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Introduction
  • Post-traumatic digital ischemia from thrombosis of ulnar artery at Guyon's canal.
  • Epidemiology
    • incidence 
      • rare
    • demographics
      • male: female ratio is 9:1
      • age bracket is 40s-50s
    • location
      • unilateral, dominant ring finger +/- small finger
      • less commonly, index and middle fingers
      • thumb is spared
    • risk factors
      • occupations using vibrating tools such as carpenters, machinists, mechanics 
      • sports such as baseball catchers, mountain biking, golf, volleyball, karate
  • Pathophysiology
    • mechanism
      • single or repetitive blunt impact on hypothenar eminence leads to ulnar artery thrombosis or aneurysm 
      • hook of hamate functions as an anvil, causing thrombosis
      • distal embolisation leads to ulceration, gangrene
Anatomy
  • Ulnar artery
    • ulnar artery branches into 2 branches as it exits Guyon's canal 
      • deep branch
      • superficial palmar arch in Guyon's canal
    • relation to hook of hamate
      • over distal 2cm, the artery is directly anterior to the hook of the hamate, covered by palmaris brevis, subcutaneous tissue and skin  
Presentation
  • History
    • occupational or sporting risks (see above)
  • Symptoms
    • pain over hypothenar eminence and ring finger
      • may involve small, middle and index fingers
    • cold sensitivity
    • paresthesia
  • Physical exam
    • inspection
      • blanching, mottling, cyanosis, pallor, gangrene
      • tenderness over hypothenar eminence
      • prominent callus (calloused skin over hypothenar eminence)
      • pulsatile mass if aneurysm is present
      • fingertip ulcerations over ulnar digits
      • splinter hemorrhages over ulnar digits
    • provocative tests
      • Allen's test
        • positive if occlusion is present
        • negative if aneurysm is present
Imaging
  • Doppler ultrasound
    • indications
      • first line test 
      • measure digital brachial index
        • <0.7 necessitates reconstruction
  • Angiogram, CT angiogram or MR angiogram  
    • indications
      • mandatory for diagnosis
    • findings
      • tortuous "corkscrew" ulnar artery
      • occlusion or aneurysm at the hook of the hamate  
Differential
  • Raynaud's disease involves the thumb but hypothenar hammer syndrome does not
Treatment
  • Nonoperative
    • lifestyle modifications, symptomatic treatment, and vascular consult
      • indications
        • thrombosis without aneurysm > 2 weeks
        • asymptomatic
        • no threat of digital loss
      • lifestyle modifications
        • smoking cessation
        • avoid recurrent trauma
      • outcomes
        • 80% success
  • Operative
    • endovascular fibrinolysis
      • indications
        • thrombosis without aneurysm < 2 weeks
    • excision of involved segment and reconstruction with or without a vein graft   
      • indications
        • digital brachial index <0.7 
        • thrombosis with aneurysm
        • ischemia in multiple digits
        • failed conservative treatment with recurrent symptoms
    • arterial ligation (Leriche procedure)
      • indications
        • digital brachial index >0.7 
 

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