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Updated: Mar 25 2022

Traumatic Hip Dislocation - Pediatric

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https://upload.orthobullets.com/topic/4017/images/hip_disloc_xr_3_yo.jpg
https://upload.orthobullets.com/topic/4017/images/nonconcentric.jpg
https://upload.orthobullets.com/topic/4017/images/osteochondral_fragment.jpg
  • summary
    • Traumatic Hip Dislocations in the pediatric population are usually posterior and may occur due to low energy sports injuries in children less than 10 years of age and high energy trauma in children greater than 10.
    • Diagnosis is made with plain radiographs. CT or MRI studies are indicated post-reduction to assess for joint congruity and articular injuries. 
    • Treatment is urgent closed reduction under general anesthesia or sedation. Open reduction may be required if there is an intraarticular fragment following reduction.
  • Epidemiology
    • Anatomic location
      • 80% are traumatic posterior dislocations
      • more common than hip fracture in pediatric patients
  • Etiology
    • 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 conditions
      • fractures
        • acetabular fractures
          • lower incidence of acetabular fractures compared with adults
          • due to cartilaginous acetabulum and ligamentous laxity
          • posterior wall fractures are most common
        • femoral head fracture
        • femoral neck fracture
        • proximal femoral physis
      • avascular necrosis of femoral head
        • increased rate if not reduced within 6 hours
  • 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
      • inferior dislocation
        • External rotation and extension
      • neurovascular exam
        • check for sciatic or gluteal nerve palsy (rare)
  • Imaging
    • Radiographs
      • recommended views
        • AP
          • most can be diagnosed on AP pelvis films
        • lateral
          • used to differentiate between anterior vs. posterior dislocation
          • scrutinize femoral neck to rule out fracture prior to attempting closed reduction
        • post reduction films
          • necessary to inspect for joint incongruity or nonconcentric reduction
      • findings
        • loss of congruence of femoral head with acetabulum
    • CT
      • indications
        • second choice behind MRI for any abnormal findings on post-reduction radiographs such as joint widening
          • radiation exposure should be considered
      • 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
    • MRI
      • indications
        • study of choice for any abnormal findings on post-reduction radiographs such as joint widening
          • decreased radiation exposure than a CT scan
      • 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 is best evaluated with MRI
        • entrapped labrum or capsule is best evaluated via MRI
  • Treatment
    • Nonoperative
      • closed reduction under general anesthesia or sedation within 6 hours
        • indications
          • urgent attempt at closed reduction is first line treatment
          • most are successful reduced with closed means (85%)
        • outcomes
          • increased risk of AVN if not performed within 6 hours
    • Operative
      • open reduction
        • indications
          • nonconcentric reduction
          • intra-articular fragment
          • unstable acetabular rim fracture, associated femoral head or neck 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 due to possibility of epiphyseolysis
        • mainly traction in flexion with gentle rotation maneuver
      • 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 years old or bracing in older children with 6-12 weeks protected weight-bearing on crutches
  • Complications
    • Osteonecrosis
      • reported in 3-15%
      • decreased incidence under age 5
      • 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 with capsulorrhaphy
    • Nerve injury
      • sciatic or gluteal nerve injury can occur, usually resolves after reduction
  • Prognosis
    • Typically associated with good long-term outcomes when treated promptly
      • most have mild or no pain
      • most return to high-demand activities
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