• Clinical science

Scaphoid fracture

Abstract

The scaphoid bone is the most commonly fractured carpal bone. Fractures are most often localized in the middle third of the scaphoid bone. Generally, scaphoid bone fractures result from indirect trauma when an individual falls onto the outstretched hand with a hyperextended and radially deviated wrist. Pain when applying pressure to the anatomical snuffbox is highly suggestive of a scaphoid bone fracture. X-ray is the initial test of choice for diagnosis. Computer tomography and magnetic resonance imaging may be indicated, if x-ray findings are negative but clinical suspicion is high. Treatment can be conservative (e.g, wrist immobilization) or in certain cases surgical (e.g., proximal pole fracture). Complications include nonunion and avascular necrosis.

Epidemiology

  • Most common carpal bone fracture (60–70%)
  • Peak incidence: 20–24 years

References:[1]

Epidemiological data refers to the US, unless otherwise specified.

Classification

  • According to the localization of the fracture[1]
    • Middle third (waist): ∼ 65%
    • Proximal third (proximal pole): ∼ 15%
    • Distal third (distal pole): ∼ 10%
    • Tuberosity: ∼ 8%

Clinical features

  • History of falling onto the outstretched hand; with a hyperextended and radially deviated wrist.
  • Pain when applying pressure to the anatomical snuffbox and scaphoid tubercle
  • Minimal reduction in the range of motion (except in dislocated fractures)
  • Decreased grip strength
  • Painful pinching and grasping
  • Pain can be induced through axial compression along the first metacarpal (scaphoid compression test)

When pain occurs in the anatomical snuffbox after trauma, the injury should be treated as a scaphoid fracture until proven otherwise!

References: [1]

Diagnostics

  • Imaging
  • Best initial test: X-ray of the wrist in a posteroanterior, lateral, 45° oblique, and possibly scaphoid view
  • If initial x-ray is negative, one of the following:
    • If the patient is not willing for wrist immobilization: MRI of the wrist
    • If the patient is willing for wrist immobilization: cast the wrist and repeat an x-ray in 10–14 days
      • If repeat x-ray is normal but continued clinical suspicion of scaphoid fracture: MRI wrist

Scaphoid fractures are often overlooked on the initial x-ray!References:[1][2]

Differential diagnoses

Lunate dislocation

  • Definition: disruption of perilunate ligaments and radiocarpal ligament with displacement of the lunate bone (usually volarly) while the rest of the carpal bones remain in a normal anatomic position
  • Etiology: high-energy trauma with dorsal extension and ulnar deviation of the wrist
  • Clinical features: : wrist swelling, pain, and signs of median nerve injury (25% of patients)
  • X-ray: the lateral radiograph shows a loss of colinearity of radius, lunate, and capitate
  • Treatment: emergent closed reduction and immobilization followed by open reduction and internal fixation

Transscaphoid perilunate dislocation

  • Definition: dorsal dislocation of the wrist around the fixated, unmoved lunate bone with a fractured scaphoid bone
  • Etiology: fall onto a hyperextended wrist, deviated toward the ulna
  • Clinical features: no pain while applying pressure to the snuffbox, pain in the wrist, possibly signs of median nerve injury
  • X-ray: most commonly, metacarpal bones displaced dorsally to the lunate bone in lateral view
  • Treatment: always surgical (reposition and decompression of the median nerve; osteosynthesis)

  • Skapholunäre Dissoziation
    • Definition: Zerreißung des Lig. scapholunatum interosseum (Band zwischen Mond- und Kahnbein) mit skapholunärer Dissoziation (SLD)
    • Ätiologie: Sturz auf die dorsalextendierte Hand
    • Klinik: Schmerzen beim Aufstützen, Druckschmerz zwischen Os scaphoideum und Os lunatum
    • Diagnostik
      • Handgelenk in 2 Ebenen
        • Konventionelles a.p.-Röntgenbild: Erweiterter skapholunärer (SL‑)Spalt
          • a.p.-Röntgenaufnahme in maximaler ulnarer oder radialer Abduktion kann den skapholunären Gelenkspalts (SL-Spalt) verdeutlichen
          • Röntgenaufnahme nach Monheim a.p.
            • Darstellung des skapholunären Gelenkspalts (SL-Spalt) in maximaler Weite
      • Arthroskopie des Handgelenks oder MRT zur Bestätigung der Verdachtsdiagnose
    • Therapie
      • Bandnaht, Reposition und Fixation des Os scaphoideum mittels Kirschnerdraht jeweils am Os lunatum und Os capitatum

References:[3][4][5]

The differential diagnoses listed here are not exhaustive.

Treatment

References:[1][6][2]

Complications

  • Avascular necrosis of the scaphoid bone in approx. 30–40%
  • Nonunion (especially in proximal fractures) in approx. 5–10%
    • Late complication of nonunion: collapse of the carpal joints ("SNAC wrist" )
  • Delayed union of fracture (more common in smokers)
  • Instability among carpal joints
  • Post-traumatic arthritis

Fractures in the distal third tend to heal better because of the retrograde blood supply reaching the bone from the distal pole!References:[1][2]

We list the most important complications. The selection is not exhaustive.