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FOOT PROBLEMS

Foot ulcers and other foot problems are one of the commonest causes of morbidity, significant disability, and, even mortality, amongst patients with diabetes.

Foot problems in persons with diabetes are usually the result of three primary factors: neuropathy, poor circulation, and decreased resistance to infection. Also, foot deformities and trauma play major roles in causing ulcerations and infections in the presence of neuropathy or poor circulation.

Prevention

The frequency and the severity of foot problems can be decreased with adequate foot evaluation and, as importantly, patient education about foot care.

All patients at the time of diagnosis and annually, must undergo a comprehensive foot evaluation which includes a complete vascular, neurological, musculoskeletal, skin and soft tissue examination.

This comprehensive evaluation does not necessarily involve the use of sophisticated, complex and costly equipment; some patients may require more sophisticated evaluation.

Patients at high, or increasing, risk may require more frequent evaluations and proactive management.

Patients with HIGH RISK
a) patients who walk barefoot.
b) patients with diabetic neuropathy.
c) patients with significant peripheral vascular disease.
d) patients who smoke or use tobacco in any form.
e) those with a foot deformity such as claw toes and hallux valgus.
f) diabetics with a history of previous ulcers or foot infections.
g) patients with abnormal gait.
h) those with significant skin and nail infections or deformitoes.
i) blind/partially sighted persons.
j) elderly patients ; especially those living alone,
k) diabetics with chronic renal failure;
l) patients with a high alcohol intake.


Importantly,

The prognosis for the second limb is poor in those who have had an amputation of the contra lateral limb.

SCREEN TESTS FOR DIABETIC FOOT PROBLEMS

A comprehensive foot exam assesses skin, circulation, and sensation. The test can be done during a routine clinic visit


Inspection


For evidence of dry, or excessively moist, skin, hair and nail abnormalities corns, calluses and infection

For presence of deformities, heel spurs, flat arches, etc.


Signs and Symptoms of Sensory Neuropathy

To assess protective sensation or feeling in the foot, a nylon monofilament should be done. Those who cannot sense pressure from the monofilament have lost protective sensation and are at risk for developing foot sores that may not heal properly. Other tests include checking reflexes and assessing vibration perception.

For a note on the use of the Monofilament Test see appendix 9a


If necessary, the following tests should be considered :

A) Nerve Conduction, and
B) EMG studies.

Vascular
  • Inquire for symptoms of intermittent claudication;
  • Palpation of pedal pulses; if foot pulses are absent examine proximal pulses
    (popliteal and femoral);
  • Take the ankle-brachial pressure index; can give a fairly good idea of the
    severity of the peripheral leg arteries, if interpreted correctly;

Interpreting the ankle-brachial pressure index

Rigid or calcified vessels or both >1.2 Risk of vascular foot ulcer very high
Normal (or calcified) 0.9 - 1.2 Risk of vascular foot ulcer is small, if vessels not calcified
Definite vascular disease 0.6 - 0.9 Risk of vascular ulcer moderate and depends on other risk factors
Severe vascular disease Less than 0.6 Risk of vascular foot ulcer very high

Note: Vascular calcification is common so spuriously high readings can be obtained. This must be taken into account when the pressure index reading is evaluated.

If necessary, the following tests should be considered :

  • Doppler studies for blood flow.
  • Arteriography.

All these investigations may not be necessary in every patient and the range of investigations should be individualised.

Clinical presentations

Clinical features of neuropathic and ischaemic foot

The clinical picture would usually be mixed depending on the presence and severiety of the nerve involvement along with the presence and degree of peripheral vascular dysfunction.

Neuropathic Ischaemic (neuroischaemic)
Warm with intact pulses Pulseless, not warm
Diminished sensation Usually diminished sensation
Ulceration, usually on tips of toes and plantar surfaces under metatarsal heads Ulceration, often on margins of foot, tips of toes, heels
Sepsis Sepsis
Local necrosis Necrosis or gangrene
Oedema Critical ischaemia, foot pink, painful, pulseless, and often cold
Charcot's joints  

Whilst nerve involvement and the peripheral vascular disease predispose to foot problems, there is usually seen a "trigger" or precipitating factor. This can be trauma, or infection or both.

Precipitating causes of foot ulceration and infection

Friction in ill fitting or new shoes
Untreated callus
Self treated callus
Foot injuries (for example, unnoticed trauma in shoes or when walking barefoot)
Burns (for example, excessively hot bath, hot water bottle, hot radiators, hot sand on holiday)
Corn plaster
Nail infections (paronychia)
Heel friction in patients confined to bed
Foot deformities (callus, clawed toes, bunions, pes cavus, hallux rigidus, hammer toe, Charcot's foot, deformities from previous trauma or surgery, nail deformities, oedema)


Management of a Foot Infection / Ulcer

Prevention is the best management, but in spite of the best efforts, foot infections and ulcers do occur. If treated early and optimally, many feet can still be salvaged.


Infection


Foot infections MUST be treated at the earliest.

The clinical diagnosis of infection usually consists of three aspects.

  • Systemic signs of fever and leukocytosis.
  • Classic signs of inflammation around the ulcer (eg, heat, redness, edema, and pain); and
  • Presence of purulent discharge from the ulcer;

It should be realized that due to the presence of varying degrees of nerve and arterial involvement, one may not see these "classic" signs. Pain and tenderness may be absent because of neuropathy. The response to injury in skin includes a local vasodilation mediated by sensory nerve fibers, which are impaired in diabetic neuropathy. Intact tissue responds to bacterial infection by increasing blood flow >20-fold in the area around the infection. However, erythema or redness may be absent in the diabetic foot because of the inability of the foot to increase its blood supply in response to infection. Furthermore, it is now established that up to 50% of patients with deep foot infections will not have leukocytosis or fever. Thus, one cannot wait for the classical signs before initiating management in all patients.

Principles of treatment

Treating Cellulitis

Empiric Antibiotic therapy


Most of the foot infections are caused by mulitimicobrial involvement. Thus, empiric treatment should cover Gram- negative aerobic as well as an aerobic organisms. The antibiotic chosen should be bactericidal as opposed to bacteriostatic. In general, bacteriostatic antibiotics require an intact immune system to function properly. The latter is often compromised in a person with diabetes.

Selected empirical antibiotic regimens for mild and non-limb-threatening infections
Oral agents Topical agents
Cephalexin Silver sulfadiazine
Cefdinir Silver powder, gels
Amoxicillin-clavulanate Mafenide acetate
Clindamycin Ciprofloxacin drops
Dicloxacillin Mupirocin
Ciprofloxacin, levofloxacin Gentamicin
Trimethoprim-sulfamethoxazole Bacitracin
Linezolid Cadexomer iodine

Aminoglycosides should not be used in combination therapy, if possible. In diabetes patients, who may have some degree of underlying nephropathy, the potential toxic effects of these agents is a prime concern, especially since less toxic alternatives are available. In addition, aminoglycosides are inactivated in an acidic environment, such as that found in abscess cavities. They have minimal penetration into bone, thus making them a poor choice for patients with osteomyelitis.

Later, the antibiotic choice would depend on the culture and sensitivity reports.

A patient who presents with mild infection should be closely monitored and if healing does not take place or the conditions worsens, it would be much better to refer the patient to people specializing in managing such problems.

Any person presenting with more serious infections or an abcess or ulcer should immediately be referred to others well versed in this management without wasting precious time.

Most Common Reasons For Non-Healing Ulcers

1) Failure to Non-Weight Bear
2) Unappreciated Depth of Wound
3) Osteomylitis
4) Vascular Compromise
5) Noncompliance
6) Poor Diabetic Contro

Education

All patients must be educated about the "Do's and Don'ts of foot care.



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