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.