Print

Diabetic Foot

July 2012 - Donna Magid, M.D., M.Ed. 

INFECTION vs NEUROPATHY

  • 6% of population (almost 16 million) and increasing.
  • $92 million/yr. diabetic-related health care
  • 25% develop foot problems (#1 admitting 'CC", hospitalized DM pts.)
  • 10% of total require amputation (56,000 non-traumatic LE amputations/yr)


PATHOGENESIS of NEUROPATHIC FOOT:

  • Diabetes, Syphilis (tabes dorsalis), Syringmyelia (UE),
  • Spina bifida,Spinal trauma, Meningomyelocele
  • Steroids, Hansen Disease
  • Decreased protective proprioception and pain sensation (deep pressure ok)
  • Modified weight-bearing w/o sense of consequences
  • Impaired immunity and healing


PLAIN FILM "6 Ds"

  • Destruction - without resorption, unlike osteomyelitis
  • Density (increased) - most important to ddx infection!!!
  • Debris
  • Dislocation
  • Distended joints
  • Disorganization - loss of archtecture, arches; deranged relationships

Ulceration due to decreased protective proprioception and focal pressure: MTP, plantar heel, toe tips, malleoli

NOT purely ischemic - pulses palpable, though SMALL vessels diseased. Once incited, slow/disinclined to heal.

80-90% COULD HEAL without surgery if total-contact casted

OPINION: TOO MANY DIABETIC AMPUTATIONS IN US ยท

  • 'Neither Tc99m nor MR affect outcomes': 1/3 of pts studied get amputation
  • Pus =s surgery ("Admission to Surgery =s amputation"--Anonymous)

TCC = ultimate orthotic, developed for Hansen disease

  • Relieves pressure areas, allows healing
  • Can be done outpt but may take one year
  • Avoids "whittling" or "ascending chops" surgery ("Die w/ yr feet on")

Once part of foot/LE amputated, odds of subsequent amputations soar

  • Unilateral BKA: increases energy expenditure/effort by 15%
  • Risk of contralat. BKA: 50%@ 3 yrs
  • Bilat BKA: 40% increase in effort/expenditure therefore wheelchair
  • Ambulatory efforts also produce stump problems, breakdowns

 

NEUROPATHIC (CHARCOT): REPAIR>DESTRUCTION

INFECTION/OSTEOMYELTIS: DESTRUCTION>REPAIR

  • Focal bone osteoporosis and/or destruction ('disappearing') indicate infection. May be no clear clinical indication of neuropathic /ulcerated leading to osteomyelitis
  • Usually afebrile
  • Radiographic changes: 10-14 days (MR helps w/ earlier bx/Rx)


RISK of OM FOOT INFECTION Increased:

  • Prior episode of infection or amputation
  • Neuropathy
  • Ulceration lasting over 2 wks, esp. over prominences: 90% of osteomyelitis due to infected ulcers
  • Bone exposed or tapped when probed (ALL considered osteomyelitis. NOT tapping down to bone does not r/o infection. Swabs, cultures, totally unreliable


OSTEOMYELITIS DX based on plain film, drainage, gangrene, tap test, BCs

OPINION: FURTHER SUBSPECIALTY IMAGING IS HIGHLY UNLIKELY TO BE HELPFUL IN THE FOOT AND WILL NOT ALLOW DDX BETWEEN INFECTION AND NEUROPATHIC DESTRUCTION.

  • ACR's conclusion is 'No Consensus" on appropriateness of any imaging after plain film
  • Institution, pt-specific, and surgeon-specific, variables for CT, MR
  • Don't advise Tc99m!!!

Tc99m scintigraphy: increased uptake all 3 phases for both. 'Fourth phase" - increased uptake @ 24 hr suggests osteomy > Charcot

MRI poor at demarcating true marrow infection from edema

Indium leukocytes are similar, perhaps slightly cheaper but harder to prep agent

  • lnd WBC w/ Tc 99m HMPOA may give better resolution???
  • Always hard, hand or foot, to tell soft tx from bone uptake - poor detail

UNCLEAR if any of these lead to earlier dx, lower cost medicine, better outcome.


July 2012 - Donna Magid, M.D., M.Ed.