Radiographic Imaging for Plantar Foot Ulcers
You need a 3-view X-ray series (anteroposterior, medial oblique, and lateral projections) for a plantar foot wound, ideally obtained with weight-bearing technique if the patient can tolerate standing. 1
Standard Imaging Protocol
The International Working Group on the Diabetic Foot (IWGDF) 2023 guidelines explicitly state that X-rays should include three standard foot views: anteroposterior (AP), medial oblique, and lateral projections. 1 This is a Best Practice Statement, meaning it represents the accepted standard of care for evaluating diabetic foot complications. 1
Weight-Bearing vs. Non-Weight-Bearing
Weight-bearing (standing) radiographs are strongly preferred because they detect dynamic abnormalities such as joint malalignment, joint subluxation, and fracture displacement that may not be apparent on non-weight-bearing films. 1
If the patient cannot bear weight due to pain, infection severity, or mobility limitations, non-weight-bearing radiographs are an acceptable alternative, though they may miss important structural changes. 1
Why Three Views Matter for Plantar Ulcers
The three-view series provides comprehensive evaluation of the osseous anatomy that cannot be achieved with fewer projections. 1 This is particularly critical for plantar ulcers because:
The medial oblique view is essential for visualizing metatarsal heads and midfoot structures that are commonly involved in plantar ulceration. 1
Lateral column involvement (detected on oblique and lateral views) is associated with worse prognosis and higher ulceration risk than medial column involvement alone. 2
Sagittal plane deformities (best seen on lateral views) are more strongly associated with foot ulceration in diabetic patients than transverse plane abnormalities. 2
Critical Diagnostic Considerations
Rule Out Osteomyelitis
For any plantar ulcer in a diabetic patient, your primary concern should be underlying osteomyelitis, which occurs in a substantial proportion of non-healing diabetic foot ulcers and dramatically worsens outcomes. 1
Plain X-rays are the appropriate first-line imaging modality, but they have significant limitations—bone changes may not appear for 10-14 days after infection onset. 1, 3
If X-rays are normal but clinical suspicion remains high (positive probe-to-bone test, ESR >70 mm/h, ulcer >2 cm²), proceed directly to MRI, which has 98% sensitivity for osteomyelitis. 1, 3
Differentiate from Charcot Neuroarthropathy
Plantar ulcers in diabetic patients with neuropathy may coexist with or result from Charcot neuro-osteoarthropathy (CNO), which requires completely different treatment than infection. 1
Bilateral comparison films are recommended to help differentiate CNO from osteomyelitis, as CNO changes may be bilateral or show characteristic patterns. 1, 3
The three-view series is essential for detecting early Charcot changes, which were found in 16% of neuropathic patients with foot ulceration history. 4
Ordering the Study Correctly
Your X-ray requisition should specify:
"Foot X-ray, three views (AP, medial oblique, lateral)" rather than just "toe films" or a two-view series. 3
"Weight-bearing if tolerated" to ensure dynamic abnormalities are captured. 1, 3
Clinical indication: "Rule out osteomyelitis" or "Plantar ulcer, evaluate for bone involvement" to guide radiologist interpretation. 3
Common Pitfalls to Avoid
Do not order only two views (AP and lateral)—the oblique view provides critical information about midfoot and metatarsal structures that are frequently involved in plantar ulceration. 1
Do not skip weight-bearing views unless the patient truly cannot stand—non-weight-bearing films miss important deformities and malalignments. 1, 3
Do not rely solely on negative X-rays to exclude osteomyelitis in a clinically suspicious case—early infection requires MRI for detection. 1, 3
Do not confuse Charcot changes with osteomyelitis—both can present with bone destruction, but treatment differs dramatically (offloading vs. antibiotics/surgery). 1