diabetic foot ulcer; diabetic foot lesion; diabetic lower extremity lesion

Etiology

• any lesion on the plantar surface of the foot caused by diabetic polyneuropathy & repetitive pressure
• risk factors
  • loss of protective sensation due to peripheral neuropathy
  • peripheral vascular disease
  • foot deformities
  • prior ulceration &/or amputation (greatest risk factor)
  • skin callus

Pathology

• mixed infection with Staphylococcus aureus, anaerobes & aerobic gram negative organisms
• osteomyelitis
  • diagnosis is difficult
  • if bone can be probed through ulcer, likelihood of osteomyelitis is high
• microvascular supply may be compromised by lack of nitric oxide

Clinical manifestations

• if the wound can be probed to the bone, highly suggestive of osteomyelitis
• excludes peripheral arterial disease, arterial ulcer
  • palpate pulses
• see wound assessment & neuropathic ulcer

* images

Laboratory

• serum glucose may increase with infection
• deep wound/tissue culture prior to antibiotic therapy if pus, risk of MRSA or deep/severe infection (see diabetic foot infection)
• uninfected wound should not be cultured
• bone culture to guide treatment for osteomyelitis

* diabetic foot infections diagnosed clinically on the basis of

• >= 2 signs of inflammation
• pus, purulent drainage, foul odor
• systemic signs (fever, chills, tachycardia, hypotension) none of which appear to be essential (NEJM knowedge+)

Diagnostic procedures

• ankle/brachial index < 0.9 = peripheral arterial disease
• bone biopsy if suspected osteomyelitis*

* confirmation by MRI helpful but not essential prior to bone biopsy

Radiology

• imaging of foot recommended for new diabetic foot infections
  • X-ray insufficient to rule out osteomyelitis
• ultrasonography if abscess suspected
• MRI if osteomyelitis suspected or bone can be probed & X-ray negative

Staging

• see grading of diabetic foot ulcer

Complications

• diabetic foot infection indicated by pus or >= 2 inflammatory signs (warmth, induration, erythema, pain, tenderness)
• osteomyelitis, amputation
• 2.5 fold increased risk of death within 5 years

Management

• see wound care
  • wound cleansing
• wound debridement
• avoid occlusive dressings to reduce risk of wound infection
• EDX110 (nitric oxide-generating) dressing may be of benefit
• offload pressure - off-loading brace or other device
• antibiotics for wound infections
  • uninfected wounds should not be treated with antibiotics
  • diabetic foot infections diagnosed clinically (see Laboratory:)
  • mild to moderate wound infections can be treated with a short course of antibiotics directed at Staphylococcus & Streptococcus
    • cephalexin if mild non-purulent infection with risk factors for MRSA
  • outpatient treatment for MRSA only if risk factors (see MRSA)
    • doxycycline vs trimethoprim-sulfamethoxazole for MRSA
    • amoxicillin clavulanate + ciprofloxaxin for 14 days if no risk factors for MRSA provides dual coverage for Pseudomonas aeruginosa
  • severe wound infections
    • treat with broad spectrum antibiotics (1st)*
      • vancomycin & piperacillin tazobactam (Zosyn)
      • some cases may be cured without surgery
      • 6 weeks of antibiotics non-inferior to 12 weeks
    • consult surgery
      • bone or joint destruction may be indication for surgery
    • bone culture to guide treatment for osteomyelitis
• reassess if ulcer does not decrease to < 50% of original size after 4 weeks of therapy
  • consider Regranex
  • consider autologous platelet-rich plasma therapy
  • consider hyperbaric oxygen therapy (covered by Medicare)
    • improves healing & prevent amputation
    • does not improve healing or prevent amputation
    • indicated only in a selected group of patients with chronic diabetic foot ulcers
    • hyperbaric oxygen does not improve outcomes in diabetic patients with ischemic foot ulcers
    • topical oxygen may improve ulcer healing
      • pressurized oxygen topically administered through a chamber placed over the extremity
      • home treatment, 5 times weekly, for 90 minutes per session
  • consider extracorporeal shock wave therapy
    • Dermapace System FDA-approved Dec 2017
  • consider synthetic or donated graft only after at least 4 weeks of therapy

* most important after blood cultures & IV fluids for hypotension

More general terms

• pressure ulcer (decubitus ulcer, bedsore)
• neuropathic ulcer
• diabetes mellitus complication

Additional terms

• cellulitis
• diabetic foot
• Wagner classification of diabetic foot ulcer

Patient information

diabetic foot ulcer patient information