Working Diagnosis:
1. Hypothenar hammer syndrome
2. Trigger finger of the left 3rd and 4th digits

Treatment:
Patient underwent left 4th digit A1 pulley release and excision of the thrombosed segment of the ulnar artery with concomitant sympathectomy.

Outcome:
Post-procedural US did not demonstrate any restriction in arterial flow. Patient symptoms completely resolved within hours of surgery. He was referred for occupational therapy evaluation with clearance to return to work after one visit. He continued to be symptom free after returning to work.

Author's Comments:
Hypothenar hammer syndrome (HHS) is an ulnar arterial insufficiency syndrome that results from obstruction of arterial flow. Causes include stenosis, thrombosis, septic emboli, fibrous compression, or aneurysmal complication. The most common cause is thought to be stenosis or thrombosis in athletes or workers that experience repetitive trauma to the hamate bone. Higher risk occupations include mechanics, carpenters, butchers, and sawmill workers while mountain bikers, tennis players, and golfers are the most commonly affected athletes. While classifications exist to explain the location of occlusion, most occur around the hook of the hamate due to the close proximity of the ulnar artery complicated by the relatively sharp angles and multiple fibrous structures nearby. Symptoms typically include ulnar sided pain, paresthesias in digits 3-5, color change (sometimes confused for Raynaud's phenomenon), hypothenar atrophy, and coldness of the affected digits. Notable exam findings include tenderness over Guyon's canal, delayed capillary refill with Allen's test or difficulty palpating ulnar flow. The diagnosis is often missed on initial presentation because of lack of symptoms. While X-rays and electrodiagnostics are often obtained initially, Doppler ultrasound with digital brachial indices is the initial diagnostic test of choice. Diagnosis is confirmed with angiogram or MR angiogram, which identifies occlusion or aneurysm. Conservative management includes padded gloves, avoidance of trauma, and medications such as calcium channel blockers or anti-platelet/anticoagulant agents. Risk factor modification (smoking cessation, lipid improvement) can also help. Surgical intervention involves removal of the affected arterial segment with venous grafting but is usually reserved for those with aneurysm formation, digital-brachial index <0.7, or symptoms refractory to conservative treatment.

Editor's Comments:
This case illustrates the importance of considering concurrent diagnoses. While trigger finger is common, this patient also demonstrates characteristic symptoms of hypothenar hammer syndrome. His gender, occupation, and age are classic for this condition as well as his clinical picture of paresthesias, cold sensitivity, and positive Allen's test.

References:
Ablett CT, Hackett LA. Hypothenar hammer syndrome case reports and brief review. Clin Med Res. 2008 May;6(1):3-8.

Abudakka, M. et al. Hypothenar Hammer Syndrome Rare or Underdiagnosed. Eur J Vasc Endovasc Surg. 2006 Sep;32(3):257-6.

Emanuele C, Spagnoli AS, Tarallo M, De Santo L, Monacelli G, and Scuderi N. Therapeutic Management of Hypothenar Hammer Syndrome Causing Ulnar Nerve Entrapment. Plast Surg Int. 2010;2010:343820.

Kumar Y, Hooda K, Lo L, et al. Ulnar artery aneurysm and hypothenar hammer syndrome. J Vasc Surg Cases Innov Tech. 2018 Apr 27;4(2):131-132.

Modarai, Bijan et al. The hypothenar hammer syndrome. J Vasc Surg. 2008 Jun;47(6):1350.

Pineda, Carlos J. et al. Hypothenar hammer syndrome. Form of reversible Raynauds phenomenon. Am J Med. 1985 Nov;79(5):561-70.

R.S.M. Dethmers, P. Houpt. Surgical management of hypothenar and thenar hammer syndromes a retrospective study of 31 instances in 28 patients. J Hand Surg Br. 2005 Aug;30(4):419-23.

Wernick, Richard et al. Bilateral hypothenar hammer syndrome. An unusual and preventable cause of digital ischemia. Am J Emerg Med. 1989 May;7(3):302-6.

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