement for venous ulcers of the lower-extremity. Although there was no significant difference in wound closure time between the groups, debridement time was significantly shorter (by an average of 6.9 minutes) in the hydrocision group.⁴³ These results are difficult to interpret, but it does seem apparent that the Versajet system allows for effective wound bed preparation with less damage to surrounding healthy tissues. In summary, both sharp debridement and tangential hydrosurgery provide the most rapid and thorough method for wound debridement and wound bed preparation. Tangential hydrosurgery appears to be more precise and causes less trauma to surrounding normal tissue. Of course, extensive surgery is not feasible in all patients, so decision for surgical debridement must take into account the overall health of the patient.

  Wesley P. Thayer is assistant professor of plastic surgery at Vanderbilt University, Nashville, TN; chief of plastic surgery at Nashville Veteran’s Hospital; wound care director at Kindred Hospital – Nashville; and consultant for ACell® Inc., Columbia, MD.

  Analise B. Thomas is a recent graduate of Vanderbilt School of Medicine and is a resident in the plastic surgery program at Duke University Medical Center, Durham, NC.

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