Stress fractures

Imaging findings

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• Conventional Radiography
• 15% sensitive in early fractures, increasing to 50% on follow-up
• Sclerotic band (due to trabecular compression and callus formation) usually perpendicular to cortex
• Intracortical radiolucent striations (early)
• Solid thick lamellar periosteal new bone formation
• Endosteal thickening (later)
• Follow-up radiography after 2-3 weeks of conservative therapy may reveal fracture not seen earlier
• Nuclear medicine
• “Gold standard" = almost 100% sensitive
• Abnormal uptake within 6-72 hours of injury (prior to radiographic abnormality)
• "Stress reaction" is a focus of subtly increased uptake
• Focal fusiform area of intense cortical uptake
• Abnormal uptake persists for months
• MRI
• Very sensitive modality
• Fat saturation technique most sensitive to detect increase in water content of medullary edema / hemorrhage
• Diminished marrow signal intensity on T1WI
• Increased marrow signal intensity on T2WI