Hand-arm vibration syndrome

Transcription

1 Hand-arm vibration syndrome Busisiwe Nyantumbu, Diploma in Occupational Health (WITS) (1997), MSc Med (WITS) (2003) Head Ergonomics Unit* Spo Kgalamono, B.Cur. (MEDUNSA) (1990), M.B., Ch. B. (MEDUNSA) (1997), Diploma in Occupational Health (WITS) (2001), Head Occupational Medicine Section, National Institute for Occupational Health, P.O. Box 4788, Johannesburg 2000 Tel: Fax: ABSTRACT Hand-arm vibration syndrome (HAVS) is a condition which affects workers who operate vibrating hand tools. The vibration damages blood vessels and nerves in the fingers. The affected workers experience numbness and tingling which incapacitate their hands. In South Africa, HAVS has not been recognised despite being compensable under the Compensation for Occupational Injuries and Diseases Act of Possible reasons could be the lack of awareness about the condition and skills to diagnose it. Recently, a Safety in Mines Research Advisory Committee project on HAVS has established the occurrence of HAVS in South African goldminers. The spinoffs from this study were technology transfer and capacity building in the diagnosis of HAVS in South Africa. Efforts now need to be directed at raising awareness about HAVS, training occupational health practitioners on how to recognize it and most importantly to develop preventive strategies to protect workers from vibration exposure. INTRODUCTION Hand-arm vibration syndrome (HAVS) is a condition which has not been recognised in South Africa, possibly because few cases of HAVS have been clinically diagnosed, due to lack of awareness about the condition and also the skills to diagnose it. Another reason could be * On the 10th of February 2005, the NIOH launched an Ergonomics Unit. The new unit is located in the Occupational Medicine Section. It has a laboratory which is equipped with one of the best available machines to diagnose hand-arm vibration syndrome. The unit is already contributing to health and safety in the workplace. It is involved in performing ergonomics risk assessments in the workplace, doing ergonomics teaching and training for occupational health practitioners and workers, disseminating ergonomics information through brochures and posters and conducting ergonomics research. Information about the unit can be obtained from Busisiwe Nyantumbu, who heads the Ergonomics Unit ( busisiwe. nyantumbu@nioh.nhls.ac.za) that local weather conditions are not as cold as in countries such as the United Kingdom where high prevalences of HAVS have been reported. 1 Cold conditions contribute to the development of HAVS and also induce its symptoms 2. A Safety in Mines Research Advisory Committee (SIMRAC) study Health 703, established the occurrence of HAVS in South African goldminers 3. This study, a joint venture of the National Institute for Occupational Health (NIOH), the Medical Bureau for Occupational Diseases and the Health and Safety Laboratory (HSL) in the United Kingdom, was conducted in a hot gold mine. Only rockdrillers were diagnosed with HAVS. The prevalence was found to be low (15%), as compared to prevalences of up to 80% in other studies 4,5,6. In this study, a high prevalence of HAVS was expected, considering the high levels of vibration measured in the rockdrills used in the South African mining industry 7. The measured vibration levels averaged 24 m/s 2, which is approximately five times higher than the European Communities Directive exposure limit of 5 m/s 2. The main reasons given for the low prevalence were the high temperatures underground and the short exposure time to the rockdrill. JULY/AUGUST

2 Execution of the study culminated in technology transfer and capacity building in the diagnosis of HAVS in South Africa. The study team received training on clinical evaluation and standardised testing for HAVS from experienced occupational health practitioners from the Health and Safety Laboratory in the United Kingdom. SIMRAC donated the HAVS equipment to the NIOH on completion of the study, which enabled the NIOH to establish a HAVS centre, the only one of its kind in South Africa. vessels and nerve fibres in the fingers are damaged and the musculo-skeletal system of the upper limb is affected. HAVS has therefore been defined as a disorder affecting the vascular, neurological and musculo-skeletal systems of the upper limb 9. SIGNS AND SYMPTOMS OF HAVS Workers, who suffer from HAVS, experience blanching or whitening, and tingling and numbness of the fingers. Tactile discrimination and HAND-ARM VIBRATION HAVS is a condition which affects workers who regularly operate vibrating hand tools such as rock drills 8. Tools associated with HAVS are listed in Table 1. Vibration produced by these tools enters through the hand and is transmitted to the rest of the upper limb. Blood FIGURE 1. BLANCHING OF FINGER TIPS. Clinical evaluation Step 1: Done by a doctor Standardised objective tests Tests for neurological damage Test for vascular damage Step 2: Done by a technologist or technician competent in the operation of HAVS machines Thermal aesthesiometry Vibrotactile thresholds Cold provocation Stockholm sensorineural staging Stockholm vascular staging Step 3: Done by a doctor FIGURE 2. STEPS IN THE DIAGNOSIS OF HAVS. TABLE 1. TOOLS ASSOCIATED WITH HAVS. Type of tool Example of tool type 1. Percussive hammers and drills used in mining, Rock drills, hammer drills, road breakers. demolition, road construction, and stone working. 2. Percussive metal working tools. Riveting tools, caulking tools, chipping hammers. 3. Forest and garden tools. Chain saws, anti-vibration chain saws, mowers. 4. Grinders and other rotary tools Handheld grinders, handheld sanders, handheld polishers. Modified from Griffin, JULY/AUGUST 2005

3 manipulative dexterity are also affected. Symptoms manifest as difficulty in using the hands in everyday activities, such as fastening buttons, writing and milking cows. Job performance may be affected 10. These workers are also prone to accidents 11. As yet the pathophysiology of HAVS has not been elucidated 12. Vascular disturbance The blanching of fingers, or Vibration White Finger, is a well-known sign of the vascular component of HAVS. In Figure 1 the white arrows point to blanched tips of the index and middle fingers. Blanching is caused by intermittent vasospasms which occlude blood flow to the fingers. In the early stages of the disease, blanching occurs in the tip/s of one or more fingers. As the condition progresses, the rest of the finger becomes affected. Thumbs are rarely affected, and if they are, it usually indicates exposure to high intensity vibration. Areas affected tend to be those in close contact with vibration. Vasospasms are induced by cold, for example holding a glass of cold beer. This can last up to one hour, and when circulation returns, reactive hyperaemia occurs, with consequent painful throbbing fingers. As the condition progresses, frequency of attacks increases. During an attack, pain, numbness, reduced manual dexterity and loss of finger coordination are experienced. tribute to an increased risk of accidents 11. Musculo-skeletal disturbance Musculo-skeletal symptoms of HAVS include pain and stiffness in hands and wrists and to a lesser extent in upper arms and shoulders 15. Impairment of grip is another common finding in workers with prolonged exposure to vibration. Reduced grip strength is due to a neuromuscular problem which causes incomplete muscle contraction 16. Bone cysts and vacuoles have also been found. These abnormalities are thought to be caused by ergonomic risk factors associated with the use of power tools, namely exertion of force, repetitiveness and awkward postures. PROGNOSIS AND TREATMENT Continued exposure to vibration after the onset of HAVS symptoms results in progression of symptoms. The degree to which symptoms regress after cessation of exposure is uncertain. Limited information available suggests Neurological disturbance Neurological and vascular effects of vibration may develop separately or simultaneously 13. It is postulated that vibration causes swelling of adjacent tissues which compress the nerve fibres 14. It can also have a direct effect where nerve fibres and myelin sheaths are damaged causing impaired transmission of nerve impulses. Workers with neurological symptoms of HAVS experience tingling and numbness in affected fingers. Sensory perception, tactile discrimination and manipulative dexterity are all reduced. Impaired hand control is not a handicap in everyday activities, but may con- JULY/AUGUST

4 that neurological symptoms do not improve, but vascular symptoms may improve after several years, provided symptoms were not at a severe stage 17. The best treatment is to avoid further exposure to vibration. There is no universally established medical treatment. Different types of physical treatments such as exercise pools and hot packs have been tried 18. Their effect is palliative. Drugs that alleviate the vascular symptoms by causing vasodilation are also available 19. These drugs are not routinely used, because some subjects find it difficult to tolerate their side effects. FIGURE 3. THERMAL AESTHESIOMETRY. DIAGNOSIS OF HAVS Diagnosis of HAVS requires specialist knowledge and techniques. Evaluation is done by a trained occupational health doctor and a technologist or technician competent in running the standardised tests. In Figure 2 steps in the assessment of HAVS are shown. This assessment method is used in the United Kingdom. Clinical evaluation Clinical evaluation consists of a clinical history, physical examination and special tests. Clinical history The clinical history includes occupational and medical histories. In the occupational history, details of all jobs performed by the worker, including their duration, formal, informal and recreational exposure to vibration and duration of exposure are collected. The medical history should elicit signs and symptoms of HAVS, including past and present medical conditions and current medication. Details of daily smoking and alcohol consumption are recorded. FIGURE 4. VIBROTACTILE THRESHOLD. Physical examination Physical examination of the hands, fingers and upper body is done to detect callosities, scars, trophic changes and skeletal abnormalities. Colour and temperature of the hands, including nicotine stains in the fingers, are noted. FIGURE 5. COLD PROVOCATION. 30 JULY/AUGUST 2005

5 Special tests Special tests are performed to exclude other conditions with symptoms similar to HAVS, for example direct trauma to extremities and thoracic outlet syndrome. Such tests include Allen s, Tinel s, Phalen s, Adson s, Purdue pegboard and grip strength. Allen s test demonstrates integrity of radial and ulnar arteries supplying the hands. Tinel s and Phalen s tests elicit symptoms of carpal tunnel compression. Adson s test detects obstruction to arterial flow in the arm at the level of the neck. The Purdue pegboard assesses dexterity of hands and fingers. Finally, grip strength assesses muscle strength of hands and fingers. Standardised tests Three standardised tests are used to support the clinical diagnosis of HAVS 20. Two are for neurological damage, and one for vascular damage. Tests for neurological damage Tests used to detect nerve damage in the fingers are Thermal aesthesiometry (Figure 3) and Vibrotactile threshold (Figure 4). Thermal aesthesiometry (TA) Thermal aesthesiometry measures temperature sensation of the fingers. The index and little fingers of both hands are tested. The Thermal aesthesiometry unit has a metal plate where warm and cool temperatures are applied. Tested fingers are placed on the metal plate and the subject presses the response button when a change in temperature is felt. Warm and cool thresholds are recorded from responses of the subject. Temperature Neutral Zone (TNZ), which is the temperature that the subject cannot perceive, is obtained from the difference between warm and cool thresholds. Damage to nerves in the fingers is indicated by a large TNZ ( 21 C). Vibrotactile threshold test (VT) The Vibrotactile threshold test measures vibration sensation of the fingers. As with the TA, the index and little fingers of both hands are tested. VT has a probe where two vibration frequencies (31,5 Hz and 125 Hz) are applied. The subject places the tested finger on the probe and when vibration is felt, a response button is pressed. When vibration dissipates, the response button is released. Vibration thresholds are calculated from the subject s responses. Damage to nerves in the fingers is indicated by high vibration thresholds of 0,3 ms 2 and 0,7 ms 2 at 31,5 Hz and 125 Hz respectively. Test for vascular damage Cold provocation (CP) Cold provocation (Figure 5) measures the rewarming times of fingers after being immersed in cold water. Fingers of both hands are tested, except for thumbs. Hands are donned with gloves and immersed in a 15 C cold waterbath for five minutes. Hands are then removed from the waterbath and allowed to rewarm for 10 minutes. The time it takes for the fingers to rewarm by 4 C is calculated. Damage to the blood vessels is indicated by long rewarming times of more than 300 seconds. Staging of symptoms Symptoms of HAVS are staged following the internationally accepted Stockholm Workshop Scales 21 (Table 2). Staging is done for both the neurological and vascular components of HAVS. Staging of neurological component Test scores of the Thermal aesthesiometry and Vibrotactile threshold tests are added together and applied to the Stockholm Workshop Neurological Scale. Maximum total score for the two tests is 16, which correlates with stage 2SN (late). Therefore, to reach stage 3SN, the subject has to report loss of dexterity, Purdue pegboard results have to be abnormal and the Thermal aesthesiometry plus the Vibrotactile threshold scores should be 9 to which value 10 is added. The score of 19 for the Thermal aesthesiometry and Vibrotactile threshold is derived in this way. Staging of vascular component Vascular component of HAVS is staged-based JULY/AUGUST

6 on subjective reports of blanching as well as Griffin Scores (Figure 6). Griffin Scores are applied to the vascular component of the Stockholm Workshop Scales. Scores of blanching are given to each phalanx according to Figure 6. Each hand is given a score, which is staged using the Stockholm Workshop Vascular Scale (Table 2). Thumbs are rarely affected. If they are, the score of each hand could go up to 33. PREVENTION AND CONTROL OF HAVS Risk of HAVS can be reduced by introducing preventive strategies following the hierarchy of controls. These controls are elimination, substitution, engineering, administrative and personal protective equipment. The first two controls are the most effective, but are not always feasible. Others are aimed at reducing exposure and are commonly used to protect vibration exposed workers. Engineering controls These controls rely on technical development of vibrating hand tools to produce low vibration levels. These tools are called anti-vibration tools, for example anti-vibration chainsaws. The principles engineers apply when developing anti-vibration tools are isolation and damping. Isolation removes most of the vibration before it reaches the operator s hand. Damping converts vibration energy to heat. Development of remote controlled vibrating hand tools is ideal in preventing the operator from being exposed to vibration. Administrative controls Administrative controls, such as rest periods and rotation of workers will, expedite vibration exposure time. If workers are multi-skilled, rotation becomes more viable. Teaching and training workers the nature of risk, signs and symptoms of HAVS and best practice, will empower them to do their work safely. Best practice includes maintaining tools regularly, gripping tools lightly, operating the tool when necessary and at reduced speeds, keeping hands warm and stopping smoking. If symptoms of HAVS appear, they should be reported immediately. Workers who have HAVS can be detected early through a medical surveillance program. Medical surveillance also helps identifying workers at high risk, so that they are placed in jobs that will not expose them to vibration. However, medical surveillance for HAVS requires a screening tool which is as yet not available in South Africa. Personal protective equipment In any risk reduction programme, personal protective equipment should be used as last TABLE 2. STOCKHOLM WORKSHOP SCALES. Vascular component Stage Grade Description Griffin Scores 0 No attacks. 1V Mild Occasional attacks affecting only tips of one or more fingers V Moderate Occasional attacks affecting distal and middle (rarely also proximal) phalanges of one or more fingers V Severe Frequent attacks affecting all phalanges of most fingers V Very severe As in stage 3 with trophic changes in fingers. Neurological component Stage Grade Description TA + VT Scores 0SN Vibration exposed but no symptoms. 1SN Mild Intermittent numbness with or without tingling. 3<6 2SN (early) Moderate Intermittent or persistent numbness, reduced sensory perception. 6<9 2SN (late) Moderate As 2SN (early) SN Severe Intermittent or persistent numbness, reduced tactile discrimination and or manipulative dexterity. 19 V=Vascular; SN= Sensori-neural 32 JULY/AUGUST 2005

7 resort. For prevention and control of vibration exposure, anti-vibration gloves have been used. Their effectiveness in attenuating vibration is questionable 22,23. Therefore, their use is not recommended. COMPENSATION HAVS is a compensable disease mentioned under Schedule 3 of the Compensation of Occupational Injuries and Diseases Act of CONCLUSION The existence of HAVS has been established in South Africa. Now that we are aware of the condition, efforts should be directed at prevention and control of vibration exposure 24. Although there are no vibration regulations in South Africa, international standards and guides can be utilised, namely International Standards Organization (ISO) 5349, British Standard (BS) 6842 and the Council of European Communities Directive (CECD) 2002/44/EC. More work still needs to be done to raise awareness about the condition. There is also a need to educate and train more occupational health practitioners on the clinical diagnosis of HAVS. The NIOH is grateful to SIMRAC for donating the HAVS equipment. Workers, who are suspected of having HAVS, can now be referred to the NIOH HAVS centre for assessment. REFERENCES 1. Palmer, K.T., Griffin, M.J., Syddall, H., Pannet, et al. Risk of hand arm vibration syndrome according to occupation and sources of exposure to hand transmitted vibration: A national survey. Am. J. Ind. Med. 2001; 39: Yu, Z.S., Chao, H., Qiao, L., et al. Epidemiologic survey of vibration syndrome among riveters, chippers, and grinders in the railroad system of the People s Republic of China. Scand. J. Work Environ. Health. 1986; 12: Nyantumbu, B., Phillips, J.I., Dias, B., et al. The occurrence of Hand Arm Vibration Syndrome in South African gold mines and the identification of the potential effects of whole body vibration. Johannesburg: Safety in Mines Research Advisory Committee; Taylor, W., Wasserman, D., Behrens, V. Effects of the air hammer on the hands of stonecutters. 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