Diabetic foot ulcers are among the most common complications of patients who have diabetes mellitus which is not well controlled. It is usually the result of poor glycemic control, underlying neuropathy, peripheral vascular disease, or poor foot care. It is also one of the common cause for osteomyelitis of the foot and amputation of lower extremities. These ulcers are usually in the areas of the foot which encounters repetitive trauma and pressure sensations. Staphylococcus is the common infective organism. The disease is typically chronic, and a multidisciplinary approach will have the best outcome. The combined involvement of podiatrist, endocrinologist, primary care physician, vascular surgeon, and an infectious disease specialist is extremely beneficial. It is a commonly encountered scenario in both outpatient settings and inpatients. Educating the patient about the complication and the need for proper medical care will reduce the risk of complications and good compliance.
The etiology for diabetic foot ulcer is multifactorial. The common underlying causes are poor glycemic control, calluses, foot deformities, improper foot care, ill-fitting footwear, underlying peripheral neuropathy and poor circulation, dry skin, etc.
The annual incidence of diabetic foot ulcer worldwide is between 9.1 to 26.1 million. Around 15 to 25% of diabetic patients will develop a diabetic foot ulcer during their lifetime. As the number of newly diagnosed diabetics are increasing yearly, the incidence of diabetic foot ulcer is also bound to increase.
The development of a diabetic ulcer is usually in 3 stages. The initial stage is the development of a callus. The callus results from neuropathy. The motor neuropathy causes physical deformity of the foot, and sensory neuropathy causes sensory loss which leads to ongoing trauma. Drying of the skin because of autonomic neuropathy is also another contributing factor. Finally, frequent trauma of the callus results in subcutaneous hemorrhage and eventually, it erodes and becomes an ulcer.
Getting a good history is vital in the care of patients with diabetic ulcer. The history should include the duration of diabetes, glycemic control, other pre-existing complications of diabetes including sensory neuropathy, history of peripheral vascular disease, callus, previous ulcer, prior treatment, and the outcome. The detailed history should also include information regarding the footwear and foot.
The clinical examination should include examining the peripheral pulses of the feet, looking for any anatomical anomalies, the presence of callus, signs of vascular insufficiency, which may indicate loss of hair, muscle atrophy, and location of the ulcer. Also assess for the presence of purulence, scabs, and evidence of neuropathy by examining with a monofilament.
The most common laboratory investigations done during evaluation of the ulcer include a fasting blood sugar, glycated hemoglobin levels, complete metabolic panel, a complete blood count, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP).
Recent guidelines and the literature suggest that in patients with diabetic foot ulcers, results of specimens for culture taken by swabbing do not correlate well with those obtained by deep tissue sampling; this suggests that superficial swab specimens may be less reliable for guiding antimicrobial therapy than deep tissue specimens.
Radiological investigations include plain x-rays to look for any underlying osteomyelitis, the presence of air in the subcutaneous tissue, any signs of underlying fractures, and presence of a foreign body. If osteomyelitis is suspected, MRI is the most preferred test. A bone scan with technetium can also be used to diagnose underlying osteomyelitis. Arterial Doppler with ankle-brachial index (ABI) is useful to rule out underlying peripheral vascular disease.
The probe-to-bone test (PTB) i dperformed by probing the ulcer with a sterile metal probe is a bedside test that can help with the diagnosis of underlying osteomyelitis. If the probe hits the bone, it is a positive test. Positive probe-to-bone test results are helpful especially when conducted on patients with diabetes mellitus.
Treatment of diabetic foot ulcer should be systematic for optimal outcome. The most important point is to identify if there is any evidence of ongoing infection, by obtaining a history of chills, fever, looking for the presence of purulence or presence of at least two signs of inflammation that includes, pain, warmth, erythema or induration of the ulcer. It should is noteworthy that even in the presence of severe diabetic foot infection, there can be minimal systemic signs of infection.
The next step is to decide if the patient’s ulcer can is manageable in the outpatient setting or inpatient setting. Need for parenteral antibiotics, concern for noncompliance, inability to care for the wound, ability to offload pressure, are few points to be considered for hospitalization. Both categories of patients should have treatment with antibiotics.
The common organisms seen in a diabetic foot ulcer are Staphylococcus aureus, Streptococcus, Pseudomonas aeruginosa, and rarely E. coli. Diabetes patients have higher carriage rate of Staphylococcus aureus in the nares and skin, and this increases the chances of infection of the ulcer.Antibiotics are only needed if there is a concern for infection. The severity of the infection dictates the dose, duration, and the type of antibiotic.
The typical outpatient antibiotics regimen includes oral cephalosporins, and amoxicillin-clavulanic acid combination, (If MRSA is not of concern). If MRSA is suspected, then the oral regimens include linezolid, clindamycin or cephalexin plus doxycycline or a trimethoprim-sulphamethoxazole combination.
Parenteral antibiotic regimens include piperacillin-tazobactam, ampicillin-sulbactam, and if penicillin allergic, then carbapenems including ertapenem or meropenem. The other combinations regimen including adding metronidazole for anaerobic coverage along with quinolones like ciprofloxacin or levofloxacin, or with cephalosporins like ceftriaxone, cefepime or ceftazidime. Intravenous agents which cover MRSA include vancomycin, linezolid or daptomycin.
The next therapeutic step is to treat any underlying peripheral vascular disease. Inadequate blood supply limits the oxygen supply and the delivery of the antibiotics to the ulcer; hence revascularization improves both, and there is a better chance for the healing of the ulcer. The subsequent step is to perform local debridement or removal of calluses. Finally, efforts should be made for prevention of new ulcers or worsening of the existing ulcer, which occurs by offloading the pressure from the site by using walkers or therapeutic shoes. If the wound fails to heal in 30 days, then hyperbaric oxygen therapy can be considered. Since the wound has low oxygen supply, there is often delay in healing of the wound. Hyperbaric oxygen therapy improves the rate of wound healing and also reduces the rate of complications.
To have the best outcome a team of health care providers including primary care physician, podiatrist, a vascular surgeon, an infectious disease specialist and wound care nursing staff are imperative.
After the diagnosis of the ulcer, it should undergo staging. One of the commonly used classifications is by Wagner from 1981. It classifies wounds into six grades based on the depth 
1 Superficial ulcer
2 Deep ulcer involving tendon bone or joint
3 Deep ulcer with abscess or osteomyelitis
4 Gangrene involving the forefoot
5 Gangrene involving the entire Foot
This classification, though, has been criticized as grading merely the depth of the ulceration and not incorporating other factors known to influence the outcome. Among others, one of the most commonly used classification today is The University of Texas Classification, which not only includes assessment of the depth, but also the type of infection, and ischemia based on the eventual outcome of the wound.
The prognosis these ulcers is good if identified early and optimal treatment initiated. Unfortunately, delays in care can have detrimental effects which can lead even to amputation of the foot. Patients who have chronic diabetic ulcer have a high risk of rehospitalization and prolonged hospitalization.
The most feared complication is amputation of the extremity. The other complications include gangrene of the foot, osteomyelitis, permanent deformity, and risk of sepsis.
Patients who end up with amputation will need comprehensive therapy including physical therapy, occupational therapy and also will need a prosthesis.
The most important preventative measure is patient education. If the patient should be made aware about the importance of good glycemic control, proper care of the foot, avoiding tobacco and the need for frequent follow-up examinations, then the risk for developing ulcer is significantly reduced. The patient should be reminded of these things during each visit with the primary care physician.
Diabetes is a chronic disease which has a significant number of complications. Diabetic foot is a common scenario which a physician will come across in daily practice. The diagnosis and subsequent management of a diabetic ulcer are optimally effective when utilizing a multidisciplinary approach to achieve the best outcome.