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Diabetic foot disorders

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Prolonged exposure to even low pressure over a bony prominence (as may be seen with ill-fitting shoes) can cause skin breakdown. Ordinarily, pressure will cause pain, and the person will shift his or her weight. With a loss of such protective sensation, loading continues to the point that the skin breaks down and ulcers appear. Without adequate blood flow, ulcers can easily progress to gangrene.  

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. Ulcer at head of talus

Charcot arthropathy is characterized by joint destruction caused by a failure to stop painful (and ultimately destructive) loading. The condition is named after Jean Marie Charcot (1825-1893) who described the collapse of the bones of the foot in patients who had lost feeling in the feet from tertiary syphilis. The three commonly affected locations in the foot and ankle are the tarsal-metatarsal joints (midfoot), the transverse tarsal joint (hindfoot just in front of the ankle), and the ankle joint. 

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Typically, the ulcers will occur over a prominent area such as the metatarsal heads, although any area of the foot that is subject to a concentrated, repetitive force is at risk for developing a diabetic ulceration. 

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Figure 2. Semmes-Weinstein 5.07 monofilament used to evaluate peripheral neuropathy

 

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. Plantar view of a patient with diabetes who presented with severe ulceration over the right foot fifth metatarsal head after wearing tight-fitting shoes for the previous 2 weeks

There are multiple classification systems to grade and characterize the type and severity of ulcers. The Wagner system rates ulcers on a zero to 6 scale, from "0: skin intact" to "6: ulcer with extensive foot gangrene"; the Brodsky system considers both the extent to the ulcer (superficial, deep and exposed bone) as well as the extent of ischemia. 

Diabetic Foot Charcot Arthropathy

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Charcot arthropathy can be painful, but not always: after all, it is caused by neuropathy.  Charcot arthropathy is commonly mistaken for an infection (eg, osteomyelitis) especially when there is an ulcer present.

 

 

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. Patient with diabetes mellitus presented with a diffusely swollen, warm and non-tender left foot due to Charcot arthropathy (credit: http://en.wikipedia.org/wiki/Charcot_arthropathy)

Objective Evidence


In patient Diabetic foot ulcers should be characterized objectively by location and severity. There are multiple classification systems to grade ulcers. The Wagner system rates ulcers on a zero to 6 scale, from "0: skin intact" to "6: ulcer with extensive foot gangrene"; the Brodsky system considers both the extent to the ulcer (superficial, deep and exposed bone) as well as the extent of ischemia. 

The vascular status of the foot should also be assessed objectively, noting the skin color and temperature, the quality of capillary refill and presence or absence of good pulses. The ankle-brachial index (ABI), namely the ratio of the blood pressure in the ankle relative to that in the arm can be assessed in the clinic, though calcification of the vessels may produce a falsely normal result.

In patients presenting with an ulcer, standard anteroposterior, lateral, and oblique radiographs of the affected foot should be obtained to evaluate for cortical bone abnormalities such as demineralization, erosion, . These films can detect deformities of the foot in general, as well as bone changes such as periosteal reaction, lucencies , and or osteolysis that would be indicated indicative of osteomyelitis. Charcot arthropathy, or a combination of those disorders. MRI with T1- and T2-weighted images

MRI may be helpful to determine the extent of bony and soft-tissue disruption, but MRI cannot differentiate between Charcot arthropathy and osteomyelitis with high specificity. Occasionally, a bone scan is indicated, although very often the results of the bone scan will not change the management and may not reveal any information that cannot be obtained from a detailed physical examination.

 

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. Anteroposterior (top) and lateral (bottom) radiographs of the patient in figure 3 demonstrating subcutaneous gas extension down to bone with cortical disruption.

In the case of failure of an ulcer to heal or cases of suspected infection, aerobic and anaerobic cultures of the wound should be obtained to help direct antibiotic therapy. Osteomyelitis is present in approximately 70% of ulcers that can be probed extend down to bone. Diabetic foot infections are generally polymicrobial but Staphylococci and Streptococci are the predominant microorganisms causing infection. A diagnosis of Charcot arthropathy is generally made clinically, but supporting plain radiographs are important. Sometimes they will show a decrease in bone density (osteopenia) or a break in the bones involved. If the process has progressed, the x-ray may show deformity of the foot or ankle. In most cases no further imaging studies are required. However if there is an ulcer, it may be difficult to differentiate Charcot arthropathy from osteomyelitis with a radiograph alone.   

Laboratory tests such as white blood cell counts, sedimentation rate, and C-reactive protein levels may indicate infection leading be used to establish the diagnosis towards osteomyelitis. A of osteomyelitis, though a a bone biopsy is the most specific method of distinguishing the two conditions. A biopsy of multiple shards of bone and soft tissue embedded in deep layers of synovium is a hallmark of Charcot arthropathy.

 

CT scans can be helpful to look at a more detailed picture of the collapse, but is not often necessary unless surgery is planned. 

Epidemiology

Diabetic foot disorders are common because diabetes itself is common. The prevalence of diabetes in the US is estimated to be around 7% approximately 10% of the population. An estimated 12-15% adult population, and in turn, about  10% of patients with diabetes will develop a lower extremity ulcer during the course of their disease . In patients with diabetes who have peripheral neuropathy and foot ulceration, the recurrence rate is close to 70%. While 7% to 20% of patients with foot ulcers will subsequently require an amputation, foot ulceration is the precursor to approximately 85% of lower extremity amputations in persons with diabetesand about 1% will develop Charcot arthropathy.

The rate of lower extremity amputations is at least 50% higher in men versus women. The estimated cost for foot ulcer care in the US ranges from $4,595 per ulcer episode to nearly $28,000 for the 2 years after diagnosis. Mexican (Hispanic) Americans, Native Americans, and African Americans each have at least a 1.5- to 2-fold greater risk for diabetes related amputations than age-matched diabetic CaucasiansPatients who develop Charcot arthropathy are usually morbidly obese and have had diabetes for more than 10 years. It is estimated that less than 1% of patient with diabetes will develop Charcot arthropathy.

Differential diagnosis


 It is  

When a patient presents with a foot ulcer, the main diagnostic question is What caused it? It is thus critical to evaluate for previous ulcerations, medical comorbidities,   level  of of diabetic control and monitoring, and tobacco and intravenous drug use.

 

The presence of sensory neuropathy should be assessed. Granted, a sensory exam is not objective, but it can be (in a cooperative patient) at least standardized. For example, a Semmes-Weinstein 5.07 monofilament nylon wire can be used to exert a consistent force (If the wire bow into a C shape when pressed against the skin for 1 second, 10g of force is applied). This is an important threshold: Patients who can’t a 10-g force have lost protective sensation.

 

 

 

Figure 2. Semmes-Weinstein 5.07 monofilament used to evaluate peripheral neuropathy

 

There are many potential causes for peripheral neuropathy such as besides diabetes that can be responsible: alcoholism, vitamin B1 deficiency, vitamin B12 deficiency, and B12 deficiencies heavy metal poisoning, among others. Therefore a A focused physical exam, history taking, and appropriate laboratory studies are vital in ruling can rule out other causes besides diabetes.

 

In the absence of diabetes, foot ulcers can be caused by atherosclerosis involving the lower extremities, vascular lesions, and even severe Raynaud’s phenomenon (vasospastic attacks in digits). A squamous cell carcinoma may also form a Marjolin’s ulcerbe responsible.

 

Charcot arthropathy may have a similar presentation as gout, cellulitis, osteomyelitis, and septic arthritis. Diabetic neuropathy is the most common cause of Charcot arthropathy, but other less common causes include spina bifida, cerebral palsy, meningomyelocoele, syringomyelia, leprosy , and alcohol abuse. Last, and advanced syphilis, the condition in which the disease was first described, is still a possible etiology.

 

 

Figure. Semmes-Weinstein 5.07 monofilament used to evaluate peripheral neuropathy

Red flags

During the physical examination, it is important to look for In all patients with diabetes, breaks in the skin , as this may suggest infection instead of Charcot arthropathy. Skin infection will often remain red when elevated while the erythema will decrease with Charcot arthropathy. Although the two can be present at the same time, it is usually one or the other. Small areas of breakdown in the skin can become major limb threatening problems in a matter of days if they are not carefully attended to. Untreated infections can also result in systemic infection and sepsis.are a red flag: infection may be present or looming. Indeed, any sign of increased pressure on focal areas of the foot (such as erythema or skin changes), as a precursor to worse problems, is best considered a red flag too.

Treatment options and Outcomes

The primary goal for treatment of diabetic ulcers is to get wound closure by offloading the affected area the wound to close without infection. Often, the best first step to offload the affected area, giving it an opportunity to heal. This is typically done with a total contact cast (TCC) or removable diabetic walker boot. TCC

Total contact casting has been shown to significantly increase the healing rate of neuropathic plantar foot ulcers at 12 weeks compared to removable cast walkers and half-shoes so it is the preferred method of treatment. It can take anywhere from 6 weeks to a year for an ulcer to heal depending on the size, depth, and duration of the ulcer. A patient should not return to unmodified shoes until the ulcer has completely healed. Unfortunately, obtaining successful healing of a diabetic ulcer often does not remove the underlying etiologies (neuropathy and pressure points) so recurrence of the ulcer over time is often high.

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Figure 6. Removable diabetic walker boot used to reduce weight-bearing during ambulation

In addition, other factors important for wound healing such as adequate perfusion have to be addressed. Treatment of the ulceration may involve surgical debridement of the callus or necrotic tissue with scalpels and curved scissors. Usually, this can be done in the clinic, although sometimes it may need to be done in the operating room if the infection involves the bone and there is some need to remove part of the infected bone. Other methods of debridement exist such as enzymatic debridement involving application of proteolytic enzymes and biological therapy that uses Lucilia sericata blowfly larva to liquefy necrotic tissue. However there are not enough controlled studies to support its use in treating diabetic ulcers. Keeping the wound moist without excess fluids can accelerate re-epithelialization of the wound. Various topical agents and dressings may expedite healing.Many new therapies that may accelerate wound healing in treatment of ulcers are currently being studied. Growth factor therapy uses various growth factors such as platelet derived growth factors, vascular endothelial growth factors, fibroblast growth factors, and keratinocyte growth factors to stimulate chemotaxis of cells that promote wound healing. Patient’s own platelet rich plasma are being used on wounds to assist with new tissue formation. Bioengineered tissue grafts in some instances have been shown to facilitate complete wound closure.   Hyperbaric oxygen therapy, ultrasonic therapy, negative pressure wound therapy, and electric stimulation are all being tested for treatment of diabetic foot ulcers.

The vascular status of the affected extremity is critical in determining the healing potential of foot ulcers and the need for possible surgical intervention.  More More than 60% of diabetic foot ulcers have decreased arterial blood flow due to concurrent peripheral vascular disease.  Further  Formal vascular studies are often needed after examination of vascular to determine status of the posterior tibial and dorsalis pedis arteries with palpation and handheld Doppler ultrasound, if palpation is inconclusive. 

Prior to casting, it is important to assess patients for equinus contractures due to either a tight Achilles or gastrocnemius tendon. Fixed plantarflexion contractures cause increased forefoot pressures and, therefore, a higher likelihood of developing plantar forefoot ulcers. Equinus contractions are extremely common in the diabetic population as glycosylation of soft-tissues tends to stiffen up muscles and tendons. The Silverskiold test can be used to differentiate isolated contractures of the gastrocnemius from the gastro-soleus complex. Patients with Wagner grade 1 and 2 ulcers and isolated gastrocnemius contracture should be treated with gastrocnemius recession (ie, Strayer procedure) followed by TCC to decrease the risk of ulcer recurrence. This is becoming an increasingly common surgical procedure because compared with TCC alone, the combination of percutaneous tendo-Achilles lengthening and TCC has been shown to result in a significant decrease in recurrence of diabetic plantar ulcers in patients with gastroc-soleus contracture.

Diabetic foot ulcers if left untreated and the need for surgical or endovascular procedures to perfuse the foot.

Because gastrocnemius contractures cause plantarflexion and thus increased forefoot pressures, patients with such a contracture may benefit from a tendon release. A percutaneous Achilles tendon lengthening prior to total contact casting markedly decreases the rate of recurrence of plantar ulcers.

Diabetic foot ulcers if not treated (or if they do not respond to treatment) can lead to gangrene, abscesses , osteomyelitis, and necrotizing fasciitis ultimately requiring amputation and osteomyelitis. Amputation of the lower extremity . Several amputation options exist, ranging from hallux amputation to below-the-knee amputations, and special considerations must be taken into account for each procedure. More information on the various types of amputations can be found here (http://www.orthopaedicsone.com/display/Main/Diabetic+foot+ulcer). Even with advances in the medical and surgical management of diabetes, may be needed. The need for this procedure, it should noted, is a marker for severe disease, as the 5-year mortality rate remains poor at following an amputation is approximately 66% after the amputation of a leg.The goal of treatment in .

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Figure. Removable diabetic walker boot used to reduce weight-bearing during ambulation

 

Charcot arthropathy is to prevent deformity so noticing early deformity is crucial to keep it resistant to easy treatment.  The best approach is to detect it early and prevent it from getting worse.  When When detected early, treatment involves a period of non-weight bearing or limited weight-bearing in either a total contact cast or a diabetic removable boot. Swelling and redness will usually resolve or improve with elevation. Later in the process, when the bones have started to stabilize, the patient can walk more and put increasingly more weight on the leg. Rolling knee walkers can help keep the weight off the bad foot while allowing patients to be mobile and not over-loading the better foot.  The treatment of Charcot arthropathy is a particularly frustrating and debilitating condition not only because it can take 6-12 months or more for the involved joints to stablize.  Furthermore, when it does get better, the foot may have collapsed and changed shape. The resulting deformity can put the patient at risk to develop an ulcer over new stabilize, but because it may resolve with a gross deformity of the foot that places patient at risk for developing an ulcer over newly prominent bony areas.

 

Some studies suggest that using bisphosphonates ( inhibitors of osteoclasts often (as would be used to treat osteoporosis) may be helpful in treating Charcot arthropathy, by trying to limit osteolysis. Most studies have shown a reduction in markers indicating bone turnover.  However, no significant differences in clinical or radiographic outcomes have been reported. limiting osteolysis, though good clinical results have not yet been attained.  Electrical bone growth stimulation to promote rapid healing of fractures has been suggested as a supplement to the treatment of acute Charcot arthropathy. Similar to bisphosphonate therapy, there is no conclusive data for its efficacy.

Surgery may be recommended as a treatment if a severe deformity has occurred or the foot or ankle has become unstable and cannot be corrected through immobilization and off-loading. Surgery ranges from exostectomy (removal of prominent bone) to reconstruction of the foot including fusion of the unstable joints after the deformity has been corrected.  This can involve the use of screws and plates, or rods that go inside the bone, or pins that come out of the bone and skin and attach to a frame on the outside of the foot and ankle. The goal of surgery is to end up with a foot that is stable, can bear weight, and can fit in a shoe or brace and not have problems with without ulcers developing over prominent areas of bone.  Most surgical procedures that involve fusion will typically require a long period of not putting any weight on the foot or leg, often 3 months or more. The average time from surgery to therapeutic shoes is approximately 7 months. Surgery for Charcot arthropathy, because of the patient’s baseline ill-health, is associated with significant risks including increased risks of infection, problems with wound healing, and non-union.

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Figure 7. Surgery using a tensioned thin wire external fixator to treat an unstable Charcot arthropathy

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Risk factors and prevention

Cigarette Because diabetic foot disorders are caused by diabetes, all factors that increase the risk of the underlying condition increase the risk of resultant foot problems. Among patients with diabetes, cigarette smoking and poor glycemic control increases the risks for diabetic foot ulcerations by worsening diabetic is associated with more diabetic neuropathy, peripheral artery disease, and the associated wound healing capacity. in turn more foot disease. In addition, inappropriate footwear and poor toenail grooming increases the risk for ulcerations.

Previous ulcerations or amputations increase the are associated with a higher risk of developing another ulcer. Another risk factor for developing an ulcer is a

A tight calf muscle (equinus contracture) , which increases the lever force of the foot driving the forefoot into the ground with more force.  

Morbid obesity may be one of the key risk factors associated with Charcot arthropathy. Charcot arthropathy on one foot greatly increases the risk of developing the same condition on the other foot. Therefore, it is important to examine both feet during the physical exam. Charcot arthropathy can develop simultaneously on both feet, but more commonly happens sometime after the other foot gets better.  

In order to prevent diabetic foot disorders, the patient’s diabetes should be well managed and blood sugar levels should be carefully monitored to stay below 100 mg/dL. This may require diet modifications, oral medications and/or insulin. Ideally, ulcerations should be treated with prevention which makes patient education a very important component of diabetes management. Patients with diabetes and particularly those who have altered sensation in their feet should always wear appropriate footwear, check the soles of their feet for skin breakdown or blisters, and keep toenails well trimmed.The patients who are at risk for ulcerations, but have not yet developed full diabetic ulceration may be treated with inserts that are designed to disperse the force away from the affected area. These inserts are typically made of Plastizote, which accommodates the forces that it is subject to, and takes on the shape of the foot to spread the force away from the ulcerated areacauses the patient to place more weight on the forefoot and increases the risk of ulcers there.

Miscellany 

There are reports of high complication rates associated with simple ankle fractures in the population of patients with diabetes, especially those with peripheral neuropathy. Many patients who present with Charcot arthropathy of the ankle initiated their disease process with an ankle fracture. Many experts recommend augmented internal fixation with prolonged non-weight-bearing to treat these ankle fractures.

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