It is July and here in the Northern Hemisphere that means two things: newly minted doctors and kids finding ways to prove that Gravity works. We have covered numerous Gravity related items previously (ex, Trampoline Injuries, Trauma Pitfalls, Concussion, C-Spine Injury, Horse-related Injuries, Abdominal Trauma). Certainly, broken bones are quite prominently encountered during the summer (ex, Wrist Fracture, UE fractures, Hand Fractures, Foot Fractures), but there is one unique aspect of pediatric fractures that should not be overlooked. Basics are important… so let us quickly review Salter-Harris Classifications:

Salter-Harris Classification

• Fractures involving the growth plates (epiphyseal plate / physis) are common in children.
• Having a system to describe them that relates to the anatomy as well as the prognosis is important.
  • There are numerous classifications systems in existence…
  • The most commonly used was described in 1963 by Robert B. Salter and W. Robert Harris. [Cepela, 2016]

• The Physis is the weakest part! [Cepela, 2016]
  • Immature bones have different fracture patterns from mature ones.
  • The ligaments and tendons may actually be stronger than the physis (see Ankle Injury).
  • Physis can be subdivided into four different zones anatomically.
    • Zone 1 – “resting zone” – adjacent to epiphysis, mostly inactive
    • Zone 2 – “proliferative zone” – active chondrocytes
    • Zone 3 – “Hypertrophic zone” – large chondrocytes – contains the zone of provisional calcification, the weakest area.
    • Zone 4 – “Zone of calcification” – where calcified cartilage begins to remodel into bone.
  • The transition point between calcified and non-calcified extracellular matrix within the physis is the weakest portion and susceptible to injury.

• Physeal Injuries have the potential for complications: [Cepela, 2016]
  • Growth arrest
  • Deformity

• Not all injuries have the same risk for complications (and is why a classification system is helpful).

Salter-Harris Classification

• Salter-Harris Classification:
  • Focused on injuries at the pressure epiphyses [Cepela, 2016]
    • There are two types of epiphyses – pressure and traction
    • Pressure type provide longitudinal growth and bear weight.
    • Traction type provide appositional growth at origin/insertion of muscles and do not bear weight.
  • Describes 5 different types (although others have also been described)

• TYPE I [Cepela, 2016]
  • Extends through the growth plate
  • Separates the epiphysis from the metaphysis.
  • More common in younger children who have a thicker physis.

• TYPE II [Cepela, 2016]
  • The most common type of epiphyseal fracture (~74%).
  • Fracture extends through the physis and exists through the metaphysis.
  • Is not intra-articular.
  • The broken off piece of metaphysis = Thurston-Holland fragment.

• TYPE III [Cepela, 2016]
  • Fracture extends through the physis and exists the epiphysis.
  • Is INTRA-ARTICULAR.
  • May lead to post-traumatic arthritis and growth arrest.

• TYPE IV [Cepela, 2016]
  • Fracture crosses the physis and extends through the metaphysis and epiphysis.
  • Is INTRA-ARTICULAR.
  • Has longitudinal INSTABILITY.
  • May lead to complete physical arrest and symmetric growth or growth deformity (if not reduced longitudinally correctly).

• TYPE V
  • A crush injury of the physis due to compressive forces.
  • May also be a stress (overuse) type injury seen with repetitive loading of force (ex, gymnast).
  • Rare.

Moral of the Morsel

• Anatomy Matters. Kids are not aliens… they are just little humans with different anatomy and physiology that must be taken into account.
• Ankle Sprain? Are you Sure? Remember, the weakest part isn’t the ligament… it is the physis.

References