Hypothenar hammer syndrome caused by posttraumatic aneurysm of the ulnar artery

The so-called hypothenar hammer syndrome is a rare entity caused by lesions of the ulnar artery secondary to repetitive trauma to the hypothenar eminence, typically found in persons working with vibrating tools. Its clinical symptoms are pain, stiffness and whitening of the smitten fingers, sometimes in combination with Raynaud's syndrome. Angiographic evaluation of the smitten forearm and hand reveals occlusions, kinking, vasospasm and stenoses of the arteries in the hand and fingers. An aneurysm of the ulnar artery causing the hypothenar hammer syndrome is an even more rare morphological finding. The difficult aspect of treating a hypothenar hammer syndrome is to reopen the occluded vessels. Eventually, circulation deteriorates and skin lesions of the fingers may occur. The advantage of an isolated aneurysm of the ulnar artery is that normal circulation can be restored by vascular surgery, for example, with a vessel interponate. Surgical removal of the isolated aneurysm helps to prevent microembolism to the distal arteries and consequent deterioration of peripheral circulation. We report a young patient who presented with clinical symptoms of the hypothenar hammer syndrome and an aneurysm of the distal ulnar artery, diagnosed by magnetic resonance angiography. The only likely cause of the aneurysm was a bicycle accident some months prior to the occurrence of the aneurysm. The patient underwent vascular surgery and has been free of symptoms during six months of follow-up. A control magnetic resonance angiography performed one month after surgery revealed a normal vascular morphology.