What is the workup for a subluxation of the right hip?

Workup for Subluxation of the Right Hip

The appropriate workup for hip subluxation should include radiographic imaging, with plain radiographs (X-rays) of the pelvis and bilateral hips as the first-line imaging modality, followed by advanced imaging such as MRI if initial radiographs are negative but clinical suspicion remains high. 1

Initial Assessment

Clinical Evaluation

• Assess for pain location (typically groin pain)
• Check for pain with internal and external rotation of the hip
• Evaluate for limb length discrepancy
• Look for asymmetric skin folds (in pediatric patients)
• Assess gait pattern (limping or toe-walking on affected side)
• Document risk factors:
  • History of trauma/falls
  • Previous hip pathology
  • Developmental dysplasia of the hip (DDH) history
  • Family history of hip disorders

Imaging Algorithm

1. Plain Radiographs (First-Line)

   • Anteroposterior (AP) view of pelvis
   • Lateral view of affected hip
   • Frog-leg view to assess reduction if neutral view is abnormal
   • Von Rosen view (legs at 45° angle with abduction and internal rotation) may help visualize subluxation not apparent on routine views 1

2. Advanced Imaging (If radiographs are negative but clinical suspicion remains high)

   • MRI: Most sensitive for detecting occult fractures, labral tears, and soft tissue injuries associated with subluxation 1
   • Consider MRI promptly if initial radiographs are negative but symptoms persist or worsen over 2-3 days 1

Age-Specific Considerations

For Pediatric Patients

• For infants <4 months: Ultrasound is the preferred imaging modality 1

  • Should be performed after 2 weeks of age (earlier ultrasounds may show physiologic laxity)
  • Evaluates femoral head position, acetabular morphology, and stability

• For children >4 months: Plain radiographs become the primary imaging tool 1

  • Assess ossification of femoral head nucleus (typically appears around 4 months)
  • Evaluate acetabular index and femoral head relationship to acetabulum

For Adult Patients

• Plain radiographs remain first-line
• MRI is valuable for evaluating:
  • Labral tears (present in 100% of traumatic dislocations/subluxations) 2
  • Chondral injuries (present in 92% of cases) 2
  • Ligamentum teres tears (present in 84% of cases) 2
  • Early signs of avascular necrosis

Common Pitfalls and Caveats

1. Missing subtle subluxation:

   • Initial radiographs may appear normal despite subluxation
   • Clinical symptoms that persist despite negative radiographs warrant advanced imaging 1

2. Delayed diagnosis:

   • Untreated subluxation can lead to early degenerative joint disease and impaired function 1
   • Late diagnosis increases risk for complications and often requires surgical correction 3

3. Inadequate follow-up:

   • For traumatic subluxation, follow-up imaging is essential to detect avascular necrosis
   • MRI at 4-6 weeks post-injury is recommended to evaluate for osteonecrosis 2

4. Overlooking underlying conditions:

   • Developmental dysplasia in children
   • Neuromuscular disorders (e.g., cerebral palsy) that may predispose to hip instability 4

By following this systematic approach to the workup of hip subluxation, clinicians can ensure timely diagnosis and appropriate management to prevent long-term complications such as degenerative joint disease and functional impairment.