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Hand Arm Vibration Syndrome (HAVS) is a medical syndrome of symptoms and signs affecting the vascular, neurological and musculoskeletal systems of the upper limb associated with occupational exposure to hand transmitted vibration. HAVS has become one of the commonest prescribed diseases of the industrial world and is a frequent source of claims.
Many occupations are associated with significant exposure to vibration and it has been estimated that 1.2 million men and 40,000 women in Britain have weekly exposures high enough to justify health surveillance¹,².
History of Hand Arm Vibration Syndrome
The first condition recognised to be associated with vibration was a form of secondary Raynaud’s phenomenon characterised by abnormal vasospasm of the palmar and digital arteries in response to cold. Maurice Raynaud first described the condition in 1862³. The high prevalence in workers using vibrating tools was first described in Italy by Loriga in 1911 and confirmed in the USA in 1918 by Dr Alice Hamilton who undertook a US Government commissioned study of Stone Cutters⁴,⁵. In these early years progression of the condition to gangrene and loss of fingers was not uncommon.
Subsequent reports confirmed this association which came to be known as Vibration White Finger (vWF) and its severity classified using the Taylor-Pelmear scale⁶. Further research identified neurological and musculoskeletal vibration related conditions which could occur either in conjunction with vWF or independently. In recognition of this multisystem involvement affecting the upper limb, an international consensus agreed to the condition being renamed Hand Arm Vibration Syndrome (HAVS) and the Stockholm Workshop Scale replaced the Taylor-Pelmear scale for the assessment and staging of the condition⁷,⁸. A recent review identified over 8000 scientific publications related to HAVS⁹.
In 1985 HAVS became a prescribed disease in the UK under the National Insurance (Industrial Injuries) Act with sufferers entitled to compensation and disability benefits¹⁰. Requirements were placed on employers to control exposure to vibration and monitor workers for the development of the condition.
Common tools associated with HAVs include pneumatic drills and hammers, chainsaws, hand- held grinders and polishers, concrete breakers, metal polishers, power hammers and chisels, needle scalers, scabblers and powered sanders but any tool imparting vibration may be implicated including lawnmowers and even motorcycle handlebars¹¹.
Estimating Vibration Exposure
Vibration can be described as an oscillatory motion characterised by three main factors: frequency, magnitude and direction. The potential for vibration to cause injury is related to the average intensity of energy imparted to the tissues¹¹.
The dose of vibration is calculated using a mathematical formula based on a specific relationship between duration and magnitude which allows the daily vibration exposure to be re-expressed in terms of the equivalent energy that would be imparted over an 8 hour reference period – a value known as A(8) expressed in units of m/s2 r.m.s. This allows the dose of vibration from different tools to be compared and cumulated and ‘safe’ daily exposures to be calculated. Using A(8) two exposure limits have been calculated and recommended to employers by the Health and Safety Executive (HSE) and specified in UK legislation¹², ¹³.
A low safe dose for all workers has never formally been defined although it is generally accepted that adverse effects below an A(8) of less than 1.0m/s2 rms are rare⁹.
The Health and Safety Executive requires employers working with vibration to know the A(8) exposure of their employees and institute a programme of education, exposure limits and health surveillance for workers who could be potentially harmed. The A(8) value is often provided by the manufacturer of the vibratory tool but this value can change if the tool becomes worn or is not serviced appropriately. The ELV can be exceeded by the use of hammer action tools for above 1 hour/ day and 2 hours/ day for some rotary-action tools. The EAV can be breached by as little as 15 minutes/day of exposure to certain hammer action tools¹¹.
The Clinical Features of Hand Arm Vibration Syndrome
The clinical features of HAVS can be divided into three main categories
Of these, it is generally accepted that there is good evidence of an association between vibration and vibration white finger, digital neuropathy and carpal tunnel syndrome, less extensive evidence for Dupuytren’s and tendonitis and limited evidence for osteoarthritis of the elbow and hands⁹.
A difficulty in diagnosing HAVS is that each of these clinical components can occur spontaneously or have alternative causes. Therefore, diagnosis is based on detailed clinical history, examination and interrogation of the medical records to assess alternative causes and establish the typical features associated with HAVS which include:
1. History of occupational exposure to vibration of sufficient duration and magnitude.
2. A latent asymptomatic period between initial exposure and the development of HAVS.
3. Exclusion of alternative causes.
In the clinic room it is unusual to have detailed information on the A(8) of each tool used but a working calculation can be made as to the total hours of exposure. Clinically, as a rule of thumb, the development of HAVS is unusual below 1000 hours’ exposure but if a claim proceeds it is usual to obtain a more accurate engineer’s report to determine a range of A(8) values based on claimant and defendant estimates of exposure⁶.
Vascular Symptoms
The main symptom is finger blanching on exposure to cold. The amount of cold needed to precipitate an attack can be mild and can occur in summertime. All the fingers can blanche but not all fingers may be affected every time. Occasionally, the distal palms may be affected. In classical Raynaud’s a tri-phasic colour change, white to blue to red, occurs, but variations have been described and the only constant feature is blanching.
It is very rare to witness an episode during the consultation, therefore, the description of the blanching by the claimant is an important feature of any claim and a range of medical opinion exists as to the what constitutes a diagnostic description. Typically, a claimant describes the blood draining out of the fingers until the fingers become deathly white and numb. There is often a clear demarcation line between normal coloured skin and the white areas, and the fingers pass through the tri-phasic colour change. Some experts argue a strict adherence to this classical description while others accept there are variations which still qualify as Raynaud’s (see Figure 1)¹⁴.
Neurological
Neurological symptoms consist of sensory symptoms of numbness, tingling and pins and needles. These symptoms are very common immediately after using vibratory tools but once they persist beyond 30 minutes after cessation of vibration then they are becoming abnormal. As the condition progresses the symptoms become more persistent and interfere with work, sleep and other daily activities of daily living.
Currently accepted theories indicate that vibration initially affects the nerve receptors in the skin and the small nerves leading from them. Results from animal studies and human nerve biopsies indicate that as the condition proceeds, demyelination of the larger nerves occurs which are similar pathological changes seen in other polyneuropathies such as diabetic ‘gloveand stocking’ neuropathy¹⁵. HAVS is a polyneuropathy that can affect all the nerves (median, ulnar and radial nerves) that supply the hand and claimants can complain of symptoms in all these nerve territories i.e. all fingers and all areas of the hand¹⁵.
Carpal tunnel syndrome (CTS) is a mononeuropathy caused by compression of the median nerve at the wrist which causes similar neurological symptoms to HAVS. This can lead to a difference in medical opinion as to the diagnosis. Further debate occurs because vibration can be one of the causes of CTS so the two conditions can co-exist in the same claimant⁶. Carpal tunnel syndrome developing in vibration workers is a reportable condition under RIDDOR and is a prescribed disease for industrial injuries compensation¹⁶.
Anatomically, the median nerve does not supply sensation to the little finger but, clinically, a recognised proportion of patients with CTS complain of symptoms affecting the little finger. Neurophysiological tests such as nerve conduction studies can help clarify which condition is dominant but false positive and negative occur in CTS and standard nerve conduction studies do not measure the function of nerve receptors and small nerves commonly affected in HAVS¹⁵.
Ultimately, it can be a matter of opinion whether the clinical features are more suggestive of CTS or HAVS and whether CTS is caused by vibration or one of the other causes of CTS including idiopathic.
Musculoskeletal
A range of musculoskeletal conditions have been associated with exposure to vibration including Dupuytren’s contracture, various muscle and tendon pathologies and arthritis affecting joints of the wrist, elbow, shoulder and cervical spine¹¹. Epidemiological studies have reported a higher prevalence of Dupuytren’s in workers exposed to vibration than would be expected but there is a strong genetic element and other well recognised causes which leads to a range of medical opinion¹¹. Currently, the scientific evidence for vibration as a cause of arthritis is not considered robust enough for compensation in the UK but it does qualify in France, Germany and Italy¹¹.
Conclusion
The regulations for control of exposure to vibration have been in place for over 30 years so all employers should be aware of their obligations. The reduction in heavy industry in this country and the success of the regulations in reducing industrial exposure means that it is unusual to see the more severe cases of HAVS that were common in the 1980-90s but significant disability still occurs.
The overwhelming majority of medical experts recognise the association of vibration with the development of HAVS but determining the diagnosis in an individual claimant with mild/moderate symptoms and the presence of alternative causes can give rise to a range of medical opinion.
Ultimately, not all the pieces of the diagnostic jigsaw may fit and causation is decided based on the balance of probabilities. In this regard the 2005 appeal court judgement in the case Montracon vs Whalley (Neutral citation number: (2005) EWCA Civ 1383), provides useful guidance where paragraph 34 of the judgement states “Where the civil standard of proof applies, it is not necessary for every piece of the evidential jigsaw to fit. To require that is too high a standard of proof”.¹⁷
References
¹. Palmer KT, Coggon DN, Bendall HE et al. Hand-transmitted vibration: Occupational exposures and their health effects in Great Britain. HMSO; London 1999.HSE Contract Research Report 232/1999
². Palmer KT, Griffin MJ, Bendall H et al. Prevalence and pattern of occupational exposure to hand-transmitted vibration in Great Britain: findings from a national survey. Occup Environ Med. 2000;57:218-228
³. Raynaud M. On asphyxia and symmetrical gangrene of the extremities. (Translated by Thomas Barlow). In Selected Monographs,1888, The New Sydenham Society, p9) - based on Raynaud M. De L’ Asphyxie Locale et de la Gangrène Symétrique des extremétés. Paris: Rignoux1862.
⁴. Loriga G. Il Labora Coi Martelli Pneumatici. Boll Ispett Lavoro 1911; 2:35 and 1913; 6:524
⁵. Hamilton A. A study of spastic anaemia in the hands of stonecutters. Bulletin 236; US Bureau of Labour Statistics 1918; 19: 53-66
⁶. Chetter IC, Kent PJ, Kester RC. The hand arm vibration syndrome: a review. Cardiovasc Surg 1998; 6: 1-9.
⁷. Gemne G, Pyykko I, Taylor W, Pelmear PL. The Stockholm workshop scale for the classification of cold-induced Raynaud’s phenomenon in the hand arm vibration syndrome. (Revision of the Taylor-Pelmear Scale). Scand J Work Environ Health 1987; 3:275-8
⁸. Brammer AJ, Taylor W, Lundborg G. Sensori-neural stages in the hand-arm vibration syndrome. Scand J Work Environ Health 1987; 13: 279-83
⁹. Hewitt S, Mason H. A critical review of evidence related to hand-arm vibration syndrome and the extent of exposure to vibration. Prepared by the Health and Safety Laboratory for the Health and safety Executive 2015; Research Report 1060.
¹⁰. Taylor W. Vibration white finger: a newly prescribed disease. BMJ 1985;291: 921-2
¹¹. Palmer KT, Bovenzi M. Rheumatic effects of vibration at work. Best Pract Res Clin Rheumatol 2015; 29(3): 424-439
¹². Health and Safety Executive.[accessed 05/03/2017] Hand-arm vibration exposure calculator. http://www.hse.gov.uk/vibration/hav/vibrationcalc.htm
¹³. The control of Vibration at Work Regulations 2005. [accessed 05/03/2017] http://www.legislation.gov.uk/uksi/2005/1093/contents/made
¹⁴. Hallet JW (Jr). [accessed 05/03/2017] Raynaud syndrome – Cardiovascular Disorders. Merck Manuals Professional Edition 2017. Springer Science+ Business Media. https://www.msdmanuals.com/en-gb/professional/cardiovascular-disorders/peripheral-arterial-disorders/raynaud-syndrome
¹⁵. Dahlin LB, Sandén H, Dahlin E et al. Low myelinated nerve-fibre density may lead to symptoms associated with nerve entrapment in vibration-induced neuropathy. J Occup Med Toxicol 2014; 9:7
¹⁶. Kozak A, Schedlbauer G, Wirth T et al. Association between work- related biomechanical risk factors and the occurrence of carpal tunnel syndrome: an overview of systematic reviews and a meta-analysis of current research. Muscul Dis 2015; 16:231
¹⁷. Montracon vs Whalley Case No: B3/2005/0017 Neutral Citation Number: [2005] EWCA Civ 1383 in the supreme court of judicature court of appeal (civil division) on appeal DN300866 Royal Courts of Justice. Strand, London, WC2A 2LL. 21st November 2005: Before : Lord Justice Chadwick, Lady Justice Smith and Lord Justice Wilson. Between: Montracon Ltd Appellant and Gregory Whalley Respondent. Transcript of the Handed Down Judgment of Smith Bernal WordWave Limited, 190 Fleet Street, London EC4A 2AG
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