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Introduction
  • Epidemiology
    • incidence
      • uncommon, only 1-2% of all pediatric fractures
      • acetabular fractures only 1-15% of pediatric pelvic fractures
    • demographics
      • avulsion injuries almost exclusively in adolescent patients
  • Pathophysiology
    • mechanism of injury
      • pelvic ring injuries
        • high energy trauma
          • automobile accidents
          • motor vehicle-pedestrian injury
      • apophyseal avulsions
        • low energy trauma (apophyseal avulsions)
    • pathophysiology
      • apophyseal avulsion
        • avulsion injury occurs from the disruption of tendon origin on the pelvis during "explosive" type activities (ie. jumping, sprinting)
    • pathoanatomy
      • apophyseal avulsion  
        • ischial avulsion (54%)
          • hamstrings and adductors   
        • AIIS avulsion (22%)
          • rectus femoris   
        • ASIS avulsion (19%)
          • sartorius 
        • pubic symphysis (3%)
          • abdominal muscles
        • iliac crest (1%)
          • abdominal muscles
        • lesser trochanter
          • iliopsoas
      • pelvic ring
        • differs from adult pelvic ring injuries
          • higher incidence of lateral compression injuries than adults, who are more commonly AP compression injuries
          • higher rate of single-bone pelvic ring fractures 
            • increased bony elasticity
            • cartilage able to absorb more energy 
            • SI joint/symphysis pubis more elastic
            • thick periosteum
            • apparent dislocations (symphyseal, SI) may have a periosteal tube that heals like a fracture
          • lower rate of hemorrhage secondary to
            • smaller vessels, which are more capable of vasoconstriction
            • injuries less commonly increase pelvic volume
      • acetabular fractures 
        • more common after triradiate closure
        • differs from adult
          • triradiate cartilage injury may cause growth arrest and lead to deformity
          • fractures into triradiate cartilage occur with less force than adult acetabular fractures
          • transverse fracture pattern more common than both column
  • Associated conditions
    • CNS and abdominal visceral injury
      • high rate (> 50%) in traumatic pelvic injuries
        • presumed secondary to the higher energy required to create a fracture in a more elastic pelvis
    • femoral head fractures/dislocations
      • associated with acetabular fractures 
    • GU injury
      • increased rate with Torode Type IV fractures
    • life-threatening hemorrhage
  • Prognosis
    • complications are rare 
    • need for operative intervention increases after the closure of triradiate cartilage
Anatomy
  • Osteology
    • pelvis undergoes endochondral ossification (like long bones) at 3 primary ossification centers  
      • ilium
        • appears at 9 weeks
      • ischium 
        • appears at 16 weeks
      • pubis 
        • appears at 20 weeks
      • all meet and fuse at 12 in girls and 14 in boys
    • acetabular growth
      • enlargement is a result of interstitial growth within the triradiate cartilage
      • concavity is a response to pressure from the femoral head 
      • depth of acetabulum results from
        • interstitial growth in acetabular cartilage
        • appositional growth in the periphery of cartilage
        • periosteal new bone formation at acetabular margin
      • 3 secondary ossification centers of the acetabulum appear at 8-9 and fuse at 17-18  
        • os acetabuli (OA)
          • forms the anterior wall
        • acetabular epiphysis (AE)
          • forms superior acetabulum
        • secondary ossification center of ischium (SCI)
          • forms the posterior wall
      • other secondary ossification centers (of the pelvis)
        • iliac crest 
          • appears at 13-15
          • fuses at 15-17
          • used in Risser sign
        • ischial apophysis
          • appears at 15-17
          • fuses at 19-25
        • anterior inferior iliac spine
          • appears at 14
          • fuses at 16
        • pubic tubercle
        • angle of the pubis
        • ischial spine
        • lateral wing of the sacrum
Classification
 
 Tile Classification 
Type A  • Stable injuries (rotationally & vertically)
 
Type B  • Rotationally unstable
 • Vertically stable

Type C  • Unstable rotationally & vertically
 
Torode/Zieg Classification (pediatric pelvic ring)
Type I  • Avulsion injuries
 
Type II  • Fractures of the iliac wing

Type III  • Fractures of the ring with no segmental instability
Type IV  • Fracture of the ring with segmental instability
 
Bucholz Classification (pediatric acetabulum)
Shearing 

 • Salter Harris I or II

Blow to pubis/ischial ramus/proximal femur leads to injury at interface of 2 superior arms of triradiate cartilage and metaphyses of ilium.

A triangular medial metaphyseal fragment (Thurston-Holland fragment) is often seen in SH II injuries.

  
Crushing/Impaction

 • Salter Harris V

Difficult to see on initial radiographs. May detect narrowing of triradiate space. Leads to premature triradiate cartilage closure. The earlier the closure, the greater the eventual deformity. 


 
Presentation
  • History 
    • pelvic ring fractures often occur secondary to motor vehicle accidents or when a pedestrian is struck by a motor vehicle
    • pelvic avulsion injuries often occur during sporting activities such as sprinting, jumping or kicking
  • Symptoms
    • pain
    • inability to bear weight
    • hemodynamic instability
  • Physical exam
    • primary exam
      • as in all trauma patients, initial evaluation should include ABC's followed by primary and secondary surveys
    • inspection
      • important to thoroughly complete a rectal/genitourinary evaluation in polytrauma patient to rule out open injury
      • log roll to inspect for soft-tissue contusions and ecchymosis
    • palpation
      • ASIS, iliac crests, SI joints, and pubic symphysis
    • provocative tests
      • posteriorly directed pressure on the iliac crests produces pain at the fracture site
      • compressing pelvic ring at iliac crests causes pain
      • excessive mobility indicative of a serious pelvic injury
Imaging
  • Radiographs 
    • recommended views
      • AP pelvis
      • Judet views (45 degree internal and external oblique views, to better evaluate the acetabulum)
      • inlet/outlet views (35 degree caudal and cranial tilt views, to better evaluate the integrity of the pelvic ring)
    • sensitivity
      • plain radiographs will miss ~50% of all pediatric pelvic fractures
  • CT 
    • indications
      • negative plain films with increased suspicion
      • when tenderness is present over the SI joints
      • preoperative planning
      • concomitant spine injury
    • findings
      • can delineate complicated fracture patterns
  • MRI
    • indications
      • occasionally required to detect apophyseal avulsion injuries
  • Bone scan
    • indications
      • may be used for evaluating occult fractures or avulsion injuries
Treatment
  • Nonoperative
    • protected weight bearing followed by therapy
      • indications
        • pelvic ring
          • dislocations of symphysis and SI joint have a potential for periosteal healing
          • Type I Avulsion Injuries with < 2 cm displacement
          • Type II Iliac Wing Fractures with < 2 cm displacement
          • Type III pelvic ring fractures without segmental instability
        • acetabulum
          • minimally displaced fractures as these are relatively stable
          • need close follow-up until skeletal maturity to detect premature triradiate closure
      • technique
        • for types I and II
          • protected weight bearing for 2-4 weeks
          • stretching and strengthening 4-8 weeks
          • return to sport and activity after 8 weeks when asymptomatic
        • type III
          • weight bearing as tolerated for 6 weeks
    • bedrest
      • indications
        • Type IV pelvic ring with instability AND < 2 cm pelvic ring displacement 
  • Operative
    • ORIF
      • indications
        • pelvic ring
          • type I avulsion injuries with > 2-3 cm displacement
          • type II iliac wing fractures with > 2-3 cm displacement
          • type III pelvic ring with displaced acetabular fractures > 2mm
          • type IV pelvic ring with instability and > 2 cm pelvic ring displacement
        • acetabulum
          • comminuted acetabular fracture when traction does not improve the position of fragments
          • joint displacement >2mm
          • joint incongruity 
          • intra-articular fragments
          • joint instability (persistent medial subluxation or posterior subluxation)
          • central fracture dislocation
          • open fractures
    • External fixation
      • indications
        • hemodynamic instability
        • increased pelvic volume
    • Pelvic arteriography
      • indications
        • continued hemodynamic instability
        • evidence of pelvic hemorrhage
Techniques
  • ORIF
    • approach
      • ilioinguinal approach
      • stoppa approach
    • instrumentation
      • physeal sparing when possible
      • when not possible, smooth pins across physis (especially triradiate) x 4-6 weeks with early removal   
      • anterior pubic symphysis plating
      • percutaneous SI screw fixation
    • complications specific to treatment
      • early triradiate closure
    • outcomes
      • older children and adolescents with unstable ring fractures may have an improved outcome with internal fixation

Complications
  • Death
    • rare
    • most often occur in association with head or visceral injury
  • Pelvic fracture-associated hemorrhage
    • rare
    • see above under death
  • Physeal cartilage injury
    • progressive acetabular dysplasia with thickening of the medial acetabular wall giving rise to shallow acetabulum (lateral hip subluxation)
    • hypoplastic hemipelvis
    • premature closure of triradiate cartilage/growth arrest (<5%)  
    • risk factors
      • < 10 old at time of injury
        • as the growth potential of the physis decreases with age, the younger the patient is at the time of injury, the more severe the growth disturbance will be
      • Bucholz crushing type (SH V)
    • treatment
      • reconstruction with physeal bar excision  
      • premature triradiate closure can still occur in spite of bar excision
      • late reconstruction with pelvic osteotomy  
  • Leg length discrepancy
    • risk factors
      • unstable fracture when vertical displacement of the hemipelvis is >2 cm
  • Malunion/nonunion
    • incidence
      • rare
    • treatment
      • malunion well tolerated due to increased remodeling potential of young children
  • Neurovascular injury
  • Heterotopic ossification 
  • Osteonecrosis of the femoral head
    • risk factors
      • acetabular fractures and hip dislocation
  • Degenerative joint disease of the hip
    • risk factors
      • patients with displaced acetabular fractures
 
other secondary ossification centers (of the pelvis)
  • do not confuse with avulsion fractures
  • iliac crest 
    • appears at 13-15y, fuses at 15-17y
    • used in Risser sign
  • ischial apophysis
    • appears at 15-17y, fuses at 19-25y
  • anterior inferior iliac spine
    • appears at 14y, fuses at 16y
  • pubic tubercle
  • angle of pubis
  • ischial spine
  • lateral wing of sacrum
 

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