What is the best diagnostic evaluation for hip pain in an 81-year-old after a mechanical fall with limited range of motion and atrophy (osteopenia) on x-ray?

Best Diagnostic Evaluation for Hip Pain in an 81-Year-Old After a Fall

For an 81-year-old with right knee pain, limited hip range of motion, and osteopenia on X-ray after a mechanical fall with negative X-ray for fracture, MRI of the hip without contrast is the recommended next diagnostic evaluation. 1, 2

Diagnostic Algorithm

1. Initial Assessment: X-rays have already been performed showing osteopenia but no fracture

2. Next Step - Advanced Imaging:

   • MRI without contrast (highest appropriateness rating 9/9) 1
   • If MRI is contraindicated or unavailable:
     • CT scan without contrast (appropriateness rating 5/9) 2, 1

Rationale for MRI

• MRI has superior sensitivity for detecting:

  • Occult hip fractures not visible on plain radiographs
  • Bone marrow edema
  • Soft tissue injuries
  • Transient osteoporosis of the hip (which can occur in elderly patients) 3

• The American College of Radiology specifically recommends MRI as the next imaging study for evaluation of acute hip pain from a fall with negative radiographs when fracture is suspected 2

• MRI can detect fractures immediately after injury, unlike bone scans which may be falsely negative for up to 72 hours 2

Important Clinical Considerations

• In elderly patients after falls, occult hip fractures are common despite negative X-rays

• Limited range of motion due to pain suggests possible intra-articular pathology that requires further evaluation 4

• The presence of osteopenia increases fracture risk, making occult fracture detection crucial

• Weight-bearing should be limited until definitive diagnosis is established to prevent displacement of potential occult fractures 1

CT as an Alternative

• If MRI is contraindicated (pacemaker, claustrophobia, etc.) or unavailable, CT without contrast is the recommended alternative 2, 1

• CT has lower sensitivity (79-94%) compared to MRI for detecting occult fractures but is superior to plain radiographs 1

Common Pitfalls to Avoid

1. Relying solely on X-rays: Radiographs have limited sensitivity for detecting occult hip fractures in elderly patients with osteopenia

2. Delaying advanced imaging: Prompt diagnosis of occult fractures is essential to prevent displacement and complications

3. Using bone scans as first alternative: These have largely been replaced by CT when MRI is contraindicated due to the delay in obtaining results and lower specificity 2

4. Overlooking transient osteoporosis: This condition can present with hip pain and limited range of motion, particularly in patients with osteopenia, and is best detected on MRI 3

The diagnostic approach should be expedited in elderly patients after falls to prevent complications and allow for appropriate treatment planning.