- Email: [email protected]
Overview of Diabetic Foot Care for the Nurse Practitioner
The Journal for Nurse Practitioners xxx (xxxx) xxx
Contents lists available at ScienceDirect
The Journal for Nurse Practitioners journal homepage: www.npjournal.org
Overview of Diabetic Foot Care for the Nurse Practitioner Jennifer Woody, MSN, FNP-C a b s t r a c t Keywords: Charcot arthropathy diabetes diabetic foot infection diabetic shoes diabetic ulcer foot care
Foot and ankle complications of diabetes result in significant morbidity, mortality, and health care expenditure. Diabetes may result in foot deformity, neuropathy, and peripheral artery disease with risk of callus, foot ulcer, infection, and subsequent amputation. Appropriate patient education, medical management, and use of therapeutic footwear can prevent many diabetic foot complications. Nurse practitioners are key members of foot care teams in both primary and specialty care. The nurse practitioner managing a patient’s diabetes is an appropriate provider to certify the need for diabetic shoes and should be authorized to do so to provide quality care without unnecessary delay. © 2019 Elsevier Inc. All rights reserved.
Foot and ankle complications related to diabetes include calluses, foot ulcers, infection, bony deformity, and Charcot arthropathy.1 Thirty-three percent of the $174 billion economic burden of diabetes is related to foot disease.2 Sixty-eight percent of people with diabetes experience complications involving their feet.3 Diabetes is increasing in prevalence and currently affects more than 29 million individuals in the United States.4 Early intervention through patient education regarding proper foot care and screening for complications is recommended through evidence-based guidelines.5 Preventative measures, including diabetic shoes and inserts, are indicated for individuals with diabetes and neurological manifestations, peripheral vascular disease, amputations, significant deformities, or preulcerations.6 A multidisciplinary approach improves outcomes in diabetic foot care. The best diabetic foot care is achieved using a team approach including the patient and clinicians in specialties including vascular surgery, podiatry, and orthopaedics.2 Specialty referral should be considered for patients with complications or impending complications related to their diabetes, such as diabetic foot ulcers, bony deformity, peripheral vascular disease, and severe skin, or nail pathology. Nurse practitioners are integral members of diabetic foot care teams both in primary and specialty care, providing diabetes management and patient education, expanding access to care, and improving outcomes.7
Pathophysiology of Diabetic Foot Complications Diabetes may result in symmetric polyneuropathy with loss of proprioception, vibratory perception, temperature perception, and https://doi.org/10.1016/j.nurpra.2019.08.011 1555-4155/© 2019 Elsevier Inc. All rights reserved.
pressure sensation.8 With decreased sensation and decreased proprioception, there is repetitive trauma to the foot causing atrophy of the plantar fat pad, which can lead to ulceration.8 Atrophy of the intrinsic muscles of the foot may lead to clawing of the toes.8 With the lumbricals and interossei relatively weak, the stronger pull from the extensor muscles may result in hammertoes, and gastrocsoleus contracture causes relative equinus contracture of the ankle.8 These changes cause increased pressure on the plantar metatarsal heads. Loss of sensation and repetitive trauma may result in calluses, blisters, and in fractures that may not be noticed by the patient. Because of autonomic neuropathy, the skin is prone to dryness, which can lead to fissuring and increased risk of cellulitis. With loss of proprioception, patients are more likely to be unsteady during ambulation and at increased risk for injury.
Foot Ulcers One in 4 individuals with diabetes develops a diabetic foot ulcer.4 Up to one-fourth of these diabetic foot ulcers do not heal, putting the patient at risk for infection and amputation. According to a study of more than 1 million patients presenting to emergency departments in the United States from 2006 to 2010 for diabetic foot ulcers, more than 80% of patients were admitted, with an annual cost of $8.78 billion.1 Of these admissions, there was a 2.0% mortality rate, 9.6% of patients were diagnosed with sepsis, and 10.5% required an amputation.1 Diabetic foot ulcers are often caused by a combination of bony deformity, neuropathy, and repetitive trauma.8 There may be delay in recognizing an ulcer due to lack of sensation and visual
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limitations of diabetic retinopathy. A patient may continue to walk on a painless ulcer, resulting in further soft tissue damage. Factors influencing the risk of amputation include the severity of soft tissue loss, ischemia, and infection.1 Diabetic foot wounds that do not heal result in >100,000 amputations in the United States annually, 60% of which started with a foot ulcer.8 Treatment of a diabetic foot ulcer requires appropriate debridement, offloading, maximizing perfusion, and infection management.8 The gold standard for offloading a diabetic foot ulcer is application of a total contact cast, a cast with plaster molded closely to the foot and ankle with a fiberglass outer layer for quicker drying and durability (Figure 1).9 Application of total contact casts requires technical skill to avoid pressure points and achieve appropriate foot and ankle alignment. Patients must keep casts dry and often find them cumbersome and difficult for ambulation. For this reason, other options, such as a postoperative shoe, padded dressing, and controlled ankle motion boot, are often used. Hyperglycemia and altered glucose metabolism result in hyperlipidemia, increased platelet viscosity, endothelial injury, and atherosclerosis. Peripheral artery disease is present in 50% to 60% of patients with a diabetic foot ulcer.1 Compared with neuropathic ulcers, ulcers resulting from arterial insufficiency carry a higher risk of recurrence and amputation.4 Presence of palpable pulses is unreliable to assess for ischemia.1 The Society for Vascular Surgery recommends measurement of toe waveforms and pressures in patients with diabetic foot ulcers because the ankle brachial index may be falsely elevated due to calcification of the arterial wall. The degree of perfusion required for healing of a diabetic foot ulcer is affected by ulcer size, location, depth, infection, and nutritional status of the patient. In patients with an ulcer, if ankle pressure is <100 mm Hg or toe pressure is <55 mm Hg, arterial studies are indicated to evaluate for occlusive lesions that could be addressed through vascular intervention.
Without preventative measures, 58% to 85% of patients with an ulcer will develop another ulcer within a year.1 Use of therapeutic shoes and inserts decreases this incidence by about 50%.1 Custom diabetic inserts are generally multiple density with a soft top layer and are molded to provide total contact with a patient’s foot. Inserts can accommodate deformity to equalize pressure and minimize friction. Patients may need extra-depth shoes, which have a removable full-length filler that when removed, provides depth to accommodate custom inserts (Figure 2). Custom molded shoes are another option and are fabricated over a model of a patient’s foot and include custom inserts.6 Extra-depth shoes or custom-molded shoes can be modified with rocker bottoms or metatarsal bars to offload the metatarsal heads, posting or wedges to shift weight laterally, and offset heels to stabilize severe hind foot deformity.6 Medicare Part B covers either 1 pair of custom-molded shoes and inserts or 1 pair of extra-depth shoes per year for patients with diabetes and severe foot disease. Two additional pairs of inserts are covered per calendar year for the custom-molded shoes, and 3 additional pairs of inserts for the extra-depth shoes. Patients pay 20% of the Medicare-approved cost as well as the part B deductible (https://www.medicare.gov/coverage/therapeutic-shoes-inserts).
Figure 1. Total contact cast with cast shoe.
Figure 2. Diabetic depth shoe and custom insert.
Foot Infections In patients with diabetes and risk factors for foot ulcers, offloading using appropriate therapeutic inserts and footwear is imperative to prevent initial ulceration as well as ulcer recurrence and to decrease the risk of infection. When presenting for care, approximately half of foot ulcers are infected based on clinical exam.1 An ulcer present for more than 30 days is at higher risk for infection.10 Additional risk factors for infection include presence of peripheral arterial disease, peripheral neuropathy, renal impairment, prior lower extremity amputation, and walking without
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shoes.10 When glycemic control is poor, leukocyte activity and complement function are altered increasing the risk of soft tissue infection. Bacteria may quickly penetrate into the deep fascia in poorly perfused skin. Foot infections result in 1 in 5 hospital admissions in patients with diabetes.10 Aerobic gram-positive cocci such as Staphylococcus aureus are the most common pathogen in diabetic foot infections.5 If infections are mild without risk factors for gram-negative pathogens, such as recent antibiotic therapy or hospitalization, ischemia, or gangrene, narrow spectrum antibiotics are appropriate.5 Clinicians should consider coverage for methicillinresistant Staphylococcus aureus (MRSA) in individuals with a history of MRSA infection, when MRSA is locally prevalent, and in severe infections.5 Severe infections should be treated with broader-spectrum antibiotics.5 In patients with diabetic complications involving the foot and ankle, osteomyelitis almost always results from extension of infection from a chronic ulcer.10 Hematogenous infection is much less likely.10 Osteomyelitis should be suspected if a diabetic foot ulcer does not heal in six weeks with appropriate antibiotic therapy and offloading.5 Ulcers that probe to bone likely have resulted in osteomyelitis. There is debate regarding the necessity and extent of surgical debridement indicated in osteomyelitis.5 Nonsurgical management should be considered if surgical debridement would result in unacceptable functional deficit; if there is ischemia due to vascular disease that cannot be addressed through endovascular or surgical intervention; if there is limited infection, especially in the forefoot; or the risks of surgery exceed the benefits.5 Urgent or emergent amputation is indicated in cases of life-threatening infection or limb necrosis.5 If there is recurrent ulceration without progressive deep
3
infection despite appropriate preventative measures, elective amputation may be indicated.5 One to 2 weeks of antibiotic therapy is sufficient for most mild to moderate soft tissue infections.5 Current data suggests no more than 6 weeks of antibiotic therapy is required for osteomyelitis with residual infected bone.11 There is no evidence to support continuing antibiotics until a diabetic foot ulcer is healed, only until the infection has been cleared.5 Charcot Arthropathy Often confused with diabetic foot infection, Charcot arthropathy is a neuropathic arthropathy most commonly occurring in the setting of diabetic neuropathy that results in destruction of bone and soft tissues. It is associated with increased mortality and decreased quality of life.9 Charcot arthropathy begins with a prodromal phase with erythema, edema, and normal radiographs (Figure 3A). In the development stage, there are radiographic findings of osteopenia, bony fragmentation, and joint subluxation or dislocation.13 The phase of coalescence is characterized by decreased warmth, edema, and erythema and bony absorption, sclerosis, and fusion.13 In the reconstruction phase, individuals have a clinically fixed deformity, bony consolidation on radiographs, and joint arthrosis (Figure 3B).13 The pathogenesis of Charcot arthropathy is not fully understood but likely explained by the combination of repetitive trauma in the setting of neuropathy and increased blood flow to the foot resulting in increased compartment pressure and deep tissue ischemia.14 Patients with peripheral artery disease seem to be protected from Charcot arthropathy due to limited arterial flow, but those with Charcot arthropathy may go on to subsequently develop peripheral artery disease.14 In Charcot
Figure 3. (A) Anterior-posterior and lateral of foot in early Charcot arthropathy (prodromal phase) and (B) Anterior-posterior and lateral of same foot 4 years after that in panel A with advanced Charcot changes (reconstruction phase).
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arthropathy, continued weightbearing without offloading may result in fracture, subluxation, and dislocation most often involving the midfoot. The diagnosis of Charcot arthropathy is primarily based on history and physical exam and requires a high index of suspicion in patients with neuropathy. Acute Charcot arthropathy is often confused with cellulitis, deep vein thrombosis, or gout because it results in a unilateral erythematous, edematous foot and ankle, which may or may not be painful. Unlike infection, the erythema associated with Charcot arthropathy will decrease with several minutes of elevation. Less than 50% of patients with Charcot arthropathy are aware of their neuropathy, and patients may report that they have normal sensation.12 As many as 40% of patients have an ulcer when they are first diagnosed with Charcot arthropathy.12 Presence of streaking erythema is not consistent with Charcot arthropathy and is suggestive of infection.14 In Charcot arthropathy, the foot is warmer to the touch than the contralateral side, often increased by 3 to 5 degrees Celsius.12 Pulses are generally palpable and often bounding.12 When presenting early in the disease process, radiographs are often normal, but the diagnosis is clinical, and advanced imaging is typically not required.12 As Charcot arthropathy progresses, radiographs show evidence of bony resorption and collapse of the medial longitudinal arch resulting in a “rockerbottom” deformity.12,14 Patients with suspected Charcot arthropathy should be referred to orthopaedics or podiatry early to manage symptoms and minimize deformity.1 Initial treatment involves immobilization and avoiding weightbearing until edema decreases and there is no further progression of radiographic changes.15 Traditional treatment is non-weightbearing in a total contact cast until edema decreases and x-rays stabilize, which may require between 9 weeks and 11 months in a cast.14 A total contact cast redistributes plantar pressure, reduces inflammation and edema, and limits bone and joint destruction associated with Charcot arthropathy.9 Recent studies suggest weightbearing in a total contact cast may not adversely affect outcomes.14 During the acute Charcot phase, casts are changed every 1 to 2 weeks or more frequently to monitor skin and ensure appropriate cast fit as edema decreases.15 While total contact casting is considered the gold standard for treatment of Charcot arthropathy, it carries risks of ulceration and deep vein thrombosis, is challenging from mobility and bathing standpoints, and requires technical skill and time in clinic. Removable boots allow patients to check their skin daily and offload the forefoot and midfoot while loading the hindfoot. There are mixed results when using boots for Charcot arthropathy involving the midfoot compared to nonremovable total contact casts.14 After the acute inflammatory phase has resolved, patients may transition to a Charcot restraint orthotic walker (CROW), which is a fully lined boot with custom foot insert intended for patients with severe deformity due to neuropathic arthropathy (Figure 4).15 The top and bottom of the boot are secured with straps to enclose the foot and ankle completely. Alternatively or after a period in a CROW, an ankle foot orthotic (AFO) may be used in combination with an extra-depth shoe and insert or custom shoe to control the ankle instability associated with Charcot arthropathy. A conventional AFO typically is constructed of two metal upright bars extending from the sole of the shoe past the ankle to a leather calf strap (Figure 5). If the ankle is stable, patients may transition to an extra-depth shoe with diabetic insert following acute Charcot arthropathy (Figure 2). Patients with severe deformity may benefit from operative reconstruction.15 Fifty percent of patients with Charcot arthropathy require at least 1 surgery.12 Fifteen percent of patients with Charcot
Figure 4. Charcot Restraint Orthotic Walker (CROW).
arthropathy require an amputation at the ankle or more proximal.16 This rate increases to 35% to 67% in patients with a related diabetic foot ulcer.12 Historically, surgery has been performed to address deformity related to Charcot arthropathy, in cases of chronic osteomyelitis, chronic wounds over a bony deformity, or in severe deformity that cannot be accommodated with a brace or orthotic device.17 In the past, nonoperative treatment was considered successful if infection was cleared and the deformity could be accommodated with a CROW, AFO, or custom insert or shoe.17 However, more recent studies have indicated that quality of life of patients is impaired after Charcot arthropathy when patients require cumbersome orthotic devices such as a CROW.17 Surgery is now considered an option to achieve a plantigrade foot and allow patients to use therapeutic shoes.17 The decision for surgery must take into account the patient’s desires, ability to comply with treatment recommendations, social support, and comorbidities. Often a patient has diabetes for more than 10 years, is morbidly obese, has long-standing peripheral neuropathy, immune deficiency, vitamin D deficiency, and osteoporosis, all factors that should be considered when evaluating the risks and benefits of surgery.17 Screening and Preventative Measures Avoiding foot and ankle complications of diabetes requires appropriate screening, medical management of diabetes, and patient education. The recommendation is to achieve a hemoglobin a1c of <7% when appropriate to reduce the risk of diabetic foot ulcer, infection, and subsequent risk of amputation.4 The American Diabetes Association recommends a foot exam at least annually for all patients with diabetes.1 Those at increased risk with substantial neuropathy or peripheral arterial disease should be assessed more frequently.1 Skin should be inspected
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necessary for patients with severe deformities. Patients should be counseled to break in shoes gradually. Those with neuropathy should avoid walking without shoes because this increases the risk of wounds.18 Barrier to Care for Patients of Nurse Practitioners
Figure 5. Conventional ankle foot orthotic (AFO).
for evidence of trauma, callus, ulceration, and foot or toe deformity. Posterior tibial, dorsalis pedis, and popliteal pulses should be palpated. If pulses are not palpable, Doppler should be utilized.8 Clinicians should assess for rest pain and dependent rubor, which are evidence of tissue ischemia. A thorough neurological exam should include evaluation of vibratory sense with a 128-Hz tuning fork, sensation with a Semmes-Weinstein 5.07 monofilament, temperature, and Achilles and patellar reflexes.8 Abnormal findings indicate increased risk of development of a diabetic foot ulcer.8 Patients should be evaluated for issues with gait and balance. It is recommended that patients with a diabetic foot ulcer have an annual ankle-brachial index, pedal and ankle Doppler arterial waveforms, and toe systolic pressure or transcutaneous oxygen pressure to assess the potential for ulcer healing and evaluate whether vascular intervention is indicated to improve healing potential. 4 Although often ordered by vascular specialists, these tests should be considered by any provider treating a diabetic ulcer. Patients with diabetic neuropathy should be educated regarding sensory loss and should check their skin daily for blisters, calluses, erythema, and ulceration. Feet should be washed and dried daily, avoiding residual moisture between the toes. Lotion should be applied to the dorsal and plantar surfaces of the foot but not between the toes.18 Nails should be trimmed straight across, filing sharp edges with a nail file to avoid ingrown nails.18 To remove a callus, patients should gently rub a wet pumice stone over the callus after bathing.18 While safer than using chemical agents on calluses, patients with neuropathy should use caution with pumice stones because of the increased potential for skin injury. Shoes should be checked before wearing to ensure nothing is in the shoe that could result in added pressure. Those with bony deformities such as hammertoes may need extra-depth shoes. Custom shoes are often
Currently, Medicare requires a physician treating the patient’s diabetes to certify the necessity of diabetic shoes or inserts.6 According to Medicare guidelines, providers knowledgeable regarding the use of diabetic shoes and inserts including nurse practitioners, physician assistants, podiatrists, clinical nurse specialists, and physicians may order the shoes or inserts.6 Nurse practitioners are authorized Medicare Part B providers and provide evidence-based diabetes management with good outcomes.7 However, to meet Medicare requirements, a physician must certify the need for diabetic shoes and must assume management of the patient’s diabetes, which can delay and sometimes limit access to appropriate care. The American Association of Nurse Practitioners is promoting legislation to address the issue. Diabetic complications involving the foot and ankle result in significant morbidity, mortality, and health care expenditure. A multidisciplinary approach has been shown to improve the quality of foot care and decrease the risk of major amputations.15 As part of foot care teams in both primary and specialty care, nurse practitioners prevent ulceration, infection, and amputation by identifying neuropathy, ischemia, deformity, and impending ulcers early and implementing appropriate treatment. Considering that many foot and ankle complications of diabetes are preventable with therapeutic footwear, patients should be able to obtain diabetic shoes when the need is certified by the nurse practitioner managing their disease, providing their education, and helping them to navigate the health care system. References 1. Boulton AJM, Armstrong D, Kirsner R, Attinger C, Lavery L, Lipsky B, et al. Diagnosis and management of diabetic foot complications. Arlington, VA: American Diabetes Association; 2018. 2. Joret M, Osman K, Dean A, Cao C, van der Werf B, Bhamidipaty V. Multidisciplinary clinics reduce treatment costs and improve patient outcomes in diabetic foot disease. J Vasc Surg. 2019;70(3):806-814. 3. Vural S, Bostanci S, Koçyigit P, Çaliskan D, Baskal N, Aydin N. Risk factors and frequency of ingrown nails in adult diabetic patients. J Foot Ankle Surg. 2018;57(2):289-295. 4. Hart T, Milner R, Cifu A. Management of a diabetic foot. JAMA. 2017;318(14): 1387-1388. 5. Lipsky BA, Berendt AR, Cornia PB, Pile JC, Peters EJ, Armstrong DG, et al. 2012 infectious diseases society of America clinical practice guideline for the diagnosis and treatment of diabetic foot infections. Clin Infect Dis. 2012;54(12): e132-e173. 6. Centers for Medicare and Medicaid Services. Medicare Benefit Policy (Publication no. 100-02). Washington, DC: Department of Health and Human Services; 2018. 7. Kuo Y, Chen N, Baillargeon J, Raji MA, Goodwin JS. Potentially preventable hospitalizations in medicare patients with diabetes: A comparison of primary care provided by nurse practitioners versus physicians. Med Care. 2015;53(9): 776-783. 8. Bandyk D. The diabetic foot: Pathophysiology, evaluation, and treatment. Semin Vasc Surg. 2018;31(2-4):43-48. 9. Petrova N, Edmonds M. Conservative and pharmacologic treatments for the diabetic Charcot foot. Clin Podiatr Med Surg. 2017;34(1):15-24. 10. Chastain C, Klopfenstein N, Serezani C, Aronoff D. A clinical review of diabetic foot infections. Clin Podiatr Med Surg. 2019;36(3):381-395. 11. Uçkay I, Berli M, Sendi P, Lipsky B. Principles and practice of antibiotic stewardship in the management of diabetic foot infections. Curr Opin Infect Dis. 2019;32(2):95-101. 12. Dodd A, Daniels T. Charcot neuroarthropathy of the foot and ankle. Bone Joint Surg Am. 2018;100(8):696-711. 13. Rosenbaum A, DiPreta J. Classifications in brief: Eichenholtz classification of Charcot arthropathy. Clin Orthop Relat Res. 2015;473:1168-1171.
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14. Strotman P, Reif T, Pinzur M. Charcot arthropathy of the foot and ankle. Foot Ankle Int. 2016;37(11):1255-1263. 15. Yousaf S, Dawe E, Saleh A, Gill I, Wee A. The acute Charcot foot in diabetics: diagnosis and management. EFORT Open Rev. 2018;3(10):568-573. 16. Centers for Disease Control and Prevention. Diabetes Report Card 2017. Atlanta, GA: Centers for Disease Control and Prevention, US Dept of Health and Human Services; 2018. 17. Pinzur M, Schiff A. Deformity and clinical outcomes following operative correction of Charcot foot: A new classification with implications for treatment. Foot Ankle Int. 2018;39(3):265-270.
18. American Diabetes Association. http://www.diabetes.org/. Accessed July 12, 2019.
Jennifer Woody, MSN, FNP-C, is a nurse practitioner in the Department of Orthopaedics, School of Medicine, The University of North Carolina, Chapel Hill, NC. She can be contacted at [email protected]. In compliance with national ethical guidelines, the author reports no relationships with business or industry that would pose a conflict of interest.
Contents lists available at ScienceDirect
The Journal for Nurse Practitioners journal homepage: www.npjournal.org
Overview of Diabetic Foot Care for the Nurse Practitioner Jennifer Woody, MSN, FNP-C a b s t r a c t Keywords: Charcot arthropathy diabetes diabetic foot infection diabetic shoes diabetic ulcer foot care
Foot and ankle complications of diabetes result in significant morbidity, mortality, and health care expenditure. Diabetes may result in foot deformity, neuropathy, and peripheral artery disease with risk of callus, foot ulcer, infection, and subsequent amputation. Appropriate patient education, medical management, and use of therapeutic footwear can prevent many diabetic foot complications. Nurse practitioners are key members of foot care teams in both primary and specialty care. The nurse practitioner managing a patient’s diabetes is an appropriate provider to certify the need for diabetic shoes and should be authorized to do so to provide quality care without unnecessary delay. © 2019 Elsevier Inc. All rights reserved.
Foot and ankle complications related to diabetes include calluses, foot ulcers, infection, bony deformity, and Charcot arthropathy.1 Thirty-three percent of the $174 billion economic burden of diabetes is related to foot disease.2 Sixty-eight percent of people with diabetes experience complications involving their feet.3 Diabetes is increasing in prevalence and currently affects more than 29 million individuals in the United States.4 Early intervention through patient education regarding proper foot care and screening for complications is recommended through evidence-based guidelines.5 Preventative measures, including diabetic shoes and inserts, are indicated for individuals with diabetes and neurological manifestations, peripheral vascular disease, amputations, significant deformities, or preulcerations.6 A multidisciplinary approach improves outcomes in diabetic foot care. The best diabetic foot care is achieved using a team approach including the patient and clinicians in specialties including vascular surgery, podiatry, and orthopaedics.2 Specialty referral should be considered for patients with complications or impending complications related to their diabetes, such as diabetic foot ulcers, bony deformity, peripheral vascular disease, and severe skin, or nail pathology. Nurse practitioners are integral members of diabetic foot care teams both in primary and specialty care, providing diabetes management and patient education, expanding access to care, and improving outcomes.7
Pathophysiology of Diabetic Foot Complications Diabetes may result in symmetric polyneuropathy with loss of proprioception, vibratory perception, temperature perception, and https://doi.org/10.1016/j.nurpra.2019.08.011 1555-4155/© 2019 Elsevier Inc. All rights reserved.
pressure sensation.8 With decreased sensation and decreased proprioception, there is repetitive trauma to the foot causing atrophy of the plantar fat pad, which can lead to ulceration.8 Atrophy of the intrinsic muscles of the foot may lead to clawing of the toes.8 With the lumbricals and interossei relatively weak, the stronger pull from the extensor muscles may result in hammertoes, and gastrocsoleus contracture causes relative equinus contracture of the ankle.8 These changes cause increased pressure on the plantar metatarsal heads. Loss of sensation and repetitive trauma may result in calluses, blisters, and in fractures that may not be noticed by the patient. Because of autonomic neuropathy, the skin is prone to dryness, which can lead to fissuring and increased risk of cellulitis. With loss of proprioception, patients are more likely to be unsteady during ambulation and at increased risk for injury.
Foot Ulcers One in 4 individuals with diabetes develops a diabetic foot ulcer.4 Up to one-fourth of these diabetic foot ulcers do not heal, putting the patient at risk for infection and amputation. According to a study of more than 1 million patients presenting to emergency departments in the United States from 2006 to 2010 for diabetic foot ulcers, more than 80% of patients were admitted, with an annual cost of $8.78 billion.1 Of these admissions, there was a 2.0% mortality rate, 9.6% of patients were diagnosed with sepsis, and 10.5% required an amputation.1 Diabetic foot ulcers are often caused by a combination of bony deformity, neuropathy, and repetitive trauma.8 There may be delay in recognizing an ulcer due to lack of sensation and visual
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limitations of diabetic retinopathy. A patient may continue to walk on a painless ulcer, resulting in further soft tissue damage. Factors influencing the risk of amputation include the severity of soft tissue loss, ischemia, and infection.1 Diabetic foot wounds that do not heal result in >100,000 amputations in the United States annually, 60% of which started with a foot ulcer.8 Treatment of a diabetic foot ulcer requires appropriate debridement, offloading, maximizing perfusion, and infection management.8 The gold standard for offloading a diabetic foot ulcer is application of a total contact cast, a cast with plaster molded closely to the foot and ankle with a fiberglass outer layer for quicker drying and durability (Figure 1).9 Application of total contact casts requires technical skill to avoid pressure points and achieve appropriate foot and ankle alignment. Patients must keep casts dry and often find them cumbersome and difficult for ambulation. For this reason, other options, such as a postoperative shoe, padded dressing, and controlled ankle motion boot, are often used. Hyperglycemia and altered glucose metabolism result in hyperlipidemia, increased platelet viscosity, endothelial injury, and atherosclerosis. Peripheral artery disease is present in 50% to 60% of patients with a diabetic foot ulcer.1 Compared with neuropathic ulcers, ulcers resulting from arterial insufficiency carry a higher risk of recurrence and amputation.4 Presence of palpable pulses is unreliable to assess for ischemia.1 The Society for Vascular Surgery recommends measurement of toe waveforms and pressures in patients with diabetic foot ulcers because the ankle brachial index may be falsely elevated due to calcification of the arterial wall. The degree of perfusion required for healing of a diabetic foot ulcer is affected by ulcer size, location, depth, infection, and nutritional status of the patient. In patients with an ulcer, if ankle pressure is <100 mm Hg or toe pressure is <55 mm Hg, arterial studies are indicated to evaluate for occlusive lesions that could be addressed through vascular intervention.
Without preventative measures, 58% to 85% of patients with an ulcer will develop another ulcer within a year.1 Use of therapeutic shoes and inserts decreases this incidence by about 50%.1 Custom diabetic inserts are generally multiple density with a soft top layer and are molded to provide total contact with a patient’s foot. Inserts can accommodate deformity to equalize pressure and minimize friction. Patients may need extra-depth shoes, which have a removable full-length filler that when removed, provides depth to accommodate custom inserts (Figure 2). Custom molded shoes are another option and are fabricated over a model of a patient’s foot and include custom inserts.6 Extra-depth shoes or custom-molded shoes can be modified with rocker bottoms or metatarsal bars to offload the metatarsal heads, posting or wedges to shift weight laterally, and offset heels to stabilize severe hind foot deformity.6 Medicare Part B covers either 1 pair of custom-molded shoes and inserts or 1 pair of extra-depth shoes per year for patients with diabetes and severe foot disease. Two additional pairs of inserts are covered per calendar year for the custom-molded shoes, and 3 additional pairs of inserts for the extra-depth shoes. Patients pay 20% of the Medicare-approved cost as well as the part B deductible (https://www.medicare.gov/coverage/therapeutic-shoes-inserts).
Figure 1. Total contact cast with cast shoe.
Figure 2. Diabetic depth shoe and custom insert.
Foot Infections In patients with diabetes and risk factors for foot ulcers, offloading using appropriate therapeutic inserts and footwear is imperative to prevent initial ulceration as well as ulcer recurrence and to decrease the risk of infection. When presenting for care, approximately half of foot ulcers are infected based on clinical exam.1 An ulcer present for more than 30 days is at higher risk for infection.10 Additional risk factors for infection include presence of peripheral arterial disease, peripheral neuropathy, renal impairment, prior lower extremity amputation, and walking without
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shoes.10 When glycemic control is poor, leukocyte activity and complement function are altered increasing the risk of soft tissue infection. Bacteria may quickly penetrate into the deep fascia in poorly perfused skin. Foot infections result in 1 in 5 hospital admissions in patients with diabetes.10 Aerobic gram-positive cocci such as Staphylococcus aureus are the most common pathogen in diabetic foot infections.5 If infections are mild without risk factors for gram-negative pathogens, such as recent antibiotic therapy or hospitalization, ischemia, or gangrene, narrow spectrum antibiotics are appropriate.5 Clinicians should consider coverage for methicillinresistant Staphylococcus aureus (MRSA) in individuals with a history of MRSA infection, when MRSA is locally prevalent, and in severe infections.5 Severe infections should be treated with broader-spectrum antibiotics.5 In patients with diabetic complications involving the foot and ankle, osteomyelitis almost always results from extension of infection from a chronic ulcer.10 Hematogenous infection is much less likely.10 Osteomyelitis should be suspected if a diabetic foot ulcer does not heal in six weeks with appropriate antibiotic therapy and offloading.5 Ulcers that probe to bone likely have resulted in osteomyelitis. There is debate regarding the necessity and extent of surgical debridement indicated in osteomyelitis.5 Nonsurgical management should be considered if surgical debridement would result in unacceptable functional deficit; if there is ischemia due to vascular disease that cannot be addressed through endovascular or surgical intervention; if there is limited infection, especially in the forefoot; or the risks of surgery exceed the benefits.5 Urgent or emergent amputation is indicated in cases of life-threatening infection or limb necrosis.5 If there is recurrent ulceration without progressive deep
3
infection despite appropriate preventative measures, elective amputation may be indicated.5 One to 2 weeks of antibiotic therapy is sufficient for most mild to moderate soft tissue infections.5 Current data suggests no more than 6 weeks of antibiotic therapy is required for osteomyelitis with residual infected bone.11 There is no evidence to support continuing antibiotics until a diabetic foot ulcer is healed, only until the infection has been cleared.5 Charcot Arthropathy Often confused with diabetic foot infection, Charcot arthropathy is a neuropathic arthropathy most commonly occurring in the setting of diabetic neuropathy that results in destruction of bone and soft tissues. It is associated with increased mortality and decreased quality of life.9 Charcot arthropathy begins with a prodromal phase with erythema, edema, and normal radiographs (Figure 3A). In the development stage, there are radiographic findings of osteopenia, bony fragmentation, and joint subluxation or dislocation.13 The phase of coalescence is characterized by decreased warmth, edema, and erythema and bony absorption, sclerosis, and fusion.13 In the reconstruction phase, individuals have a clinically fixed deformity, bony consolidation on radiographs, and joint arthrosis (Figure 3B).13 The pathogenesis of Charcot arthropathy is not fully understood but likely explained by the combination of repetitive trauma in the setting of neuropathy and increased blood flow to the foot resulting in increased compartment pressure and deep tissue ischemia.14 Patients with peripheral artery disease seem to be protected from Charcot arthropathy due to limited arterial flow, but those with Charcot arthropathy may go on to subsequently develop peripheral artery disease.14 In Charcot
Figure 3. (A) Anterior-posterior and lateral of foot in early Charcot arthropathy (prodromal phase) and (B) Anterior-posterior and lateral of same foot 4 years after that in panel A with advanced Charcot changes (reconstruction phase).
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arthropathy, continued weightbearing without offloading may result in fracture, subluxation, and dislocation most often involving the midfoot. The diagnosis of Charcot arthropathy is primarily based on history and physical exam and requires a high index of suspicion in patients with neuropathy. Acute Charcot arthropathy is often confused with cellulitis, deep vein thrombosis, or gout because it results in a unilateral erythematous, edematous foot and ankle, which may or may not be painful. Unlike infection, the erythema associated with Charcot arthropathy will decrease with several minutes of elevation. Less than 50% of patients with Charcot arthropathy are aware of their neuropathy, and patients may report that they have normal sensation.12 As many as 40% of patients have an ulcer when they are first diagnosed with Charcot arthropathy.12 Presence of streaking erythema is not consistent with Charcot arthropathy and is suggestive of infection.14 In Charcot arthropathy, the foot is warmer to the touch than the contralateral side, often increased by 3 to 5 degrees Celsius.12 Pulses are generally palpable and often bounding.12 When presenting early in the disease process, radiographs are often normal, but the diagnosis is clinical, and advanced imaging is typically not required.12 As Charcot arthropathy progresses, radiographs show evidence of bony resorption and collapse of the medial longitudinal arch resulting in a “rockerbottom” deformity.12,14 Patients with suspected Charcot arthropathy should be referred to orthopaedics or podiatry early to manage symptoms and minimize deformity.1 Initial treatment involves immobilization and avoiding weightbearing until edema decreases and there is no further progression of radiographic changes.15 Traditional treatment is non-weightbearing in a total contact cast until edema decreases and x-rays stabilize, which may require between 9 weeks and 11 months in a cast.14 A total contact cast redistributes plantar pressure, reduces inflammation and edema, and limits bone and joint destruction associated with Charcot arthropathy.9 Recent studies suggest weightbearing in a total contact cast may not adversely affect outcomes.14 During the acute Charcot phase, casts are changed every 1 to 2 weeks or more frequently to monitor skin and ensure appropriate cast fit as edema decreases.15 While total contact casting is considered the gold standard for treatment of Charcot arthropathy, it carries risks of ulceration and deep vein thrombosis, is challenging from mobility and bathing standpoints, and requires technical skill and time in clinic. Removable boots allow patients to check their skin daily and offload the forefoot and midfoot while loading the hindfoot. There are mixed results when using boots for Charcot arthropathy involving the midfoot compared to nonremovable total contact casts.14 After the acute inflammatory phase has resolved, patients may transition to a Charcot restraint orthotic walker (CROW), which is a fully lined boot with custom foot insert intended for patients with severe deformity due to neuropathic arthropathy (Figure 4).15 The top and bottom of the boot are secured with straps to enclose the foot and ankle completely. Alternatively or after a period in a CROW, an ankle foot orthotic (AFO) may be used in combination with an extra-depth shoe and insert or custom shoe to control the ankle instability associated with Charcot arthropathy. A conventional AFO typically is constructed of two metal upright bars extending from the sole of the shoe past the ankle to a leather calf strap (Figure 5). If the ankle is stable, patients may transition to an extra-depth shoe with diabetic insert following acute Charcot arthropathy (Figure 2). Patients with severe deformity may benefit from operative reconstruction.15 Fifty percent of patients with Charcot arthropathy require at least 1 surgery.12 Fifteen percent of patients with Charcot
Figure 4. Charcot Restraint Orthotic Walker (CROW).
arthropathy require an amputation at the ankle or more proximal.16 This rate increases to 35% to 67% in patients with a related diabetic foot ulcer.12 Historically, surgery has been performed to address deformity related to Charcot arthropathy, in cases of chronic osteomyelitis, chronic wounds over a bony deformity, or in severe deformity that cannot be accommodated with a brace or orthotic device.17 In the past, nonoperative treatment was considered successful if infection was cleared and the deformity could be accommodated with a CROW, AFO, or custom insert or shoe.17 However, more recent studies have indicated that quality of life of patients is impaired after Charcot arthropathy when patients require cumbersome orthotic devices such as a CROW.17 Surgery is now considered an option to achieve a plantigrade foot and allow patients to use therapeutic shoes.17 The decision for surgery must take into account the patient’s desires, ability to comply with treatment recommendations, social support, and comorbidities. Often a patient has diabetes for more than 10 years, is morbidly obese, has long-standing peripheral neuropathy, immune deficiency, vitamin D deficiency, and osteoporosis, all factors that should be considered when evaluating the risks and benefits of surgery.17 Screening and Preventative Measures Avoiding foot and ankle complications of diabetes requires appropriate screening, medical management of diabetes, and patient education. The recommendation is to achieve a hemoglobin a1c of <7% when appropriate to reduce the risk of diabetic foot ulcer, infection, and subsequent risk of amputation.4 The American Diabetes Association recommends a foot exam at least annually for all patients with diabetes.1 Those at increased risk with substantial neuropathy or peripheral arterial disease should be assessed more frequently.1 Skin should be inspected
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necessary for patients with severe deformities. Patients should be counseled to break in shoes gradually. Those with neuropathy should avoid walking without shoes because this increases the risk of wounds.18 Barrier to Care for Patients of Nurse Practitioners
Figure 5. Conventional ankle foot orthotic (AFO).
for evidence of trauma, callus, ulceration, and foot or toe deformity. Posterior tibial, dorsalis pedis, and popliteal pulses should be palpated. If pulses are not palpable, Doppler should be utilized.8 Clinicians should assess for rest pain and dependent rubor, which are evidence of tissue ischemia. A thorough neurological exam should include evaluation of vibratory sense with a 128-Hz tuning fork, sensation with a Semmes-Weinstein 5.07 monofilament, temperature, and Achilles and patellar reflexes.8 Abnormal findings indicate increased risk of development of a diabetic foot ulcer.8 Patients should be evaluated for issues with gait and balance. It is recommended that patients with a diabetic foot ulcer have an annual ankle-brachial index, pedal and ankle Doppler arterial waveforms, and toe systolic pressure or transcutaneous oxygen pressure to assess the potential for ulcer healing and evaluate whether vascular intervention is indicated to improve healing potential. 4 Although often ordered by vascular specialists, these tests should be considered by any provider treating a diabetic ulcer. Patients with diabetic neuropathy should be educated regarding sensory loss and should check their skin daily for blisters, calluses, erythema, and ulceration. Feet should be washed and dried daily, avoiding residual moisture between the toes. Lotion should be applied to the dorsal and plantar surfaces of the foot but not between the toes.18 Nails should be trimmed straight across, filing sharp edges with a nail file to avoid ingrown nails.18 To remove a callus, patients should gently rub a wet pumice stone over the callus after bathing.18 While safer than using chemical agents on calluses, patients with neuropathy should use caution with pumice stones because of the increased potential for skin injury. Shoes should be checked before wearing to ensure nothing is in the shoe that could result in added pressure. Those with bony deformities such as hammertoes may need extra-depth shoes. Custom shoes are often
Currently, Medicare requires a physician treating the patient’s diabetes to certify the necessity of diabetic shoes or inserts.6 According to Medicare guidelines, providers knowledgeable regarding the use of diabetic shoes and inserts including nurse practitioners, physician assistants, podiatrists, clinical nurse specialists, and physicians may order the shoes or inserts.6 Nurse practitioners are authorized Medicare Part B providers and provide evidence-based diabetes management with good outcomes.7 However, to meet Medicare requirements, a physician must certify the need for diabetic shoes and must assume management of the patient’s diabetes, which can delay and sometimes limit access to appropriate care. The American Association of Nurse Practitioners is promoting legislation to address the issue. Diabetic complications involving the foot and ankle result in significant morbidity, mortality, and health care expenditure. A multidisciplinary approach has been shown to improve the quality of foot care and decrease the risk of major amputations.15 As part of foot care teams in both primary and specialty care, nurse practitioners prevent ulceration, infection, and amputation by identifying neuropathy, ischemia, deformity, and impending ulcers early and implementing appropriate treatment. Considering that many foot and ankle complications of diabetes are preventable with therapeutic footwear, patients should be able to obtain diabetic shoes when the need is certified by the nurse practitioner managing their disease, providing their education, and helping them to navigate the health care system. References 1. Boulton AJM, Armstrong D, Kirsner R, Attinger C, Lavery L, Lipsky B, et al. Diagnosis and management of diabetic foot complications. Arlington, VA: American Diabetes Association; 2018. 2. Joret M, Osman K, Dean A, Cao C, van der Werf B, Bhamidipaty V. Multidisciplinary clinics reduce treatment costs and improve patient outcomes in diabetic foot disease. J Vasc Surg. 2019;70(3):806-814. 3. Vural S, Bostanci S, Koçyigit P, Çaliskan D, Baskal N, Aydin N. Risk factors and frequency of ingrown nails in adult diabetic patients. J Foot Ankle Surg. 2018;57(2):289-295. 4. Hart T, Milner R, Cifu A. Management of a diabetic foot. JAMA. 2017;318(14): 1387-1388. 5. Lipsky BA, Berendt AR, Cornia PB, Pile JC, Peters EJ, Armstrong DG, et al. 2012 infectious diseases society of America clinical practice guideline for the diagnosis and treatment of diabetic foot infections. Clin Infect Dis. 2012;54(12): e132-e173. 6. Centers for Medicare and Medicaid Services. Medicare Benefit Policy (Publication no. 100-02). Washington, DC: Department of Health and Human Services; 2018. 7. Kuo Y, Chen N, Baillargeon J, Raji MA, Goodwin JS. Potentially preventable hospitalizations in medicare patients with diabetes: A comparison of primary care provided by nurse practitioners versus physicians. Med Care. 2015;53(9): 776-783. 8. Bandyk D. The diabetic foot: Pathophysiology, evaluation, and treatment. Semin Vasc Surg. 2018;31(2-4):43-48. 9. Petrova N, Edmonds M. Conservative and pharmacologic treatments for the diabetic Charcot foot. Clin Podiatr Med Surg. 2017;34(1):15-24. 10. Chastain C, Klopfenstein N, Serezani C, Aronoff D. A clinical review of diabetic foot infections. Clin Podiatr Med Surg. 2019;36(3):381-395. 11. Uçkay I, Berli M, Sendi P, Lipsky B. Principles and practice of antibiotic stewardship in the management of diabetic foot infections. Curr Opin Infect Dis. 2019;32(2):95-101. 12. Dodd A, Daniels T. Charcot neuroarthropathy of the foot and ankle. Bone Joint Surg Am. 2018;100(8):696-711. 13. Rosenbaum A, DiPreta J. Classifications in brief: Eichenholtz classification of Charcot arthropathy. Clin Orthop Relat Res. 2015;473:1168-1171.
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14. Strotman P, Reif T, Pinzur M. Charcot arthropathy of the foot and ankle. Foot Ankle Int. 2016;37(11):1255-1263. 15. Yousaf S, Dawe E, Saleh A, Gill I, Wee A. The acute Charcot foot in diabetics: diagnosis and management. EFORT Open Rev. 2018;3(10):568-573. 16. Centers for Disease Control and Prevention. Diabetes Report Card 2017. Atlanta, GA: Centers for Disease Control and Prevention, US Dept of Health and Human Services; 2018. 17. Pinzur M, Schiff A. Deformity and clinical outcomes following operative correction of Charcot foot: A new classification with implications for treatment. Foot Ankle Int. 2018;39(3):265-270.
18. American Diabetes Association. http://www.diabetes.org/. Accessed July 12, 2019.
Jennifer Woody, MSN, FNP-C, is a nurse practitioner in the Department of Orthopaedics, School of Medicine, The University of North Carolina, Chapel Hill, NC. She can be contacted at [email protected]. In compliance with national ethical guidelines, the author reports no relationships with business or industry that would pose a conflict of interest.