Diabetic Foot Infections:

1. Diabetic Foot Infections: Diagnosis & Treatment 11/05/2008

2. 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

3. 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

4. Pathophysiology: DM LE Ulcers • Motor Neuropathy:intrinsic mm. Wasting • Fat pad displacement • Prominence metatarsal heads • Hammer toe deformity • Repetitive trauma through ADL’s

5. 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

6. 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

7. Clinic Evaluation: The Key To Prevention • Prior foot problems • Neuropathic Symptoms: Dyesthesias • Claudication • Exam: Deformity, Callus • Monofilament testing • Edema • Pulses, venous refilling time • Footwear

8. 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

9. 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

10. 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 DON’T DO SUPERFICIAL SWAB CULTURES

11. 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

12. 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

13. 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

14. IDSA Classification • Severe: foot infection and systemic toxicity and/or metabolic instability • Fever or chills • Leukocytosis • Tachycardia, hypotension • Confusion • Severe hyperglycemia or azotemia

15. Prognostic Validity of IDSA Classification • CID 2004; 39: 885-910 • N= 1666, 27 months of follow-up • 15% developed LE wound, 9% infected IDSAHospitalizationAmputation Mild 4% 3% Moderate 52% 46% Severe 89% 78%

16. 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

17. 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?

18. Imaging Test +LR -LR Plain films 2.3 0.6 WBC scan 3.0 0.2 MRI 4.0 0.14

19. 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

20. 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%

21. 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

22. Pathogens Asssociated With Clinical foot-infection Syndromes SyndromePathogens 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

23. Pathogens and Foot Syndromes-2 SyndromePathogens Long duration, non Staph, strep, healing, prior broad anarobes, non- spectrum antibiotics, fermentative GNB or the fetid necrotic foot

24. 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

25. 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

26. Newer Approaches • Dermal Matrix Integra, Graftjacket acellular dermal scaffolfd encourage epithelization and ulcer closure Infection adequately treated and wound completely debrided to viable tissue

27. 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

28. Case • 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

29. 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.

30. 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.

31. 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.