HYPOTHENAR HAMMER SYNDROME IN WORKERS OCCUPATIONALLY EXPOSED TO VIBRATING TOOLS

Among 330 vibration-exposed workers, 24 cases of hypothenar hammer syn drome 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. Th e mean age was 55 years, mean duration of vibration exposure 19.4 year s, and mean duration of episodic Raynaud's phenomenon 6.4 years. The v ascular 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 p almar arch around the hook of the hamate. Type 2b: occlusion of both s uperficial and deep palmar arches around the hook of the hamate. Type 3a: occlusion of the ulnar artery at the proximal part of the wrist. T ype 3b: occlusion of the ulnar artery near the wrist with the occlusio n of the dorsal carpal branch of the ulnar artery.