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Updated: May 22 2021

Hypothenar Hammer Syndrome

4.2

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  • summary
    • Hypothenar Hammer Syndrome is post-traumatic digital ischemia from thrombosis of the ulnar artery at Guyon's canal.
    • Diagnosis is made with vascular studies including Doppler ultrasound and CT angiography.
    • Treatment can be observation, fibrinolysis, vessel ligation or reconstruction depending on the chronicity of symptoms, the digital brachial index, and the presence of an aneurysm. 
  • Epidemiology
    • Incidence
      • rare
        • < 1 per 100,000
    • Demographics
      • male: female ratio is 9:1
      • age bracket is 40s-50s
    • Anatomic 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
  • Etiology
    • 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 an 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 (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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