Diabetic foot

The diabetic foot is "common foot problems in persons with diabetes mellitus, caused by any combination of factors such as diabetic neuropathies; peripheral vascular diseases; and infection. With the loss of sensation and poor circulation, injuries and infections often lead to severe foot ulcers, gangrene and amputation."

Diagnosis

The signs of underlying osteomyelitis are "an ulcer area larger than 2 cm², a positive probe-to-bone test result, an erythrocyte sedimentation rate of more than 70 mm/h, and an abnormal plain radiograph" according to a systematic review by the Rational Clinical Examination. A normal magnetic resonance imaging makes osteomyelitis unlikely.

The National Institute for Health and Clinical Excellence (NICE) has addressed screening and recommends annually:
Physical examination of patients’ feet:

• testing of foot sensation using a 10 g monofilament or vibration
• palpation of foot pulses
• inspection of any foot deformity and footwear

Although NICE and others have recommended monofilament testing, its contribution in the major randomized controlled trials is not clear.

Monofilament testing for diabetic neuropathy using preferred testing locations colored green.

If screening with the monofilament is done, a three site test of the plantar surfaces of the great toe, the third metatarsal, and the fifth metatarsalsis is adequate according to a systematic review of studies. Another systematic review questions the test accuracy of the monofilament exam.

The role of patient education in preventing foot ulcers is not clear according to the Cochrane Collaboration.

Prevention

"Integrated foot risk scores are more sensitive than individual clinical criteria in predicting future foot ulceration and are likely to be better screening tools."

An example of a foot risk score is the Scottish foot ulcer risk score. Low risk is defined as able to detect at least one pulse per foot, and able to feel 10 g monofilament, and no foot deformity, physical, or visual impairment. The negative predictive value of a 'low-risk score' is 99%.

Randomized controlled trials of interventions to prevent complications of diabetic foot.

Trial	Patients	Intervention	Comparison	Outcome	Results		Comment
					Intervention	Control
Litzelman 1993	395 patients • general medicine practice	Patient and provider education	Usual care	• Any foot lesion • Serious foot lesions at one year	Not reported	• 11% • 2.9%	• Insignificant • Significant reduction
Lincoln 2008	172 patients • Prior ulceration • specialist clinic	Targeted, one-to-one education	Usual care	Re-ulceration at • 1 year 2 years	• 30% • 41%	• 20% • 41%	• Insignificant • Insignificant
McCabe 1998	2002 patients • high-risk • general diabetic clinic	Screening and referral to foot-care clinic if they had prior ulcer, had low ankle–brachial index (<0.75), or had foot deformities	Usual care	• Ulceration within 2 years • Amputation rates	• 2% • 0.1%	4% 1.2%	• Insignificant • Significant
Reiber 2002	400 patients • Prior ulceration • Excluded severe deformity	Therapeutic shoes	Usual footwear	Re-ulceration	15%	17%	Insignificant difference

Other trials of lesser quality are available. The trial by Donohoe had the following problems: 1) did not define high risk foot and the outcome of appropriate referral likely had incorporation bias due to the monofilament being part of the criteria, 2) non-randomized comparison of referrals, 3) imbalanced study size the hurt the power of the nonrandomized assessment of the control group.

"Of all methods proposed to prevent diabetic foot ulcers, only foot temperature-guided avoidance therapy was found beneficial in RCTs" according to a meta-analysis. Three trials are available.

Treatment

"Currently there is no research evidence to suggest that any type of hydrocolloid wound dressing is more effective in healing diabetic foot ulcers than other types of dressing" according to the Cochrane Collaboration.

"There is some evidence to suggest that hydrogel dressings are more effective in healing (lower grade) diabetic foot ulcers than basic wound contact dressings however this finding is uncertain due to risk of bias in the original studies" according to a meta-analysis by the Cochrane Collaboration.