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Introduction
  • Epidemiology
    • incidence
      • uncommon, only 1-2% of all pediatric fractures
    • demographics
      • avulsion injuries almost exclusively in adolescent patients
  • Pathophysiology
    • apophyseal avulsion  
      • result of low energy trauma
      • avulsion injury occur from the disruption of tendon origin on the pelvis during "explosive" type activities (ie. jumping, sprinting)
        • ischial avulsion (54%) = hamstrings and adductors   
        • AIIS avulsion (22%) = rectus femoris   
        • ASIS avulsion (19%) = sartorius 
        • pubic symphysis (3%)
        • iliac crest (1%) = abdominal muscles
        • lesser trochanter = iliopsoas
    • pelvic ring
      • result of high energy trauma
        • often result from pedestrian vs MVA or rear seat passenger MVA
        • although rare, can be open
      • differences from adult pelvic ring injuries
        • higher incidence of lateral compression injuries than adults, who are more commonly AP compression injuries
        • differences from adults
          • higher rate of single pelvic ring break (rather than complete ring) 
          • increased bony plasticity
          • cartilage able to absorb more energy 
          • SI joint/symphysis pubis more elastic
          • thick periosteum
            • apparent dislocations (symphyseal, SI) may have periosteal tube that heals like fracture
        • lower rate of hemmorhage secondary to
          • smaller vessels, which are more capable of vasoconstriction
          • injuries less commonly increase pelvic volume than in adult
    • acetabular fractures 
      • only 1-15% of pelvis fractures
      • more common after triradiate closure
      • differences from adult
        • triradiate cartilage injury can 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
      • classified using Letournel 
  • Associated conditions
    • CNS and abdominal visceral injury
      • high rate (> 50%) in traumatic pelvic injuries, presumed secondary to higher energy required to create fracture
    • femoral head fractures/dislocations
      • associated with acetabular fractures 
    • GU injury
      • increased rate with Torode Type IV fractures
    • life threatening hemmorhage
  • Prognosis
    • complications are rare 
    • need for operative intervention increases after closure of triradiate carilage
Anatomy
  • Pelvis undergoes endochondral ossification (like long bones) at 3 primary ossification centers  
    • ilium appears at 9 wks
    • ischium appears at 16 wks
    • pubis appears at 20 wks
      • all meet and fuse at 12yr in girls, 14yr in boys
  • Acetabular growth
    • enlargement is a result of interstitial growth within triradiate cartilage
    • concavity is a response to pressure from femoral head 
    • depth of acetabulum results from
      • interstitial growth in acetabular cartilage
      • appositional growth in periphery of cartilage
      • periosteal new bone formation at acetabular margin
  • Puberty
    • 3 secondary ossification centers of the acetabulum appear at 8-9yr and fuse at 17-18yr  
      • os acetabuli (OA, forms anterior wall)
      • acetabular epiphysis (AE, forms superior acetabulum)
      • secondary ossification center of ischium (SCI, forms posterior wall)
    • 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
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 
    • pediatric 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
      • important to thoroughly complete a rectal/genitourinary evaluation in polytrauma patient
Imaging
  • Radiographs 
    • recommended views
      • AP
      • 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 integrity of the pelvic ring)
    • sensitivity
      • plain radiographs will miss ~50% of all pediatric pelvic fractures
  • CT 
    • indications
      • negative plain films with increased suspicion
      • preoperative evaluation
  • MRI
    • indications
      • occasionally required to detect apophyseal avulsion injuries
        • apophyseal avulsion injuries are usually easily detected and adequately imaged with plain radiographs
Treatment
  • Nonoperative
    • protected weight bearing followed by therapy
      • indications
        • pelvic ring
          • dislocations of symphysis and SI joint
            • 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 and non-displaced acetabulum
        • acetabulum
          • few indications for non-op treatment
          • results often poor, especially with comminution, joint incongruity
          • if non-op chosen, needs close followup for 1-2yr to detect premature triradiate closure
      • technique
        • for Type I and II
          • protected weight bearing for 2-4 weeks
          • stretching and strengthening 4-8 weeks
          • return to sport and activity after 8 weeks and 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
      • principles
        • physis sparing where possible
        • where not possible, smooth pins across physis (especially triradiate) x 4-6wks with early removal   
      • indications
        • pelvis
          • 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 position of fragments
          • joint displacement >2mm
          • joint incongruity
          • joint instability (persistent medial subluxation or posterior subluxation)
          • central fracture dislocation
          • intra-articular fragments
          • open fractures
    • External fixator +/- ORIF
      • vertical shear or anterior posterior compression(APC) injury with hemodynamic instability
        • may place binder in trauma bay followed by external fixator
          • alignment of lateral compression fractures will not be improved by binder
Complications
  • Death
    • rare
    • most often occur in association with head or visceral injury
  • Pelvic fracture-associated hemmorhage
    • rare
    • see above under death
  • Physeal cartilage injury
    • premature closure of triradiate cartilage/growth arrest (<5%)  
      • highest risk 
        • <10yr old at injury
        • Bucholz crushing type (SH V)
      • diagnosis
        • high level of suspicion
        • CT scan
      • consequences
        • progressive acetabular dysplasia with thickening of medial acetabular wall giving rise to shallow acetabulum (lateral hip subluxation)
        • hypoplastic hemipelvis
      • treatment
        • early reconstruction with physeal bar excision  
          • premature triradiate closure can still occur in spite of bar excision
        • late reconstruction with pelvic osteotomy  
    • leg length discrepancy
  • Malunion/nonunion
    • rare
    • significant pelvic asymmetry may contribure to scoliosis, lower back pain, Trendelenberg gait, sacroiliac joint tenderness
  • Neurovascular injury
  • Heterotopic ossification 
 

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