Diabetic Foot
July 2021 - 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
Radiography "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 onRADIOGRAPHY 1st, drainage, gangrene, tap test, BCs
OPINION: MOST 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 'MAY be appropriates" on MR, variable/lower appropriateness of any other imaging after radiography
- 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 variable at demarcating true marrow infection from edema (ie precise margins)
Indium leukocytes are similar, perhaps slightly cheaper but harder to prep agent-- "Usually not appropriate"
- 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.Diagnosis and care of the diabetic foot is constantly evolving. Imaging, clinical criteria, and lab/tissue values all play a part in decisions.
July 2021 - Donna Magid, M.D., M.Ed.