![Figure](https://www.cmaj.ca/content/cmaj/172/8/1001/F1.medium.gif)
Figure. Photo by: Art Explosion
Background and epidemiology: Hand–arm vibration syndrome (HAVS) refers to a constellation of vascular, neurological and musculoskeletal signs and symptoms that may occur in workers who use handheld vibrating tools, in particular drills, grinders, electrical drills and saws, and jackhammers. Commonly afflicted occupational groups are shown in Box 1.1
The burden of HAVS is underreported, and the syndrome is often misdiagnosed as carpal tunnel syndrome. This is not surprising, since the 2 syndromes can coexist and HAVS can present with various degrees of sensory, vascular, muscular and osteoarticular involvement. It is important to distinguish the 2 syndromes, however, since some surgeries that are effective with carpal tunnel syndrome do not alleviate HAVS.
Typical clinical signs of HAVS are shown in Box 2. Symptoms do not present in a predictable order, although in general the vascular changes have a longer latency period than the sensorineural deficits but are more commonly reported.2
The pathophysiologic features of HAVS are not well understood. Anatomic vascular changes occur with hypertrophy of the vessel wall and endothelial cell damage. The cold-induced vascular spasm is thought to be mediated by α-2 adrenoreceptors in vessel walls. Pathologic changes have also been described in the digital tuft mechanoreceptors (Pacinian corpuscles) and among myelinated digital fibres.1
Physical characteristics of exposure that appear to play a role in the development of HAVS include the type of vibration (frequency, amplitude and direction), the vibratory force and impulse type, the cumulative hours of exposure, the intermittency of exposure, the state of tool maintenance and a cold environment.2 Biodynamic factors such as the grip force required to use the tool, the operator's control of the tool and the surface area of the tool handle, as well as factors such as the patient's medical history of injury, susceptibility and protective practices also play a role (www.ccohs.ca/oshanswers/phys_agents/vibration/vibration_effects.html#_1_3). Symptoms typically do not appear until after 2000 hours of exposure to vibrations,2 although the latency period can vary considerably.
Clinical management: Diagnosis is based on a history of exposure to hand or arm vibration and sensorineural or vascular symptoms. Sensorineural tests in the clinic include electric current perception threshold, Semmes–Weinstein monofilaments, vibration perception threshold (tuning fork), 2-point discrimination and digital perception of small objects. Laboratory testing includes nerve conduction study and vibrometry testing. Several tests are used to assess the vascular component of HAVS. Plethysmography before and after cold provocation is the laboratory test accepted for evaluating vascular manifestations of HAVS by the Stockholm Hand–arm Committee.1 Additional tests include digital thermometry at baseline and after cold-water immersion and Doppler blood pressure and flow measurement. However, a recent review of the diagnostics of vascular symptoms concluded that taking a good patient history was the best method for diagnosing blanched fingers triggered by cold.3
Treatment includes maintaining core body temperature, avoiding exposure to cold and vibrating tools, job modification or a change of job, and splinting at night to treat neuropathies. Medications include calcium-channel blockers, pentoxyphylline to improve flexibility of red blood cells and drugs to reduce platelet deposition. Surgical intervention is neither successful nor warranted.1
Prevention: Preventive measures in the workplace are extremely important. They include the use of ergonomic tools, antivibration padding and gloves to keep hands dry and warm, and reduction in the intensity of vibration to the hand through damping techniques, job rotations and scheduled rest periods.2 Efforts are underway to establish evidence-based limits to vibration exposure. Smoking cessation is also recommended, given the vasoconstrictive effects of cigarette smoking on the peripheral arteries.