Wagner classification
0
Ulcer absence standing high risk
1
Shallow ulcer
2
Deep ulcer, penetrating ligaments and muscles, but without bone involvement
3
Deep ulcer with cellulitis, abscess, or osteomyelitis
4
Located gangrene restricted to the toes
5
Extensive gangrene
Ischemic ulcers have flat, dry, dystrophic, and painful lesions, especially in toes. The neuropathic ulcers lesions are usually located in the plantar region of the midfoot, in sites of previous callus and hyperkeratosis. The neuroischemic ulcers have characteristics similar to neuropathic and ischemic ulcers together [31].
According to SVS-WIfI classification system , ulcer (or wound) is described as in four grades as follows [29]:
Grade 0: No ulcers or gangrene;
Grade 1: Shallow ulcer without bone exposure (except if it is limited to the distal phalanx);
Grade 2: Deep ulcer in the forefoot/midfoot, with bone involvement, joint or tendon, superficial ulcer in calcaneus, or gangrene restricted to the toes;
Grade 3: Extensive and deep ulcer in the forefoot/midfoot; deep ulcer on the heel; wide gangrene on forefoot/midfoot; or deep gangrene of the calcaneus.
Diagnosis
The diagnosis of diabetic foot is complex due to a variety of signs and symptoms and the broad spectrum of the clinical manifestations of the disease [32]. The diabetic foot is the result of peripheral neuropathy and peripheral arterial disease. Each one of these factors has its proper diagnosis and should be evaluated individually to identify the diabetic foot [18, 21, 25, 32].
Diabetic Neuropathy Evaluation
The neurologic exam is performed using validated instruments: the Semmes-Weinstein 10 g monofilament and the 128 Hz tuning fork for sensory evaluation and the hammer to test reflexes in the ankle [4, 9].
The patient with diabetic neuropathy is unable to perceive injuries as a result of sensory damage. It is established by an abnormal response to a 10 g monofilament test (esthesiometer) and another instrument, such as tuning fork (for vibration perception threshold) or pinprick sensation test or Achilles reflex test [9, 32]. The application of monofilament and the tuning fork and tests are recommended by The International Working Group on the Diabetic Foot as shown in Figs. 13.1, 13.2, and 13.3 [7]. The protective sensation is considered absent when the patient responds to two out of three incorrect answers to the stimulus of the monofilament and the tuning fork [33].
Fig. 13.1
Application of the monofilament . Reprinted with permission from: “Apelqvist J, Bakker K, Van Houtum W, Nabuurs‐Franssen M, Schaper N. International consensus and practical guidelines on the management and the prevention of the diabetic foot. Diabetes/metabolism research and reviews. 2000;16(S1):S84–S92”
Fig. 13.2
Sites to be tested with monofilaments . Reprinted with permission from: “Apelqvist J, Bakker K, Van Houtum W, Nabuurs‐Franssen M, Schaper N. International consensus and practical guidelines on the management and the prevention of the diabetic foot. Diabetes/metabolism research and reviews. 2000;16(S1):S84–S92”
Fig. 13.3
How to use a tuning fork
Symptoms of neuropathy can also be registered or measured through the use of specific questionnaires such as the neuropathy disability score and the neuropathy symptom score [34].
The reduction in muscle strength during dorsiflexion and plantar flexion indicates motor impairment related to diabetic polyneuropathy. However, musculoskeletal foot deformities are the best evidence for muscle imbalance. The motor muscle impairment ranges from muscle weakness to paralysis, depending on the severity of the neuropathy. The joint mobility of foot and ankle must be checked; musculoskeletal deformities should be identified, and hyperkeratosis areas associated with deformities must be inspected and registered [7, 9, 14]. Gait analysis can be performed by observing the patient walking. Footprinting mat, baropodometry , and quantitative-computerized gait analysis, if available, can also be used [20].
Symptoms and signs of autonomic dysfunction include resting tachycardia, intolerance to exercise, orthostatic hypotension , sudoriferous dysfunction (manifested as anhidrosis of the extremities, which may be accompanied by hyperhidrosis in the trunk), and potentially autonomic failure in response to hypoglycemia [35].
Vascular Assessment
Vascular assessment of the diabetic foot patient should start with pulse palpation. The presence, at least, of one palpable pulse—posterior tibial or dorsallis pedis—indicates enough perfusion to heal wounds and fight infection.
In the pulseless patient, it is mandatory to evaluate limb perfusion with non-invasive tests, such as the ankle-brachial index , pulse volume recording, toe systolic pressure measurement, or transcutaneous oxygen measurement [24].
The ankle-brachial index is the most used test. It is a simple and reproducible test, which gives the physician valuable information about the limb perfusion. An index lower than 0.9 is diagnostic of arterial disease. However, an ankle-brachial index higher than 1.3 indicates that lower limb arteries are barely compressible due to wide medial calcinosis. In this scenario, another non-invasive test should be used.
Pulse volume recording uses photoplethysmography to create graphic forms of arterial pulses. Dampening of these waveforms indicates an upstream stenotic lesion. It is not affected by medial calcinosis.
Toe pressure measurement is also reliable in patients with incompressible ankle-brachial index because toe vessels are usually sparred from calcification. It also is used as a predictor of wound healing, with values lower than 30 mmHg indicating little healing potential [24].
Arterial duplex scanning does not have diagnostic value. It is a complementary test to determine which is the best treatment modality, conventional surgery or endovascular technique. Revascularization should be considered in ischemic patients [24].
Treatment
The treatment of patients with the diabetic foot is complex and requires a multidisciplinary team [10, 18]. Interventions range from preventive and basic modalities to surgical interventions such as revascularizations and limb amputations [8, 25, 32]. Patients with neuropathy or evidence of increased plantar pressure should be properly instructed on foot self-care and supplied with therapeutic footwear and devices to redistribute pressure [8]. Patients with deformities need extra wide and deep shoes, and those with severe deformity (Charcot’s foot) need custom-molded shoes. The nonweight bearing will be imperative in the management of plantar ulcers [36]. Total contact cast or other casting techniques or removable devices should be prescribed for this purpose [32, 35, 37].
Antibiotic Treatment
All infected wounds should be treated with antibiotics and adequate wound care. Empiric antibiotic should be provided according to infection severity until antibiotic susceptibility data is available (Table 13.2) [30]. For mild to moderate infections, the regime should target gram-positive cocci. In case of severe infection, broad-spectrum antibiotics should be promptly initiated and directed according to culture results.
Table 13.2
Antibiotic according to infection severity
Infection severity | Route of administration | Environment | Antibiotic spectrum | Duration |
|---|---|---|---|---|
No infection | – | – | Not necessary | – |
Mild | Oral | Outpatient | Gram-positive cocci | 1–2 weeks |
Moderate | Oral/parenteral | Outpatient/hospitalized | Gram-positive cocci | 1–3 weeks |
Severe | Parenteral | Hospitalized | Broad-spectrum (including MRSA) | 2–4 weeks |
The suggested empiric antibiotic therapy is based on the Infectious Diseases Society of America Guideline for Diabetic Foot Infection [30].
For mild infections, oral cephalexin or amoxicillin-clavulanate showed to be effective in treating diabetic lesions. If there is a risk for methicillin-resistant Staphylococus aureus infection, the antibiotic should be Doxycycline or Trimethoprim/Sulfamethoxazole [30].
On the other hand, moderate and severe infections should be assessed more aggressively. Initial empiric therapy should consist of Ampicillin-sulbactam, Ertapenem, or Imipenem-cilastatin if the probable pathogen is a multi-sensible Staphylococcus aureus, Streptococcus sp., or Enterobacteriaceae. If meticillin-resistant Staphylococus aureus is suspicious, vancomycin is the choice [30].
Surgical Treatment
Debridement
Debridement is the removal of devitalized tissue of the wound bed to expose viable tissue [4]. In the presence of peripheral arterial disease, debridement can increase the wound bed due to tissue necrosis. Therefore, it is appropriate to investigate and optimize the treatment of peripheral arterial disease before and after surgical debridement, except for abscess where infection control must be immediate [38].
To prevent the formation of new wounds, debridement of sites in the foot with hyperkeratosis and calluses at intervals of 1–4 weeks is recommended [39].
The debridement may be performed by different methods: mechanical, autolytic, enzymatic, or surgical. Applying moist gauze to the wound bed performs the mechanical debridement, but it is in disuse because it is painful and is not selective to necrosis, removing viable tissues as well [4]. The autolytic method uses the body’s natural action of enzymes leading to lysis of necrotic tissue, through products that keep moist the wound bed. Surgical debridement is the most effective and fast procedure through sharp, sterile blades [4]. Currently, studies have featured the use of maggot therapy from the decomposition of nonviable tissue and remove the bacteria from the wound bed [40].
Revascularization Procedures
In the presence of important peripheral arterial disease, it is necessary to improve foot perfusion if the patients’ conditions are satisfactory. Revascularization can be achieved by conventional or endovascular surgery [24, 25].
The conventional surgery uses a graft to bypass the arterial obstruction, restoring the blood flow to the foot. On the other hand, the endovascular technique uses intra-arterial sheaths and guide-wires that, in combination with balloon catheters and stents, promotes the reestablishment of intra-arterial lumen [24, 25].
Limb Amputation
Diabetes is the leading cause of non-traumatic limb amputation [21]. In patients with severe involvement of the foot, amputation may be the only therapeutic choice. The indications are extensive gangrene of toes or the foot, chronic osteomyelitis, and deep tissues invasive infection.
Lower limb amputation can be divided as minor or major. Minor amputation preserves the ankle, therefore allowing the patient to walk without the use of a prosthesis. On the other hand, major amputation is performed above the ankle, with the removal of the entire foot preventing the patient to have a normal gait and consequently being able to ambulate only with a prosthesis.
Wound Care
Dressings
After the effective debridement, it is necessary to choose the dressing (described in Chap. 15) to prepare the wound bed to accelerate the process of granulation and healing [4]. The ideal dressing should keep moist the wound bed, without steep edges, must be safe, non-toxic, hypoallergenic (for health professionals and patient), and non-adherent to the wound bed. Moreover, be accepted by the patient, promote relief of pain and odor, guarantee mobility, be easy to handle, and cost-effective [39]. There is some evidence to indicate a preference for the use of hydrogel and negative pressure therapy [41, 42]. The choice between the options should consider the cost and the properties of each bandage and the characteristics wound [4, 38, 41–45]. Described below are the most used in the market:
- (a)
Hydrogel : Consists of insoluble polymers (carboxymethyl cellulose) and up to 96 % water [42]. It can be found as amorphous gels and sheet and may be associated with alginate (this increases the power of debridement). It is indicated to keep humidity, maintain optimal pH, promote pain relief, and assist in autolytic debridement (removal of dead tissue). The exchange period can reach up to 7 days for the sheets and 1 day for the gel [46].
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