Managing the Neuropathic Foot

The neuropathic foot is frequently associated with chronic medical conditions and it is not infrequent for individuals to be slaves to long-standing foot and ankle problems. Apart from ulcerations and deformities, loss of lifestyle and independence is profound. These problems cause immense emotional and financial losses and cause restriction of activity with loss of productivity.

Among individuals who are diagnosed with diabetes mellitus, the prevalence of foot ulcers is 4% to 10%, while the annual population-based incidence is 1.0% to 4.1%, and the lifetime incidence may be as high as 25%. Nonhealing ulcers lead to amputation 85% of the time. The key risk factors of diabetic foot ulceration and indeed for any non-healing ulcer includes a combination of neuropathy, deformity, and repetitive stress (trauma).

A) Peripheral neuropathy
This is present to some degree in more than 50% of diabetic persons above the age of 60 years. Peripheral neuropathy must usually be profound before leading to loss of protective sensation. The consequent vulnerability to physical and thermal trauma increases the risk of foot ulceration by 7-fold. Diabetes is the commonest medical disorder causing peripheral neuropathy.

B) Excessive plantar pressure
This is related to both limited joint mobility (at the ankle, subtalar and first metatarsophalangeal joints) and to foot deformities. In one study of patients with peripheral neuropathy, 28% with high plantar pressure developed a foot ulcer during a 2.5-year follow-up as compared to none with normal pressure.

C) Repetitive physical unrecognised trauma such as extremes of temperature while bathing, injuring while paring of nails and ill-fitting and traumatic innerwear and footwear.

A) Atherosclerotic peripheral vascular disease is twice as common in persons with diabetes when compared to persons without diabetes and particularly affects the femoropopliteal and smaller vessels below the knee, while frequently sparing the pedal vessels.

B) Intrinsic wound-healing disturbances,
Immunohistological changes include impaired collagen cross-linking and matrix metalloproteinase function and poor polymorphonuclear leukocyte function

C) Higher rate of onychomycosis and toe-web fulminant and recurrent fungal infections that lead to skin disruption

A) International Working Group on the Diabetic Foot (IWGDF)

This group classifies patients based on presence of risk factors concurrent with neuropathic or vascular disease and eventual outcomes.

• Group 0: patients without risk factors
• Group 1: patients with neuropathy
• Group 2: patients with neuropathy and a deformity of vascular disease
• Group 3: patients with a history of ulcer or amputation

B) Texas Foot Risk Classification

• Group 0 (no Peripheral Neuropathy, no Peripheral Arteriolar Occlusive Disease)
• Group 1 (with Peripheral Neuropathy)
• Group 2 (with Peripheral Arteriolar Occlusive Disease)
• Group 3 (with current or past ulceration)
• Group 4 (patient with an existing amputation)

I) General Preventive advice includes:

• Regular foot examinations for redness, corns, callosity formations, fungal infections and developing deformities
• Patients are advised to keep the feet clean and dry. The feet should be washed daily with lukewarm water. The water should be checked against extremes of temperatures. The dry foot should be liberally dusted with an antifungal powder.
• Don't expose feet to extreme heat or cold. Always use closed footwear.
• Never walk barefoot even at home.
• Wear comfortable shoes. Shoes should be washed regularly with an antiseptic solution and should be completely dry before usage. Deformed feet may need customised or plastazote footwear.
• Socks should fit properly. These should be ideally seamless and with out rough sewn or lumpy edges. A common recommendation is to wear the socks inside out to encourage the rough areas to face away from insensate skin.
• Corn and callus should only be treated by a doctor or a qualified podi atrist. It is not advisable to pare the nails too close to the skin. This may give rise to ingrown toenails and predispose to chronic fungal infections and nail fold abscesses. Ingrown toenails should be trimmed straight across

II) Identification of at-risk populations.

Preventing foot complications also begins with identifying those at risk. These include:

• Previous foot ulceration
• Prior lower extremity amputation
• Diabetes of more than 10 years duration
• Poor glycemic control (glycosylated haemoglobin 9%)
• Impaired vision (acuity20/40)
• Examination of the feet for structural abnormalities (e.g. calluses, hammer or claw toes, flat feet, bunions), reduced joint mobility, dry or fissured skin, tinea, or onychomycosis, and also inspect footwear to ensure proper fit and comfort.

III) Screening for Loss of Protective Sensation

A) Monofilament Testing

The most frequently used instrument for detecting neuropathy is the nylon Semmes-Weinstein monofilament.

Testing for Large-fibre neuropathy.
Inability to perceive the 10 g of force from a 5.07 monofilament applied, is associated with clinically significant large-fibre neuropathy. In 3 prospective studies, the Semmes-Weinstein monofilament identified persons at increased risk of foot ulceration with a sensitivity of 66% to 91%, a specificity of 34% to 86%, a positive predictive value of 18% to 39%, and a negative predictive value of 94% to 95%. While authorities recommend testing 8 to 10 anatomic sites, testing just 4 plantar sites on the forefoot (great toe and bases of first, third and fifth metatarsals) identifies 90% of patients with an insensate site.

Monofilament Test for Light Touch Sensation
The 5.07 Semmes-Weinstein monofilament consists of a plastic handle supporting a nylon filament. The filament is placed perpendicular to the skin, and pressure is applied until the filament buckles. The filament is held in place for approximately 1 second, and then released. Testing 10 sites (as shown) evaluates all dermatomes of the foot and may improve the sensitivity and specificity compared with testing a single site.

B) Biothesiometer
A biothesiometer is a handheld device that asse