We have discussed the potential hazards of being a child on numerous occasions (ex, Injury Prevention, Trampolines, Lawn Mowers, Submersions, Electricity, Firearms), but nothing leads to more injuries than motor vehicles (sometimes, even when they are standing still – Vehicle Hyperthermia). Certainly, the use of a seat belt can save a life; however, if positioned incorrectly, it can also lead to injury. Let us review one such injury- the Pediatric Chance Fracture:

Pediatric Chance Fracture: Basics

• Due to a flexion-distraction injury.
  • Significant flexion of the lumbar spine leads to distraction of posterior segments.
  • Can lead to compression of the anterior segment as well.

• Initially described as a purely osseous injury.
  • Fracture line passes through spinous processes, pedicles, and superior endplate of the vertebral body.
  • Involves all three columns of the spine.
  • But… now known to include several variants, one which is a purely soft-tissue injury involving the intervertebral disc and ligamentous structures.

• Several classification systems:
  • Most are not appropriate for children as they do not account for the growth plates.
  • Use of MRI imaging can categorizing and defining Pediatric Chance Fractures. [de Gauzy, 2007]
    • Type I – Physeal injury of the superior growth plate
    • Type II – Osseous injury
    • Type III – Physeal injury of the inferior growth plate

• Was thought to be rare, but is often initially missed initially.
  • Often misdiagnosed as compression fractures (even by spine surgeons). [Andras, 2016]
    • Pediatric Chance Fracture may have a compression component, but involves posterior elements as well.
    • Misdiagnosis can lead to suboptimal management and prolonged morbidity. [Andras, 2016]
  • Accounts for significant proportion of pediatric vertebral injuries – (42-100%). [Le, 2011]

Pediatric Chance Fracture: Different than Adult

Children have several anatomic features that alter the fracture pattern: [Le, 2011]

• Presence of growth plates (weaker than bone, disc, & ligaments)
• Healthy intervertebral discs (stronger than in adults)
• Increased head-to-body ratio (changes center of gravity and torque angle => greater distraction forces)
• Pelvis and femurs are smaller
  • Smaller iliac crest 
    • Difficult for lap restraint to secure the pelvis
    • Belt should be beneath the anterior inferior iliac crest, but difficult to secure in the young.
  • Shorter Femurs
    • If not in booster, shorter legs cause child to slouch in seat, aligning the lap belt with abdomen (which is bad!).
    • Child can slide under belt, even is align properly at first (this is why there is a crotch strap for very young children).

Pediatric Chance Fracture: Mechanism

• Hyperflexion injury leading to either: [Le, 2011]
  • All 3 columns failing in tension (being pulled apart), OR
  • Middle and Posterior columns failing in tension and the Anterior column failing in compression.
  • Fracture pattern is dependent upon the axis of rotation.
  • Ligamentous and soft tissue injuries also occur.

• Seen with children inappropriately restrained: [Le, 2011]
  • Lap belt (2-point restraint) only
    • Allows for hyperflexion
    • Since 2007, new cars sold in the US are mandated to have 3-point restraints in all seating positions.
  • Inappropriately worn 3-point restraint
    • Children who purposely sit with shoulder restraint behind the torso.
    • Children too small for lap belt to restrain the pelvis, allowing pelvis to slip under it and leading to flexion around the abdomen.

Pediatric Car Restraint Primer

• Each car restraint device has manufacturer recommendations for positioning and child weights – follow them.
• Infants and Toddlers should be rear-facing for as long as possible… but ~2 years of age is average (~40 lbs).
• Car Seats should be used forward facing from 2-4 years of age (65-80 lbs … see manufacture guidelines).
• Booster Seats (that help appropriately position the lap and should belts) should be used until ~ 8 years of age … when child’s legs are long enough to have feet flat on floor and hips at the back of the seat (preventing slouching).
• Children under 13 years should continue to ride in the rear seat of the vehicle.

Pediatric Chance Fracture: Complications

• Pediatric Chance Fractures are associated with concomitant injuries:
  • “Seat Belt Syndrome” 
    • Abdominal Wall Ecchymosis
    • Lumbar Spinal Injury
    • Visceral injury – ~66% will have intra-abdominal injury
  • Spinal cord injury
    • Paraplegia seen in ~15% of children (rare in adults)
  • Aortic Injuries also reported.

Moral of the Morsel

• Seat Belts save lives… but inappropriately worn can cause damage!
• Seat Belt Sign? Don’t just think about the intestines being injured. Look at that spine!
• Compression fracture in a child? Scrutinize the potential for it being a Pediatric Chance Fracture. May need MRI.
• Always discuss appropriate car safety and restraints at every opportunity! An ounce of Prevention… is worth a child’s spine!

References