Background
The term “diabetic foot” refers to complications occurring in a foot that has decreased sensation (i.e., hypesthesia) from diabetic polyneuropathy. These complications include ulceration, Charcot arthropathy, and infection such as osteomyelitis.
Quick facts on foot ulcers in DM:
- The lifetime risk of a foot ulcer for patients with DM may be as high as 34%!
- Foot ulcers in patients with DM are associated with a 2.5-fold increased risk of death (at 5 years) compared to patients with DM without foot ulcers.
Neuropathy, which is present in over 80% of patients with DM who have foot ulcers, promotes ulcer formation in multiple ways:
- by decreasing pain sensation and perception of pressure
- by causing anatomic deformities (e.g., hammer toes from greater flexor muscle tone compared with extensor tone, loss of arch, and/or rocker bottom feet associated with Charcot foot)
- by impairing the microcirculation and the integrity of the skin
Monofilament Testing
Monofilament testing is designed to identify loss of protective sensation (LOPS), which predisposes a patient to ulceration. Ideally, the monofilament test should be performed with at least one other assessment (pinprick, temperature or vibration sensation using a tuning fork, or ankle reflexes). Absent monofilament sensation suggests LOPS, while at least two normal tests (and no abnormal test) rules out LOPS.
- Key point: About half of patients with diabetic ulceration lack numbness and can still detect the touch of a cotton wisp or pinprick.
To use the monofilament, the patient should be lying supine with eyes closed, and the monofilament should be applied perpendicular to the skin with enough force to buckle it for approximately 1 second. The patient responds “yes” each time they sense the monofilament, as the clinician randomly tests each site on the foot multiple times.
Source: UpToDate- Testing the plantar surface at the first and fifth metatarsal heads may be the most efficient and, overall, the most accurate bedside maneuver.
Charcot Arthropathy
Charcot joint (neuroarthropathy) refers to accelerated degenerative changes and eventual joint destruction following repetitive trauma to insensitive, neuropathic joints. In patients with DM, the Charcot joint characteristically affects the foot, including the ankle, tarsometatarsal, and metatarsophalangeal (MTP) joints.
- Most patients present with a limp, difficulty in putting on shoes, or swelling.
- Characteristic exam findings are anesthetic/hypesthetic feet, bony deformities (e.g., collapse of the arch of the midfoot, atypical bony prominences), and soft tissue swelling.
- In the acute phase, soft tissue swelling typically appears at the ankle and midfoot, sometimes with marked redness and warmth mimicking arthritis or cellulitis.
Foot Care Recommendations from the ADA
The American Diabetes Association (ADA) “Standards of Medical Care in Diabetes” includes the ADA’s current clinical practice recommendations, including the following recommendations on foot care:
- Perform a comprehensive foot evaluation at least annually to identify risk factors for ulcers and amputations. B
- Patients with evidence of sensory loss or prior ulceration or amputation should have their feet inspected at every visit. B
- Obtain a prior history of ulceration, amputation, Charcot foot, angioplasty or vascular surgery, cigarette smoking, retinopathy, and renal disease and assess current symptoms of neuropathy (pain, burning, numbness) and vascular disease (leg fatigue, claudication). B
- The examination should include inspection of the skin, assessment of foot deformities, neurological assessment (10-g monofilament testing with at least one other assessment: pinprick, temperature, vibration), and vascular assessment, including pulses in the legs and feet. B
- Patients with symptoms of claudication or decreased or absent pedal pulses should be referred for ankle-brachial index and for further vascular assessment as appropriate. C
- A multidisciplinary approach is recommended for individuals with foot ulcers and high-risk feet (e.g., dialysis patients and those with Charcot foot or prior ulcers or amputation). B
- Refer patients who smoke or who have histories of prior lower-extremity complications, loss of protective sensation, structural abnormalities, or peripheral arterial disease to foot care specialists for ongoing preventive care and lifelong surveillance. C
- Provide general preventive foot self-care education to all patients with diabetes. B
- The use of specialized therapeutic footwear is recommended for high-risk patients with diabetes, including those with severe neuropathy, foot deformities, ulcers, callous formation, poor peripheral circulation, or history of amputation. B
Further Reading!
- Steven McGee’s Evidence-Based Physical Diagnosis
- JAMA’s The Rational Clinical Examination
- ADA’s Standards of Medical Care in Diabetes
Blog post based on Med-Peds Forum talk by Julia Solomon, PGY3, and Cameron Ulmer, PGY2