Hip dislocation

Background

• Orthopedic emergency; reduction should occur w/in 6hr due to high risk of AVN
• High-energy trauma is primary mechanism

Types

• Posterior
  • 90% of hip dislocations
  • Acetabular fractures may result as well
• Anterior
  • 10% of hip dislocations
  • Can be superior (pelvic) or inferior (obturator)
  • Neurovascular compromise is unusual

Clinical Features

• Posterior Dislocation
  • Extremity is shortened, internally rotated, adducted
  • Often Knee-to-Dashboard
• Anterior Dislocation
  • Extremity is extended (superior) or flexed (inferior), externally rotated, abducted
  • Similar to hip fracture

Differential Diagnosis

Hip pain

Acute Trauma

• Femur fracture
  • Proximal
    • Intracapsular
      • Femoral head fracture
      • Femoral neck fracture
    • Extracapsular
      • Intertrochanteric femur fracture
      • Trochanteric femur fracture
  • Shaft
    • Mid-shaft femur fracture (all subtrochanteric)
• Hip dislocation
• Pelvic fractures
  • Acetabular pelvic fractures
  • Open book pelvic fracture
  • Straddle pelvic fracture
  • Pelvic avulsion fracture

Chronic/Atraumatic

• Hip bursitis
• Psoas abscess
• Piriformis syndrome
• Meralgia paresthetica
• Septic arthritis
  • Septic arthritis of the hip (peds)
• Obturator nerve entrapment
• Avascular necrosis of hip

Diagnosis

• Hip AP and lateral views
  • Posterior Dislocation: AP view femoral head posterior and superior to acetabulum
  • Anterior Dislocation: AP view shows femoral head in obturator foramen (inferior to acetabulum)
• Also consider Judet views or CT to evaluate acetabulum for subtle fractures (esp for posterior dislocation)

Management

• Reduce
  • Posterior
    • Allis Maneuver: supine patient on table: deeper sedation (propofol helps with tissue relaxation); firm distal traction at flexed knee to pull head back into acetabulum; assistant stabilizes pelvis by pushing on ASISs
  • Anterior
    • Reduction: traction, internal rotation, and then external rotation once the femoral hip clears the acetabular rim

Complications

• Post-traumatic arthritis
  • 20% in simple dislocations
  • high in complex dislocations
• Femoral head osteonecrosis
  • 5-40% incidence
  • Delay in treatment >6 hours can lead to avascular necrosis of the femoral head => osteonecrosis
• Sciatic nerve injury
  • 8-20% incidence
  • associated with longer time to reduction
• Recurrent dislocations: <2%

References

• Review of Orthopaedics, 6th Edition, Mark D. Miller MD, Stephen R. Thompson MBBS MEd FRCSC, Jennifer Hart MPAS PA-C ATC, an imprint of Elsevier, Philadelphia, Copyright 2012
• AAOS Comprehensive Orthopaedic Review, Jay R. Leiberman. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2009