What is the most appropriate way to assess a diabetic patient with a 2 cm ulcer on the first metatarsal, intact distal pulses, and signs of infection, including swelling and discharge?

Plain Radiographs Are the Essential First Step

In a diabetic patient with a 2 cm ulcer on the first metatarsal, intact distal pulses, and signs of infection (swelling and discharge for 4 days), plain radiographs in multiple views are the mandatory initial imaging study to assess for osteomyelitis, soft tissue gas, foreign bodies, and bone architecture changes. 1, 2

Why Plain Radiographs Come First

• The American College of Radiology designates plain radiographs as the mandatory initial imaging for all non-superficial diabetic foot infections, detecting osteomyelitis in 50-70% of cases 1, 2
• Weight-bearing films in at least two views should be obtained immediately, with a radio-opaque marker placed at the ulcer site to correlate anatomic location 1, 2
• Plain films provide essential baseline information about bone involvement, soft tissue gas, foreign bodies, and Charcot foot deformities that guide all subsequent management decisions 1, 2

Why the Other Options Are Incorrect

Duplex ultrasound (Option A), conventional angiography (Option B), MRA (Option C), and CT with contrast (Option D) are all vascular imaging modalities used to assess arterial perfusion—not infection. 2

• These vascular studies would only be indicated if distal pulses were absent, ankle-brachial index <0.9, toe-brachial index <0.75, or there were other clinical signs of peripheral arterial disease 2
• Since this patient has intact distal pulses, there is no immediate indication for vascular imaging 2
• The clinical presentation (swelling, discharge, ulcer) indicates infection requiring assessment for osteomyelitis, not vascular insufficiency 2

Critical Next Steps After Plain Radiographs

• Perform a probe-to-bone test during wound examination—a positive result (feeling bone with a sterile probe) is largely diagnostic of osteomyelitis 2, 3
• Obtain deep tissue cultures after debridement, not superficial wound swabs, as deep specimens provide reliable microbiological data 2
• Check inflammatory markers (ESR and CRP), as markedly elevated values suggest osteomyelitis 2
• Start empirical intravenous antibiotics immediately after obtaining cultures in this moderate infection 2

When Advanced Imaging Is Needed

• If plain radiographs are negative but clinical suspicion for osteomyelitis remains high (positive probe-to-bone test, elevated inflammatory markers), then MRI should be performed as it has the highest diagnostic accuracy (96.4% sensitivity, 83.8% specificity) 2
• Normal early radiographs do not exclude osteomyelitis, as plain films have poor sensitivity (61.9%) and may not show changes for 2-3 weeks 2

Common Pitfalls to Avoid

• Never delay plain radiographs to pursue vascular imaging first when infection is present—X-rays provide essential baseline information about bone involvement 1
• Never assume adequate perfusion based solely on palpable pulses in diabetic patients, but formal vascular assessment is not the priority when infection dominates the clinical picture 1
• Never delay antibiotic therapy to obtain imaging—treatment should not be postponed in moderate-to-severe infections 2