Causes / typical injury mechanism: An aneurysm is usually considered to be localized dilation of an artery up to 150% of its normal size. Upper extremity and hand aneurysms are uncommon to begin with, but digital artery aneurysms are exceedingly rare (< 1 case per 100 000).

Classic history and presentation: All digits can be affected. Digits most commonly affected are the thumb, followed by the index finger and ring finger.

Prevalence: Since the first case of digital artery aneurysm was described in 1982, a literature review of publications spanning 1982-2017 found only 42 case reports and 4 case series of digital artery aneurysms. Of those, 21 were true digital artery aneurysms and 26 were false aneurysms.

Given the lack of cases in the medical literature, it is hard to define a demographic.

• The youngest patient recorded was 8 months old, while the oldest patient was 70 years old.
• Both sexes appear to be affected equally, despite female sex being a risk factor for aneurysms in general.

Risk factors: Risk factors include occupational or recreational predisposition to frequent blunt microtrauma (ie, sports, manual labor), recent upper extremity surgery, health conditions resulting in inflammation or atherosclerosis, and diseases causing weakening of the blood vessel walls.

Pathophysiology:
Traumatic –

• Blunt microtrauma
• True aneurysm
  • Arterial wall weakened over time from repeated blunt trauma
  • Results in a uniformly shaped dilation
  • Involves all 3 tunica layers (intima, media, and adventitia)
• Penetrating trauma
• False aneurysm or pseudoaneurysm
  • Perforation of arterial wall causes blood to leak into peripheral tissue
  • Results in a sac-like hematoma
  • Hematoma develops organized thrombus with fibrous scar tissue lining, then recanalizes
  • Involves only tunica adventitia
• Can include iatrogenic causes (upper extremity surgery)

Nontraumatic –

• Mycotic (infectious): can be either primary cause or secondary
• Congenital anomalies
• Atherosclerosis
• Inflammation
• Idiopathic