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Management of the Neuropathic Foot

Elftman, Nancy CO, CPed

JPO Journal of Prosthetics and Orthotics: April 2005 - Volume 17 - Issue 2 - p S4-S27
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This overview of the diabetic/neuropathic pathways has been utilized as a basic teaching document in the health care field. The information provided applies to the education of patients as well as professionals with a basic understanding of the progression of complications and prevention of catastrophic events. Detailed descriptions include evaluation techniques that can be used for early neuropathy detection, footwear and modification requirements, and follow-up protocol. Chronic complications are detailed to allow health care professionals to detect and refer for proper treatment. Off-loading techniques provide optimal wound healing for wound clinical settings. (Adapted with permission from Wound Care, A Collaborative Practice Manual for Physical Therapists and Nurses, Sussman C, Barbara M. Bates-Jensen, eds. Gaithersburg, MD: Aspen Publishers; 2000).

NANCY ELFTMAN, CO, CPed, is affiliated with Hands on Foot, Inc., La Verne, California.

Adapted with permission from: Sussman C, and Bates-Jensen, B.M., editors. Wound Care: A Collaborative Practice Manual for Physical Therapists and Nurses. Gaithersburg, MD: Aspen Publishers Inc., 2000.

Correspondence: Nancy Elftman, CO, CPed, Hands on Foot, Inc., 2076 Bonita Avenue, La Verne, CA 91750; e-mail: nancy@handsonfoot.com.

Medical research has provided advancements in medication and technology that now extend the lives of patients with previously fatal diseases: the prognosis has changed from fatality to chronic complications.1 The chronic disease complication addressed here is neuropathy. The objective of management of the problem is to control progression and reduce amputations conservatively.

The patient with neuropathy often has dysvascular components that must be addressed by a medical team, rather than one specialty. With the team approach, the limb can be evaluated, treated, and monitored through follow-up to provide continued ambulation for the patient.2 The team goal is the prevention or delay of amputation and/or limb salvage of lower extremities. In the formation of clinical teams there has been a trend to include practitioners of several disciplines, including wound care nurse, advanced practice nurse, or enterostomal therapy nurse, diabetologist/endocrinologist, vascular surgeon, physical therapist, orthotist/pedorthist, orthopedic surgeon/podiatrist, and dermatologist.

The multidisciplinary approach to treating foot problems is an optimum intervention for prevention of amputations. The disciplines playing the most important roles are nurse educators, who encourage high-risk patients to modify their behavior; orthotists, for recommendation of suitable footwear, stockings, and orthoses; and primary care providers, to remove calluses, treat minor trauma, and provide health care. Referrals should be available to vascular surgeons and other specialists when specified by a physician.3

The multidisciplinary clinic requires special training in treatment of chronic disabilities. Although the individual training programs of professionals include normal foot anatomy and biomechanics, few describe the neuropathic foot and associated complications, leading to inadequate medical advice or treatment.4 In the clinical setting no initial problem is too small to address. The clinical team is important and must treat minor trauma immediately to prevent deterioration of the condition. There is a destructive chain of trauma surrounding the neuropathic foot:

  1. Trauma
  2. Inflammation
  3. Ulceration
  4. Infection
  5. Absorption
  6. Deformity
  7. Disability

This chain can be broken with proper objective measurements, treatment, and patient education.2

The patient with neuropathy requires a consistent follow-up schedule relating to level of insensitivity, history of complications, and general physical condition. A patient with loss of protective sensation (10 g of force) and no history of ulceration requires less frequent follow-up than does the patient with a chronic breakdown history. Records should reflect as many objective measurements as possible and a method of classification of patient types. Management of the neuropathic and dysvascular limb is a process of continuing evaluation. The process of history, examination, and charting details cannot be overemphasized. All clinical findings should be charted and relayed to the patient’s primary care provider.5

Although neuropathy exists in many disease processes, there are concerns about the growing number requiring management. When breakdown occurs in one neuropathic limb, the contralateral limb is commonly involved within 18 to 36 months, so prophylactic measures are especially important. Many considerations must be addressed by the team treating the neuropathic and dysvascular limb before a treatment plan is developed. Once the plan is in place it is imperative to educate and involve the patient in the plan.

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PATHOGENESIS

The neuropathic process is poorly understood, and there are many theories regarding its etiology. When evaluating the patient with neuropathy, the medical team encounters the following obstacles:

  • Lack of clear definition of diabetic neuropathy;
  • Absence of single repeatable tests of neuropathy that are not dependent on either expensive technology or subjective clinical judgment;
  • Varied manifestations of neuropathy: distal symmetric, mononeuropathies, autonomic neuropathies;
  • Separation of diabetes from other potential etiologies of neuropathy.

The neuropathic foot is affected by a trineuropathy, which consists of three phases that occur simultaneously; manifestations of two of these phases are shown in Figure 1.

Figure 1.

Figure 1.

  1. Sensory neuropathy is the loss of sensation, leaving the patient incapable of sensing pain and pressure. The patient has no sense of identity with the feet.
  2. Motor neuropathy is the loss of intrinsic muscles, resulting in clawed toes (Figure 2) and eventual foot-drop. The ankle jerk reflex is absent.6
  3. Figure 2.

    Figure 2.

  4. Autonomic neuropathy is the loss of autonomic system function, resulting in the absence of sweat and oil production and leaving skin dry and nonelastic.

Until recently, all forms of neuropathy were lumped together. It is now clear that there are different types, which develop differently. Peripheral neuropathy can be broken down into two major groups:

  1. Gradual onset: those that develop gradually and are usually painless. The exact cause is unknown but may be related to duration of diabetes and level of blood sugar control. Symptoms may include numbness, tingling, burning, and a pins-and-needles sensation.
  2. Sudden onset and disappearance: those that develop suddenly (or acutely) and are almost always painful, then the pain disappears, leaving sensory loss.

Many believe that neuropathy is caused by hyperglycemia: high levels of glucose in the blood. Tight control may be the best prevention of severe neuropathy.7

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MEDICAL HISTORY

The medical history is a useful way to identify potential neuropathy that may be present in many disease processes. The neuropathy may be isolated (nerve damage or entrapment), but for most chronic disease processes the effect is peripheral. The most common disease processes resulting in peripheral neuropathy are:

  • Diabetes;
  • Spina bifida;
  • Hansen’s disease;
  • Systemic erythematosus lupus;
  • Acquired immunodeficiency syndrome (AIDS), human immunodeficiency virus infection, AIDS-related complex;
  • Cancer;
  • Vitamin B deficiency;
  • Multiple sclerosis;
  • Uremia;
  • Vascular disease; and
  • Charcot-Marie-Tooth muscle disease.

Toxins and toxic syndromes can also cause insensitivity in the limbs, including those related to overuse of or exposure to alcohol, arsenic, lead, steroids, gold, and isoniazid.

Many other chronic complications may result in neuropathy, but the list provided indicates why all patients must be evaluated for neuropathy, regardless of reported history. Congenital sensory loss, as in spina bifida, is important to the examiner because the patient has never experienced normal sensation and cannot evaluate his or her own sensory status.8–10

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DIABETIC NEUROPATHY

The most common disease process seen in neuropathy is diabetes, which results in true peripheral neuropathy. Statistics on diabetes are growing, and the medical cost related to diabetes in the United States is currently $14 billion per year. Included in this cost are 54,000 lower extremity amputations per year, of which 50 to 70% could have been prevented by team management. It is estimated that 50 to 84% of the lower extremity amputations were preceded by a foot ulcer. More than 14 million Americans have diabetes (half are undiagnosed), with 700,000 cases diagnosed per year. In the general population, 1 in 20 has diabetes. Many patients receive a diagnosis of diabetes when they present a nonhealing foot ulcer.11–16 Of major concern is the mortality rate after amputation, which is 50% within 3 to 5 years. The rate of contralateral amputation is 50% within 4 years.17

Although there are several different divisions of diabetes, the two main categories are insulin-dependent diabetes mellitus (IDDM), or type I, and non–insulin-dependent diabetes mellitus (NIDDM), or type II. In IDDM the insulin deficiency is caused by pancreas islet cell loss. It occurs at any age but is common in youth. NIDDM is more common in adults but occurs at any age. Most patients with NIDDM are overweight.18

The dysvascular patient may also have diabetes, which leads to impaired healing of a limb that cannot deliver antibiotics sufficiently to combat extremity infection. One limb may be severely insensitive, whereas the other is mildly affected (Figure 1). The loss of vascularity caused by calcified arteries or a disease process is first referred to the vascular surgeon for possible correction or improvement.

The four types of stress that lead to ulceration and destruction of tissue in the neuropathic limb are:

  1. Ischemic necrosis is usually seen on the lateral side of the fifth metatarsal head and is caused by wearing a shoe that is too narrow. The ischemia is caused by a very low level of pressure (2 to 3 psi) over a long period, causing death of the tissue.
  2. Mechanical disruption occurs when a direct injury caused by high pressure (600+ psi) inflicts immediate damage to tissue. This can also be caused by heat or chemicals that damage the skin. Such injuries commonly occur by stepping on a foreign object.
  3. Inflammatory destruction occurs with repetitive moderate pressures (40 to 60 psi). Inflammation develops and weakens the tissue, leading to callus formation and ulceration from thousands of repetitions per day.
  4. Osteomyelitis (and other sepsis) destruction is the result of a moderate force in the presence of infection. Infection is spread as forces are applied by intermittent pressure.19

The highest incidence of ulceration occurs at sites of previous ulceration. The history should be reviewed carefully for previous ulcers or infection.20 A newly healed ulcer is covered by thin skin that is likely to tear. In completely healed ulcer areas, scar tissue may adhere to underlying structures. The healed areas are composed of tissues of different density that compress uniquely, causing shear between opposing tissue durometers.21,22

The progression of breakdown continues at the metatarsal heads because of migration of fat pads, leaving bone and skin to absorb shock. The neuropathic limb has lost heat and cold sensation and reflex response. The incidence of ulceration is 71% on the forefoot, with the third metatarsal head most commonly affected, followed by the great toe and first and fifth metatarsal heads. Once breakdown has begun on the foot, 53% of the contralateral limbs follow the progression of breakdown within 4 years. Newly healed wounds need time to mature and become strong, yet there will always be a potential for breakdown in a previous area of ulceration. Scar compresses at a different rate than other tissue, and the area of adherence will be prone to shear stresses.23

Of all amputations, 86% could have been prevented by patient education and appropriate footwear.3 The aging process alone will produce changes in appearance and alterations in sensitivity, joint motion, and muscle-force production, any of which can lead to dysfunction.24 Improper nutrition can also delay healing.25 Most amputations are caused by gangrene (90%), followed by infection (71%) and nonhealing ulcers (65%).26 The dry, dark ulcers of gangrene are usually found on toes or bony parts of the foot. Neuropathic ulcers are usually moist and draining.15 Diabetic neuropathic ulcers occur in a foot with severe sensory impairment, yet they typically have adequate blood supply for healing.24,27

There are two types of gangrene: wet and dry. Dry gangrene is caused by loss of nourishment to a part, followed by mummification. The area is dry, black, and shriveled and results in a well-defined line of demarcation with specific localization and self-amputation (autoamputation; Figure 3A). Wet gangrene is the necrosis of tissue, followed by destruction caused by excessive moisture. Bacterial gases accumulate in the tissue. The line of demarcation is ill defined, and the limb is painful, purple, and swollen. Wet gangrene is common when infection exists.28,29Figure 3B shows wet gangrene of the fifth toe. Do not debride. The patient needs immediate referral to a surgeon.

Figure 3.

Figure 3.

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SYSTEMS REVIEW AND EXAMINATION

A multisystems review and examination for the patient with neuropathy is required to determine the co-impairments that will affect wound healing and require management. Four systems to review for this patient population are the neuromuscular system, the vascular system, the musculoskeletal system, and the integumentary system.

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NEUROMUSCULAR SYSTEM

A foot with neuropathy is dry, with small fissures, has toes that are clawed, and is incapable of sensing trauma. The rigid anesthetic foot is more likely to break down than is a flexible anesthetic foot.30 The insensitive foot should be evaluated carefully and bilaterally. Any form of peripheral neuropathy can produce the discomfort of paresthesia: prickling, burning, and jabbing sensations.31,32 The length of this period of discomfort is unknown; it varies among patients. Neuromuscular system examinations to assess for neurological changes are the focus of the foot screening process and are described in detail in this article.

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RESEARCH WISDOM: INTERVENTIONS FOR PARESTHESIA

Paresthesia may be helped by use of a transcutaneous electronic nerve stimulator unit, which generates small pulses of electricity similar to an electric massage. Another method of controlling the discomfort is with topical creams.33,34

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VASCULAR SYSTEM

Peripheral vascular disease (PVD) is a serious complication affecting millions of Americans. Of the 500,000 vascular-related ulcerations, 10% are arterial and 70% are venous ulcerations; some individuals have both venous and arterial diseases. Many patients with neuropathy also have PVD. Thus, it is critical to review the vascular history before planning any intervention to identify strategies to manage vascular problems that will affect the prognosis and outcome for the patient.

Atherosclerosis is also known as hardening of the arteries. The interior wall of arteries is usually smooth, but with atherosclerosis platelets, calcium, and connective tissue deposit on the walls. In early stages the patient may experience intermittent claudication or cramping in the lower limb, which goes away with rest. As the disease progresses, symptoms appear when the patient is not walking (rest pain).15 Arterial compromise can be noted by the loss of hair growth, shiny skin, atrophy, and cool skin over the toes.35 Atherosclerosis leads to impaired circulation in the legs and is one of the most important causes of gangrene, leading to amputation.36 Arterial ulcers are located on tips or between toes, heel, metatarsal heads, side or sole of foot, and above the lateral malleoli. The ulcer will look punched out, with well-demarcated edges, and be nonbleeding (Figure 4). The ulcer base may be deep and pale or black and necrotic. Treatment involves vascular reconstruction, bed rest, and immobilization. Arterial ulcers have a poor prognosis. Misdiagnosis of an arterial ulcer as a venous ulcer can lead to serious complications.

Figure 4.

Figure 4.

The venous stasis ulceration has a better prognosis for healing than does the arterial ischemic ulceration. Veins are less elastic than arteries. The valves within veins no longer function to return blood to the heart against gravity, leaving blood to pool in the lower limb. The pooling does not allow new oxygenated blood into the area, and the cell walls of the veins begin to break down. The waste blood products begin to weep through the lower limb. Venous stasis ulcerations are commonly located in the anteromedial malleolus area and pretibial area. The ulcerations are irregular in shape, surrounded by bluish, brown skin. These ulcers are exudative and show evidence of bleeding.

Treatment of venous stasis ulcerations begins with leg elevation.37 The limb must be treated with compression bandages or an Unna boot. The Unna boot is a semirigid dressing of gelatin and zinc oxide. Its application protects vulnerable skin from the weeping exudate, especially below the ulcer site. The Unna boot is applied wet. When it dries it forms a nonelastic, nonexpandable, nonshrinkable, porous mold that sticks to the skin. This treatment has been used on venous stasis for 100 years. It is a means of controlling edema when it is applied across a joint. The motion of the joint generates a pumping action.1

The chronic venous stasis lower limb without an open ulceration will show signs of edema that must be controlled. The presence of small water blisters or weeping will be a sign that compression should begin (Figure 5). This limb should be treated with pressure-gradated stockings as daily prevention; an Unna boot with Ace bandage wrap is required for severe edema or periods of breakdown. Pressure-gradated stockings have a graduated pressure to facilitate pumping action and assist the venous system in removing fluids from the lower limb. Antiembolism stockings are not designed for the ambulatory patient and do not supply the pumping action required. Antiembolism compression is for the recumbent hospitalized patient.

Figure 5.

Figure 5.

Compression can be ordered to begin at the metatarsal heads and decrease pressure in the calf (neuropathic compression stocking) as an additional assist to the venous system. Most patients do well with compression in the range of 30 to 40 mm Hg at the foot and ankle. When using these stockings for the patient with neuropathy/dysvascular disease, remember to avoid seams around bony prominences, and never place a zipper over the malleoli.

When venous stasis ulceration occurs on one limb, begin compression therapy on the contralateral side. The appearance of small water blisters or weeping is a sign that compression should begin. The prosthetic shrinker sock should be used after a major limb amputation to reduce edema and shape the residual limb. The prosthetic shrinker applies both circumferential and vertical (distal to proximal) compression.

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MUSCULOSKELETAL SYSTEM EXAMINATION

The musculoskeletal system examination includes examination of joint integrity, range of motion, skeletal deformity, and muscle strength. Motor neuropathy distorts skeletal alignment, and Charcot joint leaves a foot deformed. An analysis of abnormal gait should also be included. Beginning with the joint range-of-motion review, it is important that the foot has a dorsiflexion range of at least 10° to allow ambulation without harm to the great toe.38 The forces on the plantar surface can peak to 275% of body weight when running and 80% when walking.39 With limited motion in the joints, the trauma can result in ulceration. It is important to test range of motion, as well as perform manual muscle testing.2,40 There is an absence of the ankle jerk reflex when neuropathy is advanced to glove-and-stocking distribution.41

Leg length discrepancy affects 70 to 80% of the population and often does not cause pain or deformity. A discrepancy can relate to chronic complications, such as bunions, hammer toes, hallux valgus, and referred joint disruption of the ankle, knee, hip, and low back. A 2-cm discrepancy is sufficient to cause symptoms and requires shoe lifts with physical therapy. Any lift greater than ¼ inch should be placed on the sole of the shoe and added gradually to allow the body to respond to changes as the pelvis levels.

There is a constant concern with toe deformities that may result in ulceration. In the case of claw toe deformity, the toes are dorsiflexed at the metatarsal-phalangeal joints with flexion at the interphalangeal joints.42 The great toe should be examined for deformity. A fibrous proximal joint can cause ulceration that is especially difficult to relieve. Great toe extension can be seen when weightbearing because the patient thrusts the toe into extension when ambulating, causing calluses and discoloration on the distal tip near the nail from contacting the shoe. Great toe pronation is seen on the medial/plantar surface of the great toe. Hallux rigidus refers to limited range of motion in the proximal great toe metatarsal/phalangeal joint and requires a rigid rocker bottom shoe to allow ambulation without excessive pressure on the great toe. Hallux valgus (bunion) is the increased valgus angle of the great toe in relation to the metatarsal, requiring a shoe that can be modified and molded to conform to the medial bunion formation.

Toe amputations may be for single or multiple toes (see Figure 1). The amputation may be a disarticulation or a resection (metatarsal shaft is removed). The distal end of the amputation site must be followed carefully and protected from trauma.

There are common complications to be addressed with the neuropathic limb. Bursa formation over the navicular prominence is caused by the constant high forces and must be provided an area of pressure relief before ulceration occurs. A sinus tract formation results when previous areas of ulceration heal over a pocket of bacteria, instead of healing from internal to external tissues. The small pocket of bacteria is moved anteriorly through the tissues, causing infection to spread.

A common complication of the patient with neuropathy is severe foot deformity after neuropathic fractures or Charcot arthropathy including joint subluxation or dislocation. The presence of severe foot deformity has been shown to be predictive of prolonged healing time for patients treated with total-contact casting. Sinacore et al.43 found that fixed foot deformity prolonged healing of ulcers with total-contact casting when located in the midfoot and rearfoot. Ulcers located in the midfoot healed in 73 ± 29 days, rearfoot ulcers 90 ± 19 days. Individuals without fixed deformities with chronic diabetes mellitus and those with forefoot ulcers healed in 41 days. Therefore, early detection during the musculoskeletal examination of a fixed foot deformity in a patient with an ulcer located in the midfoot or rearfoot can be used to determine a prognosis that healing time will be significantly longer when a total-contact cast is used as the treatment intervention.

Motor neuropathy produces common abnormal gait characteristics in the neuropathic population. The shoes are worn on the lateral side of the sole because of a varus deformity (Figure 6A). This weakness often causes ankle injuries. After additional deterioration, footdrop can occur. The stiffness in the complex joint structures leads to abnormal motion in the foot’s function.

Figure 6.

Figure 6.

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CLINICAL WISDOM

MODIFICATION OF A STANDARD-DEPTH SHOE

To compensate for varus gait abnormalities, shoes need to be modified. The modifications required are 1) a full, lateral-flare sole as shown in Figure 6B; 2) a strong counter to support the heel; and 3) a high top to support the ankle. A standard-depth shoe can be modified by an orthotist, or a shoe repairperson may be able to do the job if guided. Although not all orthotists will agree to modify an existing shoe, others will. This will save the patient money.

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INTEGUMENTARY SYSTEM EXAMINATION

Integumentary system examination of the foot includes the toenails. Toenail deformities are commonly seen in the neuropathic foot. Hypertrophic nails are caused by fungus and are common in the diabetic population. The nails tear shoe lining and create areas of rough surface to abrade the toes (Figure 7). Nail care for onychomycosis (fungus), ingrown toenails, and trimming must be performed by trained medical personnel to ensure injury is not inflicted. Soft corns are hyperkeratotic lesions found between toes (usually between the fourth and fifth toes) caused by pressure of an opposing toe in a region that is moist.29 Injury and maceration of the toes is commonly controlled by the use of lamb’s wool between the toes or tube foam to space toes and prevent friction (Figures 8A and B). Buildup of callus is indicative of high pressures and stress of an isolated area that must be relieved. The thickening of the skin in the area of a callus is preceded by abnormal pressure or friction.29,44 Areas of excess pressure require pressure redistribution in the clinic setting, rather than scheduling additional appointments.

Figure 7.

Figure 7.

Figure 8.

Figure 8.

Dryness of the skin is the result of autonomic neuropathy in which the sweat and oil production is decreased and moisture must be replaced. Loss of hair growth may be indicative of vascular impairment. Ulcerations that are necrotic are debrided to allow healing to progress from internal to external tissues for optimum closure of the ulcer site.

Another common occurrence is burns, caused by heat or chemicals, such as over-the-counter remedies. Soaking the foot in hot water is a specific cause of burns. A common wisdom is that patients with neuropathy should never soak their feet. The insensitive foot cannot produce the warning signals necessary to prevent severe burns.

Dermatologic conditions can affect treatment programs until they are resolved. Necrobiosis lipoidica diabeticorum may be seen on the shin (along the tibia) as a dermatological condition in the diabetic population. The condition manifests as irregular patches of degenerated collagen with reduced numbers of fibrocytes. The dry scaly areas have been infiltrated with chronic inflammatory cells.28 Necrobiosis can be confused with venous stasis disease but does not require or respond to extensive treatment. The round, firm plaques of reddish brown to yellow are seen three times more often in women.45,46 These ulcerations are common along the tibia and require only protective dressings.

The callous (or tyloma) is a yellowish-gray lesion that may be flat or raised and spread over a large area. The callous is caused by friction (shear), irritation or pressure. There is hyperemia and thickening of the skin. The skin is compressed, and superficial layers of callous are laid down. The callous may be reduced mechanically with tools and the forces to the area reduced. Many facilities use sanding tools and callous reducers to break the chain of callous buildup. The pumice stone is used as a wet tool on wet skin. The callous reducer debrides dry callous with a dry tool.28

Keratoderma plantaris, characterized by keratin cracks and ulcerations, is caused by the loss of sweat and oil elasticity in the skin (autonomic neuropathy). As keratin builds up, it creates small fissures that allow entrance of bacteria, and infection begins. The entire sole around the margin of the heel will undergo diffuse thickening and develop painful fissures if the foot is sensate or go undetected if insensate (Figure 9). Prevention includes reduction of keratin buildup and retention of skin moisture.29 There are many forms of rashes and dermatological conditions that must be evaluated and treated in the neuropathic limb. These usually are discovered by inspection, rather than patient discomfort. Typical skin conditions in the diabetic population include shin spots and diabetic bullae (with less frequency than necrobiosis).45

Figure 9.

Figure 9.

Infections are commonly seen in the neuropathic foot, including Pseudomonas infection, which is bacterial growth that occurs within a moist environment. Signs and symptoms of infection usually are absent in the neuropathic foot, even though the infection is present and virulent, because of impaired circulation and immunosuppression. Both are other common co-impairments of neuropathy. The problems of infection are identified during the integumentary system review.

Dry gangrene is another finding that may be discovered during the integumentary system review. When dry gangrene is present, there is a line of demarcation at which the body will auto-amputate the affected area. This process of autoamputation could take weeks to months42; it is nature’s way of protecting the body from infection and should not be disturbed. Figure 3A (Wagner grade 5) is a photograph of a foot with dry gangrene. A patient with dry gangrene needs immediate referral to the surgeon.

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ADDITIONAL VISUAL AND PHYSICAL ASSESSMENTS

Examination of the neuropathic limb includes additional visual and physical examination to avoid future complications. The patient is never asked for his or her own foot evaluation. The shoes are removed to allow the practitioner to examine the foot. The patient with neuropathy will not limp, even with a foot ulceration (Figures 9 and 10). Inspection should be both weightbearing and nonweightbearing.

Figure 10.

Figure 10.

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FOOTWEAR ASSESSMENT

The footwear must be examined for wear of orthosis and sock patterns indicating excessive pressure. The ends of the toes should be examined for injury caused by a short shoe. Figure 10 shows a toe wound caused by a short shoe. Notice the toe is to the end of the shoe insole. In the current article, Interventions describes orthotics and adaptive equipment and includes instructions in footwear interventions. Shoes should show a normal wear pattern on the lateral heel of the sole as contrasted with the pattern in Figure 6A. Shoes should be resoled on a regular basis to keep sides from wearing down. Inserts are replaced as required when relief modifications are no longer sufficient and shock absorption is decreased.

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WOUND ASSESSMENT

The Wagner scale47 for grading neuropathic ulcers classifies ulcer severity in six grades based on the depth of the ulcer and the presence of infection or necrosis. Ulcer grading is useful for prognosis and for selection of treatment intervention. In addition, the Wagner ulcer grading system is a uniform system that is used by health care practitioners of different disciplines to describe ulcers in neuropathic limbs. Ulcers with low grades are managed by conservative measures, whereas ulcers with higher grades are a direct threat to limb loss and require surgical management. The neuropathic limb often also has dysvascularity, so the system often is used for both populations. The Wagner ulcer classification system differs from other grading systems by including a grade of 0, which describes preulcerative skin, healed ulcers, and the presence of a bony deformity where the skin is intact. Preulcerative areas include calluses located under the metatarsal heads or areas of weightbearing.48 For continuity of documentation and communication, the team must understand the Wagner scale of ulcer grading and use it consistently. Wagner ulcer grades 0 to 5 are shown in Figure 11. The preferred conservative method of treatment is guided by the Wagner grade:

Figure 11.

Figure 11.

  • Grade 0 may be treated with extra-depth shoe and insert.
  • Grade 1 treatment includes a cast or Plastazonte healing shoe, reducing weight to ulceration, and antibiotic intervention as required.48
  • Grade 2 treatment is debridement and casting, with antibiotic intervention as required.48
  • Grade 3 treatment removes infected tissue with casting and antibiotic intervention as required.49
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SENSATION TESTING

When evaluated for insensitivity, most patients who had hypoesthesia could sense pinprick and cotton wisp applications. Patients with foot ulcers were observed to have less pressure sensation than those without foot ulcers.50 In 1898 von Frey attempted to standardize the stimuli for testing the subjective sense of light touch by using a series of horse hairs of varying thicknesses and stiffness. Wienstein used nylon monofilaments mounted on Lucite rods as substitutes for the hairs.51 The Semmes-Wienstein monofilaments can be obtained commercially in elaborate sets for precise measurement, but research at Carville Hansen’s Disease Center, Carville, Louisiana, has consolidated the testing to three sizes of monofilaments for grading the insensitive foot. The 4.17 monofilament supplies 1 g of force and is indicative of normal sensation. If the patient cannot feel the next monofilament (5.07), he or she does not have the protective sensation level of 10 g and cannot sense trauma to the foot to cease weightbearing. Failure to sense the 10-g monofilament is used as the determining factor for use of protective footwear and accommodative orthotics. No patient with protective sensation can ambulate on an ulcerated foot. A large percentage of patients do not feel the largest monofilament (6.10), which indicates a loss of sensation at 75 g. This largest-diameter monofilament indicates an insensate foot that must be accommodated and followed up closely. Use of the monofilament is not to be confused with the testing for sharp/dull sensation. The sharp/dull test stimulates multiple nerves, as opposed to a single-point perception test.

The monofilament is a single-point perception test and requires the examiner to place the monofilament on the skin, press until the monofilament bends (diameter of monofilament controls point of bend), and remove the monofilament from the skin surface. The monofilaments are tested and determined to be reliable at the 95% confidence level.52 The patient is to respond when he or she feels the pressure sensation. To avoid errors in testing, the monofilament is never used in areas of scarring, calluses, or necrotic tissue. The bilateral testing for sensation is especially important for the unilateral and bilateral amputee to determine areas of insensitivity and progression of the neuropathy. Figure 12 shows the proper method for the monofilament testing procedure. Note the bend of the monofilament. This must occur to measure correct pressure sensation.

Figure 12.

Figure 12.

Birke,53 at Hansen’s Disease Center, developed a risk classification system based on the loss of protective sensation. Loss of protective sensation, history of ulceration, and reduced circulatory perfusion are important factors in the development of foot ulcers. A risk classification system based on these factors is useful in identifying patients who would benefit from different levels of intervention. Risk is classified by four grades: 0, no loss of protective sensation; 1, loss of protective sensation (no deformity or history of plantar ulceration); 2, loss of protective sensation and deformity or abnormal blood flow without history of plantar ulcer; and 3, history of plantar ulcer. Three interventions have proven effective in reducing risk of ulceration: protective footwear, patient education, and frequent clinic follow-up. For example, when a patient’s ulcer is grade 0, preulceration, and the patient can sense the 10-g monofilament (has protective sensation), he or she will sense pain before damage occurs to the feet. Patients in this category usually do well with a standard shoe of correct sizing and a simple shock-absorbing pad.

The patient without protective sensation will not cease ambulating when damage begins to tissues. Patients with feet such as those in Figure 9 who walk into the clinic are insensate. They require extra-depth shoes with a total-contact accommodative insert to distribute pressure and reduce forces on areas of potential breakdown. The insert may be molded to the patient or fabricated on a cast. The cast does not have corrective forces added, only accommodation.

The accommodative insert does not apply correction; it fills only the spaces between the flat shoe and the foot contours. Any force added will receive full weightbearing, and breakdown will occur. If the addition of metatarsal head (MTH) pads or scaphoid pads is requested, these pads must be of a soft durometer. Rigid pad additions will cause excess pressure and ulcerations. The MTH pads are placed proximal to the metatarsal heads to redistribute the weight from the heads to the metatarsal shafts.

Testing for vibratory sensation may be accomplished by using the bioesthesiometer. This instrument is essentially an electrical tuning fork that uses repetitive mechanical indentation of skin delivered at a prescribed frequency and amplitude.54 The simple graduated tuning fork is a rapid means of sensory testing.55,56 The purpose of all sensory testing equipment is to identify those at risk.57

Upper and lower extremity peripheral neuropathy is present when sensation testing reveals that the level of sensation loss is symmetric and equidistant from the spine in both arms and legs. The hands of these patients should be considered in the evaluation process. Physical signs of upper extremity involvement include chaeroarthropathy (motor neuropathy in upper extremity), when the patient cannot touch his palms together in the prayer position. Another physical sign is atrophy of the web space between the thumb and first finger. This is the first sign of motor neuropathy in the hand. Consideration of the hand deficit must be taken into account for donning, doffing, and choice of closures for orthotics and footwear.40 Little attention has been paid to the diabetic hand syndrome, or limited joint mobility (LJM), in which the joints of the fingers and wrists become limited. This condition occurs in 30 to 50% of people who have had type I diabetes for more than 15 years. One test for LJM is performed by having the patient place the hands flat on a table. Patients with severe LJM will not be able to flatten the fingers onto the table. The skin will also be thick and can be tented on the back of the metacarpophalangeal joint58 (Figure 13).

Figure 13.

Figure 13.

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BODY TEMPERATURE TESTING

Since Hippocrates, physicians have known that body temperature variations offer important clues for diagnosing disease. Diagnostic tools convert infrared radiation and display it on monitors with the use of thermography.56 There are many methods of acquiring surface temperatures. Thermistors or thermocouples are accurate recording devices that, when touched to the skin for 10 seconds, give a numeric display of temperature.59 Wound temperature depends on the vascularity of the area and can be measured by thermography. In a study of vascular wounds, vascularity was measured indirectly by measuring skin temperatures. The subject surgical site was measured before surgery and after surgery for 8 days at a specified time. The first through third day temperatures increased at the surgical wound and a wide surrounding area. Days 4 through 8 had lower temperatures, and the zones of warm surrounding area became narrower. The stitches were removed at day 7, and by day 8 the area assumed preoperative temperatures, except in the very narrow incision site. Documentation noted that the persistence of a wider zone of increased temperatures after day 4 predicts wound infection and disturbed healing. The infrared unit allows accurate immediate spot temperature reading and allows the feature of scanning the foot quickly.

The use of temperature is valuable as an objective measurement of tissue damage and inflammation produced by repeated mechanical (pressure) trauma.60 When evaluating the limb, the most distal aspects of extremities are cool. Muscular areas with good blood supply are warmer than bony regions. Arches are several degrees warmer than heels or toes.59 Excessive heat in an area of the foot is a vascular response to trauma. The trauma may be caused by external forces, infection, Charcot joint, or other internal complications. The examiner can feel the increased heat manually and determine where complications may reside, but without instrumentation to record actual numbers, there will not be objective documentation for follow-up and comparison.

With the use of a surface-sensing temperature device (thermocouple or infrared), temperatures are recorded in predetermined areas, usually those related to common areas of breakdown. When there is one definite area with a temperature 3°F higher than that of adjacent areas, it can be assumed to be an area of high pressure or stress. If there is no current breakdown, this area must be relieved of pressure and the pressure distributed over the remaining weightbearing surfaces. Upon follow-up of this same patient, the temperature differentiation should decrease as healing of tissue progresses.

In a comparison of contralateral limbs, vascular impairment should be suspected when one limb is significantly colder or distal portions of the foot show an extreme drop in temperature. A chronic hot spot points to the existence of a chronic stress or an underlying bone or joint problem. Increased temperature indicates there is a problem and where it is, not what it is!21

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PRESSURE TESTING

A rubber mat was developed by R.I. Harris that would print light foot pressures in large light squares (formed by tall grid ridges) and heavier pressures in darker smaller squares (deep ridges).2 The Harris mat gives a grid analysis of pressure distribution at a relatively low cost per patient. The Harris mat can be used for static and dynamic assessment and to provide permanent records. Figure 14 shows an imprint on a Harris mat. The darker areas are areas of high pressure.

Figure 14.

Figure 14.

Force plates have given us valuable information regarding peak pressures during ambulation but represent a single step upon the plate. Attempts to place sensors in the shoes have been unreliable because of the sensor structure and attachment within the shoe.61 The new age of computer-aided documentation provides color replicas of three-dimensional pressure recordings and illustrations that can be used for static or dynamic documentation. Although costs of the computer-aided devices are high, technology is advancing to provide unrestricted data collection.62 Progress is also being made to produce live scanning of the foot to produce a positive mold for orthotics, as well as custom shoes.63 With the use of computed three-dimensional digitizing computer graphics, a plastic sock may be molded to the patient and converted to a shoe cast.64

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CHARCOT JOINT EXAMINATION

Charcot joint (Charcot arthropathy) is a relatively painless, progressive, and degenerative arthropathy of single or multiple joints caused by underlying neuropathy. The neuropathy may be periosteal and not cutaneous. There are several theories behind the causes of Charcot joint:

  • Multiple microtraumas to the joints cause microfractures. These fractures lead to relaxation of the ligaments and joint destruction.65
  • There is increased blood flow (osteolysis) and bone reabsorption. Patients with Charcot joints have bounding pulses.
  • Changes in the spinal cord lead to trophic changes in bones and joints.
  • Osteoporosis is accompanied by an abnormal brittleness of the bones, leading to spontaneous fracture.66

In clinical observations, the limb is usually painless, swollen, and red. Unhealed painless fractures often are radiographically present. In advanced Charcot disease, there are multiple fractures accompanied by extensive bone demineralization and reabsorption. Later stages reveal architectural distortion of the foot with shortening and widening of the joint.46 The foot joints most commonly affected are tarsometatarsal (30%), metatarsophalangeal (30%), tarsus (24%), and interphalangeal (4%).

Charcot joint frequently is misdiagnosed and mistreated, leaving the patient with deformities that require additional medical intervention or expensive footwear (Figure 15). The acute stage will show a foot that is 5° to 10° hotter than the contralateral limb in the same area. The red, hot, swollen foot usually will not have a skin opening or ulceration. Laboratory tests, including radiographs, may not show changes in the acute stage to differentiate Charcot disease from other diagnoses.

Figure 15.

Figure 15.

The duration of the catastrophic destruction, dissociation, and eventual recalcification found with Charcot joint varies with the individual, but the average healing time in a cast for the hindfoot is 12 months; for the midfoot, 9 months; and for the forefoot, 6 months. By evaluating with comparative temperature measurements of the contralateral foot, the stages usually can be verified by radiograph. As the involved foot temperature increases, the destruction and dissociation are taking place. The temperature gradually decreases as recalcification occurs. A radiograph shows that recalcification is complete when temperatures bilaterally are within 3°F.

The treatment plan for acute Charcot joint is the total-contact cast. The cast must be changed in 1 week to accommodate volume changes. After the period of volume changes, the cast should be changed every 2 to 3 weeks. When the temperature is equal to that of the other limb, the patient may be weaned gradually from the cast to a splint and then to shoes. Follow-up should continue to ensure that there is no recurrence of an episode of Charcot joint.

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OSTEOMYELITIS EXAMINATION

The clinical observations for Charcot joint and osteomyelitis are similar, and the patient should be monitored closely to verify the diagnosis. Laboratory test results also are similar. The only exception would be the presence of an opening in the skin to allow an entrance for bacteria to infect the bone (Figure 16A). Take the temperature over the best surrounding skin. Refer for immediate medical management. The recalcification would not occur radiographically as in Charcot disease (Figure 16B.) Verification may be made for osteomyelitis with a three-phase bone scan or biopsy.20

Figure 16.

Figure 16.

Patients with diabetes and foot ulcers that expose bone should be treated for osteomyelitis, even if there is no evidence of inflammation.67

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INTERVENTIONS

ORTHOTICS AND ADAPTIVE EQUIPMENT

Treatment of the neuropathic foot requires accommodation, relief of pressure/shear forces, and shock absorption. Regardless of materials used for accommodative inserts, the combination of materials must be compressible by one half of the original thickness to accommodate for pressure relief through the gait cycle.21 It is important to evaluate the materials used in the manufacture of inserts. Cellular polyethylene foams such as Aliplast, Plastazote, and Pelite are composed of a mass of bubbles in a plastic and gas phase. The bubbles are cells with lines of intersection called ribs or strands, and the walls are called windows. In closed-cell materials the gases do not pass freely; open-cell material has no windows, leaving many cells interconnected so that gas may pass between cells. Cell walls are not totally impermeable to the flow of gases. Under a sustained load (especially the heavy patient) gases are squeezed out; when the load is removed, gases are drawn back into the cells.68 These materials bottom out from compaction of the materials as cells fracture under repetitive stress. The advantages are low-temperature molding, nontoxicity, water resistance, and washability without absorbency of fluid.69 Plastazote has a limited effective period of about 2 days; Poron (PPT) remains effective for 6 to 9 months. The two materials can be combined for their attributes and perform well as a single unit.70,71 There are different types of inserts, including soft (cushioning/accommodation, improves shock absorption), semirigid (some cushion/accommodation; affords pressure relief), and rigid (hard, single layer of plastic; it controls abnormal foot and leg motion).72

The Aliplast/Plastazote insert is an immediate preparation and can be provided within a clinic setting, but it has a relatively short life of compressibility (6 to 8 months). Plastazote is a closed-cell polyethylene foam that can be heated to 280°F and molded directly onto the patient’s foot.22 Care must be taken never to mold the toes or create ridges that the toes will ride over as the patient ambulates. By combining materials over a cast model of the foot, the composite type of insert can achieve all goals of the accommodative insert and provide a life of 1 year minimum.

An insert with a Plastazote surface in contact with the foot can be used as an excellent diagnostic tool for future follow-up. The self-molding properties of Plastazote reveal deep sock prints in areas of high pressure. These high-pressure areas should be noted and relieved in future insert design for the patient. With the use of temperature as a tool for evaluation, the areas of high trauma are noted as increased temperature locations. After the patient has worn accommodative inserts, the temperature differentiation decreases if the proper accommodation has been achieved. If the temperature has not decreased in the area, the relief may require enhancement, or there may be other underlying complications to be investigated. All relief areas are applied on the underlying surface in contact with the shoe, never in contact with the foot. The surface in contact with the foot is always a solid, uninterrupted surface that will not apply edges for the foot to receive shear forces. Figure 17 diagrams the fabrication of several different layers into an accommodative insert.

Figure 17.

Figure 17.

Shoes for the insensitive foot should be of soft leather that will conform to abnormalities on the dorsal surface and allow for the depth of an accommodative insert. Figure 18 shows modifications of the depth shoe appropriate for the insensitive foot.

Figure 18.

Figure 18.

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CLINICAL WISDOM

CHOOSE CREPE SOLE SHOES FOR PRESSURE RELIEF

Crepe soles, which are full of air cells, provide pressure relief to the plantar surface, whereas air or water “pillows,” which are enclosed in an inflexible compartment, create pressure.

Leather gradually adapts to the slope of the foot and will retain shape between wearings. The leather will breathe and absorb perspiration.69 The patient should not depend upon the “feel” of a shoe for correct size. The shoe must be full width and girth and allow ½- to ¾-inch space beyond the longest toe to prevent distal shoe contact through the gait cycle. Standard modifications of extra-depth shoes for the patient with neuropathy include stretching of the soft toe box for clawed toes, flared lateral soles to discourage varus instability, and shank/rocker bottom for a partial foot, hallux rigidus, or decreased motion at the metatarsal heads. A rocker bottom should be added to the shoe when metatarsophalangeal extension is to be avoided.22 When properly fit, the instep leather should not be taut. There are three tests to determine the proper fit of shoes (Figure 19):

Figure 19.

Figure 19.

  1. Length: Allow ½ to ¾ inch of space in front of longest toe.
  2. Ball width: With the patient weightbearing, grasp the vamp of the shoe and pinch the upper material; if leather cannot be pinched, the shoe is too narrow. The ball should be in the widest part of the shoe.73
  3. Heel to ball length: Measure the distance from the patient’s heel to the first and fifth metatarsal heads. Bend the shoe to determine toe break, and repeat measurements on the shoe. They should be close to the same measurements.74

The simple addition of shoes, instead of being barefoot, may correct many deformities.75 Laced shoes will give the best control, but they must be broken in slowly, beginning with 2 hours per day and slowly adding time.22 Caution should be taken with cutout sandals regarding the possibility of irritation along the borders of the sandal and straps.76 To evaluate pressures within a shoe, there is a pressure-sensitive sock that is coated with dye-filled wax capsules. The capsules fracture when a certain pressure threshold is exceeded, leaving dye stains in areas of high pressure.69 To protect a healing area in which dressings will be applied, a healing shoe lined with Plastazote will allow greater circumference and volume adjustability.

Socks for the neuropathic limb should have no mended areas or seams over bony prominences. A cotton/acrylic blend will assist in the wicking of perspiration away from the foot.77 The sock should be fully cushioned and have a nonrestrictive top. The partial foot requires a sock that will conform to the shape without distal prominent seams or excess material at the distal end. For the active patient, socks can be obtained with silicone over high-stress areas to prevent shear for full or partial feet.

The partial foot may require a block within the shoe for the area of amputation. The purpose of a block is to reduce migration of the partial foot and medial/lateral shear for the toe amputation. No block or “prosthetic toe” is to be used for a central digit amputation. The low pressures applied by a block to central digits cause ischemic ulcerations on opposing surfaces. Medial or lateral amputations (first and fifth toes) may require a block to hold the foot in the correct position within the shoe. The forefoot block holds the shoe leather away from the distal end of the foot and discourages distal migration of the foot. All forms of blocks must have space from the amputation site and be an integral part of the insert, not added to an existing orthotic. Forefoot blocks require a rigid rocker sole to prevent ulceration to distal end.

By using state-of-the-art foams and room temperature vulcanized silicone elastomers, shear can be reduced in areas of skin grafts, chronic ulcerations, and calcanectomies within more rigid orthotics. The viscoelastomer gel is a two-part gel that can be adjusted for the durometer desired. The mixture can be used for shock absorption and shear reduction. Scar-adherent areas can benefit from a medium durometer mixture. The disadvantage is weight, so it should be used in small areas. Low-density foams can be designed into orthotics, such as toe breaks and forefoot blocks and reliefs. Reliefs for heel pain can be designed into the insert or shoe sole as a Sach heel. Sach heels use soft and medium durometer soling to simulate plantar flexion and provide shock absorption at heel strike.

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TOTAL-CONTACT CASTING

The total-contact casting (TCC) method provides decreased plantar pressures by increasing weightbearing over the entire lower leg (Figure 20). It has been successful as a treatment for plantar ulcerations but requires careful application, close follow-up, and patient compliance with scheduled appointments to minimize complications.78 The total-contact cast was introduced in the United States in the 1950s to redistribute walking pressures, prevent direct trauma to the wound, reduce edema, and provide immobilization to joints and soft tissue. The average healing time for ulcerations treated with the healing cast was 6 weeks.76 This method has been used for patients with and without evidence of severe peripheral vascular disease.79 The cast spreads weight evenly over the lower limb so that no part of the foot takes more than 5 psi. There is never a window cut in the cast, or there may be localized swelling, shear stresses, and eventually a secondary wound.22

Figure 20.

Figure 20.

Application methods of the total-contact healing cast vary with different institutions. The healing cast was originally designed with minimal padding, but padded variations are used. Although the steps for application of the Carville-type TCC are given, remember that it is most important to have the cast applied by a skilled technician because harm can occur from improper application. The following are steps for fabrication of the Carville-type TCC:

  1. The ulcer is covered with a thin layer of gauze.
  2. Cotton is placed between the toes to prevent maceration.
  3. A stockinet is applied.
  4. A ¼-inch piece of felt is placed over the malleoli and anterior tibia.
  5. Foam padding is placed around toes.
  6. A total-contact plaster shell is molded.
  7. The shell is reinforced with plaster splints.
  8. A walking heel is attached.
  9. A fiberglass roll is applied around the plaster.

The patient is instructed to ambulate only 33% of his/her usual activity. The cast is removed in 5 to 7 days and reapplied. New casts are applied every 2 to 3 weeks.78 To allow thorough drying, the patient should not stand or walk on the cast for 24 hours.76

Although not as effective as total contact, a posterior splint covers the posterior lower leg and plantar foot surface and is held in place with elastic wrap. The splint acts to protect the plantar surface. This casting procedure may be chosen for the patient with a limb compromised by poor circulation or when the patient cannot tolerate the confinement of a cast.

There have also been attempts to heal ulcers by using a healing cast shoe molded of plaster. This healing cast shoe must be changed in 3 days and reapplied every 10 days. Results have reported healing of plantar ulcers in 39 days.80 Contraindications for the use of a healing cast shoe include infection (redness, swelling, warmth, fever) and hypotrophic skin (thin, shiny appearance, marked dependent edema).76

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ORTHOTIC DYNAMIC SYSTEM SPLINT

The orthotic dynamic system (ODS) splint (Figure 21) was developed to take advantage of the casting method of a total-contact cast with the inclusion of a custom-molded insert that could be removed and reliefs modified. With all of the advantages of the total-contact cast, the advantages added with the ODS splint include the possibilities for daily inspection, regular cleaning/dressings/debridement, and adjustments to areas of excessive pressure and/or friction.

Figure 21.

Figure 21.

The Plastazote/Aliplast insert is first molded to the patient’s foot and trimmed to follow the plantar surface, with ¼ inch of length added beyond toes. A stockinet is placed on the leg, the insert is positioned, and another stockinet is applied to hold the insert in place. A padded total-contact cast is applied, using fiberglass only. The cast is bivalved, straps are added, edges are finished, and the insert is removed, relieved, and replaced to de-weight the area of ulceration. After the insert is modified, it is replaced within the splint, and the patient may ambulate with a rocker bottom cast shoe under the splint. The patient is instructed on volume control with sock thickness.

The disadvantage lie with compliance of the patient. The splint design allows donning and doffing by the patient, thus allowing him or her to remove the cast. The total contact of a healing cast cannot be compared in its superiority, but in the clinical experience of the author, the daily inspection and relief adjustability have been found to be great assets in the treatment protocol.

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NEUROPATHIC WALKER

The neuropathic walker is a combination of an ankle-foot orthosis (AFO) and a boot that is custom designed to be total contact for weight distribution. The ankle is locked to reduce force through the Lisfranc joint and/or ankle. The design is indicated for the patient with changes of Charcot joint in the tarsal and ankle joints, chronic recurrence of Charcot disease, and chronic ulcerations. The orthosis is easily donned and doffed and fabricated of a copolymer plastic with a closed-cell lining. The removable insert may be adjusted to reassign weightbearing areas on the plantar surface. The insert may also be formed over chronic breakdown areas, such as the malleoli, posterior heel, and bunions, to reduce pressure. The rocker sole allows for easy ambulation, but the contralateral shoe must be adjusted for height.

When casting for the neuropathic walker, the patient’s limb is wrapped and placed on a soft foam block until the plaster is set. The plantar surface is accommodative without excessive pressures on bony prominences. Modifications of the positive model include smoothing the plantar surface but never removing plaster. Any area that has had plaster removed during modification will be an area of excess pressure in the finished orthosis. The distal end is built up at the medial and lateral metatarsal areas and the length extended ½ inch to allow room for the toes and decrease the chances of maceration.

Fabrication is completed on the modified positive cast. The insert is first fabricated, finished, and placed in position. The posterior Plastazote lining is pulled over the insert, followed by the copolymer (plastic) vacuum-formed shell. The entire posterior section is finished and trimmed. The anterior Plastazote is positioned, and the copolymer shell is applied over the entire posterior. There should be a ½- to 1-inch overlap of copolymer on the finished orthosis. The Velcro straps and rocker bottom are attached (apex of rocker proximal to MTH; Figure 22).

Figure 22.

Figure 22.

The patient must be instructed to check skin for redness and possible breakdown. The patient should be followed up and temperatures of the plantar surface recorded for possible adjustment of insert pressures. Sock management is very important to continue a snug fit of the orthosis and volume control.

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TOTAL-CONTACT ANKLE-FOOT ORTHOSIS

Similar to the neuropathic walker, the total-contact AFO is used for the patient who has an area of trauma in the midfoot or hindfoot. The orthosis includes a custom removable insert and is lined with Plastazote. This orthosis must be fit within a shoe, which may be difficult in standard shoes. The casting procedure is the same as that for the neuropathic walker. The toes are open, and the anterior shell terminates at midfoot.

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OTHER DEVICES

Short leg walkers and orthopedic walkers have been used by some clinics, but they compromise the total-contact feature. The walkers have become popular as alternatives to cast immobilization, but the indications for their use are for foot and ankle fractures, sprains, acute ligament/muscle, and postoperative immobilization. Although prefabricated walkers are not custom made to provide total contact, they contain some features that may assist in reducing movement of the limb within the walker. The walkers can be improved in function with the addition of a wide base, rocker sole, and custom off-loading insert. The low-risk patient does well in the orthosis with a custom insert. The high-risk patient with sensory neuropathy may be better served by a custom total-contact orthosis.

Patellar tendon-bearing (axial resist) designs are intended to decrease forces on the plantar weightbearing surface of the foot. With this design as a casting procedure, there have been attempts at its use in place of plaster cast immobilizations.81 The design transmitted considerable axial forces from the knee region onto the cast, but it did not offer rotary stability. The results offered little effectiveness in reducing the load on the lower leg.82 The patellar tendon-bearing design AFO has been used successfully for the calcanectomy, plantar skin graft, and heel ulceration. This orthosis is contraindicated in the patient with vascular impairment because of the excess restriction in the popliteal area of arterial flow.

The prosthosis has been the orthotic replacement when the amputation case is complicated and the patient is not a candidate for prosthetic management. The prosthesis becomes a useful device for transfers and limb protection. This is always a creative design, with no two the same, unique to the individual and his or her needs.

The nonambulatory patient must be examined carefully for pressure ulceration caused by positioning. Heel ulcers are particularly difficult to off-load in the recumbent position. The prefabricated soft AFO is constructed of a soft foam over a semirigid posterior/plantar support. The device allows decreased pressure at the posterior, medial/lateral, and plantar areas of the heel. The soft outer construction decreases trauma to the contralateral leg.

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OFF-LOADING OF FOOT ULCERATIONS

In the treatment of foot ulcerations, there must be wound care protocol with debridement/cleansing and simultaneous off-loading of the affected area. This combination has shown optimal results in the healing of wounds. There are prefabricated, as well as custom, applications that the team must consider for each individual patient. Many patients are given crutches, a walker or a wheelchair, but they must have the upper body strength, cardiovascular reserves, and/or motivation to use assistive devices. Bed rest eliminates the pressures on the foot but promotes deconditioning of the patient.

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PLASTAZOTE HEALING SANDALS

The custom Plastazote sandal contains a molded foot bed and has a rigid rocker sole. The device is lightweight but requires considerable time and experience to fabricate. The Carville sandal has been used as a successful off-loading shoe and interim device after the total-contact cast and before definitive footwear.

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PREFABRICATED OFF-LOADING ALTERNATIVES

There are inexpensive alternatives for off-loading ulcerations with wound care protocol. For optimal healing the wound must be off-loaded in conjunction with moist healing methods. More than one third of the patients seen by home care practitioners have wounds. There is a low use of specialty dressings in home care, and the methods usually are clean, rather than sterile. Introduction of off-loading devices enhances the home care protocol. The following prefabricated products are improved in function by the addition of a customized accommodative off-loading insert. The area of off-loading can be designed using the patient’s floor reaction imprint (Harris mat) as a pattern. Follow-up appointments should include temperature measurements to ensure proper off-loading. If the temperatures have increased, the off-loading area must be increased; if the temperature differential is lower, there is an indication of decreased inflammation and healing is occurring.

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POSTOPERATIVE/MEDICAL SURGICAL/CAST SHOE

An inexpensive alternative for wound off-loading would be the postoperative (rigid sole) and cast shoes (roller sole) to contain the ulcerated foot and off-loading insert. These shoes adjust for bandage volume but do not offer an intimate fit to control foot motion. These shoes usually require extensions to Velcro straps and minor modifications. Use of the shoes as off-loading devices requires careful monitoring of the patient.

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WEDGED SHOE

The wedged shoe has full contact with the plantar surface of the foot but reduces load forces applied from the ground. The sole angle is designed to shift weightbearing away from the ulcerated area. The wedge shoe is contraindicated when the patient does not have the range of motion to accompany the shoe angle. A patient with poor proprioception may not be able to ambulate without assistive devices.

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HALF SHOES

Many clinics use the half shoe to suspend the ulcerated area, providing complete off-loading of the ulcerated area. The forefoot half shoe provides a pressure free area for the forefoot and especially the common ulcerations of the hallux. The heel relief shoe suspends the heel for noncontact. These devices may be contraindicated for the patient with limited ankle motion or balance problems associated with proprioception. Assistive devices may be required to reduce the incidence of falls.

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WOUND HEALING SYSTEM

The wound healing system was designed for the practitioner who does not have casting facilities or available support to off-load ulcerations by total-contact casting or ODS splint. The wound care provider can supply off-loading properties in conjunction with the wound care protocol to deliver optimal healing of ulcerations in any environment. The basic wound shoe provides a base that allows relief of pressure for the dorsum, medial, lateral, and posterior ulceration. The plantar contact system enables the practitioner to off-load plantar ulcerations with four layers (multiple durometer) of material. The system is to be worn until the ulceration has healed. Upon final closure of the wound, a long-term material layer is added, and the wound shoe becomes the casual slipper to be worn at all times when definitive off-loading footwear is not being used. A previous ulceration site is susceptible to breakdown repeatedly and the wound shoe used as a casual slipper ensures that pressure relief is achieved at all times. The patient must never walk barefooted.

The floor reaction imprint (Harris mat) is helpful as a pattern for the off-loading position but is not necessary. The top layer to contact the foot is always a solid interface that will mold to the foot contours. There are two layers of higher durometer that are relieved using available tools (scissors, scalpel, blade). The lower grades (Wagner 0 and 1) use one off-load layer, whereas the higher grades have two off-loading layers available. Upon wound closure, a shock-absorbing layer is to be added to prolong use of the system as a slipper.

For nonweightbearing ulcerations (not plantar surface), the double layer upper construction can be trimmed to off-load pressure areas without allowing window edema to occur. The Velcro system is adjustable for bandage volume. The off-loading system allows for minimal dressings that usually add excess pressure areas when the patient is weightbearing. The goal of the wound healing system is to allow partial weightbearing while off-loading the high-risk foot with ulcerations. The combination of state-of-the-art wound care preparations and off-loading delivers optimal outcomes, as well as unlimited adjustments to forces applied.

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SURGICAL MANAGEMENT

The most conservative treatment of foot infections is used to rehabilitate, but antibiotic therapy alone is not always sufficient for treating aggressive virulent foot infections.83 Surgical intervention may be in the best interest of the patient if conservative therapy is not an option or has proven ineffective. Options should be discussed with the patient and the family, who should be involved in the final outcome when possible. Surgical debridement of all osteomyelitis and nonviable tissue must be completed.84 The surgeon will preserve as much length and width as possible to balance the motor function.9 The goal of amputation is ambulation and reconstruction. Typical locations of partial foot amputations are shown in Figure 23.

Figure 23.

Figure 23.

Metatarsal osteotomies can eliminate the intrinsic stresses caused by elongated or plantarflexed metatarsal joints in neuropathic limbs and decrease the number of amputations.85 Toe resections are the most distal amputation choices available. Expected outcomes of each toe resection are:

  • First toe: Interphalangeal disarticulation for an infected distal phalanx gives good balance. When possible a wafer of the proximal phalanx should be left to maintain the position of the sesamoids beneath the first metatarsal head.
  • Second toe: Disarticulation results in loss of lateral support of the first toe. A second ray resection usually is better to avoid secondary hallux valgus.
  • Third or fourth toes: The remaining toes tend to shift to close the gap.
  • All five toes: A long forefoot lever is left with good weightbearing properties.9

The advantages of the partial foot amputation are:

  • It preserves end weightbearing function.
  • It preserves proprioception.
  • It provides for limited disruption of body image.
  • It requires shoe modification/orthosis or limited prosthesis.

Limitations of the partial foot amputation are the loss of normal foot function related to loss of forefoot lever length and associated muscles, and the challenges presented in selecting appropriate adaptive equipment.

The Chopart amputation is selected when a patient retains sensation in the heel pad. Metatarsals and tarsals are removed, leaving a very short limb. It is difficult to suspend a shoe without the aid of an AFO or prosthesis.

The transmetatarsal/Lisfranc amputation is preferred for the resultant length of foot; amputation is through the metatarsals. The longest partial foot amputation is the distal metatarsal amputation, in which the toes are amputated. This level requires a short shoe or forefoot block to prevent forward motion.

In all partial feet, it is important to watch for an equinus deformity. The toes are no longer present, and visual inspection is more difficult without their reference.

Whether from trauma or chronic infection, the partial removal of the calcaneus is a follow-up challenge for the orthotist. Removing weightbearing from the heel is difficult, and the patient who has had a calcanectomy must be followed up carefully.

The most successful methods of controlling future breakdown have involved the patellar tendon-bearing (axial resist) orthosis or the neuropathic walker. A soft, room-temperature vulcanized foam has been used to fill a void between the orthosis and the heel area. The same orthotic treatment is useful for chronic heel ulcers and plantar skin grafts that require reduction in weightbearing and shear forces.

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DOCUMENTATION

Documentation continuity is essential for all patients and requires a standard form to be used for assessment and future follow-up (see Appendix 1 for a Foot Evaluation Form). Tracing the ulceration on transparent film allows for accuracy of detailed healing progression. Providing the patient with a duplicate tracing can improve compliance because the patient can follow his or her own progress. Photographs of ulceration sites are important for noting improvement in depth and granulation of ulceration.

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SELF-CARE TEACHING GUIDELINES

FOOT INSPECTION

The patient is the most important member of a clinical team approach to the treatment of his or her neuropathic limb. There is no complication too small to be addressed, and the patient must bring abnormalities to the team’s attention. Self-care begins with daily inspections of the feet with the help of mirrors, magnifying glasses, and family members, when necessary. Examination includes footwear and orthotics for wear and foreign objects. The patient with diabetes must understand that this examination may be complicated by other disease processes, including retinopathy, autonomic neuropathy (loss of smell and sensory signals), and decreased mobility of joints. These patients are handicapped by the lack of pain as a warning signal and require systematic instruction to educate them in the proper skills required for daily inspection and detection of impending trauma.

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PRECAUTIONS AND RISK REDUCTION METHODS

There are several precautions for the patient with a neuropathic limb. The skin is susceptible to damage and infection and must be treated carefully. It is advised that the patient not soak the feet in water because the chance of burns is always present, and soaking leaves the skin moist and susceptible to fungal infection. Prolonged soaking can remove the natural protective barrier from the skin and lead to other infections. Feet should be washed with a nondrying soap and towel dried. After foot washing, petroleum jelly can be applied to retain natural moisture and the feet covered with socks. Care should be taken not to use creams with perfumes (alcohol) because they dehydrate the skin.

Dehydrated skin is especially susceptible to trauma. Adhesives of any form should never be applied directly to the skin of a neuropathic limb. Upon removal of the adhesive, there is a risk of loss of the outer layer of skin, leaving an area open to infection. The adhesives could be in the form of tape, a Band-Aid, or over-the-counter self-adhesive pads.

When the patient selects footwear, he or she should choose not only the correct size and width, but also shoes with no stitching over the forefoot. The stitched areas will never mold to the foot, but instead will cause breakdown of the skin, especially over bony areas.

Socks for the neuropathic foot should be seamless and without holes or repairs. Tube socks do not contour to the foot without folds that can cause irritation. The socks should be a blend to wick perspiration and be nonconstricting at the calf. The use of white or light colors enables the patient to easily detect drainage caused by trauma. With a new shoe, the break-in period should be completed with two thin socks on each foot. The double socks will allow shear to occur between them and decrease the probability of blistering from new leather.

The partial foot sock is designed of highly elastic fibers. The sock shape conforms to partial foot length and shape. The single size fits a Chopart amputation, as well as a long transmetatarsal amputation. There are no folds or seams to cause friction.

Toe socks decrease maceration between toes. The moist environment between the toes encourages fungal growth and may lead to ulceration and bacterial infection. The seamless construction helps reduce overlapping of lesser toes but must be compensated for in shoe size if the socks are to be worn with shoes.

Keep current on recalled products. For example, one hair removal system published a product alert on its device because of problems occurring with patients with diabetes. Small areas were bleeding after hair was removed, leaving an entrance for bacteria and possible infection. More than 50% of the over-the-counter foot care products should never be used by a patient with a neuropathic limb or diabetes. There are occasionally warnings, but they often are in very fine print.

Care must be taken with exercise programs. When we walk, each step carries one and a half times our body weight; jogging increases the force to three times the body weight.86 The patient with a neuropathic limb would be advised to choose an exercise program that includes aerobics, swimming, cycling, dance, or chair exercises. Even walking should include slow, short steps only; no jogging.87

The patient with a neuropathic limb should never walk barefoot. Even in the pool or on the beach, water shoes should be worn. Hot sand can cause burns, and undetected objects in the sand can cause injury. Burns can be caused by the floorboard of an automobile, as well as any warmth-producing equipment. The interior of the shoe must be examined before every donning. Small objects can easily drop into a shoe.

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COMPLIANCE ISSUES

The practitioner must understand compliance problems of patients with neuropathic limbs, especially patients with diabetes. They do not willfully neglect self-care activities but simply are not aware of the possible dangers and are not taught adequately or motivated sufficiently.2 Patients with diabetes may have other complications that the practitioner does not consider in the compliance of their activities. Many cannot see (retinopathy), feel (sensory neuropathy), or smell (autonomic neuropathy) when there is an infection or a potential problem. Those with vision impairments need help from a family member or caregiver to perform self-care guidelines.

Patients with neuropathic and dysvascular limbs require knowledge and skills to administer self-examination and self-care. The medical community must educate the patients, as well as the medical team, to treat conservatively and accommodate the chronic complications that exist in a growing portion of the population.

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APPENDIX 1

Appendix 1.

Appendix 1.

© 2005 American Academy of Orthotists & Prosthetists