Hands are, obviously, useful. They allow kids (and all of us) to explore, interact, and manipulate the world. This utility, however, often places them in precarious situations and hazardous locations. Hand injuries are commonly encountered in our EDs (ex, Subungal Hematoma, Wrist Fractures) and, since the hand is such an important tool, it deserves specific attention. Let us take a moment to digest a Morsel of Metacarpal Fractures:

Metacarpal Fractures: Basics

• The hand is one of the most frequently injured body part of a child. [Mahabir, 2001; Hastings, 1984]
• The most common metacarpal fracture is the Boxer’s Fracture (neck of the 5th metacarpal). [Vadivelu, 2006; Mahabir, 2001]
• Fracture displacement is more common with metacarpal fractures. [Hastings, 1984]
• Almost all metacarpal fractures will heal clinically by 3-4 weeks. [Hastings, 1984]

Metacarpal Fractures: Age Matters

• Pediatric hand fractures have a biphasic peak. [Vadivelu, 2006]
  • Small peak in toddlers and preschool children.
    • More mobile and curious, but not super coordinated to get out of trouble
    • Younger children are more often injury their fingers (ex, getting them crushed in doors– little fingers vs doors — never a good thing).
  • Larger peak in 2nd decade of life (10-20 years). [Godfrey, 2017; Mahabir, 2001; Hastings, 1984]
    • Sporting events are often associated  [Vadivelu, 2006; Mahabir, 2001]
    • Repeated hand fractures found to be associated with psychiatric illness. [Ozer, 2010]

• The physis makes pediatric hand fractures unique.
  • Angular forces can lead to epiphyseal injuries.
  • Salter-Harris type II fractures are the most common type of epiphyseal fracture.
  • Nonepiphyseal fractures are more common, though, in the metacarpals than in the phalangeal bones.  [Vadivelu, 2006; Mahabir, 2001]
    • Metacarpals usually get axial compressive forces, which the epiphyses is resistant to.
    • Fighting / punching and sporting events lead to compressive forces.

Metacarpal Fractures: Location Matters

Metacarpal fractures are categorized as involving the:

• Head
  • Rare
  • Intra-articular
  • Associated with avascular necrosis and growth arrest. [Williams, 2013]
  • Require anatomic fixation
  • Can be challenging to appreciate in children. [Godfrey, 2017]
• Neck
  • Commonly seen with 2nd-5th metacarpals. [Mahabir, 2001]
  • Compressive forces are more likely to lead to fractures here. [Mahabir, 2001]
• Shaft
  • Uncommon
  • Distributed among 2nd-5th metacarpals
  • Often have an oblique or spiral pattern (rotational forces)[Sivit, 2013]
• Base
  • Commonly seen with 1st digit and 5th metacarpals [Sivit, 2013]
  • Are high energy injuries.
  • May develop compartment syndrome.
  • Can be either intra- or extra-articular
    • Extra-articular fractures are more common
    • In skeletally immature children, these may involve the physis.
  • Bennett’s Fracture [Godfrey, 2017]
    • An intra-articular fracture and dislocation at the base of the 1st metacarpal.
    • Mechanism = fall on flexed thumb
    • The metacarpal subluxes proximally and radially with small fragment remaining attached to the ligaments.
    • Pediatric variants include Salter-Harris type III and IV fractures. [Godfrey, 2017]
    • These are unstable and require surgical repair.
    • Reverse Bennett’s Fracture – similar fracture pattern involving the 5th metacarpal.

Metacarpal Fractures: Deformed?

• Rotational deformity is not tolerable.
• Angular deformity can be tolerated … to some degree:
  • 2nd Metacarpal Neck – <10 degrees
  • 3rd Metacarpal Neck – <20 degrees
  • 4th Metacarpal Neck –<30 degrees
  • 5th Metacarpal Neck – <40 degrees

• Radially angulation is typically more stable than ulnarly angulated fractures. [Williams, 2013]
• May require surgical repair for rotation or substantial angulation.

Moral of the Morsel

• Age plays a role in hand injury patterns. Younger – fingers; Older – metacarpals
• No rotation allowed! Angular deformity is ok… know the degrees!
• Be leery of the thumb fracture! Bennett’s fracture is not a simple metacarpal fracture.

References