How should I write an order for an MRI of the lower extremities (without contrast) to evaluate for stress fracture in a runner with leg pain and no contraindications?

How to Order an MRI for Suspected Running-Related Stress Fractures

Order an MRI of the specific anatomic area of interest (e.g., "MRI bilateral lower legs without contrast" or "MRI left foot without contrast") - contrast is not needed and provides no additional diagnostic value for stress fractures. 1

Specific Ordering Details

What to Write on the Order:

• Imaging modality: MRI without IV contrast

• Anatomic area: Be specific about the location based on clinical examination findings:

  • "MRI bilateral lower legs (tibia/fibula) without contrast" for shin pain
  • "MRI left foot without contrast" for foot pain
  • "MRI bilateral feet without contrast" if bilateral symptoms
  • "MRI pelvis without contrast" for hip/pelvic pain
  • "MRI left knee without contrast" for knee pain

• Clinical indication: "Rule out stress fracture in runner with [location] pain"

• Clinical history: Include relevant details such as:

  • Recent increase in training intensity or mileage
  • Duration of symptoms
  • Point tenderness on examination
  • Negative or indeterminate radiographs (if already obtained)

Why MRI Without Contrast is the Correct Choice:

MRI without contrast is the gold standard imaging modality after negative radiographs, with sensitivity ranging from 68-99% and specificity from 4-97%. 1, 2 The 2024 ACR Appropriateness Criteria explicitly state that MRI with contrast (either with or without pre-contrast sequences) provides no additional diagnostic information for stress injuries and should not be ordered. 1

MRI demonstrates stress fractures through:

• Linear T1 and T2 hypointense signal representing fracture lines
• T1 hypointense and T2 hyperintense signal in surrounding bone marrow representing edema
• Detection as early as bone scintigraphy but with superior specificity 1

Clinical Algorithm for Imaging Stress Fractures:

1. Initial imaging: Plain radiographs of the affected area

   • Sensitivity only 12-56%, but inexpensive and may show periosteal reaction or fracture line 2
   • Often negative initially, especially in early stages 3

2. If radiographs negative but clinical suspicion remains high:

   • Proceed directly to MRI without contrast 1
   • Do NOT wait 10-14 days for repeat radiographs in high-risk scenarios or when urgent diagnosis needed 1
   • Do NOT order bone scan - while sensitive (50-97%), it has lower specificity (33-98%), involves ionizing radiation, and cross-sectional imaging should supersede scintigraphy 1, 2

3. If MRI equivocal: CT without contrast may serve as adjunctive imaging, though it has lower sensitivity than MRI (32-38%) 1, 2

Common Pitfalls to Avoid:

• Don't order MRI with contrast - this wastes time, money, and exposes patients to unnecessary gadolinium without improving diagnostic accuracy 1
• Don't order "MRI legs" generically - be anatomically specific based on your physical exam to avoid imaging the wrong area or requiring repeat studies
• Don't delay MRI waiting for repeat radiographs in athletes who need rapid return-to-play decisions or in high-risk fracture locations (navicular, femoral neck, anterior tibial cortex) 1, 3
• Don't confuse stress fractures with medial tibial stress syndrome (shin splints) - the latter shows diffuse tenderness along the posteromedial tibial shaft without focal edema, while stress fractures show localized tenderness 3, 4

High-Risk vs Low-Risk Locations:

Understanding fracture location helps determine urgency:

• High-risk locations (prone to nonunion, may need surgery): femoral neck, anterior tibial cortex, tarsal navicular, talus, fifth metatarsal base, hallucal sesamoids 5
• Low-risk locations (usually heal with conservative management): calcaneus, cuboid, cuneiforms, most metatarsal shaft fractures 5

For high-risk locations, expedite MRI imaging and consider early orthopedic consultation. 5