Updated: 12/19/2017

Hip Dislocation

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Snapshot
  • A 31-year-old woman presents to the emergency room with severe left hip pain. She was sitting in the passenger seat of a car when the car was hit head-on by another vehicle. On physical exam, she has significant pain and deformity in her left hip. She is unable to move her hip or bear weight. She is neurovascularly intact distally. 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, groin, thigh, knee, or leg pain
  • Physical exam
    • hip position
      • posterior dislocation
        • hip will be adducted, flexed, and internally rotated
      • anterior dislocation
        • hip will be abducted, flexed, and externally rotated
    • pain with passive or active movement
    • 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
    • indications
      • anteroposterior (AP) pelvis radigraph always indicated when hip dislocation is suspected
      • post-reduction Judet views may be indicated if acetabular fracture 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
      • suspicion for associated injuries
    • finding
      • associated fractures to acetabulum, femoral head, and femoral neck
Differential
  • Femoral neck fracture
    • hip will remain in acetabulum on AP pelvis radiograph in an isolated femoral neck fracture
  • Acetabular fracture
    • hip will remain in acetabulum on AP pelvis radiograph in most isolated acetabular fractures
Treatment
  • Conservative
    • closed reduction under conscious sedation
      • indication
        • closed reduction should be attempted in all traumatically dislocated hips 
      • contraindication
        • ipsilateral femoral neck fracture
  • Operative
    • open reduction 
      • indications
        • failure of closed reduction
        • radiographic evidence of incarcerated intra-articular fragments
Complications
  • Avascular necrosis of femoral head
  • Sciatic nerve injury
  • Post-traumatic osteoarthritis
 

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