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Introduction
  •  Epidemiology
    • location
      • 80% are traumatic posterior dislocations
      • more common than hip fracture
  • Pathophysiology
    • mechanism of injury
      • age <10
        • may have low energy sports injury, or trip and fall
      • age >10
        • mostly high energy (e.g. MVA)
  • Associated injuries
    • femoral head, proximal femur physis, or femoral neck fracture 
    • acetabular fractures
      • lesser incidence of acetabular fractures compared with adults
      • due to cartilaginous acetabulum and ligamentous laxity
  • Prognosis
    • typically associated with good long-term outcomes when treated promptly
      • most have mild or no pain
      • most return to high-demand activities
Presentation
  • Symptoms
    • pain, inability to bear weight
  • Physical exam
    • posterior dislocation (most common)
      • slight flexion, adduction, and internal rotation of the limb
      • clinical limb length discrepancy
      • if large posterior wall acetabular fracture, can appear shortened without malalignment
    • anterior dislocation
      • slight flexion, abduction, and external rotation
    • neurovascular exam
      • check for sciatic or gluteal nerve palsy (rare)
Imaging
  • Radiographs
    • recommended views
      • ap and lateral
        • most can be diagnosed on AP pelvis films   
        • lateral hip radiographs will confirm anterior vs posterior dislocation
      • post reduction films
        • necessary to inspect for joint incongruity or nonconcentric reduction   
  • post reduction CT or MRI
    • indications
      • any abnormal findings on post reduction radiographs such as joint widening 
    • findings
      • inspect for joint incongruity or nonconcentric reduction
      • osteochondral fragments can be seen in older children and are easily detected by CT 
      • interposed soft-tissue can be difficult to appreciate on CT scan  
      • entrapped labrum or capsule is best evaluated via MRI  
Treatment
  • Nonoperative
    • closed reduction under general anesthesia 
      • indications
        • urgent attempt at closed reduction is first line treatment
        • most are successful reduced with closed means (85%)
  • Operative
    • open reduction
      • indications
        • nonconcentric reduction 
        • intra-articular fragment
        • unstable acetabular rim fracture
        • irreducible by closed means
      • technique
        • surgical approach is typically performed in direction of dislocation (most commonly posterior) 
Techniques
  • Closed reduction technique
    • reduction
      • adequate anesthesia or sedation during reduction is mandatory in order to decrease the risk of displacing an unrecognized fracture of the proximal femoral epiphysis 
      • reduction under fluoroscopy has been recommended to decrease risk of displacement
    • post-reduction
      • test hip stability before weaning sedation
      • obtain post-reduction imaging
      • some advocate spica cast or bed rest with abduction splint for 4 weeks in patients < 10 yo or bracing in older children with 6-12 weeks protected weight-bearing on crutches
Complications
  • Osteonecrosis
    • reported in 3-15%
    • less frequent than in adults if there is an absence of an associated femoral neck fracture
    • if present, thought to be related to delayed reduction  
  • Coxa magna
    • common radiographic finding (20%)
    • not associated with functional limitation
  • Redislocation
    • rare sequela
    • treatment
      • prolonged immobilization
      • if recurrent and recalcitrant to immobilization: address withcapsulorrhaphy
  • Nerve injury
    • sciatic or gluteal nerve injury can occur, usually resolves after reduction
 

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