OnExam

• More than 75% of diabetic ulcers appear on the toes or plantar surface of the metatarsal heads. The remaining ulcers usually occur on the heel, plantar midfoot, or at sites of previous amputation.

  • In addition to ulceration, complications to the diabetic foot include Charcot arthropathy and infection.
  • Most important contributing factor is neuropathy – test with Semmes-Weinstein monofilament test.

The Monofilament Test

Performing the Test:
  1. Patient should be lying supine with eyes closed
  2. Touch the monofilament to the patient’s forehead or sternum so the sensation is understood
  3. The monofilament should be applied perpendicularly to the skin with enough force to buckle it for approximately 1 second
  4. Patient should respond “yes” each time he or she senses the monofilament
  5. Foot should be tested at the dorsum of the great toe proximal to the nail bed, as well the planar surface of the foot and base of the fifth metatarsal.
  6. Perform the stimulus in an arrhythmic manner so the patient does not anticipate when the stimulus will be applied
  7. An abnormal result would be an inability to consistently identify the presence of the monofilament at any site
  8. 10g monofilament most commonly used
  9. Perform a stimulus 4 times per foot. For each of the 8 stimuli, assign a score of 0 if not perceived, 0.5 if it is substantially less than that perceived on forehead or sternum, and 1 if it is perceived as normal.
    • A score of 3/8 or less means that the presence of neuropathy is likely
    • A score of 3.5 to 5 means the risk of new onset neuropathy in the next four years is high
    • A score of 5.5 or greater indicates there is a low risk of neuropathy in the next four years

Charcot's Foot

  • Today, diabetes is the leading cause of Charcot joint. This refers to degenerative changes and destruction that follows repetitive trauma to insensitive neuropathic joints.
  • Characteristically affects the foot, including the ankle, tarsometatarsal, and metatarsalphalangeal joints.
  • Ask about symptoms of Charcot feet
    • Limp
    • Difficulty putting on shoes
  • Look for signs of Charcot joint
    • Anesthetic or hypesthetic feet
    • Bony deformities
    • Soft tissue swelling (acutely, typically presents at ankle and midfoot with marked rubor/warmth)
    • Abnormal callus formation
    • Ulceration
    • Abnormal projections on the plantar arch “rocker sole”

  • In diabetics with foot ulceration and underlying radiographic abnormalities of the bone, it is very difficult to distinguish Charcot foot from osteomyelitis.
    • If ulceration present, test for osteomyelitis with the “probe test”
    • Gently probe the ulcer base with sterile blunt stainless steel eye probe
    • Three findings increase the probability of underlying osteomyelitis
      • Ulcer size >3 cm (+LR 3.5), >4cm (+LR 7.3), >5cm (+LR 11)
      • Positive probe test (+LR 5.3)
      • Ulcer depth of more than 3mm of exposed bone (+LR 3.9)

References

  1. Bickley L, Szilagyi P. BATES’ Guide to Physical Examination and History Taking. 9th edition. Lipincott Williams & Wilkins; 2007.
  2. McGee, S. Evidence Based Physical Diagnosis. St. Louis Missouri. Saunders Elsevier. 2007.
  3. Canadian Diabetes Association Clinical Practice Guidelines Expert Committee. Canadian Diabetes Association 2008 clinical practice guidelines for the prevention and management of diabetes in Canada. Can J Diabetes. 2008; 32(suppl 1): S1-S201.
  4. Gardner D, Shoback D. Greenspan’s Basic & Clinical Endocrinology. 8th Edition. USA. McGraw-Hill. 2007.