Hypothenar hammer syndrome in workers occupationally exposed to vibrating tools.

Among 330 vibration-exposed workers, 24 cases of hypothenar hammer syndrome in 29 hands were diagnosed by arteriography. The right hand was involved in 13, the left hand in six, and both hands in five cases. The mean age was 55 years, mean duration of vibration exposure 19.4 years, and mean duration of episodic Raynaud's phenomenon 6.4 years. The vascular lesions of the ulnar arteries were classified into three major types with subtypes. Type 1: stenosis of the superficial palmar arch around the hook of the hamate. Type 2a: occlusion of the superficial palmar arch around the hook of the hamate. Type 2b: occlusion of both superficial and deep palmar arches around the hook of the hamate. Type 3a: occlusion of the ulnar artery at the proximal part of the wrist. Type 3b: occlusion of the ulnar artery near the wrist with the occlusion of the dorsal carpal branch of the ulnar artery.