What imaging and referral are recommended for a 57-year-old female with recurrent hip instability?

Imaging and Referral for Hip Instability in a 57-Year-Old Female

For a 57-year-old female with recurrent hip instability ("hip keeps giving out"), radiographs of the pelvis and hip should be the first imaging study, followed by MRI of the hip without IV contrast if radiographs are negative or equivocal, and referral to an orthopedic specialist is recommended. 1

Initial Imaging Approach

First-line Imaging:

• Plain radiographs of the pelvis and hip are the essential first step 1
  • Anteroposterior (AP) view of the pelvis
  • Lateral view of the symptomatic hip (frog-leg lateral)
  • These views provide assessment of bone structure, joint space, and potential arthritis 1, 2

Second-line Imaging (if radiographs are negative/equivocal):

• MRI of the hip without IV contrast is the most appropriate next step 1
  • Rated 9/9 (highest appropriateness) by ACR guidelines for evaluating soft tissue abnormalities after negative radiographs 1
  • Highly sensitive for detecting:
    • Soft tissue injuries that may cause instability
    • Tendon pathology (abductor tendinosis/tears)
    • Labral tears
    • Ligamentous injuries
    • Early arthritic changes not visible on radiographs 1, 3

Referral Recommendations

• Orthopedic specialist referral is indicated for patients with hip instability 4
  • Specifically to an orthopedic surgeon with expertise in hip disorders
  • Timing: Should occur after initial imaging but can be expedited if radiographs show significant abnormalities

Clinical Considerations for Hip Instability

Diagnostic Algorithm:

1. Radiographs first to rule out fracture, arthritis, and bony abnormalities 1
2. If radiographs negative but symptoms persist → MRI hip without contrast 1
3. If labral tear or impingement is suspected → Consider MR arthrography (highest sensitivity for labral pathology) 1, 3
4. If instability continues despite normal imaging → Consider referral for dynamic assessment by an orthopedic specialist 4

Common Causes of Hip Instability in Middle-Aged Women:

• Abductor tendon tears/tendinosis
• Labral tears
• Femoroacetabular impingement
• Early osteoarthritis
• Ligamentous laxity
• Neuromuscular disorders affecting hip stability 1, 4

Important Caveats

• Imaging should never be used in isolation but combined with clinical signs and symptoms 1
• Occult hip fractures may be present despite normal radiographs in patients with persistent symptoms - MRI is the test of choice in these cases 5, 3
• "Giving out" sensation may represent referred pain from spine or other sources - consider expanded imaging if hip studies are normal 1
• Ultrasound may be considered as an alternative or adjunct (rated 7/9 for appropriateness) for evaluating soft tissue structures if MRI is contraindicated 1

By following this evidence-based approach to imaging and referral, you can effectively diagnose the cause of hip instability in this 57-year-old female patient and ensure appropriate treatment to improve her mobility, reduce pain, and enhance quality of life.