Introduction

Foot problems in a person with diabetes are one of the most common complications seen in India. Although intensive efforts need to be made to avoid these foot complications, it is more easily said than done, especially in our country where walking barefoot is much more common than in the West. The reality is such that often the presenting complaint of a person with diabetes is a major foot infection, often with non healing ulceration. The morbidity, and sometimes, the mortality, associated with these complications are immemnse not only from the purely medical viewpoint, but also from the socioeconomic and psychological aspects. In fact, it has been shown that after accidents, diabetes associated foot problems are the secong most common cause of lower limb amputations in India. Patients with diabetes mellitus may present to the diabetes mellitus may present to the primary care practitioner with dangerous lower-extremity sequelae that are extremely challenging to treat. The high incidence of amputation in this patient population is, line large part, the result of uncontrolled infection and ulceration of the foot.

Cellulitis

All diabetic patients are prone to developing infections of the foot . Once established, these infections are more severe and more treatment - refractory than in nondiabetics. If left unchecked these infection may progress to cellulitis.

Pathogenesis

Foot infection in diabetics develops because of coexisting angiopathy, immunopathy, and neuropathy. Angiopathy begins at the microvascular level, with thickening of the basement membrane and reduced blood flow. This often leads to platelet aggregation and a further decrease in perfusion and oxygenation of foot tissues, together with reduced chemotaxis of neutrophils, macrophages, and other protentially protective cells. Immunopathy is the result of prolonged periods of hyperglycemia, which reduce the ability of these cells to phagocytize bacteria.

Neuropathy impairs the structural integrity of the foot while decreasing the perception of injury. Bacteria gain access via open wounds, including fissures and punctures in the insensate foot. However , many diabetic patients who present with a cellulitic foot do not have an obvious open wound, cellulitis may be the result of hematogenous bacterial spread from a urinary or respiratory tract infection to which diabetics are also susceptible. these patients present with the cardinal signs of infection - erythema, edema, and calor.

Causative pathogens

The causative pathogens are varied and can range from aerobic organisms such as Staphylococcus aureus, group B Streptococcus, Enterococcus, Coagulase-negative Staphylococcus, Proteus mirabilis, Proteus vulgaris, Enterbacter, Citrabacter, and Serratia. Pseudomonas has also been isolated from diabetic foot infections secondary to long - standing open ulcerations. In addition , anaerobic organisms such as Bactericides, Peptococcus, and peptostreptococcus are often identified.

Infection with several organisms is common. One should therefore perform both aerobic and anaerobic cultures, from sample material taken from the deeper parts of the wound.

TREATING CELLULITIS

Empiric Antibiotic therapy

Because of the frequency of polymicrobial involvement empiric treatment should cover Gram- negative aerobic as well as an aerobic organisms. The antibiotic chosen should be bactericiadal as opposed to beacteriostatic. In general, bacteriostatic antibiotics require an intact immune system to function properly.

Mild or Moderate Infections

Treat mild infections with broad - spectrum oral antibiotics such as amoxicillin/clavulanic acid, clindamycin, cefuroxime axetil, or cephalexin. This can be done on an outpatient basis. It is not necessary to culture superficial diabetic wounds. Moderate infection require treatment with intravenous antibiotics on an impatient basis. Broad - spectrum antibiotics such as imipicillin/sulbactam,piperacillin/tazobactam,ticarcillin/clavulanic acid, clindamycin or a fluoropuinolone should provide adequate coverage. Although clindamycin is a bacteriostatic antibiotic, its antibacterial activity has been shown to be bacteriocidal at higher dose concentrations. The newer third - and fourth - generation fluoroquinolones, some not yet widely available in India,-levefloxacin, grepafloxacin, sparfloxacin, and trovafloxacin - are particularly effective against polymicrobial infections.

Abscesses

After 2 to 3 days of antibiotic therapy, cellulitis often localizes to one area of the foot resulting in the formation of an abscess. Proper management of the abscess entails incision and drainage. In addition,obtain deep specimens intraoperatively for culture and sensitivity testing. These abscesses are often polymicrobial and filled with many contaminants. After removing all necrotics debris , irrigate the wound with normal sterile saline using a power irrigation pulse lavage system, which will enable you to dilute the concentration of invading bacteria. A bacterial count of at least 10⁵ per mm³ of soft tissue will establish an infection; therefore , dilution of bacteria in infected tissue is an essential adjunct to infection control.

Severe Infections

Severe infections (which are all life threatening )are characterized by massive cellulitis with ascending lymphangitis. The patient is likely to have sepsis, fever, and a significantly elevated white blood cell count. Narcotizing facetious with liquefaction necrosis and gas formation in the soft tissues may also be present. The antibiotic of choice is imipenem/cilastatin. However, ampicillin/sulbactam has proved effective in treating limb-threatening infections Synergistic antibiotic therapy including third - or - fourth - generation cephalosporin, ticarcillin/clavulanic acid, piperacillin/tazobactam, imipenem, or meropenem, each together with an aminoplycoside, are also effective attaints limb threatening infections.

In addition, one should seek surgical consultation for wide incision and drainage, debridement, and possibly, for ablative open guillotine amputation as a life-saving measure.

In investigating the different treatment options for foot infections in patients with diabetes without systemic infection, one study has found that the least expensive approach was prolonged treatment with oral antibiotics following initial hospitalization for surgical debridement; the most expensive approach was immediate amputation. A second study has found that debridement and , if indication , revascularization, resulted in long - term salvage of threatened feet, even in high - risk patients even with gangrene. A third study has found that early amputation in patients with foot infections who were not candidates for arteroa; reconstruction permitted early rehabilitation, decreased long - term morbidity, and reduced overall cost.

Ulceration's

Diabetic foot ulceration's will heal under four conditions- adequate peripheral perfusion, control of infection, off-loading of pressure-sensitive or ulcerated areas, and control of diabetes, including concurrent systemic diseases. off - loading the wound can be accomplished externally or internally. Shoe modification padding, debridement of surrounding hyperkeratotic tissue , and total contact casting are forms of external off-loading. Bunionectomy, hammer toe correction, metatarsal head resection, and other exostosectomies are means of off-loading internally . If the diabetic patient has adequate peripheral perfusion and is stable, surgical removal of pressure areas can accelerate ulcer healing.

Wagner Ulcer Grade Classification

Various classification schemes have been devised to aid in the diagnosis treatment, and prognosis of ulceration's. The most valuable scheme to be the one developed in 1981 by F. William Wagner. This scheme is based on the depth of the lesion and involves six stages ranging from no ulcer to gangrene of the entire foot. Wagner's scheme serves three very important purposes: to help standardize treatment plans; to help standardize treatment plans; to increase the level of communication between practitioners caring for the same patient; and to identify positive and negative changes in the progress of treatment

Grade O

The treatment of Wagner grade ) lesions - prominent osseous structures (e.g., bunions, hammer toes) and calluses - mainly involves prevention. For example, if a callus has formed because of abnormal stress on an area of the foot, remove the source of stress by padding the shoes or by recommending better- fitting shoes . In some cases , it may be beneficial to debride the callus as well. DeBridement serves to offload the area and permit identification of any ulceration under the callus that might have gone unnoticed. Padding the shoes is also recommended if a significant bony prominence is present without a callus. The main goal is to prevent the progression of a grade ) lesion to the status of a superficial ulcer.

Grade 1

These are superficial ulcers, which often have a base of necrotic tissue. The chronic neuropathic ulcer matrix is hypoxic, acidic and hypoglycemic. Attempted healing via smooth muscle myofibril contraction is often inadequate to close the wound. Necrotic tissue that is present both inhibits epithelialization and provides a culture medium for bacterial growth ; thus , it is impotent to debride the wound. The purpose of debridement is to convert the chronic would matrix into an acute wound. Matrix by removing necrotic debris, bacteria and surrounding hyperderatitic tissue. Aggressive sharp debridement provides a good granular, bleeding bed at the base of the wound which permits an influx of platelets and platelet - derived growth factors needed for healing . Debridement should be performed on a weekly basis until healing is complete.

Wet - to - dry dressings (soaked in saline but allowed to dry before removal) applied every 6 to 8 hours provide a moist environment for the wound to heal . Once the dressing dries , removal serves the function of debridement by eliminating any necrotic tissue adhering to the bandage. One now implements wet-to-moist dressing changes because we believe that removal of the dry dressings tends to damage the wound , impairing reepithelialization by inhibiting retye peg formation the subsequent epidermis is fragile and easily damaged which results in a high recurrence of locer formation the patient should perform wet-to-moist dressing changes once or twice daily. (Wet-to-dry dressing changes should be done once a day.)

In addition to aggressive debridement and wet-to-moist dressing changes, one can apply a new topical gel to diabetic wounds. Becaplermin 0.1% is a recombinant endogenous human platelet-derived protein growth factor(PDGF-BB) gel that has a chemoattractant effect on local and surrounding undifferentiated mesenchymal cells recruiting fibroblasts and inflammatory and smooth muscle cells. It is indicated for the treatment of diabetic neuropathy rekated lower-extremity ulcers that extend into the subcutaneous tissue or beyond and have an adequate blood supply. The PDGF binds with the alpha receptor sites found in the acute wound matrix. Therefore, initial wide debridement of a nonhealing diabetic foot ulcer is recommended to convert the chronic wound matrix into an acute wound matrix exposing a significant number of these alpha receptor sites. With the application of becaplermin routine debridement of the ulcer on subsequent office visits is discouraged, as that tends to disrupt these receptor sites, thereby decreasing the effectiveness of PDGF. Debridement of the hyperkeratotic periphery of the ulcer is recommended to off-load undue pressure on the surrounding skin. If significant necrotic or fibrous tissue redevelops during the course of PDGF treatment, intermittent wide debridement by a qualified have shown that the combination of good wound care - aggressive debridement , infection control and pressure relief - and the application of becaplermin gel increase the rate of wound healing .

Grade 2

These are deepulcers that extend toligaments , tendons , muscle, and / or bone . Treatment is essentially the same as that for grade 1 ulcer . The main emphasis is on prevention of infection, which may necessitate amputation . Some patients with grade2 ulceration's require aggressive debridement in an operating room setting.

Grade 3

These deep ulcers are marked by abscess formation cellutlitis , osteomyelitis, and /or tendinitis. They require a more aggressive form of treatment. A new class of antiniotis , which works by attacking the bacterial cell's membrane has been developed . The first antibiotic in this class , the topical gel pexiganan acetate, is currently being studied for the treatment of diabetic foot ulcers. The result look promising. If clinical signs and plain x-rays suggest ostemoyelitis, order a 3 phase technetium bone scan. Technetium-labelled white blood cell bone scan are specific for osteomyelitis and can confirm the diagnosis when other osseous abnormalities cannot be ruled out. Once the diagnosis of osteomyelitis is confirmed, the treatment usually entails surgical excision of all infected bone and tissue . It is often necessary to amputate digits and / or remove portions of the metatarsals. In cases with minimal bone involvement , a 6 week course of intravenous antibiotics is recommended.

Grade 4

These deep lesions involve gangrene of any part of the forefoot. When one deals with gangrenous changes, the main goal is to prevent "wet "gangrene from developing . A combination of gangrenous changes, deep infection and gas in the tissues almost always spreads rapidly up the leg (narcotizing fascists). Amputation of all gangrenous and infected tissue is the treatment of choice

Grade 5

These deep lesions involve gangrenous changes in the rearfoot or the entire foot. They often require below the knee amputation.

Another classification which has been seen to be of significant value in the valuation and management of the diabetic foot is The University of Texas Diabetic Foot Classification.

Recent Advances in Treatments for Diabetic Foot Ulceration

The moist wound healing concept is widely accepted in treating DFUs. Some of the benefits of this approach include prevention of tissue dehydration and cell death, acceleration of angiogenesis, and facilitating the interaction of growth factors with the target cells. The standard of care recommended by the American Diabetes Association is saline-moistened gauze. The "wet-to-dry" concept is no longer acceptable because if the gauze becomes dry before the next dressing change, it may cause damage to the wound bed and disrupt the healing process. Hydrocolloid dressings and hydrogels can maintain the moist wound environment while providing some autolytic debridement. Enzymatic debridement agents can be helpful for necrotic tissues. The alginates and absorptive dressings absorb drainage well and maintain moist wound environments. Other dressings are impregnated with collagen, zinc, or other factors that stimulate wound healing. Some dressings have a coated antimicrobial barrier. Composite dressings have more than one characteristic promoting wound healing. Contact-layer dressings prevent damage to the wound bed. Foam dressings may provide some padding in addition to absorbency. There have been no large, controlled studies to show the efficacy of hyperbaric oxygen therapy and electrical stimulation on DFUs.

Becaplermin gel is a platelet-derived growth factor (PDGF) of recombinant human origin. PDGF stimulates and recruits macrophages, neutrophils, and fibroblasts; stimulates angiogenesis; and stimulates granulation tissue formation, wound contraction, and wound remodeling. Becaplermin gel should be used in wounds that have adequate blood supply and a clean wound bed (one without infection or necrosis). When used in conjunction with appropriate wound care, becaplermin gel has been shown to increase the incidence of complete wound closure (50% versus 35% for placebo) and decrease the time to complete wound closure (86 versus 127 days).

The amount of becaplermin gel applied varies by wound size (see Table 1). The amount should be measured out onto a clean surface and the gel applied using an application aid (Q-tip, etc.) to a thickness of 1/16 inch. The gel should be covered with a saline-moistened gauze pad and left in place for 12 hours. After 12 hours, remove the gauze, rinse the ulcer with saline, and apply a new moistened dressing (without becaplermin gel) for the remaining 12 hours. Repeat this application process once daily.

Table 1. Calculations for Becaplermin Gel Dosage

In inches Measure the greatest length and width of ulcer in inches. Calculate the length of gel (in inches) required from a 15 gram tube by multiplying the length x width x 0.6. Each square inch of ulcer surface requires approximately 2/3-in. length of of gel.

In centimeters Measure the greatest length and width of the ulcer in centimeters. Calculate length of gel that should be squeezed from a 15 gram tube by multiplying the length x width divided by 4. Each square centimeter of ulcer surface requires approximately 0.25-centimeter length of gel.