Hand Arm Vibration Syndrome

Synonyms: HAVS,Vibration white finger, VWF

Hand Arm Vibration Syndrome results from many years of use of vibrating tools. Vibration white finger is the vascular component of this disease and is classified as an industrial disease. The neurological component is not so classified but this may soon change. It became a prescribed industrial disease in 1985. This means that those who suffer may be able to claim compensation under the industrial injuries scheme but only those with more severe disease and those in specified industries are able to benefit. Further information should be available from the trade union, local Citizens Advice Bureau, local Health and Safety Executive (HSE)Area Office or the Environmental Health Department of the local council.

Disability is not limited to time at work or when using these tools but can interfere with hobbies and recreation.

The number of new recorded cases of vibration white finger (VWF) assessed for Industrial Injuries Disability Benefit was 645 in 2005/06 down from 865 in 20004/05. This is the lowest number of new cases in the last ten years.¹ The Medical Research Council survey of 1997-98 gave a prevalence estimate of 288,000 sufferers from VWF in Great Britain of whom 255,000 were males and 33,000 females.² In the past, numbers claiming compensation have been considerably swollen by former coal miners. It is estimated that up to 300,000 working days are lost each year in the UK due to hand-arm disability related absences.³

Risk factors

An essential risk factor is the use of vibrating tools. This is a sine qua non for any industrial claim. Frequencies ranging from 2 to 1500 Hz are potentially damaging but the most serious is the 5 to 20 Hz range. This may be a pneumatic drill, hammer drill, chain saw or many other implements.⁴ Other risk factors are said to be beta-blockers, cigarette smoking and exposure to cold.⁵ The evidence with regard to smoking may be inconclusive but smoking is known to have an adverse effect on circulation.^6,7 Vascular features are more common in a cold and damp climate. It is substantially a male disease but this probably reflects employment practices rather than predisposition. As a general rule, is caught early and effective action is taken prevent further insult, recovery will occur but it may not in advanced cases.
It is unusual for VWF to present in less than 10 years exposure and duration and intensity of exposure are certainly risks. A study of Swedish car mechanics confirmed this but found that quite brief exposure to vibration each day was enough to induce the disease.⁸

The main features are vascular and neurological.

• Vascular features are blanching of the fingers, especially after exposure to cold and with delayed or poor recovery thereafter. This is Raynaud's phenomenon of which HAVS is just one of many causes. Patients often report white fingers in the morning or after outdoor activity.
• Neurological features are responsible for the subjective numbness, tingling and pain and the neurological signs of sensory deficits, especially to fine touch discrimination and temperature. There is also reduced manual dexterity and muscle weakness with impaired strength of grip.
• There may be other manifestations from damage to bone and muscle. Dupuytren's contracture can result from cumulative trauma to the palm of the hand. Other effects that have been reported include exostoses and cysts in carpal bones, carpal tunnel syndrome and osteoarthritis.

For diagnosis the following are required:⁹

• Evidence of long term exposure to vibration.
• Episodes of digital pallor, with or without confirmed sensorineural effects.
• Exclusion of other causes of Raynaud's phenomenon or sensory changes.
• Diagnosis would be supported by finding of associated musculoskeletal features, calluses on hand, loss of sensation in digits affected and muscle weakness. These may not be apparent in the early stages of disease.

• Raynaud's disease
• Scleroderma
• Buerger's disease
• Hypothenar hammer syndrome¹¹
• Rheumatoid arthritis
• Thoracic outlet syndrome¹²

For the purpose of assessing possible industrial compensation it is necessary to have a number of standardised tests. Tests available include:

• The Vibrotactile threshold test is used to test the mechanoreceptors. They respond to stretch, edge and texture and the receptors respond at different frequencies. Measurements are taken from the median nerve (index finger) and the ulnar nerve (little finger) in each hand at 2 frequencies.
• The Thermal Aesthesiometry test assesses the thermal receptors' threshold. Readings are again taken from the median nerve and the ulnar nerve.
• The Purdue Pegboard test is a measure of dexterity and detects loss of fine movement to both hands.
• The Grip Force measurement test measures the grip strength of both hands. This test is not scored but is a useful indication of vibration damage to muscles of the hand and forearm.
• In addition tests may be used to assess the vascular component. Finger systolic blood pressure measurement follows cooling of the digits and measures interruption of blood flow in response to cold.
• The Cold Provocation Test provides visual evidence of blanching.

In 1999 a large number of coal miners needed assessment to provide evidence for legal proceedings. Pragmatically, it was considered that a symptomatic history, occupational history, and a combination of vibrotactile thresholds, thermal aesthesiometry and cold water provocation testing would be sufficient to diagnose most cases.¹³

The Stockholm system is used to grade severity:

Vascular component

• Stage 1 - mild, with only occasional attacks affecting tips of one or more fingers
• Stage 2 - moderate, occasional attacks affecting distal or middle phalanges of one or more fingers
• Stage 3 - severe, frequent attacks affecting all phalanges of most fingers
• Stage 4 - very severe, as stage 3 plus trophic changes in fingertips

Sensorineural component

• 0SN - exposed to vibrations but no symptoms
• 1SN - intermittent numbness +/- tingling
• 2SN - numbness (intermittent or continuous) with loss of feeling of touch.
• 3SN - numbness (intermittent or continuous) with loss of discrimination by touch +/- manual dexterity.

The hazard to health from vibration is usually assessed from the average acceleration level of the vibrating surface. A weighting is applied to take into account the variation in damage at different frequencies to give a frequency-weighted acceleration 'A' normally expressed in m/s². If the implement is to be used for up to 4 hours a day this is called the A4 and for up to 8 hours a day the A8.¹⁵

Non-drug

Eliminate the source of vibration if possible or consider redeployment, keeping the body warm, stopping smoking.¹⁶ Apply the principles outlined under prevention.

Drugs

These have little part to play. Nifedipine or another calcium channel blocker may be useful. Iloprost has been reported as promising in advanced disease.¹⁷

Early redeployment can halt or reverse progression of symptoms but in severe cases these continue even after removal of source of vibration.¹⁸ A longitudinal study from Japan found that the earlier the disease the more likely was recovery to occur. Continued use of vibrating tools was a bad prognostic feature but age, medical history and smoking seemed to have no effect.⁶

If possible a different technique should be used to avoid the exposure to vibration. Tools must be well maintained. Appropriate antivibration gloves can reduce damage. They should be changed when wet. Duration of exposure should be minimised and frequent breaks taken. For those at risk periodic assessment is advised.

The Control of Vibration at Work Regulations 2005 which came into force in July 2005, placing a legal obligation on employers to assess and identify measures to eliminate or reduce risks from exposure to hand-arm vibration, ensure that control measures to reduce vibration are properly applied; and provide information, training and health surveillance.²⁰