Updated: 7/29/2021

Hip Dislocation

Review Topic
  • A 27-year-old woman presents to the emergency room with severe hip pain after being a passenger in a head-on motor vehicle accident. On physical exam, she has significant pain and deformity in her left hip. Her left hip is adducted, flexed, and internally rotated.
  • Clinical definition
    • condition in which the femoral head is pushed out of the acetabulum
      • in adults, almost always occurs in the setting of significant trauma
  • Epidemiology
    • incidence
      • rare injury
      • most common mechanism of injury is motor vehicle accident
      • 90% of dislocations are posterior
      • 10% of dislocations are anterior
    • demographics
      • 4:1 male-to-female ratio
      • most commonly affects adolescents and adults aged 16-40
    • risk factors
      • significant trauma
  • Etiology
    • traumatic
    • developmental
      • developmental dysplasia of the hip
    • neuromuscular
      • cerebral palsy
  • Pathoanatomy
    • normal anatomy
      • hip joint is inherently stable due to
        • bony ball-and-socket architecture
        • soft tissue constraints
          • labrum, joint capsule, and hip musculature
      • significant trauma is therefore required to overcome the inherent stability of the joint
    • mechanism
      • axial loading on adducted femur predisposes to posterior dislocation
        • dashboard injury
      • axial loading on abducted and externally rotated femur predisposes to anterior dislocation
  • Associated conditions
    • 95% incidence of concomitant injuries to other areas of the body
      • acetabular and femoral head or neck fractures
      • knee ligamentous and meniscal injuries
      • closed head injuries
  • Prognosis
    • favorable
      • anterior dislocations 
      • simple dislocations (no associated fractures)
  • Symptoms
    • severe pain and immobilty in the affected hip
    • may also complain of lower back, thigh, knee, or lower leg pain
  • Physical exam
    • hip position
      • posterior dislocation
        • hip will be flexed, adducted, and internally rotated 
      • anterior dislocation
        • hip will be flexed, abducted, and externally rotated
    • pain with passive or active movement
    • thorough head-to-toe examination following Advanced Trauma Life Support (ATLS) protocols must be performed given high incidence of concomitant head and extremity injuries
  • Radiographs
    • indication
      • anteroposterior (AP) pelvis radiograph always indicated when hip dislocation is suspected
    • finding
      • posterior hip dislocation
        • femoral head smaller than contralateral side and superior to acetabulum
        • femur appears adducted
        • internal rotation of femur noted as lesser trochanter will be poorly visualized
      • anterior hip dislocation
        • femoral head appears larger than contralateral side and inferior to acetabulum
        • femur appears abducted
        • external rotation of femur noted as lesser trochanter will be in full profile
  • Computerized tomography (CT) scan
    • indication
      • high suspicion for associated fractures
    • finding
      • associated fractures to acetabulum, femoral head, and femoral neck
  • Femoral neck fracture
    • hip will remain in acetabulum on AP pelvis radiograph
  • Acetabular fracture
    • hip will remain in acetabulum on AP pelvis radiograph
  • Conservative
    • closed reduction under conscious sedation
      • indication
        • closed reduction should be attempted in all traumatically dislocated hips 
  • Operative
    • open reduction 
      • indication
        • failure of closed reduction
  • Avascular necrosis of femoral head
  • Sciatic nerve injury
  • Post-traumatic osteoarthritis

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