Hypothenar hammer syndrome is a condition of the hand in which the blood flow to the fingers is reduced. Hypothenar refers to the group of muscles that control the movement of the little finger. Some of these muscles make up the fleshy edge of the palm (hypothenar eminence). It occurs when workers repeatedly use the palm of the hand (especially the hypothenar eminence) as a hammer to grind, push, and twist objects. These activities can damage certain blood vessels of the hand especially the ulnar artery. This artery goes through the hypothenar area of the palm and supplies blood to the fingers. Damage to the ulnar artery results in a reduction of blood flow to the fingers.

Symptoms of hypothenar hammer syndrome are pain, pins and needles and loss of sensation in the affected hand. The fingers become sensitive to cold and they change colour.

The diagnosis of hypothenar hammer syndrome is based on symptoms, medical history and job history. The diagnosis is confirmed with tests showing the obstruction of the blood vessels.

The treatment of hypothenar hammer syndrome begins by avoiding those activities that caused the syndrome. Certain drugs will help restoring the blood flow. For some cases surgery may be necessary.

Prevention should focus at improving work practices and avoid using the palm of the hand as a hammer to pound, push or twist objects.