Wound control includes debridement, dressings, advanced wound healing products, vacuum-assisted closure (VAC), ultrasound, hyperbaric oxygen and skin grafting.
Debridement. Debridement is the most important part of wound control and is best carried out with a scalpel. It allows removal of callus and devitalized tissue and enables the true dimensions of the ulcer to be perceived. It reduces the bacterial load of the ulcer even in the absence of overt infection, restores chronic wounds to acute wounds and releases growth factors to aid the healing process (34). It also enables a deep swab to be taken for culture. The larvae of the green bottle fly are sometimes used to debride ulcers (35) especially in the neuroischemic foot (36). Maggot debridement therapy has recently been shown to reduce short-term morbidity in nonambulatory patients with diabetic foot wounds, decreasing antibiotic use and risk of amputation (37).
Dressings. Although moist wound healing is generally carried out in the management of chronic wounds, the situation with diabetic foot ulcers is more complex (38). Indeed, a fine balance is needed to avoid maceration of tissues whilst, on the other hand encouraging conditions that prevent eschar formation and assist cell migration within the wound (39).
There is no firm evidence that any dressing is better or worse than any other. A review that assessed 10 randomized trials and two controlled trials concluded that there was no evidence to support the effectiveness of any one type of protective dressing over any other for treating diabetic foot ulcers (10). Sterile, nonadherent dressings should cover all ulcers to protect them from trauma, absorb exudate, reduce infection and promote healing. Wounds should be inspected frequently to ensure that problems or complications are detected quickly, especially in-patients who lack protective pain sensation.
The following dressing properties are essential for the diabetic foot: ease and speed of lifting, the ability to be walked on without suffering disintegration and good exudate control. Dressings should be lifted every day to ensure that problems or complications are detected quickly, especially in patients who lack protective pain sensation.
Advanced Wound Healing Products. When ulcers do not respond to basic treatment, advanced products to stimulate wound healing may have to be put into practice (40). These are expensive treatments and should only be used when basic treatments have failed. Clinical decisions about when to use advanced or more experimental therapies may be based on healing rates. Studies in venous and diabetic ulcers suggest that advancement of more than 0.7mm per week is 80% sensitive and specific for eventual wound closure (41). Advanced wound healing products include:
■ Growth factors
■ Skin substitutes
■ Extracellular matrix proteins
■ Protease inhibitors
■ Vaso-active compounds growth factors. Platelet derived growth factor (Regranex), stimulates fibroblasts and other connective tissue cells located in the skin and is beneficial in enhancing wound healing processes of cell growth and repair. Four placebo-controlled trials of PDGF-BB in neuropathic ulcers have been carried out. The pivotal study of 382 patients demonstrated that Regranex gel (100mcg/g) healed 50% of chronic diabetic ulcers, which was significantly greater than the 35% healed with a placebo gel (42). Recombinant human epidermal growth factor (hEGF) had a positive effect on healing in a small double-blind randomized controlled study.
skin substitutes. Dermagraft is an artificial human dermis manufactured through the process of tissue engineering. Human fibroblast cells obtained from neonatal foreskin are cultivated on a three-dimensional polyglactin scaffold. This results in a metabolically active dermal tissue with the structure of a papillary dermis of newborn skin. A randomized controlled multicenter study of 281 patients with neuropathic foot ulcers demonstrated that at 12 weeks, 50.8% of the Dermagraft group experienced complete wound closure that was significantly greater than in the controls, of whom 31.7% healed (43). In another 12-week randomized study with living foreskin fibroblasts in a vicryl mesh, incidence of complete wound closure of neuropathic foot ulcers was 30% in the active group and 18% in the control group (44).
Apligraf consists of a collagen gel seeded with fibroblasts and covered by a surface layer of keratinocytes (45). In a randomized 12-week trial of 208 patients with neuropathic ulcers, the bilayered construct, Apligraf, led to complete wound closure in 56% of patients, compared with 38% in controls (P = 0.0042). There was a reduced the time to complete closure (65 days vs 90 days, P = 0.0026).
Bilayered Cellular Matrix (BCM) is a porous collagen sponge containing cocultured allogeneic keratinocytes and fibroblasts harvested from human neonatal foreskin. Patients with chronic, diabetic, neuropathic foot ulcers were randomized a multicenter, randomized, controlled, parallel-group pilot study to receive either standard care (moist saline gauze cover for up to 12 weeks (n = 20)) or to active treatment (n = 20) of standard care plus an application of BCM at each weekly visit for up to six total applications, followed by standard care alone for an additional six weeks or until complete healing. By 12 weeks, 7 of 20 wounds (35%) treated with BCM showed complete healing compared with 4 of 20 wounds (20%) treated with standard care (46).
extracellular matrix proteins. There has also been considerable interest in the application of extracellular matrix proteins to accelerate healing of diabetic foot ulcers, including hyaluronic acid and collagen.
Hyaff is an ester of hyaluronic acid, which is a major component of the extracellular matrix Hyaff-based autologous grafts both dermal and epidermal have been used to treat two groups of diabetic foot ulcers: plantar ulcers and postoperative wounds located on the dorsum of the foot. Patients in both groups had offloading, which was total contact casting for plantar ulcers and a rigid-sole shoe for dorsal ulcers. After 11 weeks there was no difference in the rate of healing in patients with plantar ulcers but in the dorsal ulcers, the autologous bioengineered graft showed increased rate of ulcer healing compared with control group (67% vs 31%, p = 0.049) (47).
OASIS wound matrix (Cook Biotech, Lafayette, IN) is derived from the pig small intestine submucosa. This consists of a natural collagenous, three-dimensional extracellular matrix that act as a framework for cytokines and cell adhesion molecules for tissue growth. A recent study has compared the healing rates at 12 weeks for full-thickness diabetic foot ulcers treated with OASIS Wound Matrix, an acellular wound care product, vs Regranex Gel. This study reported that complete wound closure after 12 weeks of treatment was observed in 49% of the OASIS-treated patients (n = 18), compared with only 28% of the Regranex-treated group (n = 10), p = 0.055 (48).
protease inhibitors. Promogran is a protease inhibitor that consists of oxidized regenerated cellulose and collagen. It inhibits proteases in the wound and protects endogenous growth factor. In a 12 week study, of 184 patients, 37% of Promogran treated patients healed compared with 28% of saline gauze treated patients, a nonsignificant difference (49).
vaso-active compounds. The effect on dalteparin on ulcer outcome in diabetic patients with peripheral arterial occlusive disease has been investigated in a prospective, randomized, double-blind, placebo-controlled trial. A total of 87 patients were randomized to treatment with subcutaneous injection of 5000 units dalteparin (Fragmin, Pharmacia Corporation; n = 44) or an equivalent volume of physiological saline (n = 43) once daily until ulcer healing or for a maximum of 6 months. There was a better ulcer outcome (p = 0.042) and a greater number of patients healed with intact skin or decreased the ulcer area > 50% in the Dalteparin group compared with the placebo group (50).
Chrysalin(R) a thrombin peptide, in saline or saline alone was applied topically, twice weekly, to diabetic ulcers with standardized care and offloading. A dose-dependent effect was seen in the per-protocol population where 1 and 10 mug Chrysalin(R) treatment resulted in 45% and 72% more subjects with complete healing than placebo treatment. Chrysalin(R) more than doubled the incidence of complete healing (p < 0.05), increased mean closure rate approximately 80% (p < 0.05), and decreased the median time to 100% closure by approximately 40% (p < 0.05).
Vacuum-assisted Closure (VAC). In this technique, the VAC pump applies gentle negative pressure to the ulcer through a tube and foam sponge that are applied to the ulcer over a dressing and sealed in place with a plastic film to create a vacuum. Exudate from the wound is sucked along the tube to a disposable collecting chamber. The negative pressure improves the vascularity and stimulates granulation of the wound. In a recent study, 162 patients with postoperative wounds, following partial foot amputation, were enrolled into a 16-week, 18-center, randomized clinical trial in the USA. More patients were healed in the VAC pump group than in the control group (43 [56%] vs 33 [39%], p = 0.040). The rate of wound healing, based on the time to complete closure, was faster in the VAC pump group than in controls (p = 0.005) (51). A recent consensus statement on negative pressure wound therapy (VAC Therapy) for the management of diabetic foot wounds has recently been published and summarizes current clinical evidence (52)
Hyperbaric Oxygen. Adjunctive systemic hyperbaric oxygen therapy has been shown to reduce the number of major amputations in ischemic diabetic feet (53). Studies involving relatively small groups of patients have shown that hyperbaric oxygen accelerates the healing of ischemic diabetic foot ulcers. It is reasonable to use hyperbaric oxygen as an adjunctive in severe or life threatening wounds (54). A recent Cochrane review concluded that hyperbaric oxygen significantly reduced the risk of major amputation and may improve the chance of healing of foot ulcers at 1 year. Although this should be regarded cautiously because of modest number of patients, methodological shortcomings in previous studies (55).
Skin Grafting. To speed healing of ulcers that have a clean granulating wound bed, a split skin graft may be harvested and applied to the ulcer. If chosen from within the distribution of sensory neuropathy, the donor site will be less painful.
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