Updated: 7/29/2021

Hip Dislocation

Review Topic
  • Snapshot
    • 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.
  • Introduction
    • 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)
  • Presentation
    • 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
  • Imaging
    • 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
  • Differential
    • Femoral neck fracture
      • hip will remain in acetabulum on AP pelvis radiograph
    • Acetabular fracture
      • hip will remain in acetabulum on AP pelvis radiograph
  • Treatment
    • 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
  • Complications
    • Avascular necrosis of femoral head
    • Sciatic nerve injury
    • Post-traumatic osteoarthritis
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