Causes / typical injury mechanism: Phalanx fractures are caused by acute trauma to the hand.

Classic history and presentation: The patient will present with an inciting event to the hand, which can include crushing, twisting, compression, blunt, penetrating, or other acute injury mechanisms. There is typically swelling, ecchymosis, and acute point tenderness with or without visible deformity.

Prevalence:

• Can occur at any age, although 70% of cases occur between the ages of 11 and 45 years.
• 58% male predominance.
• Phalanx fractures account for 10% of all fractures.
• Border digits are most commonly affected.
• The distal phalanx is the most commonly injured phalanx.

Pathophysiology:

Distal phalanx

• Fractures can include the tuft (tip), shaft, or articular surface.
• Tuft fractures are often associated with surrounding soft tissue injuries and should be considered open with associated nail bed injury (see Seymour fracture).
• Shaft fractures may have transverse or longitudinal orientation.
• Intraarticular fractures may result in tendon avulsion:
• Mallet finger – Avulsion of the terminal extensor tendon from the dorsal lip of the distal phalanx.
• Jersey finger – Avulsion of the flexor digitorum profundus from the volar lip of the distal phalanx.

Middle phalanx

• Divided into phalangeal head, neck, shaft, base, and pilon fractures.
• Angulation is determined by fracture location in relationship to the flexor digitorum superficialis (FDS) and central slip of the extensor tendon insertions.

Proximal phalanx

• As with the middle phalanx, divided into phalangeal head, neck, shaft, base, and pilon fractures.
• Typically result in apex volar angulation based on proximal fragment flexion from interossei pull and distal fragment extension from central slip forces.

Grade / classification system:

Salter-Harris fracture classification for pediatric fractures

• Type I: Through the physis only
• Type II: Through the metaphysis and physis
• Type III: Through the epiphysis and physis
• Type IV: Through the epiphysis, physis, and metaphysis
• Type V: Crush injury to the physis

Weiss and Hastings phalangeal head articular fracture classification

• Class I: Stable fracture without displacement
• Class II: Unicondylar, unstable fracture
• Class III: Bicondylar, comminuted fracture