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Diabetic Foot Infections:. Diagnosis & Treatment 11/05/2008. Epidemiologic Considerations. 7% US population, 21 M have DM 15-20% will develop LE ulcer (LEU) lifetime 5-7%/year with neuropathy 15% LEU will require amputation. Epidemiologic Considerations 2. 65% LE amputations in the US-DM

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diabetic foot infections

Diabetic Foot Infections:

Diagnosis & Treatment


epidemiologic considerations
Epidemiologic Considerations
  • 7% US population, 21 M have DM
  • 15-20% will develop LE ulcer (LEU) lifetime
  • 5-7%/year with neuropathy
  • 15% LEU will require amputation
epidemiologic considerations 2
Epidemiologic Considerations 2
  • 65% LE amputations in the US-DM
  • Hispanics, AA, NA have 2-fold risk
  • DM foot wound treatment accounts for ¼ DM based hospital admissions
pathophysiology dm le ulcers
Pathophysiology: DM LE Ulcers
  • Motor Neuropathy:intrinsic mm. Wasting
    • Fat pad displacement
    • Prominence metatarsal heads
    • Hammer toe deformity
    • Repetitive trauma through ADL’s
pathophysiology 2
Pathophysiology: 2
  • Sensory neuropathy: insensate foot
  • Autonomic neuropathy: fissuring-portal for bacterial entry
  • Arthropathy: decreased mobility at ankle, subtalar joint and MTP
  • Impaired healing:
    • Macro/microvascular disease
    • PMN dysfunction 2ry hyperglycemia
greatest risk lue
Greatest Risk : LUE
  • Prior ulcer
    • 1/3 develop new ulcer < one year
    • 2/3 within 5 years

Amputations: 40% probability of contralateral amputation at 2 years

clinic evaluation the key to prevention
Clinic Evaluation: The Key To Prevention
  • Prior foot problems
  • Neuropathic Symptoms: Dyesthesias
  • Claudication
  • Exam: Deformity, Callus
    • Monofilament testing
    • Edema
    • Pulses, venous refilling time
    • Footwear
preventive foot care
Preventive Foot Care
  • Examine daily for cracks, callus, skin breakdown
  • Warm soapy water bathing
  • Moisturizing cream
  • Toenails trimmed straight across, toe level
  • Clean cotton or wool socks
  • Well fitting comfortable shoes
diabetic foot infection 1
Diabetic Foot Infection-1
  • Criteria for ulcer infection
    • A) > 2 of erythema, warmth, tenderness, swelling
    • B) purulent discharge from ulcer or nearby sinus tract

*Culture of clinically uninfected ulcers is not necessary, unless done for surveillance purposes

diabetic foot infection 2 culture technique
Diabetic Foot Infection-2Culture Technique
  • CID 2006; 42: 57-62
  • Percutaneous bone biopsy culture compared to surface swab cultures
    • Concordance rate overall 22%
    • Concordance rate for S. aureus 43%
    • Isolate from bone culture isolated from only 30% of swab cultures


collection of soft tissue cultures from diabetic foot lesions
Collection of Soft Tissue Cultures From Diabetic Foot Lesions
  • Cleanse and mechanically debride lesion
  • Use a sterile dermal curette or scapel blade to obtain material from debrided base of lesion
  • Collect aerobic and anaerobic specimens
wagner classification of diabetic foot infections
Wagner Classification of Diabetic Foot Infections
  • Grade 1 superficial dermal ulcer
  • Grade 2 deep ulcer penetrating to tendon or joint capsule
  • Grade 3 deep ulcer to bone or joint
  • Grade 4 localized gangrene forefoot/heel
  • Grade 5 gangrene of entire foot
idsa diabetic foot infection classification
IDSA Diabetic Foot Infection Classification
  • Uninfected: lacking purulence or signs of inflammation
  • Mild:infection limited to superficial tissue, cellulitis < 2 cm around ulcer, no systemic signs
  • Moderate: Systemically well & metabolically stable, > 1 of- cellulitis > 2 cm from ulcer, deep tissue involvement, abscess, gangrene, involvement of muscle, tendon, joint or bone
idsa classification
IDSA Classification
  • Severe: foot infection and systemic toxicity and/or metabolic instability
    • Fever or chills
    • Leukocytosis
    • Tachycardia, hypotension
    • Confusion
    • Severe hyperglycemia or azotemia
prognostic validity of idsa classification
Prognostic Validity of IDSA Classification
  • CID 2004; 39: 885-910
  • N= 1666, 27 months of follow-up
  • 15% developed LE wound, 9% infected


Mild 4% 3%

Moderate 52% 46%

Severe 89% 78%

clinical diagnosis of osteomyelitis
Clinical Diagnosis of Osteomyelitis

Exam+LR -LR

+ Swab culture 1.0 1.0

Ulcer inflammation 1.5 0.84

Bone exposed 9.2 0.70

Probe to bone 6.4 0.39

Wagner grade > 3 5.5 0.40

ESR > 70 11 0.34

JAMA 2008; 299: 806-813

clinical applications
Clinical Applications
  • Case 1: 52 Y.O F. 2.2X1.5 cm ulcer that probes to bone. ESR = 82, X-ray: cortical erosions bone contiguous to ulcer. Would you order an MRI to “prove” osteo?
  • Case 2: 62 Y.O.M 1cm ulcer with 1 cm surrounding erythema and swelling. Superficial Wagner grade1. ESR 25. Would you order an MRI to R/O osteo?

Test +LR -LR

Plain films 2.3 0.6

WBC scan 3.0 0.2

MRI 4.0 0.14

management considerations
Management Considerations
  • Define extent & severity of injury clinically
  • Plain x-rays: bone, gas, foreign bodies
  • Use IDSA classification with additional description of size, depth of lesion, undermining, involvement of tendon, joint, bone, gas, gangrene
  • Vascular status: pulses, venous filling time, Doppler ABI
  • Culture if infected, use appropriate technique
management 2
  • Offload
  • Debridement of non-viable soft tissue and bone by experienced surgeon/podiatrist
  • Moist dressing approach +/- enzymatic debriding agent or antibacterial absorbing agent
  • Additional vascular evaluation and imaging if necessary
  • Control sugar < 150 mg%
management 3
  • Antibiotic Therapy: Myth vs. Data

Arch Intern Med 1990; 150: 790-7

Curette cultures, initial infection

90% Staph, Strep A, B, C, G, 42% sole pathogen

36% Aerobic GNB*

13% anaerobic*

* Always polymicrobial, and role of GNB unclear, increasing GNB with chronicity

pathogens asssociated with clinical foot infection syndromes
Pathogens Asssociated With Clinical foot-infection Syndromes


Cellulitis, no ulcer Staph, hemolytic Strep.

Infected ulcer, no Staph & Strep,

prior antibiotic therapy

Infected ulcer, chronic, Staph & Strep, non-

prior antibiotics Pseudomonal GNB, unless

macerated from soaking

pathogens and foot syndromes 2
Pathogens and Foot Syndromes-2


Long duration, non Staph, strep,

healing, prior broad anarobes, non-

spectrum antibiotics, fermentative GNB

or the fetid necrotic foot

surgical intervention
Surgical Intervention
  • Most data support resection of infected bone, including ray and transmetatarsal amputations to accelerate recovery

Curr Clin Top Infecti Dis 194; 14: 1-22

N=110, ray resection, transmet.

88% cure with 2 weeks post op antibiotics

* Revascularization if indicated

newer approaches
Newer Approaches
  • Becaplermin (Regranex) Gel
    • Recombinant platelet derived growth factor
    • Increases granulation tissue ingrowth rate
    • Expensive
    • Statistical association with increased rate of malignancy in those with > 3 prescriptions
newer approaches26
Newer Approaches
  • Dermal Matrix

Integra, Graftjacket

acellular dermal scaffolfd

encourage epithelization and ulcer closure

Infection adequately treated and wound completely debrided to viable tissue

hyperbaric oxygen
Hyperbaric Oxygen
  • Indication: Wagner grade > 3, not responding to conventional therapy. Better response compared to controls if ABI low
  • Mechanism: increased bone marrow mobilization of endothelial precursor cells
  • Local deposition of stromal derived growth factor-1 alpha into wound recruits EPC
  • 55 YO man with DM-2. Acute foot pain and swelling after minor trauma. No skin breakdown or sinus tracts. Foot is edematous, red, warm with pounding pulses and dilated pedal veins. Patient is afebrile with normal WBC and ESR=19
case 1
Case 1
  • What is your diagnosis, what additional tests would you order, why is he having acute pain, what is appropriate therapy?
  • Plain x-ray: deformity of midfoot without evidence of osteo.
case 2
Case 2
  • 55 YO man with foot ulcer. Present for two months. No prior antibiotic therapy. Some purulent discharge. Probe down to tendon. No cellulitis or systemic toxicity. Plain film with small cortical erosions adjacent to ulcer.
case 231
Case 2
  • Is the patient infected?
  • What is the Wagner and IDSA classification? What is his chance of requiring an amputation within 2 years?
  • Are other diagnostic tests indicated for osteomyelitis?
  • Describe your therapeutic approach.