What tests can determine if a fracture is old or new?

Tests to Determine if a Fracture is Old or New

Radiographic imaging remains the primary method for determining fracture age, supplemented by bone scans, CT, and MRI when necessary, with fractures generally considered "old" after 3 weeks.

Primary Diagnostic Methods

Radiography (X-rays)

• First-line imaging modality for fracture age determination
• Key radiographic findings by fracture age:
  • New/acute fractures: Sharp fracture lines, absence of callus formation, minimal displacement
  • Healing fractures (1-3 weeks): Early callus formation, blurring of fracture edges
  • Old fractures (>3 weeks): Visible callus formation, remodeling, sclerotic edges 1

Bone Scintigraphy (Nuclear Medicine)

• Highly sensitive for detecting radiographically occult fractures
• Particularly useful for:
  • Rib fractures, scapular fractures, spinal fractures, and pelvic fractures 2
  • Cases where immediate determination is needed (cannot wait 2 weeks for follow-up X-rays)
• Shows increased uptake at fracture sites within 24-72 hours of injury
• Note: In older osteopenic individuals, it may take 48-72 hours for increased radionuclide activity to develop at fracture sites 2

Advanced Imaging Techniques

Computed Tomography (CT)

• Superior for detecting:
  • Radiographically occult fractures 2
  • Anterior and posterior rib fractures (more sensitive than X-rays) 2
  • Fracture dating (acute, subacute, or chronic) 2
• Low-dose CT protocols can be used to minimize radiation exposure

Magnetic Resonance Imaging (MRI)

• Excellent for detecting occult fractures when metal artifact reduction techniques are used 2
• Particularly useful for:
  • Vertebral fractures
  • Stress fractures
  • Fractures in areas with complex anatomy
• Can show bone marrow edema in acute fractures, which diminishes over time

Ultrasonography

• Emerging tool for fracture detection, especially in pediatric patients
• Can identify:
  • Cortical discontinuity (direct sign of fracture) - visible in 92% of cases 3
  • Step-off deformities, tiny avulsed bone fragments, double-line appearance of cortical margins 3
  • Particularly useful in pediatric patients with immature bones

Clinical Context and Timing

Fracture Age Classification

• Fresh fracture: Generally considered less than 3 weeks old 1
• Old fracture: Generally refers to fractures more than 3 weeks old 1
• Note: Different bones may have different timelines for healing:
  • Metatarsal: Considered "fresh" until week 7
  • Ankle: Considered "fresh" until week 9
  • Humerus: Considered "fresh" until week 10
  • Femur and radius: Considered "fresh" until week 12 4

Clinical Assessment

• History of trauma (timing, mechanism)
• Physical examination findings:
  • Acute fractures: Localized tenderness, swelling, ecchymosis
  • Older fractures: Less tenderness, reduced swelling, healing ecchymosis
• Risk factors for fracture (e.g., osteoporosis, corticosteroid use, older age) 2

Pitfalls and Caveats

1. Bone-specific variation: Different bones heal at different rates, affecting the definition of "old" vs "new" 4

2. Patient factors affecting healing:

   • Age (younger patients heal faster)
   • Body mass index
   • Open vs. closed fracture 4
   • Comorbidities (diabetes, peripheral vascular disease)
   • Medications (steroids, bisphosphonates)

3. Radiographic limitations:

   • It is not possible to exactly date fractures by radiography alone 2
   • Some fractures may be radiographically occult initially
   • Follow-up imaging 10-14 days after initial assessment may reveal previously undetected fractures

4. Diagnostic accuracy considerations:

   • Physical examination alone has limited sensitivity (15-100%) and specificity (13-98%) for fracture detection 5
   • Combined imaging approaches may be necessary for definitive dating

Remember that determining fracture age is important for both clinical management and in cases where timing may have medicolegal implications, such as suspected physical abuse in children.