Work Related Neck and Uper Limb Musculoeskeletal Disorders

R E S E A R C H

work-related neck and upper limb

European Agency for Safety and Health at WorkENEN

OFFICE

L-2985

OF THEFOR OFFICIAL PUBLICATIONSEUROPEAN COMMUNITIES

Luxembourg

EUR

E u r o p e a n A g e n c y f o r S a f e t y a n d H e a l t h a t W o r k

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ntIn order to encourage improvements,

especially in the working environment, as

regards the protection of the safety and

health of workers as provided for in the

Treaty and successive action programmes

concerning health and safety at the

workplace, the aim of the Agency shall be

to provide the Community bodies, the

Member States and those involved in the

field with the technical, scientific and

economic information of use in the field of

safety and health at work.

54 A

S-24-99-712-E

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European Agency for Safety and Health at Work

Gran Vía 33. E-48009 Bilbao Spain

Tel: +34 94 479 4360 . Fax: +34 94 479 4383

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ISBN 92-828-8174-1

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Price (excluding VAT) in Luxembourg: EUR 7


W o r k - r e l a t e d n e c k a n d u p p e r l i m b

musculoskeletal disorders

R E S E A R C H


Report prepared by

Professor Peter Buckle and Dr. Jason Devereux The Robens Centre for Health Ergonomics

European Institute of Health & Medical SciencesUniversity of Surrey

Guildford, Surrey, U.KGU2 5XH

A great deal of additional information on the European Union is available on the Internet.It can be accessed through the Europa server (http://europa.eu.int).

Cataloguing data can be found at the end of this publication.

Luxembourg: Office for Official Publications of the European Communities, 1999

ISBN 92-828-8174-1

© European Agency for Safety and Health at Work, 1999Reproduction is authorised provided the source is acknowledged.

Printed in Belgium


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Following a request from the EuropeanCommission (DGV) and the approval bythe Administrative Board, the EuropeanAgency for Safety and Health at Worklaunched in May 1998 a research informa-tion project on "Work-related Upper LimbDisorders (WRULD)" in order to collect rel-evant research results and to describe andassess these findings. The scope of thestudy included the size of the problemwithin Member States of the EuropeanUnion, the epidemiological evidence forcausation by work, the pathological basisfor work causation and intervention stud-ies demonstrating the effectiveness ofwork system changes.

The European Agency invited the RobensCentre for Health Ergonomics, Universityof Surrey, U.K. to facilitate this work. Thisreport on "Work-related Neck and UpperLimb Musculoskeletal Disorders" has been

prepared by Professor Peter Buckle and Dr.Jason Devereux.

A special consultation process was carriedout in the summer of 1999 by sending themanuscript to the members of theThematic Network Group on Research -Work and Health, to DGV, to theEuropean social partners and to otherexperts on the topic. After the consulta-tion process the final report was preparedand published.

The European Agency wishes to thank theauthors for their comprehensive work andall those individuals involved in the reviewprocess. We especially thank the partici-pants who attended the expert meeting inAmsterdam during October 1998 whoprovided the foundation of the contentswithin the report.

Bilbao, 31 August 1999

European Agency for Safety and Health atWork

F O R E W O R D

w o r k - r e l a t e d n e c k a n d u p p e r l i m b m u s c u l o s k e l e t a l d i s o r d e r s


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C o n t e n t sFOREWORD 3CONTENTS 5WORK-RELATED NECK AND UPPER LIMB MUSCULOSKELETAL DISORDERS - Summary 7Introduction 7Assessment of work-related neck and upper limb musculoskeletal disorders (WRULDs) 7Size of the WRULDs problem 7Biological mechanisms 8Work-relatedness of WRULDs 8Scope for prevention 91. INTRODUCTION 11

1.1 Approaches used to prepare the report 122. THE NATURE OF THE DISORDERS 15

2.1 How are the disorders measured? 162.2 How many experience these disorders in the EU? 182.3 The cost of the problems 232.4 Scientific basis for prevention 252.5 Summary - The Nature of the Disorders 28

3. THE RELATIONSHIP BETWEEN WORK AND NECK AND UPPER LIMB DISORDERS 293.1 Models for the pathogenesis of the disorders 303.2 Biological responses and pathology 333.3 The epidemiological evidence of work-relatedness 393.4 Interventions in the workplace 433.5 Summary - The Work-relatedness of neck and upper limb

disorders 464. STRATEGIES FOR PREVENTION 47

4.1 Introduction 484.2 Health and work system assessment 524.3 Definition of risk and concept of action zones 534.4 Assessment of risk: work system assessment 554.5 Definitions of work system factors to be assessed 56

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5. RISK FACTORS REQUIRING ASSESSMENT 595.1 General aspects of posture 605.2 Neck 615.3 Shoulders and arms 635.4 Wrists 655.5 Interactions 685.6 Hand Arm Vibration (Hand-Transmitted Vibration) 695.7 Work organisation and psychosocial factors 71

6. HEALTH AND RISK SURVEILLANCE 757. DEVELOPMENTS IN THE CONTEXT OF OTHER EUROPEAN UNION

INITIATIVES 778. SUMMARY - STRATEGIES FOR PREVENTION 789. CONCLUSIONS 83

9.1 Diagnostic criteria 849.2 Size of the problem 859.3 Pathogenesis 869.4 Work-relatedness 879.5 Scope for prevention 88

10. REFERENCES 89

A N N E X E S11. APPENDICES 105

Appendix 1. Project organisation 106Appendix 2. Summary of consultation 107Appendix 3. Literature search terms and databases 108Appendix 4. Summary tables of postural risk factors 110Appendix 5. Annex I of the Minimum health and safety requirements

for themanual handling of loads 113


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I n t r o d u c t i o n

The European Commission (Directorate-General V) has requested the assistance ofthe European Agency for Safety andHealth at Work to conduct a review of theavailable scientific knowledge regardingrisk factors for work-related neck andupper limb musculoskeletal disorders(WRULDs). The European Agency invitedProfessor Peter Buckle and Dr. JasonDevereux of the Robens Centre for HealthErgonomics, University of Surrey, U.K. tofacilitate this study and to prepare areport.

The report has drawn together knowledgefrom an extensive set of sources. Theseinclude the contemporary scientific litera-ture, the views of an expert internationalscientific panel, current practice, employerand employee representatives and a num-

ber of official authorities from memberstates. The report is not a comprehensivereview of all original research sources, butrather utilises authoritative reviews of suchsources, where appropriate. Emphasis hasbeen placed on those reviews that wereagreed to be acceptable to the expertpanel of scientists.

A s s e s s m e n t o f w o r k - r e l a t e d n e c k a n du p p e r l i m b m u s c u l o s k e l e t a l d i s o r d e r s( W R U L D s )

There is little evidence of standardised cri-teria for use in the assessment of WRULDsacross European Union (EU) memberstates. This is reflected in the nationallyreported data as well as the research liter-ature. Those studies that have reachedconsensus criteria for WRULDs assess-ments should be disseminated widely forfurther consultation, with a view to stan-dardisation. However, it should be notedthat the assessment criteria for primarypreventative use in workplace surveillanceand occupational health are different fromthe criteria used for some clinical interven-tions.

S i z e o f t h e W R U L D s p r o b l e m

There is substantial evidence within the EUmember states that neck and upper limbmusculoskeletal disorders are a significantproblem with respect to ill health andassociated costs within the workplace. Itis likely that the size of the problem willincrease because workers are becomingmore exposed to workplace risk factors forthese disorders within the EuropeanUnion.

W O R K - R E L A T E D N E C K A N D

U P P E R L I M B

M U S C U L O S K E L E T A L

D I S O R D E R S - S U M M A R Y

Estimates of the cost of the WRULDs prob-lem are limited. Where data do exist (e.g.the Nordic countries and the Netherlands)the cost has been estimated at between0.5% and 2% of Gross National Product.

The lack of standardised assessment crite-ria for WRULDs makes comparison of databetween member states difficult. In addi-tion, little is known of the validity of thereported data. The true extent of ill healthand associated costs within the workplaceacross member states is, therefore, diffi-cult to assess. Despite this, studies thathave used a similar design have reportedlarge differences in prevalence ratesbetween member states. The reasons forthese differences require further investiga-tion.

A number of epidemiological studies havefound that women are at higher risk forwork-related neck and upper limb muscu-loskeletal disorders, although associationswith workplace risk factors are generallyfound to be stronger than gender factors.The importance of gender differences,and their implication for work systemdesign, is largely outside the scope of thisreport but requires more substantialdebate.

B i o l o g i c a l m e c h a n i s m s

Understanding of the biological mecha-nisms of WRULDs varies greatly withregard to the specific disorder in question.For carpal tunnel syndrome, for example,the body of knowledge is impressive,bringing together biomechanics, mathe-matical modelling and direct measure-ment of physiological and soft tissue

changes. A coherent argument is provid-ed from these sources that is persuasive ofthe biomechanically induced pathology ofsuch disorders. For those disorders wherethe knowledge base is smaller, plausiblehypotheses do exist and are currently thesubject of much research interest.

W o r k - r e l a t e d n e s s o f W R U L D s

The scientific reports, using defined crite-ria for causality, established a strong posi-tive relationship between the occurrenceof some WRULDs and the performance ofwork, especially where workers werehighly exposed to workplace risk factors.Thus, the identification of workers in theextreme exposure categories shouldbecome a priority for any preventativestrategy.

Consistently reported risk factors requiringconsideration in the workplace are postur-al (notably relating to the shoulder andwrist), force applications at the hand,hand-arm exposure to vibration, directmechanical pressure on body tissues,effects of a cold work environment, workorganisation and worker perceptions ofthe work organisation (psychosocial workfactors). The limited understanding ofinteractions between these variablesmeans that the relationships describingthe level of risk for varying amounts ofexposure to risk factors in the workplace(i.e. exposure-response relationships) aredifficult to deduce. However, those work-ers at high risk can be identified using cur-rent knowledge.


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S c o p e f o r p r e v e n t i o n

The report has not identified a specificform of action, however, it has provided abasis on which action could be formulat-ed. The recommendations made are con-sistent with European directives on healthand safety issues. The importance of ahealth and risk surveillance programmehas been emphasised, and is supported byboth existing European Union directivesand a number of internationally recog-nised professional commissions and asso-ciations.

Many organisations have sought to imple-ment ergonomic programmes and inter-ventions aimed at primary prevention ofWRULDs. This would suggest that theyalready believe in the effectiveness ofergonomic and occupational health strate-gies aimed at preventing the developmentof this group of disorders. They should beencouraged to help promote any furtheraction. Organisations involved in preven-tion programmes are important role mod-els for others. There is limited but persua-sive evidence on the effectiveness of worksystem interventions incorporatingergonomics although the ability of organ-isations to implement the availableergonomics advice requires further consid-eration.

Appropriate ergonomics interventionon workplace risk factors for any sin-gle specific disorder is likely to helpprevent other disorders. For example,reducing the exposure to hand-armvibration will not only reduce the like-lihood of the development ofRaynaud's disease, but may also

reduce the need for high force exer-tion at the hand and, thus, reduce therisk for hand/wrist tendinitis. Suchbenefits arise because of the commonbiological pathways involved in someof the disorders.

Scientists with experience of policy settingaffirmed their belief that it was prudent toconsider fatigue as a potential precursorto some of the disorders. Its use in sur-veillance programmes was also suggested.The role of fatigue is evident in some exist-ing European health and safety directivesand standards.

The report has considered the ability ofthose at the workplace (e.g. practitioners,worker representatives) to make riskassessments. Advice as to how suchassessments could be made, given suchrestrictions, has been provided. Theagreement of valid, standardised methodsfor the evaluation of working conditionsand assessment of risk factors is required.The ergonomics work system approachmust take due regard of the work risk fac-tors identified in this report and a threelevel model of risk assessment has beenproposed.

The report concludes that existing scientif-ic knowledge could be used in the devel-opment of preventative strategies forWRULDs. These will be acceptable tomany of those interested in preventionand are practical for implementation.

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1.This report has addressed the followingquestions:

What is the extent of work-related neckupper limb musculoskeletal disorderswithin European member states?

What is the epidemiological evidenceregarding work risk factors?

Is their coherent supporting evidence fromthe literature on underlying mechanisms

and physical changes to the neck andupper limbs?

Does intervention in the workplace reducethe risks of work-related neck and upperlimb musculoskeletal disorders?

What strategies are available to preventwork-related neck and upper limb muscu-loskeletal disorders?

It is important to recognise that this reviewwas not intended to cover individual andother non-work factors and their relation-ship with neck and upper limb muscu-loskeletal disorders. It was not also intend-ed to consider the role of clinical manage-ment, rehabilitation or return to work.

I N T R O D U C T I O N


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1.1A P P R O A C H E S U S E D T O

P R E P A R E T H E R E P O R T

This information has been collected froman expert meeting, literature review andconsultation with further experts andinterested parties.

Feedback has been sort on the initial draftof this report from approximately 40 indi-vidual experts, research groups and otherorganisations (available from theEuropean Agency for Safety and Health atWork). Of the 20 responses, all but onehas been wholly supportive of the generalfindings of the report. The exceptionrequested an enlarged scope for the pre-ventative measures in order to considerwider social systems interventions. Therespondent's comments have, where fea-sible, been addressed in this final report.

1 . 1 . 1 E x p e r t M e e t i n g

The meeting of experts (see appendix 1for membership of the panel) was held in

Amsterdam, The Netherlands 7-11thOctober 1998. The aims of this meetingwere to consider firstly whether there wasagreement on the type and nature of neckand upper limb musculoskeletal disordersto be considered. Secondly, to review thedata on the extent of neck and upper limbmusculoskeletal disorders in the he work-place. Thirdly, whether there was suffi-cient evidence that these disorders arework related (considering both the epi-demiological and pathogenic evidence).Fourthly, whether there was evidence thatworkplace interventions would reduce therisks associated with these disorders.Fifthly, to consider the optimal ergonomicapproaches to prevention and finallywhether further research studies wererequired. Each of these areas was con-sidered during the four days in committee.

1 . 1 . 2 T h e L i t e r a t u r e S e a r c h

The literature review has includedobtained from the following sources:l Scientific peer reviewed journalsl Conference proceedingsl Abstractsl Recent textbooksl Internally reviewed government or reg-

ulatory body reportsl CD ROM and online commercial and

regulatory agency databasesl Bibliographies of recent and relevant

articlesl Non-english literature articles consid-

ered relevant and translated intoEnglish

l Publisher on-line table of contents serv-ices for the latest research articles

l Reports not yet submitted or papers inpress to scientific peer reviewed jour-


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nals and provided by individualresearchers.

The literature search has focused upon thefollowing areas:l Prevalence of disordersl Epidemiology of disordersl Mechanisms of disordersl Intervention case studies and clinical

case studies

The search terms have been included inthe appendix 3.

Note: Although not included here, a fullbibliography of sources is available.

1 . 1 . 3 C o n s u l t a t i o n a n d L i a i s o n

Consultation and liaison with a number ofestablished authorities or centres has alsotaken place (see appendix 2 for details). Itis recognised that the opportunities andresources available for this process havebeen limited. It is hoped that wider con-sultation and more extensive views will begathered following final publication of thereport.



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2.The scientific committee for musculoskele-tal disorders of the InternationalCommission on Occupational Health(ICOH) recognise work-related muscu-loskeletal disorders which describe a widerange of inflammatory and degenerativediseases and disorders that result in painand functional impairment (Kilbom et al.,1996).

Such conditions of pain and functionalimpairment may affect, besides others,

the neck, shoulders, elbows, forearms,wrists and hands. The conditions forthese regions are collectively referred to asthe neck and upper limb musculoskeletaldisorders (ULDs).

According to the World HealthOrganisation, work-related musculoskele-tal disorders arise when exposed to workactivities and work conditions that signifi-cantly contribute to their development orexacerbation but not acting as the soledeterminant of causation (World HealthOrganization, 1985).

To give some indication of the specificconditions of neck and upper limb muscu-loskeletal disorders identified within theliterature, Hagberg et al., (1995) have clas-sified them according to whether a disor-der is related to the tendon, nerve, mus-cle, circulation, joint or bursa. The disor-ders under each type are listed in table 1.

T H E N A T U R E O F

T H E D I S O R D E R S


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2.1H O W A R E T H E D I S O R D E R S

M E A S U R E D ?

Clinical diagnostic criteria for health sur-

veillance of these conditions across Europe

are not yet available. Clinicians and

researchers have relied upon different

bodies of knowledge to justify the criteriaused. However, general diagnostic criteriafor work-related neck and upper limb dis-orders have been developed within indi-vidual member states, for example:

l UK – (Harrington et al., (1998), Cooperand Baker (1996))

l The Netherlands (Sluiter et al., (1998))

l Finland (Waris et al., (1979))

l Sweden (Ohlsson et al., (1994))

l Italy (Menoni et al., (1998))

The evaluation systems in each memberstate include a category for musculoskele-tal conditions that are non-specific (i.e.where a specific diagnosis or pathologycannot be determined by physical exami-nation but pain and/or discomfort isreported.) According to data sources inthe U.K. approximately 50% of the casesthat present with upper limb pain are clas-sified as a non-specific upper limb condi-tions (Cooper and Baker, 1996).

T a b l e 1 . C l a s s i f i c a t i o n o f s o m e n e c k a n d u p p e r l i m b m u s c u l o s k e l e t a l d i s o r d e r s a c c o r d i n g t o p a t h o l o g y . ( H a g b e r g e t a l . , 1 9 9 5 )

Tendon-related Nerve-related Muscle-related Circulatory/vascular Joint-related Bursa-relateddisorders disorders disorders type disorders disorders disorders

l Tendinitis/ l Carpal tunnel l Tension neck l Hypothenar l Osteoarthritis l Bursitisl peritendinitis/ l syndrome l syndrome l hammer syndromel tenosynovitis/ l Cubital tunnel l Muscle sprain l Raynaud’s l synovitis l syndrome l and strain l syndromel Epicondylitis l Guyon canal l Myalgia and l De Quervain’s l syndrome l myositisl disease l Pronator teres l Dupuytren’s l syndromel contracture l Radial tunnel l Trigger finger l syndromel Ganglion cyst l Thoracic outlet

l syndromel Cervical syndromel Digital neuritis

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Consultation with the expert panel has ledto a detailed consideration of the need forspecific and sensitive diagnostic criteria.Whilst the desirability of specific diagnos-tic criteria are recognised, the expert panelsuggested that, in general, the preventionstrategies recommended or put into prac-tice to avoid the risks of these disorderswould not be dependent upon the diag-nostic classification. It was also thoughtimportant that musculoskeletal disor-ders without a specific diagnosis orpathology be considered in healthmonitoring and surveillance systems.

This conclusion is supported by a recentepidemiological study (Burdorf et al.,

1998). The experience of symptoms ofmusculoskeletal disorders in the neck,shoulder and upper limbs has been shownto increase the risk of worker absence(recorded by the company) by approxi-mately 2-4 times compared to workers notexperiencing symptoms in a 2 year follow-up study.

The relationships between symptoms,injury reporting, impairment and disabilityremain unclear. A greater understandingof these relationships, along with the clin-ical natural history of these disorderswould be beneficial (National ResearchCouncil, 1999).

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2.2H O W M A N Y E X P E R I E N C E

T H E S E D I S O R D E R S

I N T H E E U ?

The prevalence rates of clinically verifiableneck and upper limb disorders using stan-dardised diagnostic procedures acrossEuropean member states are not currentlyavailable. However, surveys and injuryreports to occupational health agencieshave been used to estimate the size of theproblem within Europe.

Evidence of the size of the problem can bederived from self-reports of musculoskele-tal conditions across the European mem-ber states. Table 2 shows that the preva-lence of self-reported symptoms of mus-culoskeletal disorders varies substantiallybetween countries. Although such dataare useful, the prevalence of self-reportedsymptoms may be under or overestimatedin surveys because of methodological dif-ficulties.

A programme in the Netherlands entitled"SAFE" commissioned a survey to collectinformation concerning the prevalence ofwork-related neck and upper limb disor-ders. In a study population of 10,813employees in 1998, 30.5% had experi-enced self-reported neck and upper limbsin the previous 12 months (Blatter andBongers, 1999). The study group waschosen to be representative of theNetherlands distribution of industrial sec-tors, company sizes and regions. However,a survey by the Central Bureau forStatistics in the Netherlands estimatedthat the prevalence of work-related com-plaints in the neck, shoulder, arm or wristswithin the previous year in Dutch industrywas approximately 19% in 1997 (Otten etal., 1998).

Despite such differences, the approximatesize of the problem can be appreciated bysurveys, and each consistently shows thata substantial proportion of workers in theEuropean Union experience work-relatedmusculoskeletal conditions that affect theneck and upper limbs.

Further information is available in somemember states(1), although definitions ofboth exposures and health outcomes arenot standardised. This position has beenrecognised in a survey conducted by theEuropean Trade Union Technical Bureaufor Health and Safety (TUTB) in Brussels,Belgium (Tozzi, 1999). This showed thatthe information collected on muscu-loskeletal disorders by each EU memberstate was different in both definition andmethod of reporting. For these reasons it

(1) For example, the Spanish National Work Conditions Survey 1997, as supplied by the Instituto Nacional deSeguridad e Higiene en el Trabajo.

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is not often possible to compare outcomesfrom different countries.

One study that has used a commonapproach is the Second European Surveyon Working Conditions (Paoli, 1997).Figure 1 shows the percentage prevalenceobtained for each member state. The sizeof the problem using this outcome meas-

ure varies across each member state.However, in most the proportion ofrespondents reporting muscular pains inthe arms and legs is considerable.

Some literature reflects the use of theInternational Classification of Disease-9thRevision (ICD-9). The accuracy of ICD-9 foridentifying soft tissue disorders of the

T a b l e 2 . T h e p r e v a l e n c e o f s e l f - r e p o r t e d s y m p t o m s o f m u s c u l o s k e l e t a l d i s o r d e r s w i t h i n s o m e E U m e m b e r s t a t e s .

Country Study/ Occupations Prevalence OutcomeOrganisation Definition

The Netherlands TNO Work & Employment General Industry 30.5% Self-reported neck and Amsterdam 1999 upper limbs in the last Blatter & Bongers 1999 12 months

Belgium Blatter et al., 1999 39.7%

The Netherlands POLS Population Survey General industry 19% Self-reported job Central Bureau for related complaints of Statistics pain in the neck,Otten et al., 1998 shoulders, arm or wrist

in the last year

2nd European Union European Foundation for General industry 17 % Self-reported muscular Survey, Indicators of the Improvement of pains in arms or legs working conditions in Living and Woking affected by workthe EU Conditions, Dublin Paoli,

1997

Great Britain SWI General industry 17% Self-reported The Health & Safety symptoms in the neck Executive and upper limbs in Jones et al. 1998 the last 12 months

Denmark National Institute of General industry 29% of men, Neck musculoskeletal Occupational Health 46% of woman problemsBorg & Burr, 1997 26% of men, Shoulders musc.

44% of woman problems14% of men, Hands musc.20% of woman problems

(all in the last 12 months)

Sweden The Working Environment General industry Approximately 20% men Self-reported pain in Statistics Sweden, 1997 Approximately the upper part of the (Am 68 SM 9801) 33% woman back or neck, or in

the shoulders or arms after work every week

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neck and upper limbs has been studied(Buchbinder et al., 1996). Results showthat the accuracy of ICD-9 is poor whencompared to data taken from medicalrecords.

Pilot data on recognised cases (classifiedaccording to the European Schedule ofOccupational Diseases and collected byEurostat) do not yet provide reliable esti-mates of the size of the problem. Differentinsurance systems and lists of prescribeddiseases in the member states makes anaccurate assessment of the size of theproblem very unlikely.

Nevertheless, the data are available toenable suitable estimates on thenature, characteristics and trends ofneck and upper limb musculoskeletaldisorders to be made.

This view (TUTB, 1998) is also held by theEuropean Trade Union Technical Bureaufor Health and Safety (TUTB) and theEuropean Trade Union Confederation(ETUC).

Some European member states have datafrom cases reported to national insuranceand occupational health boards. InSweden, for example, occupationalinjuries are reported to the National Boardof Occupational Safety and Health.Diagnoses obtained in 1995 for work-related diseases of muscles, skeleton andother soft tissues for employed and self-employed workers totalled =9 398. Ofthese, 217 cases of rotator cuff tendonitis,538 cases of epicondylitis, 215 cases ofpain in the neck and 133 cases of pain inthe neck and shoulders were identified(Broberg, 1997). Between 1990 and 1992disorders of the musculoskeletal system(which include the lower limbs, back,neck, shoulders and upper limbs) repre-sented at least 70% of all reports inSweden. The prevalences of reportedmusculoskeletal disorders in Denmark andFinland were the largest of all reportedoccupational injuries (36% and 39%respectively). In Norway, musculoskeletaldisorders constituted 15% of all reportedoccupational injuries (Broberg, 1996).

T a b l e 3 . R e p o r t e d c a s e s o f o c c u p a t i o n a l d i s e a s e s b y d i a g n o s i s i n 1 9 9 0 - 1 9 9 2 . T h e t o t a l n u m b e r o f c a s e s N a n d t h e n u m b e r o f c a s e s

p e r 1 0 0 0 0 e m p l o y e d p e r y e a r ( f r e q ) .Denmark Finland Norway Sweden

N freq N freq N freq N freq

Carpal tunnel syndrome 456 0,6 90 0,1 6 - 1 288 1,1Rotator cuff syndrome 633 0,8 6 - 145 0,3 3 350 2,9Epicondylitis - - 4 224 6,0 23 - 6 614 5,7Frozen shoulder - - 127 0,2 - - 286 0,2Synovitis, bursitis 7 142 9,1 5 286 7,6 389 0,7 1 571 1,4Myalgia, myositis 2 141 2,7 22 - 171 0,3 12 773 11,0Insertion tendinitis in hand/wrists - - 2 - 7 - 902 0,8Unspecified vibration injury –Raynauds syndrome etc. 536 0,7 84 0,1 111 0,2 840 0,7Source: (Broberg, 1996)

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Table 3 shows of the size of the problemwithin the Nordic countries. The design ofthe workers’ compensation systems in dif-ferent countries probably influences thereporting behaviour and thereby the mag-nitude of the problems. There are alsofactors such as under/over-reporting andmisclassification of reported diagnosesthat affect comparisons between memberstates.

A significant proportion of all reportedmusculoskeletal diagnoses were consid-ered to be associated with ergonomicwork risk factors – Norway 15%,Denmark and Finland 40% and Sweden70% (Broberg, 1996).

In Italy, musculoskeletal disorders, otherthan vibration white finger, have onlybeen compensated in the last 2-3 years.According to the management of theNational Institute for Insurance of Injuriesand Occupational Diseases, the claims formusculoskeletal disorders have beenincreasing strongly in this period.Musculoskeletal disorders from biome-chanical overload increased from 873reports in 1996 to 2000 in 1999.

In 1998, 60% of claims for musculoskele-tal disorders in the upper limbs wererecognised as occupational diseases andso resulted in compensation. More than60% of the conditions were carpal tunnelsyndrome and the remainder was tendini-tis and tenosynovitis of the hand andwrist, and epicondylitis of the elbow(2).

These musculoskeletal conditions are notincluded in the official list of occupational

diseases in Italy but, following a high courtruling in 1979, it is possible to compen-sate workers if it can be demonstratedthat a clear exposure-response relation-ship for a specific disorder exists (Bovenzi,1999).

Between 1988-1998 in Italy, there were5360 cases compensated for vibration-induced disorders of the upper limbs witha maximum number of cases (n=863) in1991 and a minimum in 1998 (n=169). Inthe same decade, vibration-induced disor-ders as a percentage of all compensatedoccupational diseases ranged between3.9% and 5% per year. The percentageof compensated cases for vibration-induced disorders of the upper limbstends to remain stable. There is a generaltendency towards a comparable reductionin the number of compensated cases forvibration-induced disorders and the totalnumber of compensated occupational dis-eases.

According to the Institut National deRecherche et de Sécurité (INRS) in France,the percentage of recognised and com-pensated musculoskeletal disorders com-pared to the total number of occupationalill health diseases has steadily increasedfrom 40% (n=2,602) in 1992 to 63%(n=5,856) in 1996.

In Great Britain, a labour force survey con-ducted by the Health and Safety Executiveestimated that 506 000 workers experi-enced a self-reported condition thataffected the neck or upper limbs in 1995.The types of disorders reported included

(2) Data kindly provided by Dr. Bovenzi, University of Trieste, Italy and Prof. Grieco, University of Milan, Italy.

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carpal tunnel syndrome, frozen shoulder,tenosynovitis, tennis or golfer’s elbow andRSI. Limitation of movement was report-ed by 86% of the survey respondents(Jones et al., 1998). As a result of thenumber of workers experiencing theseconditions, approximately 5.5 millionworking days were lost annually due tomusculoskeletal disorders of the neck andthe upper limbs and, in addition, 110 000working days were lost annually due tovibration white finger, according to thesurvey (Jones et al., 1998). The number ofdays lost annually for neck and upper limbmusculoskeletal disorders was equivalentto the number for back disorders.

Ex t rapo la t ionfrom a survey ofgeneral practi-tioners in Britainsuggests that 20000 cases ofw o r k - re l a t e dcarpal tunnelsyndrome occurper year. Thisdisorder waseither caused orexacerbated bywork or inter-fered with theability to work. This represents approxi-mately half of the number of cases withcarpal tunnel syndrome seen by thosedoctors that responded to the survey(Health and Safety Commission, 1995).

In Great Britain, data are collected on thenumber of assessed cases of disablementfor a range of upper limb musculoskeletaldisorders that result in benefit paid (severe

disablement) or unpaid. The assessedconditions include beat hand, beat elbow,tenosynovitis, vibration white finger andcarpal tunnel syndrome. The data indicatethat the number of claims resulting inbenefit compared to the total number ofassessed claims has risen from 1.7% in1990 to 22.5% (n=949) in 1996/97.

Therefore, the number of claims that haveresulted in disablement benefits hasincreased while the number of claims forupper limb musculoskeletal disordersresulting in no benefits has decreased(Health and Safety Commission, 1998). Ofall the prescribed industrial disease claims(that included physical, biological and

chemical agents)in 1996/7 thatresulted in bene-fits, approxi-mately 62%were due toupper limb mus-culoskeletal dis-orders. The totalnumber ofclaims assessedfor upper limbmusculoskeletaldisorders was4220. In com-

parison, the total number of claimsassessed for occupational deafness was413 (approximately 1/10th of the 4220cases of ULDs). The perception in the U.K,however, is that there is a much higherincrease in work-related upper limb disor-ders that are presented to medical expertsand dealt with through the legal systemand which are not prescribed industrialdiseases (Helliwell, 1996).

0

5

10

15

20

25

30

35

40

Belgiu

m

Denmark

Former W

est Germ

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Spain

France

Irelan

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Luxem

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Netherla

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Former E

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nAus

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F i g u r e 1 . D a t a o b t a i n e d f r o m t h e 2 n d E u r o p e a n S u r v e y o n W o r k i n g

C o n d i t i o n s i n t h e E u r o p e a n U n i o n i n 1 9 9 6 .

Perce

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Percentage of self-reported muscular pain in the arms or legs

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2.3T H E C O S T O F T H E P R O B L E M S

Not every European member state collectsinformation on the costs of neck andupper limb musculoskeletal disorders.Toomingas (1998)(3) estimated that about20-25% of all expenditure for medicalcare, sick leave and sickness pensions inthe Nordic countries in 1991 was relatedto conditions of the musculoskeletal sys-tem, of which 20-80% were work related.

Half of these conditions were attributed toneck and upper limb musculoskeletal dis-orders and, in Sweden, these problemsconstituted 15% of all sick-leave days and18% of all sickness pensions in 1994(Statistics Sweden, 1997).

Estimates by Toomingas (1998) haveshown that the total expenditure for neckand upper limb musculoskeletal disorders

was approximately 0.5-2% of the grossnational products in the Nordic countries(Data from Morch, 1996; Hansen andJensen, 1993.)

In Britain, the Health and Safety Executive(HSE) estimated that work-related upperlimb disorders incurred approximate costsof £1.25 billion per year (Davies andTeasdale, 1994).

The direct costs from compensation ofmusculoskeletal disorders are appreciatedfar more than the indirect costs associatedwith disruptions in productivity and quali-ty, worker replacement costs, training andwork absence costs. It is believed that thedirect costs due to compensated workrelated musculoskeletal disorders are onlya relatively low proportion (30-50%) ofthe total costs (Hagberg et al., 1995).Borghouts et al. (1999) have estimatedthat the direct costs of neck pain in theNetherlands for 1996 were $160 milliondollars and the indirect costs were $527million. The total cost of neck pain repre-sented 0.1% of the gross domestic prod-uct in 1996.

There is substantial evidence to sug-gest that neck and upper limb muscu-loskeletal disorders are a significantproblem within the European Union.Some member states have identified amajor ill-health and financial burdenassociated with these problems.

(3) Estimate based on "Working environment and national economies in the Nordic Countries" by the Nordic Councilof Ministers (Report No. 556, 1993 by Hansen,M. and Jensen,P.)

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2 . 3 . 1 R e s e a r c h P r i o r i t i e s

Survey results from the Netherlands andthe U.K. have identified a priority need forresearch in the topic of work-relatedupper limb musculoskeletal disorders.

The research priority needs in theNetherlands were assessed by surveyingthe occupational health and safety servic-es, scientific research institutions, govern-ment and companies (Van der Beek et al.,1997). It was collectively decided thatpreventive measures and control solutionswere the highest priority area in order toimprove work conditions.

Two surveys conducted in the U.K. by theInstitute of Occupational Health(University of Birmingham) provided infor-mation regarding the priorities in researchaccording to occupational physicians andpersonnel managers (Harrington, 1994;Harrington and Calvert, 1996). Bothoccupational groups acknowledged back,neck and upper limb musculoskeletal dis-

orders as an outcome that needed priorityresearch but personnel managers consid-ered practical strategies more importantthan risk factor identification, which wasthe reverse view of the physicians.

Trade union initiatives in EU memberstates have shown increasing employerawareness regarding musculoskeletal dis-orders. A need to increase this awarenesshas been identified according to surveysconducted by trade unions in France,Spain, the United Kingdom and Denmark(TUTB, 1996).

This review suggests that neck andupper limb musculoskeletal disordersare increasingly recognised as a signif-icant occupational health problem byoccupational doctors, employers, aca-demia, trade unions and governments.There are data that support the needto address these disorders within theEuropean Union.


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2.4S C I E N T I F I C B A S I S F O R

P R E V E N T I O N

Ergonomic interventions may reduce theoccurrence by approximately 30-40%(Hansen and Jensen, 1993). This is basedupon the number of musculoskeletal dis-orders cases considered to be work relat-ed in the Nordic countries. For occupa-tions that are highly exposed to work riskfactors for musculoskeletal problems theproportion may be as high as 50-90%(Hagberg and Wegman, 1987).

The expert panel suggested that onepreventative strategy might com-mence by identifying groups that arehighly exposed to risk factors for neckand upper limb musculoskeletal disor-ders. They considered that the great-est benefits, relative to the resourcesrequired, might be realised by reduc-ing the risks in these groups.

2 . 4 . 1 I n d u s t r i e s a t r i s k

Data from the 2nd European Survey onWorking Conditions (Paoli, 1997) identi-fied the industries (across the Europeanmember states) where 40% or more ofthe workers were exposed to three ormore of the following risk factors for atleast 25% of the working time:l Working in painful positionsl Moving heavy loadsl Short repetitive tasksl Repetitive movements

The industries where the greatest expo-sures were identified included:l Agriculture, forestry and fisheriesl Mining, manufacturingl Constructionl Wholesale, retail and repairsl Hotels and restaurants

High exposures were also found in otherindustries.

The occupational groups with the greatestexposures were agriculture and fisheryworkers, craft and retail trade workers,plant and machine operators and workersin elementary occupations.

The industries with the least exposure tothese risk factors included:l Transport and communicationl Financial and intermediationl Real estate and business activityl Public administration

In the Netherlands (Blatter and Bongers,1999), some of the highest annual preva-lence rates of work related neck andupper limb symptoms have been found inthe industries that are the most highlyexposed to the risk factors for neck and


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upper limb musculoskeletal disorders andinclude:l Hotel, restaurant and catering (40%)l Construction (38%)l Production (33%)

2 . 4 . 2 O c c u p a t i o n s a t R i s k

Tailors (47%), building construction work-ers (43%), loaders/unloaders (42%), sec-retaries and typists (38%) were some ofthe occupations with the highest annualprevalences of symptoms. This comparedto the lowest prevalence found for com-mercial occupations (21%). These datacame from a study in the Netherlands of10,813 employees and used self-reportedwork-related neck and upper limb symp-toms (Blatter and Bongers, 1999).

The Second European Survey (Paoli, 1997)found that the occupational groups withthe least exposures were legislators andmanagers, professionals, technicians andclerks. It is important to note that indus-trial sector or occupational classificationsmay be misleading when identifying areasrequiring priority action. This is because ajob title may consist of a wide range of jobtasks associated with risks, and the dura-tion and distribution of these tasks mayvary considerably between each worker(Kauppinen, 1994). It has been shownthat these data can be used to form broadcategories of jobs with similar exposure towork demands (de Zwart et al., 1997).These may provide informative patterns ofwork related disorders. Therefore, it isimportant to assess each job that is per-formed rather than rely on crude esti-mates of risk for industrial sectors or occu-pational groups.

Not only are many workers in theEuropean Union highly exposed to workrisk factors for neck and upper limb mus-culoskeletal disorders but the magnitudeof the exposure seems to be increasing,according to research by the EuropeanFoundation for the Improvement of Livingand Working Conditions, Dublin, Ireland(Dhondt and Houtman,1997).

In the four years between the first andsecond European Surveys on WorkingConditions in Europe, the percentage ofworkers exposed for greater than 50% ofthe working time increased for the follow-ing: l Working in painful posturesl Handling heavy loadsl Working at high speed l Working with deadlines

It would seem, therefore, that there isconsiderable potential for reducingthe exposure to work related risk fac-tors of neck and upper limb muscu-loskeletal disorders.

2 . 4 . 3 G e n d e r a s a r i s k f a c t o r

A number of epidemiological studies havefound that women are at higher risk forwork related neck and upper limb disor-ders (e.g. Hagberg and Wegman, 1987),whilst other studies report no such differ-ences (e.g. Silverstein, 1985).Comparisons between work and genderfactors frequently find stronger associa-tions with workplace risk factors (Burt,1998). Other factors thought to be impor-tant in understanding the observed gen-der differences are that females are oftenemployed in more hand intensive tasks


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and that anthropometric differences (e.g.body size, strength) might disadvantagethe female worker in work systems whereno consideration has been taken of suchdifferences (Nordander et al., 1999). Thismight apply, in particular, to tool design

(Pheasant, 1991, 1996) and work surfaceheights. The importance of gender differ-ences is largely outside the scope of thisreport but requires more substantialdebate.


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2.5S U M M A R Y - T H E N A T U R E

O F T H E D I S O R D E R S

There is substantial evidence within theEU member states that neck and upperlimb musculoskeletal disorders are a sig-nificant problem with respect to ill healthand associated costs within the work-place.

There are few estimates of the cost ofthese problems. Where data do exist (e.g.Nordic countries) the cost has been esti-mated at between 0.5% and 2% of GNP.It is likely that the size of the problem willincrease as exposure to work-related riskfactors for these conditions is increasingwithin the European Union.

A number of member states (e.g. Sweden,Great Britain) have studied representativesamples of the workforce with regard tothe site of musculoskeletal disorders.Results have shown that problems for theneck and upper limb are second in impor-tance only to back disorders, as judged

through self-reported symptom preva-lence.

There is little evidence of the use of stan-dardised criteria across member states.This is reflected in the nationally reporteddata as well as the research literature andmakes comparison between memberstates difficult. Studies that have reachedconsensus diagnostic criteria should bedisseminated widely for further consulta-tion, with a view to standardisation. Thisreport recognises that the criteria for pri-mary preventative use in workplace sur-veillance and occupational health will bedifferent from the criteria used for someclinical interventions.

Those studies that have used the samemethodological criteria have reportedlarge differences in prevalence ratesbetween member states. The reasons forthis require further investigation.

A number of epidemiological studies havefound that women are at higher risk forwork related neck and upper limb disor-ders, although associations with work-place risk factors are generally found to bestronger than gender factors. The impor-tance of gender differences, and theirimplication for work system design, islargely outside the scope of this report butrequires more substantial debate.

T H E R E L A T I O N S H I P B E T W E E N

W O R K A N D N E C K A N D U P P E R

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3.1M O D E L S F O R T H E

P A T H O G E N E S I S O F T H E

D I S O R D E R S

of the body over time (termed a dose).The dose causes effects such as increasedcirculation, local muscle fatigue and othervarious physiological and biomechanicaleffects i.e. there is a response by the bodyinitiated by internal stimuli, which them-selves arise from external factors. Theresponse of the body may increase ordecrease the ability to maintain or improvethe capacity to cope with further respons-es.

Over time, a reduced capacity may affectthe dose and the subsequent response. Toclarify, if there if insufficient time to allowthe capacity of the tissues to regeneratethen a further series of responses is likelyto further degenerate the available capac-ity. This may continue until some type ofstructural tissue deformation occurs thatmay be experienced, for example, as pain,swelling or limited movement.

Whilst this model is useful for explainingthe cumulative nature of neck and upperlimb musculoskeletal disorders, it was

recognised bythe experts thatthere are alter-native pathwaysnot consideredin this model.Other models(Van der Beekand Frings-Dresen, 1998;Winkel andM a t h i a s s e n ,1994) suggestthat a pathwaybetween workcapacity and

Researchers from Denmark, Finland,Sweden, England and the United Statesdeveloped a conceptual model to promotethe understanding of the possible path-ways that could lead to the developmentof neck and upper limb musculoskeletald i s o r d e r s(Armstrong etal., 1993).

This model,shown in figure2, describes foursets of interact-ing concepts -exposure, dose,capacity andr e s p o n s e .Worker activityproduces internalforces actingupon the tissues

F i g u r e 2 . A c o n c e p t u a l m o d e l o f n e c k a n du p p e r l i m b m u s c u l o s k e l e t a l d i s o r d e r s t h a t

d e s c r i b e s t h e p a t h w a y s i n v o l v e d i n t h ep a t h o g e n e s i s o f t h e s e d i s o r d e r s . F r o m A r m s t r o n g e t a l . , ( 1 9 9 3 ) .

Exposure(Work Requirements

Capacity

DoseResponse 1

Response 2...

EXTERNAL

INTERNAL


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the work activity may exist, such that areduction in capacity may result in areduction in the amount of work per-formed. This reduction in work activitymay be sufficient to allow worker capacityto increase.

The concept of exposure in figure 2 can beexpanded to include the model proposedby Dutch researchers (Van der Beek andFrings-Dresen, 1998).Figure 3, therefore,shows the exposure orwork requirementsoperationalised as theworking situation, theactual workingmethod, and posture,movements and exert-ed forces.

The working situationis characterised bywork demands andjob decision latitude.The latter is defined asthe extent of autono-my and opportunitiesfor workers toimprove (or to makeworse) the working situation by alteringthe work demands. The working situationis, therefore, characterised by the organi-sation of work (work organisation factors)and the perceptions held by workersregarding the way the work is organised(psychosocial work factors).

The working situation constructs the waya worker performs the work activity. Thiscan be affected by individual characteris-tics such as anthropometry, physical fit-

ness, age, gender, and previous medicalhistory.

The method that an individual workeradopts will affect the level, duration andfrequency of exposure to work postures,executed movements and the forces exert-ed. This will affect the internal factorspreviously discussed (see figure 2.)

The model shown infigure 4 (NationalResearch Council,1999) provides addi-tional concepts forthose factors that lieexternal to the indi-vidual (i.e. those thatcomprise exposure inthe Armstrong et al.(1993) model). Whilstnot all of these factorsare considered withinthis report, it wasconsidered appropri-ate to provide abroader view thatshowed the potentialimportance of factorssuch as non-work

activities and individual factors. Workorganisation, production rates and thetime taken to perform a work task affectthe frequency and duration of force exer-tions. In some instances, the time takenfor a process change can determine softtissue recovery times. The postures adopt-ed in the workplace are affected by thedesign of work equipment, the location ofobjects, the size and shape of handles andthe orientation of objects.

F i g u r e 3 . E x p a n s i o n o f t h e e x p o s u r eb o x s h o w n i n f i g u r e 2 . A d a p t e df r o m V a n d e r B e e k a n d F r i n g s -

D r e s e n ( 1 9 9 8 ) .

Working situation

Actual working

PostureMovement

Exerted forces

Internal factors shown in figure 2

Exposure


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In conclusion, the three models show con-siderable agreement. They serve as a use-ful basis for exploring research hypothe-ses. They also provide a framework forunderstanding both the pathogenesis andthe relationship of these disorders withwork.

F i g u r e 4 . C o n c e p t u a l f r a m e w o r k o f p h y s i o l o g i c a l p a t h w a y s a n d f a c t o r s t h a tp o t e n t i a l l y c o n t r i b u t e t o m u s c u l o s k e l e t a l d i s o r d e r s ( N a t i o n a l R e s e a r c h

C o u n c i l , 1 9 9 9 ) .

Load

Response

Physiologicalpathways

Impairment

Disability

Symptoms Adaptation

Work procedures,equipment andenvironment

Organisational factors

Social context

Individual, Physicaland Psycho-logical

Factors and Non-work related

activities


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3.2B I O L O G I C A L R E S P O N S E S

A N D P A T H O L O G Y

The 1999 National Research Councilreview provides a contemporary andauthoritative overview of the response ofsoft tissue to physical stressors encoun-tered during work system practices(National Research Council, 1999). It hashighlighted the importance of consideringthe biological responses of tissues to bio-mechanical stressors. The expert panelinvolved in this report did not feel thatthere was one single common pathwayfor all exposures although the importanceof the biomechanical pathway was recog-nised.

It has been shown that activities at work,daily living and recreation may often pro-duce biomechanical loads upon the bodythat approach the limits of the mechanicalproperties of soft tissues. Up to certainlimits some types of soft tissue, like mus-

cle, adapt to repetitive loading while othertissue such as nerves are less adaptable.

The expert panel was of the opinion thatthe biomechanical stressors needed to beconsidered in conjunction with individualfactors, the concept of internal loads andresponses to internal loads (see Armstronget al., 1993) and non-biomechanical fac-tors (e.g. work organisational, social andother psychological factors).

All soft tissues including muscles, tendons,fascia, synovia and the nerve will fail whensufficient force is applied (NationalResearch Council, 1999). Ethical issues inexperimental research prevent many suchstudies from having been performed within-vivo human tissue. However, cadaverstudies and animal modelling have provid-ed supportive evidence of the limits forsuch tissues before failure occurs. The tis-sue response may be in the form of defor-mation leading to inflammation, musclefatigue and failure at a microscopic level.

The extent to which the tissues fail withregard to single event, cumulative orrepetitive action has also been document-ed in a number of studies. The NationalResearch Council (1999) review considersthese and also describes how these find-ings can be applied to humans in theworkplace. It notes that the laboratorystudies meet the causal criteria laid downwith regard to: temporal ordering, causeand effect covariation, the absence ofother plausible explanations for theobserved effect, temporal contiguity; andcongruity between the cause and effect.


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The following section provides examplesof how each of the soft tissues at risk inthe neck and upper limb has been consid-ered with regard to the responses andfatigue/failure that may occur. It is notintended to be a comprehensive overviewof the area, but rather is intended todemonstrate that there is suitable docu-mented scientific literature that allows usto establish that mechanisms can and doexist, whilst also acknowledging thatsome aspects require further research. Itshould be appreciated that an holisticunderstanding of the full pathogenesis ofeach disorder is not yet available.However, where mechanisms have yet tobe determined, plausible hypotheses havebeen developed and are being tested.

Recent reviews by Ashton-Miller (1999),Hägg (1998), Rempel et al., (1999),Radwin and Lavender (1999) and Winkeland Westgaard (1992) have proved espe-cially helpful in preparing this section.

3 . 2 . 1 M u s c l e p a t h o l o g y

Hägg (1998) has reviewed the literatureregarding muscle fibre abnormalities inthe upper trapezius muscle with respect tooccupational static load and work relatedmyalgia in the shoulder/neck region. Thisis a common complaint in workersexposed to high static or repetitive load inthe shoulder region. The review recognis-es that the underlying physiological mech-anisms causing this myalgia are only par-tially understood.

Early hypotheses suggested that generalischemia due to high static load with theresultant occlusion or impedance of circu-

lation was a causative factor (Jonsson,1982). However, later research byVeiersted et al. (1993) has shown thatproblems of myalgia can occur at very lowcontraction levels. This, and otherresearch, led Hägg (1991) to the hypothe-sis that specific muscle fibres or motorunits may be selectively affected. Thiscould result from patterns of recruitment.It is also evident that some aspects of psy-chological stress can cause additional stat-ic load on the trapezius muscle (Waerstedand Westgaard, 1996; Melin andLundberg, 1997). Methodological difficul-ties exist in taking muscle fibre fromhuman subjects. For ethical reasons, thenumber of samples that can be taken andthe size of such samples is extremely limit-ed. There is evidence of change in charac-teristics of the fibres in those exposed tohigh repetitive and static workload com-pared to those who have not beenexposed to these factors. The irregularitiesobserved appear to be related to the fibremitochondria. Hägg (1998) suggests thatmitochondrial disturbances are a result ofstatic and/or repetitive workload in theupper trapezius muscle.

However, the research does not determinewhether the disturbances lead necessarilyto myalgia. The relationship betweenabnormality in muscle fibre and the subse-quent perception of pain by subjectsrequires further study. Hägg (1998) hasindicated that these types of muscleabnormalities may be a necessary but notsufficient condition for pain perception.Of further interest, is the observation thattype I muscle fibres show mitochondrialdisturbances - type I fibres being those


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that are recruited first when static loadsare exerted.

Hagberg et al. (1995) have considered thepotential role of impact loads on upperlimb disorders. It is recognised that thosewho, in the course of their work, use thehand as a hammer have the potential tocause vascular disorders. Similarly, eccen-tric contractions are recognised as havinga high potential for muscle damage(Edwards, 1988). These have been con-sidered further by Ashton-Miller (1999).Such rapid eccentric contractions of mus-cles may be seen to occur when the work-er absorbs the "kick-back" or torque onpowered tools, such as screwdrivers.

3 . 2 . 2 T e n d o n / l i g a m e n t

Tendons, mainly formed of collagenoustissue, provide a link between muscle andbone. Under some conditions of repeatedloading the tendons may becomeinflamed. This seems to occur especiallywhere the tendons are loaded both bytensile forces (generated by or transferredto the muscle) and in a transverse direc-tion by reaction forces (Armstrong et al.,1984). This seems most likely to occurwhen the tendons pass over adjacent softand hard structures (e.g. bony structures)especially in awkward postures or at endof range of motion. Friction between thetendon and adjacent surfaces may alsolead to degeneration of the surface of thetendon. Chaffin and Andersson (1991)have noted that in some instances colla-gen fibres become separated. The result-ant changes can cause swelling and pain.The same authors have considered thebiomechanics of the tendon and the prob-

able changes that would occur should thesupporting synovia become inflamed. Theresultant changing coefficient of frictionhas given rise to the concept that repeat-ed compression would then further aggra-vate synovial inflammation and swelling.

Experimental studies (e.g. Backman et al,1990) have provided evidence that repeti-tive loading of the tendon can induce his-tological changes. Further study isrequired of the characteristics of mechan-ical loading and how they cause tendondysfunction including preventing healingand adequate remodelling. Studies arealso required in order to investigate thepotential for slowed healing. Cumulativemicro-strain is considered a plausiblehypothesis for tendon/ligament injury inupper limb disorders (e.g. Goldstein et al.,1987).

3 . 2 . 3 N e r v e

Elevated pressures around the nerve caninhibit intraneural, microvascular flow,axonal transport, nerve function andcause endoneurial oedema with increasedintrafascicular pressure and displacementof myelin in a dose-response mannerRempel et al. (1998). Such effects canoccur within minutes or hours. Viikari-Juntura and Silverstein (1999) state thatacute effects on the nerve are usually fol-lowed by rapid recovery but prolonged orvery high pressure can result in irreversibleeffects. In one animal model, extraneuralpressures of 4kPa applied for two hoursinitiated a process of nerve injury andrepair. It also was shown to cause struc-tural tissue changes, which persisted forone month. Rempel et al. (1998) point


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out that whilst a dose-response relation-ship with pressure occurs, the critical pres-sure/duration values for nerve injury areunknown. It is known that in healthyhumans, non-neutral wrist and forearmpostures and force exertion at the finger-tips can elevate extraneural pressure in thecarpal tunnel in a dose-response manner.Such pressures are consistent with thelevel at which intraneural microvascularblood flow may become affected.

Exposure to vibrating hand tools at workcan lead to permanent nerve injury. Thepathophysiological process associatedwith a neuropathy induced by vibration isnot fully understood, but animal modelshave been developed which evaluate theevents taking place in peripheral nervesfollowing vibration exposure. Changesnoticed include intraneural oedema, struc-tural changes in myelinated and unmyeli-nated fibres in the nerve, as well as func-tional changes of both the nerve fibresand non-neuronal cells.

Strömberg et al. (1997) have consideredthe structural nerve changes at wrist levelin workers when exposed to vibration.They show severe nerve injury at the dor-sal interosseous nerve just proximal to thewrist. This and other studies have shownthat long term use of hand held vibratingtools can induce changes in peripheral cir-culation such as white fingers, as well assensory disturbances and muscle weak-ness (Brammer et al., 1987; Pyykkö,1986). In animal models, structuralchanges have been reported in the myeli-nated and unmyelinated nerve fibres afterexposure to vibration. Finger biopsiesfrom patients with vibration induced

white fingers show changes in the nervefibres as well as in the connective tissuecomponents of peripheral nerves(Strömberg et al., 1997). Their findingssuggest that such pathology may occur inthe carpal tunnel following exposure tovibration. They identify two possible path-ogenic mechanisms in carpal tunnel syn-drome in those exposed to vibration. Thefirst being nerve compression and theother being changes introduced by vibra-tion itself.

Plausible hypotheses, such as these, arecommon in the literature. It is also impor-tant to consider exposure to several fac-tors simultaneously. The interactionsbetween the soft tissues and the subse-quent effects of the interactions are stillonly partially understood.

3 . 2 . 4 C i r c u l a t i o n

Circulatory changes following exposureto hand arm vibration or varying frequen-cy and acceleration magnitudes. Recentstudies (e.g. Bovenzi et al., 1998) wouldsuggest that, in addition, the duration ofexposure contributes to the reaction ofthe digital vessels to acute vibration. Somestudies (e.g. Egan et al, 1996) suggest thata central vasomotor mechanism may beinvolved in the immediate response of fin-ger circulation to vibration exposure.

3 . 2 . 5 L o c a l M e c h a n i c a l P r e s s u r e

Hagberg et al. (1995) have considered thepossible relationship between localmechanical pressure and the onset ofmusculoskeletal problems. Directmechanical pressures on tissues can occur


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with, for example, poorly designed toolsand handles. Thus, pressure from metaltools, such as scissors can lead to digitalneuritis and there are a number of vulner-able sites in the palm of the hand. Sauteret al. (1987) have also considered thepotential pressures on the wrist from sup-porting weights. Buckle (1994) hasreviewed the potential neurological out-comes of such mechanical pressuresincluding the carrying of loads. Others(e.g. Fransson-Hall and Kilbom, 1993)have considered other effects of directmechanical pressure.

3 . 2 . 6 C o l d

Hagberg et al., (1995) evaluated cold as arisk factor. Cold may act directly as a riskfactor for neck and upper limb muscu-loskeletal disorders. Alternatively, it mayact indirectly as a result of the additionalproblems for the worker that arise whenwearing personal protective equipment.Difficulties in researching this issue are evi-dent. For example, Chiang et al. (1990)identified cold as a risk factor for carpaltunnel syndrome, however all the subjectsworking in cold environment were alsowearing gloves. Others, for exampleVincent and Tipton (1988), have foundreductions in maximum grip strength of13-18% following immersion in coldwater. Such findings suggest that thephysiological demands on muscle andrelated tissues will be greater in a coldenvironment for any given work task.Increased muscle activity, as observed bySunderlin and Hagberg (1992), may arisefrom direct cooling of tissue or posturalchanges, designed to be protective fromthe cold.

3 . 2 . 7 P a i n s e n s i t i s a t i o n

Muscle pain is the most common symp-tom of musculoskeletal disorders(Sjøgaard, 1990). Painful and nonpainfulchemical stimulii from a musculoskeletaldisorder may increase the sensitivity of theinjured tissues. This phenomenon, referredto as sensitisation (Blair, 1996; Besson,1999), has been observed in clinical casesthat experience persistent symptoms andongoing musculoskeletal problems.

Levine et al. (1985) have reported thatmusculoskeletal trauma or repetitivemotion may produce painful and non-painful stimulii that generate a release ofadrenergic chemicals from sympatheticnerve fibres. These chemicals affect joints,muscle spindles, primary C-fibres and themuscle itself.

In the joints, for example, a chain reactionof chemicals is initiated as a direct effectof the activation of the postganglionicsympathetic fibres. Norepinephrine, dis-charged from the fibres, will affectsmooth muscle and secretory, lymphoidand inflammatory cells. Blair (1996) andBesson (1999) believe that this triggers therelease of several inflammatory mediatorssuch as bradykinin, prostaglandins, sero-tonine, histamine, substance P, neurokininA that activate the C-fibre nociceptor, onetype of the peripheral nerves that carrypain signals to the central nervous system.

The nerve endings become more sensitivewith the continued release of inflammato-ry mediators and this lowers the thresholdfor stimulation i.e. smaller external loadsto the injured area result in spontaneouspain (Blair, 1996). With chronic pain syn-


n38

drome, the intensity of pain is frequentlyout of proportion to the original injury ortissue damage (Loeser and Melzack,1999).

A model proposed by Johansson andSojka (1991) implied that sustained mus-cle contractions, inflammation, and/orischaemia could begin a ‘vicious circle’ ofmuscle stiffness to primary and secondarymuscles and thereby preserve or increasethe production of metabolites and thehigh activity in the chemosensitive nerveendings. The model has been used toexplain the observation that muscle ten-sion and pain tend to propagate from onemuscle to surrounding muscles in many

chronic musculoskeletal pain syndromes.Research, for example (Djupsjöbacka etal., 1995; Pedersen et al., 1997;Wenngren et al., 1998) has supported thismodel. In addition, Bergenheim et al.(1995) have noted an additional pathwaywhere contraction metabolites andinflammatory substances may alter musclecoordination, thus, increasing the load onactive muscle motor units. Increased mus-cle activity (i.e. highly active muscle motorunits) measured using electromyographyduring stereotyped tasks in workers withpain and/or chronic pain (e.g. myalgia) hasbeen demonstrated (Veierstad et al.,1990).


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3.3T H E E P I D E M I O L O G I C A L

E V I D E N C E O F W O R K -

R E L A T E D N E S S

The National Institute of OccupationalSafety and Health (NIOSH), U.S.A., havecritically reviewed the epidemiological evi-dence for work-related musculoskeletaldisorders, including the neck and upperlimbs (NIOSH, 1997).

Work related physical risk factors wereidentified for the neck/shoulders, shoulderregion, elbows and hands/wrists (see table 4).

The epidemiological studies for each typeof musculoskeletal disorder were sum-marised with regard to determinants ofcausality that included:l Strength of the association between

work exposure and musculoskeletaloutcome

l The consistency of the associationacross studies

l The temporal effect between becomingexposed and developing the disorder(s)

l Evidence of an exposure-response rela-tionship

l Coherence of the epidemiological evi-dence with respect to other types of sci-entific evidence e.g. laboratory studies

Table 4 shows that there is consistent epi-demiological evidence supporting thework-relatedness of many musculoskeletaldisorders of the neck and upper limbs.The report also concluded that high levelsof exposure, especially in combinationwith exposure to more than one physicalfactor provided the strongest evidence ofwork relatedness for these disorders. Inaddition, the strongest evidence camefrom studies in which workers wereexposed daily and for whole-shifts.

It was acknowledged that individualfactors (e.g. previous medical history)may influence the degree of risk fromspecific exposures and it is likely thatthe reviewed disorders may also becaused by non-work factors. This didnot substantially alter the associationwith work factors.

Psychosocial work factors were consideredwithin the NIOSH review and, despite theevidence not being entirely consistent, itwas concluded that intensified workload,low job control, low social support andperceived monotonous work may beinvolved in the development of work-related upper limb disorders.

A more recent review of the evidence hasbeen prepared by a scientific steeringcommittee and scientists (NationalResearch Council, 1999). This review,approved by the Governing board of theNational Research Council, U.S.A., exam-


n40

ined the current state of the scientificresearch base. It considered the epidemio-logical evidence as well as the potentialbiological mechanisms and the evidencefrom effective interventions

The review concluded that there was apositive relationship between the occur-rence of musculoskeletal disorders (back,neck and upper limbs) and the perform-ance of work, when considering the high-

est levels of exposure to biomechanicalwork factors and the sharpest contrasts inexposure among study groups.

There was compelling evidence that areduction in the biomechanical loadresults in a reduction in the prevalence ofmusculoskeletal disorders. This evidencefurther supports the relationship betweenwork activities and the occurrence of mus-culoskeletal disorders.

T a b l e 4 . T h e w o r k r e l a t e d n e s s o f m u s c u l o s k e l e t a l d i s o r d e r s : P h y s i c a l w o r k r i s k f a c t o r s . S o u r c e : N I O S H , ( 1 9 9 7 ) .

Body part Strong evidence Evidence Insufficient evidence Evidence of noRisk factor effect

Neck and Neck/shoulderRepetition ✔

Force ✔

Posture ✔

Vibration ✔

ShoulderRepetition ✔

Force ✔

Posture ✔

Vibration ✔

ElbowRepetition ✔

Force ✔

Posture ✔

Combination ✔

Hand/wristCarpal tunnel syndrome

Repetition ✔

Force ✔

Posture ✔

Vibration ✔

Combination ✔

TendinitisRepetition ✔

Force ✔

Posture ✔

Combination ✔

Hand-armvibration syndromeVibration ✔


41n

There was less definitive evidence that lowlevels of biomechanical stressors are asso-ciated with musculoskeletal disorders,although there are some high quality stud-ies suggesting causal associations thatshould serve as a basis for furtherresearch. Where low levels of biomechan-ical stress are experienced it was thoughtimportant to consider also the possiblecontribution of other factors to muscu-loskeletal disorders (e.g. social and organ-isational factors).

This study also found that a more rigorouselimination of studies in the earlier NIOSHreview would not have substantiallyaltered the conclusions that had beenreached.

Individual, organisational and social fac-tors were characterised. It was recognisedthat individuals differ in their susceptibilityto the incidence, severity and aetiology ofmusculoskeletal disorders. Age and priormedical history are two individual factorsthat have biological plausibility to accountfor the strong relationships observed inepidemiological studies.

Organisational and social factors havebeen referred to under one term known aspsychosocial work factors. These are fac-tors directly associated with levels ofworkplace stress such as job content anddemands, job control and social support.In general, reviews in the scientific litera-ture have shown that poor job content(poor task integration and lack of taskidentity) and high job demands were relat-ed to musculoskeletal disorders. In theory,these factors may act biologically throughincreased biomechanical strain, physiolog-

ical vulnerability, or symptom attributionand reporting. It was considered that psy-chosocial factors had a moderate effect onthe impact of work-related musculoskele-tal disorders (National Research Council,1999).

Despite a lack of standardised methods,the resultant variability enabled the exam-ination of a common set of musculoskele-tal conditions from a multiple perspective.This was considered to strengthen thecausal inferences made.

It was noted that the time order betweenbeing exposed to the physical work fac-tors and the development of muscu-loskeletal disorders (or the clinical course)was less consistently demonstrated.

Finally, the relative contribution of workrelated factors to the incidence or preva-lence of musculoskeletal disorders in thegeneral population could not be consid-ered because of scarce evidence.

Researchers (Grieco et al., 1998) at theUniversity of Milan, Italy compared theresults from the NIOSH review (1997) withthe review of the work relatedness of neckand upper limb musculoskeletal byHagberg et al. (1995). They also consid-ered the biological plausibility of the asso-ciations between work and the disorders.They concluded that there was satisfacto-ry evidence of an association betweenwork and shoulder, hand and wrist ten-dinitis, carpal tunnel syndrome and ten-sion neck syndrome. However, they con-sidered that the evidence was tentativeand contradictory for lateral epicondylitisand cervical radiculopathy, although plau-sible biological mechanisms for the devel-


n42

opment of these disorders were postulat-ed. This contrasts with the findings of theNIOSH (1997) review where considerableevidence for the association betweenwork and lateral epicondylitis was report-ed.

A Finnish researcher (Viikari-Juntura,1997) has also summarised a number ofexisting reviews, supplemented by recentstudies that have demonstrated the asso-ciation found between physical aspects ofthe work place and the development ofmusculoskeletal disorders including theneck and upper limbs, as has Buckle(1997) in the U.K.

Data from experimental studies providesupportive evidence and should be usedto provide exposure values that are testedin epidemiological studies. It is concludedfrom the Finnish review of the scientificbasis of regulations for the prevention of

musculoskeletal disorders (Viikari-Juntura,1997) that existing scientific knowledgecan be used in the development of guide-lines that are acceptable and that are con-sidered practical for implementation.

Bovenzi (1998) has reviewed the expo-sure-response relationship with respect tothe hand-arm vibration syndrome. He hasconcluded that there is epidemiologic evi-dence for an increased occurrence ofperipheral sensorineural disorders in occu-pational groups working with vibratingtools. An excess risk for wrist osteoarthro-sis and for elbow arthrosis and osteophy-tosis has been reported in workersexposed to shocks and low frequencyvibration of high magnitude from percus-sive tools. Occupational exposure to handtransmitted vibration is significantly asso-ciated with an increased occurrence ofdigital vasospastic disorders, known asvibration-induced white finger.


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3.4I N T E R V E N T I O N S I N T H E

W O R K P L A C E

The limited literature on work interven-tions provides some evidence, both incontrolled and uncontrolled studies, of thepotential benefits of workplace interven-tions.

The expert panel concluded that therewas good evidence that work systeminterventions had been shown to be effec-tive for reducing neck and upper limbmusculoskeletal disorders, although suchinterventions were most likely to be suc-cessful amongst workers in high risk/ highexposure groups. It was also consideredprudent to reduce problems of dis-comfort and fatigue through interven-tions, as this was likely to reduce thesubsequent incidence of any upperlimb disorders.

Several field research studies have provid-ed evidence that demonstrates the effectsof multi-factorial interventions in the

workplace upon exposure to risk factorsand reductions in several musculoskeletalhealth outcomes (National ResearchCouncil, 1999). Smith et al. (1999), in theNRC report, provides the evidence show-ing that some intervention strategies canprevent the development of muscu-loskeletal disorders in specific industriesand occupational groups (e.g. nurses,meatpackers, assembly and postal work-ers). Examples were found where multipleergonomics redesign, movement patterntraining and physical therapy interventionsresulted in a reduction in recorded neckand upper limb musculoskeletal disorders,lost workdays, numbers of days of restrict-ed activity and employee turnover (Harmaet al., 1988; Orgel et al., 1992; May andSchwoerer, 1994; Parenmark et al., 1988).

There was also a number of both labora-tory and field studies (Smith et al., 1998;Schoenmarklin and Marras, 1989;Keyserling et al., 1993) that identified areduction in biomechanical stressors fol-lowing ergonomics redesign (e.g. redesignof hand tools or workstations), therebyreducing the risk of upper limb disorders.For example, Aarås and Oro (1997) com-pared the muscular load required to oper-ate a traditional computer mouse with anewly developed design. A reduction inthe muscular load was observed in theforearms and also in the neck (trapezius).Aarås et al. (1999) then introduced thenew mouse design to a group of officeworkers. The subjects were randomlyassigned to an intervention or controlgroup. Six months after the intervention asignificant reduction in the intensity andfrequency of wrist/hand, forearm, shoul-der and neck pain was observed in the


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group with the new design compared tothe control group that used a traditionalmouse design.

A recent critical review of the literature onintervention studies was conducted byNorwegian and Swedish researchers(Westgaard and Winkel, 1997). Theyreviewed studies that had changed jobexposures considered harmful to muscu-loskeletal health. They included interven-tions on mechanical exposure (e.g. postur-al load) and other risk factors for muscu-loskeletal problems; production systemand/or organisational culture alterationsaffecting mechanical exposures; and inter-ventions that attempted to modify thebehaviour and/or capacities of individualworkers (e.g. exercise/relaxation pro-grammes, physiotherapy or health educa-tion). Despite the methodological difficul-ties in conducting intervention research inthe workplace (Rubenowitz, 1997;Zwerling et al., 1997), there was evidenceto show that reducing the mechanicalexposure(s) resulted in the reduction ofneck and upper limb musculoskeletal dis-orders(4). These interventions involvedeither reducing the mechanical exposuredirectly (through modified workstationdesign) or indirectly through alterations inorganisational culture. Organisational cul-ture was defined by Westgaard andWinkel (1997) as: "Systematic activities ofmajor stakeholders within an organisa-tion, relating to health, safety and envi-ronment and comprising measures toinfluence, e.g. management systems,behaviour and attitudes, for dealing with

potential or manifest musculoskeletalhealth problems of the workforce."Measures included ergonomic pro-grammes with management, ergonomicstraining and systems for problem identifi-cation and solution.

However, it should be noted that the rela-tively few studies on production systeminterventions for reducing neck and upperlimb musculoskeletal disorders precludescomparison with work organisational cul-ture and mechanical exposure interven-tion effectiveness (Westgaard and Winkel,1997).

It was also found that interventions active-ly including the worker (medical manage-ment of workers at risk, physical or activetraining in worker technique or combina-tions of these approaches) often achieveda reduction in musculoskeletal problemsincluding those of the neck and upperlimbs.

The conclusions from this contemporaryand authoritative review were to focusinterventions on factors within thework organisation, not solely on theworker (e.g. training/work hardening). Itwas also emphasised that the active sup-port and involvement of the individuals atrisk and other stakeholders in the organi-sations was highly recommended.

Häkkänen et al. (1997), for example, hasshown that relatively simple and low-costergonomics solutions can result in a reduc-tion in exposure to work risk factors forupper limb musculoskeletal disorders.

(4) It was also noted that reductions in mechanical exposure might be most beneficial for musculoskeletal health inwork situations where the levels are high.


45n

Examples of the cost effectiveness ofergonomics interventions for these disor-ders have been reported by, amongst oth-ers, Schneider (1998) and Hendrick(1996). The odds of a work related mus-culoskeletal disorder resulting in lost timewithout an ergonomics intervention wasthree times greater than with an interven-tion (Schneider, 1998). This study alsofound that the return on investment i.e.the benefit/cost of intervention in an

office environment was 17.8 ($1693/$95).Ergonomics intervention to redesign anassembly line process was shown toreduce workers compensation costs forwork-related musculoskeletal disordersfrom $94000 to $12000 in a telecommu-nications organisation (Hendrick, 1996).Between 1990-1994, ergonomics inter-vention saved $1.48 million in workercompensation costs for the same organi-sation.


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3.5S U M M A R Y - T H E W O R K -

R E L A T E D N E S S O F N E C K A N D

U P P E R L I M B D I S O R D E R S

The scientific reports, using defined crite-ria for causality, established a strong posi-tive relationship between the occurrenceof some neck and upper limb muscu-loskeletal disorders and the performanceof work, especially where high levels ofexposure to work risk factors were pres-ent.

Understanding of the pathogenesis ofthese disorders varies greatly with regardto the specific condition in question. Formany of the disorders, (e.g. carpal tunnelsyndrome) the body of knowledge isimpressive, bringing together biomechan-ics, mathematical modelling and directmeasurement of physiological and soft tis-sue changes. These form a coherent argu-ment that is persuasive of the biomechan-ically induced pathogenesis of such condi-tions. For those conditions where theknowledge base is smaller, plausible

hypotheses do exist and are currently thesubject of much research interest.

Both the National Research Council (USA)and the National Institute of OccupationalSafety and Health (USA) reports make ref-erence to the potential importance of psy-chosocial and work organisational factors.Both conclude that there is increasing evi-dence that these factors are important inthe development of work related muscu-loskeletal disorders. The expert panel hasconsidered these reviews to be helpful inthe preparation of this report and agreedwith the general findings. The panel fur-ther noted the limitations of such reportswith respect to the criteria set for inclusionof studies for review.

The expert panel concluded that existingscientific knowledge could be used in thedevelopment of preventative strategies.These will be acceptable to many stake-holders and are practical for implementa-tion. There is limited but persuasive evi-dence on the effectiveness of work systeminterventions incorporating ergonomics.

S T R A T E G I E S F O R

P R E V E N T I O N


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RE

SE

AR

CH

4.


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4.1I N T R O D U C T I O N

The strategies have been derived from thefollowing areas:

1 . C o n t e m p o r a r y S c i e n t i f i cL i t e r a t u r e

The evidence relied upon has been identi-fied earlier in this report. Additionalsources have been listed below whereapplicable. The methods used for the liter-ature searches have been included in theappendices.

2 . E x p e r t o p i n i o n

The nature and extent of the expert viewssought has been identified in section 1.

Position papers from established groupshave also been considered. For example,

the Scientific Committee forMusculoskeletal Disorders of theInternational Commission onOccupational Health (ICOH) provided asubstantive argument regarding both riskfactors and prevention (Kilbom et al.,1996). They identified the application ofergonomic principles in the workplace asan important method for prevention.

The International Ergonomics Associa-tion(5) has produced relevant review docu-ments and guidance for the assessment ofexposure to risk factors for upper limb dis-orders.

Similarly, employee representative groups(e.g. the European Trade Union TechnicalBureau for Health and Safety, TUTB) haveprovided much supportive material.Examples include Ringelberg andVoskamp (1996) and a series of wellinformed debates and meetings(6) .

3 . E x i s t i n g f r a m e w o r k o f M e m b e rs t a t e , E u r o p e a n a n d I n t e r n a t i o n a lD i r e c t i v e s , s t a n d a r d s a n d g u i d a n c e .

A number of European Directives are rele-vant to prevention (e.g. Manual Handlingof Loads, Display Screen Equipment, Useof Work Equipment and FrameworkDirectives) as well as a number ofEuropean Standards. Many of these showthe direction and support already given toworkplace surveillance and ergonomicinterventions in preventing and controllingmusculoskeletal problems.

(5) IEA Technical Working Group, Chair: Professor Antonio Grieco, University of Milan, Italy.(6) See the Newsletter of the European Trade Union Technical Bureau for Health and Safety No. 6,1997 pp2-5;

No.4,1996 pp 20-21.


49n

Related guidance and ordinances areavailable in a number of member states.For example, a recent ordinance fromSweden "Ergonomics for the Preventionof Musculoskeletal Disorders, AFS1998:1" presents guidance on risk assess-ment for the postural/biomechanical stres-sors. It was considered by the panel ofexpert scientists as an important and well-informed document. Some elements ofthis ordinance are reflected in this docu-ment. Other such guidance includes"Work related upper limb disorders: Aguide to prevention" by the HSE in1990.

4 . E x i s t i n g P r a c t i c e

Many organisations have sought to imple-ment ergonomic programmes and inter-ventions aimed at primary prevention ofthe problems. This would suggest thatthey already believe in the effective-ness of ergonomic and occupationalhealth strategies aimed at preventingthe development of this group of dis-orders. Organisations involved in suchprogrammes provide important rolemodels for others wishing to initiatepreventive programmes. That said, it isless clear how beneficial suchapproaches have been.

The extent and scope of the informationand approaches currently advocated hasbeen particularly evident when reviewing"in-house" materials and those freelyavailable from sources such as the inter-net. Whilst there are few data on the suc-cess or usefulness of such materials, theyare clearly sought after and widely used.This report might therefore be used toinform, guide and harmonise such

sources. Such a process might beenhanced further through appropriate useof the newly established Topic Centre onGood Safety Health Practice concern-ing Musculoskeletal Disorders. This is arecent initiative from the EuropeanAgency for Safety and Health at Work.

5 . T h e n e e d s a n d c a p a c i t i e s o f t h o s ew h o m a y u s e e r g o n o m i c s a p p r o a c h e st o p r e v e n t i o n

Any proposed strategies and guidancedesigned for the workplace must meet theneeds and capacities of those responsiblefor its application, if it is to be successful.Kilbom (1995) has posed the questionthus: "Can the knowledge of the risk fac-tors be operationalised in a way that issufficiently simple to be useful for persons- labour inspectors, occupational healthservice staff, safety stewards etc. - with alimited knowledge about musculoskeletaldisorders and ergonomics?"

Thus this report, unlike most other con-temporary reviews, has considered thiswhen proposing possible strategies forprevention.

4 . 1 . 1 P r a c t i t i o n e r s a b i l i t y t o m a k er i s k a s s e s s m e n t i n t h e w o r k p l a c e :

There is a limited literature on what prac-titioners can reliably be expected to riskassess in the workplace, particularly withregard to risk factors for musculoskeletaldisorders. That said, if action requires riskassessment to be made at the workplace,then an understanding of end-userrequirements must be an integral part ofthe knowledge base required. One recent


n50

study from England (Li and Buckle, 1998,1999) has approached this problemthrough a participatory approach, where-by a method for the assessment of expo-sure to risk factors for musculoskeletalproblems was developed by practitionersand for practitioners. Experts wereinvolved only in facilitation and the subse-quent assessment of reliability and validityof the method. Such studies have enableduser requirements to be established.

4 . 1 . 2 M e t h o d s o f R i s k A s s e s s m e n t :

Exposures to physical risk factors for work-related musculoskeletal disorders havebeen assessed with a variety of methods,including pen and paper based observa-tion method, videotaping and computeraided analysis, direct or instrumental tech-niques, and approaches to self-reportassessment. These have been criticallyreviewed elsewhere (e.g. Li and Buckle,1999). The application of these tech-niques in ergonomics and epidemiologicalstudies were considered, and their advan-tages and shortcomings were highlighted.A strategy that considers both theergonomics experts’ view and the practi-tioners’ needs is therefore required.

According to some research experts, suit-able analytical methods are still not avail-able for efficiently reducing and quantify-ing physical exposure (Radwin et al.,1994). Whilst some observational meth-ods for analysing postures and move-ments have been developed (e.g. RULA,(McAtamney and Corlett, 1993)) they areoften time-consuming and labour inten-sive (Wiktorin et al., 1995).

Most exposure assessment methods/toolsinvolve two (usually contradictory) quali-ties, precision and generality (Winkel andMathiasson, 1994). High generality in anobservation method is usually compensat-ed by low sensitivity. For example, OWAS(Karhu et al., 1977) has had a wide rangeof use but the results can be low in detail.In contrast, NIOSH (Waters et al., 1993)requires detailed information about spe-cific parameters of the posture to givehigh precision with respect to the definedindices, but no general information aboutthe task.

Burdorf et al. (1992) concluded that someof the ‘best known’ direct observationmethods, such as OWAS and posture tar-getting, lack precision, are less repro-ducible in dynamic work situation, are notcontinuous, and are subject to intra- andinter-observer variability. Hagberg (1988)reviewed published methods for the sys-tematic observation of occupational mus-culoskeletal loads and found that none ofthese methods were widely accepted.

More recently, Colombini et al. (1998) pre-pared a consensus document in associa-tion with the International ErgonomicsAssociation technical group for work-related musculoskeletal disorders. Itincluded a review of authoritative check-lists and a search for models to describeand evaluate each of the principle risk fac-tors. They defined terms that enable com-mon understanding of the analyticalrequirements including: tasks, cycles andtechnical actions. They also provided amethod for exposure assessment that con-siders the risk factors of repetitiveness (fre-quency); force; awkward postures and


51n

movements; recovery time in addition to anumber of complementary factors (e.g.high precision tasks, vibrations, local com-pression, blows and wrenching move-ments).

The authors acknowledged the difficultiesinvolved in validating methods wheremany interactions occur. They also recog-nised that, in the absence of a completeepidemiological knowledge base, otherareas of knowledge (e.g. fatigue studies)may have to be relied upon in assessingtasks. Nevertheless, this approach isimportant for setting up exposure assess-ment methods and demonstrates theneed for common definitions and agreedassessment methods for single risk fac-tors. The same research institute(Occhipinti, 1998) has also suggested aformula for an expert risk assessment(OCRA) that considers a number of riskfactors (frequency, posture, rest pauses,other factors).

4 . 1 . 3 M a i n c r i t e r i a f o r e x p o s u r ea s s e s s m e n t m e t h o d s :

Some of the major points are summarisedbelow:l The method has to be cheap, easy to

learn and quick to use (Corlett, 1990;Sinclair, 1990, Li and Buckle, 1998)

l The method should be applicable to allsections of working life, and shouldtake environmental and psychosocialaspects into consideration (Rohmertand Landau, 1983)

l The measurements have to be repeat-able under described conditions, i.e.within the range of movements normal-ly occurring in the actual work situation(Aarås and Stranden, 1988)

l The recording method should not inter-fere with the movements being record-ed (Aarås and Stranden, 1988) andshould not interfere with the worker’swork (Wilson, 1990; Kirwan andAinsworth, 1992)

l The method should have high validity,reliability and sensitivity (Pinzke, 1994)

l Assessment data should be readilycoded for storage and analysis(Colombini et al., 1985)

Any action proposed must consider thesecriteria. The proposals that follow havetaken account, wherever possible, of theissues identified above. It must also berecognised that where there are com-peting criteria a pragmatic outcomemust be sought. This will, on occasions,necessitate compromises.


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4.2H E A L T H A N D W O R K S Y S T E M

A S S E S S M E N T

Generally accepted principles of the man-agement of health and safety at work pro-vide a framework, under which the specif-ic actions required for neck and upperlimb disorders may be considered.

The most important aspects of the gener-al requirements can be summarised as fol-lows:

1. Assessment of risk to enable the identi-fication of necessary preventive andprotective measures.

2. Make arrangements for putting intopractice the health and safety measuresidentified in (1).

3. Provide appropriate health surveillanceof employees where necessary.

4. Provide employees with appropriateinformation and training about healthand safety matters.

5. Review the effects of the changes

This section of the report will address, inparticular, issues 1 and 3 of these generalrequirements.

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4.3D E F I N I T I O N O F R I S K A N D

C O N C E P T O F A C T I O N Z O N E S

4 . 3 . 1 R i s k ( a n d r i s k f a c t o r s )

Risk has been defined by Last (1983) as "aprobability that an event will occur e.g.that an individual will become ill or diewithin a stated period of time or age."However, the meaning of risk factor is notas clear, as researchers and authors are notalways consistent in their use of the term.In this report it is taken to mean an attrib-ute or an exposure that is not necessarilycausal but that does increase the probabil-ity of a specific outcome (e.g. the occur-rence of a disorder of the upper limb).

4 . 3 . 2 A c t i o n Z o n e s

Increased exposure to risk factors can bethought of as a basis for establishing pri-orities for action. Those in the groups with

the highest exposure to risk factors wouldnormally be expected to attract the high-est priority. Whilst current epidemiologicalknowledge does not allow a full descrip-tion of the exposure/dose-response rela-tionship for each risk factor, there was ageneral recognition amongst the expertsthat extreme exposure groups both couldand should be identified; and that theseshould be specifically targeted in the firstinstance(7).

Targeting those at the extremes of theexposure spectrum has additional advan-tages as the knowledge, experiences andcompetence gained will enhance the like-lihood of the successful transfer of riskidentification and risk removal/reductionstrategies to those at lower risk.

Methods and approaches developed else-where (including the development of stan-dards) and the experience of the expertshas led us to propose a three-zone modelfor action, for most of the recognised riskfactors. The zones may be thought of as:

(7) The failure to provide full descriptions of exposure/dose-response relationships has generally arisen from thenature of the epidemiological study groups. These have often been selected to compare those at the extremes ofthe exposure spectrum, and thus give limited understanding of the shape of the exposure-response relationship.

1 High Risk This zone identifies those at high-est risk for the development ofupper limb disorders and whereaction is almost certainly required.

2 Medium risk Work factors require close atten-tion and remedial actions may benecessary.

3 Low Risk Areas of least concern, althoughsome action may be prudent.Assessment may provide usefulinformation to inform workplaceinterventions elsewhere. Routineassessment and surveillanceshould be extended to this group.



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The proposed 3 zone model can be com-pared with that in the CEN standard:Safety of Machinery - Ergonomic designprinciples. Part 1. Terminology and gener-al principles EN 614-1 (1995).

Red "The risk of disease or injury is obvi-ous and exposure can not be accepted forany part of the operator population inquestion"

Yellow "There exists a risk of disease orinjury that can not be neglected, for the

whole or part of the population in ques-tion."

Green "The risk of disease or injury isnegligible or is at an acceptable level forthe whole operator population in ques-tion."

It is therefore apparent that similar modelsare already in use within the framework ofEuropean Union action


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4.4A S S E S S M E N T O F R I S K :

W O R K S Y S T E M A S S E S S M E N T

In considering the risk assessment of thework system, we have chosen to considerthe systematic approach advocatedthrough the discipline of ergonomics. Thisapproach is implicit in many of the existingEuropean Union Health and Safety direc-tives (e.g. Manual Handling of Loads,Display Screen Equipment). It recognisesthe need to consider the work system as aset of interacting elements, with a strongfocus on the needs and capacities of theworker (or equipment user) in both riskassessment and work design.

This approach is endorsed in a number ofCouncil Directives, including 89/391/EECon the Introduction of measures toencourage improvements in the safetyand health of workers at work. ThusArticle 6 states:

"(d) adapting the work to the individual,especially as regards the design of

work places, the choice of workequipment and the choice of workingand production methods, with a view,in particular, to alleviating monoto-nous work and work at a predeter-mined work-rate and to reducingtheir effect on health"

Further, Article 4 of the Manual handlingof loads directive states:

"Organization of workstations

Wherever the need for manual handlingof loads by workers cannot be avoided,the employer shall organize workstationsin such a way as to make such handling assafe and healthy as possible and:

(a) assess, in advance if possible, thehealth and safety conditions of thetype of work involved, and in particularexamine the characteristics of loads,taking account of Annex I;

(b) take care to avoid or reduce the riskparticularly of back injury to workers,by taking appropriate measures, con-sidering in particular the characteristicsof the working environment and therequirements of the activity, ………."

In order to be harmonious new strate-gies should aim to both support andencourage a similar systematicergonomics approach.


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4.5D E F I N I T I O N S O F W O R K

S Y S T E M F A C T O R S T O B E

A S S E S S E D

The interactions between factors in worksystems require an understanding of thework organisation, tasks undertaken,workspace and equipment demands aswell as their impact on the worker.

Whilst the immediate focus for a riskassessment might be, for example, theposture required to undertake a giventask, the wider ergonomic assessment ofthe work system may enable solutions to

be found regarding removal or reductionof risk.

Each physical work factor is thought of ashaving three dimensions. Thus the postureof the wrist during a task can be thoughtof as comprising an amplitude/magnitudedimension, a repetition or frequencydimension and a duration dimension.Radwin and Lavender (1999) have devel-oped this concept and the following table 5 is modified from that source andprovides some examples of physical expo-sures.

Whilst this table reflects the dimensionsfor each physical exposure, others (e.g.Kilbom, 1994) have chosen to expressthese factors in an alternative form. Forexample, physical exposure can also beexpressed as force x time, posture x timeand vibration x time. These generic riskfactors can be operationalised in differentways (e.g. average force, repetitions perminute).

4 . 5 . 1 D u r a t i o n o f W o r k

The expert panel discussed the definitionof action zones with regard to the dura-tion of working tasks.

T a b l e 5 . T h e a m p l i t u d e , f r e q u e n c y a n d d u r a t i o n o f s o m e p h y s i c a l e x p o s u r e s .

PHYSICAL EXPOSURE PROPERTY

Amplitude or Magnitude Repetition Duration

Force Force generated or applied Frequency of application Time that force is applied

Posture Joint angle Frequency Time held

Motion Velocity, acceleration Frequency of motion Time of motion exposure

Vibration Acceleration Frequency that vibration Time of vibration exposureoccurs


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It was recognised that there is no standardlength of a working shift. Particular diffi-culties were noted with regard to theapplication of guidance to part time work-ers having a number of jobs throughoutthe day. The expert panel discussed atlength the relationship between genericexposure to a task that involves a numberof physical exposures (e.g. heavy physicalwork) versus the duration of exposure to aspecific risk factor (e.g. vibration).

It was noted that some epidemiologicalstudies have shown that, when the dailyexposure time exceeds 4 hours, the ratesof WMSD complaints increase in theshoulder/neck, particularly for seated taskssuch as VDU operation (e.g. Winkel andWestgaard, 1992).

The current approach used for settingvibration exposure levels was considered.It was noted that the development ofexposure levels and limits for physicalagents (e.g. vibration) is based on a similarstrategy (see CR 1030-1 and ENV 25349).

Thus although there was someresearch evidence in support of aduration of exposure(s) of four hoursplacing work tasks in the high"action" zone, further debate on thisissue is required.

Task duration is an important risk factorfor disorders of the shoulder/arm, neck,and hand/wrist. This factor should beconsidered in the exposure assessment ofeach of these body regions. Since the timeavailable for practitioners to assess a jobor task can be very limited, other means ofassessing the duration to exposure mighthave to be sought. These could include

worker interviews, organisational recordsor time sampled observations.

4 . 5 . 2 R e p e t i t i v e w o r k a n d r e c o v e r yf r o m w o r k

One of the difficulties in comparing stud-ies is the variation in the interpretation ofkey concepts. Thus the use of the termrepetitive with respect to work has beendebated by, amongst others, Mathiassenand Winkel (1991) and Kilbom (1994).The issue of repetitiveness within work isclosely linked to the concept ofwork/recovery. It is, for example, fre-quently assumed that when a worker isnot actively engaged in the task underinvestigation, then recovery time is beingprovided. However, this may not be thecase if that worker moves from one taskto another with similar postural or forcedemands. Thus a distinction betweenrepetitive work and work recovery isrequired when interpreting data andproviding recommendations. Repetitivecontinuous work was considered, by theexpert panel, to be work involving rapidhand movements which were almost con-tinuous and involved rapid steady motion.

Latko et al., (1997) have considered theneed for a single metric for assessingexposure to repetitive work. They providean observational method with decisionrules and examples to aid in rating tasks.They also suggest the use of verbalanchors combined with a visual ratingscale. They report acceptable levels ofsensitivity for the parameters of move-ment frequency and recovery time in handintensive tasks. This approach offersmuch promise in the application of action


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levels, although research questions stillremain regarding the use of such methodsby those with little prior experience.

4 . 5 . 3 T h e v a l u e o f f a t i g u e a n df a t i g u e s t u d i e s

Many of the scientists felt that studies offatigue were important to assist in settinglimits. For example, Westgaard andWinkel (1996) have reviewed existingguidelines for physical exposure, many ofwhich rely on fatigue studies. This wasalso seen to be coherent with theapproach taken in other EuropeanDirectives and Standard setting groups.

For example, the Council Directive90/270/EEC on the minimum safety andhealth requirements for work with displayscreen equipment includes, in its Annex, arecognition of the importance of fatiguewith respect to keyboard use:

"(c) Keyboard. The keyboard shall betiltable and separate from the screen so asto allow the worker to find a comfortableworking position avoiding fatigue in thearms or hands. "

Similarly, the "Safety of machinery -Human physical performance - Part 3

Recommended force limits for machineryoperation (prEN 10005-3)" considers onepart of the risk assessment (Step C) as fol-lows:

"The risk assessment focuses on muscu-loskeletal disorders, and is preferentiallybased on the assumption that decreasingfatigue during work is effective in reduc-ing disorders."

The expert group of scientists felt therewas some congruence between epidemio-logical and experimental data with regardto the relationship between biomechani-cal and psychophysical factors and theonset of fatigue or disorder. Thisapproach is reflected in the NationalResearch Council report (1999).

Scientists with experience of policysetting affirmed their belief that itwas prudent to consider fatigue as apotential precursor to some of the dis-orders under consideration. This viewis also evident in the NationalResearch Council Report (1999).

Where appropriate, therefore, guidancebased on fatigue studies or data might beconsidered.

(8) prEN documents are draft standards yet to be agreed by the European Standards Organisations

R I S K F A C T O R S

R E Q U I R I N G A S S E S S M E N T


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RE

SE

AR

CH

5.


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5.1G E N E R A L A S P E C T S O F

P O S T U R E

5 . 1 . 1 I m p o r t a n c e o f P o s t u r a lD e m a n d s

The importance of postural demands bothwith regard to the epidemiological/biome-chanical literature and any surveillance/riskassessment in the workplace has beenconsidered. There is an extensive liter-ature on the relationships betweenadverse postural demands at theworkplace and upper limb disorders.

Key reviews have been identified earlier inthis report. The importance of such pos-tural demands is also recognised in docu-ments such as the draft CEN standard"prEN 1005-4 Safety of machinery -Human physical performance Part 4.Evaluation of working postures."

5 . 1 . 2 A s s e s s m e n t o f P o s t u r a lD e m a n d s

Assessment of posture in epidemiologicalstudies has frequently relied on observa-tional or direct (instrumented) measure-ment. Any action requires observationsto be made in the workplace and appro-priate observational methodologies havetherefore been considered in this report.

A linear/ordinal scale assessment (devel-oped by the University of Michigan, USA)was considered as an example of a prom-ising methodology (Latko et al., 1997).This approach, developed with the help ofexperts, might be contrasted with themethods developed by and for practition-ers (e.g. Li and Buckle, 1998, 1999).

The Swedish Ordinance (SwedishOrdinance on Ergonomics for thePrevention of Musculoskeletal DisordersAFS 1998:1 Statute Book of the SwedishNational Board of Occupational Safety andHealth) considered posture definition andthe acceptability of postures. For example,prolonged work tasks that required thehand or elbow to be held at or aboveshoulder height were likely to be consid-ered unacceptable.


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5.2N E C K

The scientists agreed that the epidemio-logical data were not conclusive withregard to specific neck postures and therisk of developing the disorders underconsideration in this report. A summarytable (see appendix 4) of postural risk fac-tors for the neck was produced byHagberg et al. (1995). NIOSH (1997) con-sidered 31 studies of the associationbetween extreme or static posture andneck or neck/shoulder musculoskeletaldisorders. Of these, they identified threestudies (meeting their criteria for accept-ability) that found significant associationsbetween posture variables and neck mus-culoskeletal disorders. However, none ofthese studies had reported measures ofrisk. Despite the limitations of these stud-ies the actions and guidance provided by,for example, the Swedish Ordinance wereconsidered to be appropriate by the expertgroup.

The uncertainty over the epidemiolog-ical data led the expert panel to rec-ommend that a further considerationof the current experimental datashould be undertaken. These datamight provide additional guidance.

For example, tilting the head/neck forwardmore than 30º greatly increases the neckextensor fatigue rates, but an angle ofaround 15º produces almost no subjectivediscomfort or EMG changes even after 6hours work (Chaffin, 1973). A recentreport indicated that the time spent in for-ward neck flexion (with the critical angleof 15º) was significantly associated withneck and neck/shoulder disorders(Ohlsson et al., 1995).

One further difficulty has been highlightedby Li and Buckle (1998). This relates to theability of practitioners to make simple andreliable assessments of such postures.They found that it is difficult for theobservers to determine a specific neckangle through simple observation, andthat practitioners prefer to use descriptiveword(s) such as ‘excessively bent or twist-ed’ rather than using angular values.

The scientific experts also voiced concernover whether rapid twisting movements atthe neck could lead to problems. Thereappeared to be few data available to assistwith risk determination. This is an areathat requires further research.

There was a general consensus that worksystems requiring restrained postures andlimited freedom of movement of thehead, neck and shoulders should be anarea for risk assessment. Definitions of


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high, medium and low risk zones arethought to require further considerationfor the neck.


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5.3S H O U L D E R S A N D A R M S

Working above shoulder height iswidely recognised as a risk factor forshoulder musculoskeletal disorders. Asummary table (see appendix 4) of postur-al risk factors for the shoulder was pro-duced by Hagberg et al. (1995).

NIOSH (1997) concluded that there wasevidence for a relationship betweenrepeated or sustained shoulder postures,with greater than 60 degrees of flexion orabduction and shoulder musculoskeletaldisorders. They found evidence for bothshoulder tendinitis and non-specific shoul-der pain. Only one of thirteen studiesreviewed failed to show a positive rela-tionship.

The provisional standard prEN 1005-4(Safety of machinery - Human physicalperformance Part 4-Evaluation of workingpostures in relation to machinery) alsoconsiders shoulder postures. It suggests

that tasks requiring shoulder flexion orabduction of greater than 60 degrees areunacceptable for static posture or highfrequency movement (greater than orequal to 2 per minute).

Assessment of postural angles in riskassessment is known to present difficultiesfor practitioners. Thus, whilst 60 degreesof shoulder flexion or abduction has beencited as a possible border of acceptability,it is unlikely that reliable assessments canbe made through observation in theworkplace. A better approach is to relatethe position of the hands to other bodyparts. Therefore, the expert panel notedthat work at or above shoulder height, forexample, could be reliably assessed andmight be considered as a posture in thehigh risk zone.

Reach distance has not been widely recog-nised as an independent risk factor forshoulder disorders, although a greaterreach distance may result in more awk-ward postures of the back and shoulder.Reach, in combination with load or forceexertion, is recognised as a risk factor indirectives and guidance that considermanual handling at work.

Highly repetitive arm and shoulder move-ment increases the risk of shoulder tendondisorders (e.g. Bjelle et al., 1981, Ohlssonet al., 1989, 1994, 1995; NIOSH 1997).However, the movement of the shouldermay be very different (in terms of the pat-tern and speed) from that of thehand/wrist.

Epidemiological studies have not yet pro-vided sufficient information to define theexposure-response relationship regarding


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the frequency of repetitive shoulder move-ments.

The ability of practitioners to reliablyassess such patterns suggests that theclassification of zones for action should bedefined by the pattern or manner of thearm movement, rather than by the num-ber of times the arm moves within a givenperiod (Latko et al., 1997).

NIOSH (1997) reviewed the evidenceregarding force/load and duration as riskfactors associated with shoulder/arm dis-

orders. They found that there was insuffi-cient evidence to enable firm conclusionsto be reached regarding the relationshipbetween force and shoulder disorders.This was because the available studies hada considerable diversity of exposureassessment approaches and health out-comes.

Li and Buckle (1999) have found that prac-titioners find it difficult to make exposureassessments regarding the force/load andalso the duration of the task with respectto the shoulder/arm.


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5.4W R I S T S

The expert panel agreed thatextremes of wrist movement shouldbe included in risk assessments. Thiswas based on both epidemiological (e.g.NIOSH, 1997) and biomechanical labora-tory based data. The NIOSH review con-cluded that there was an associationbetween any single factor (posture, forceor repetition) and hand/wrist tendinitis.They also concluded that there was strongevidence that job tasks requiring a combi-nation of risk factors increase the risk forhand wrist tendinitis. It is important torecognise that whilst the epidemiologicalevidence is stronger with regard to somedisorders (e.g. hand/wrist tendinitis) thanto others, there is general agreement that,because of common pathways, any inter-vention on this risk factor is likely tohave benefits for other upper limbmusculoskeletal disorders.

An earlier review (Hagberg et al., 1995)considered studies that reported posturalrisk factors for the wrist/hand (see appen-dix 4).

The expert panel agreed that use of exper-imental data (e.g. contact pressures andcarpal tunnel pressures) should be madefor establishing appropriate action levels.It was noted that the levels of carpal tun-nel pressure when the wrist is deviatedfrom a neutral position are conservativerelative to the mechanical contact pres-sure at the wrist. It was further recog-nised that the biomechanical and epi-demiological data are consistent withregard to hand/wrist tendinitis.

Difficulties exist with respect to the assess-ment of wrist movements and postures.Direct measurement is both difficult andcostly (Li and Buckle, 1999).

Thus whilst the epidemiological and bio-logical evidence in support of the need foraction is strong, there are difficulties inproviding suitable tools to allow riskassessment to be made in the work place.Laboratory and epidemiological researchstudies may have access to sophisticatedmethods for wrist movement, but thepractitioner is the workplace is often limit-ed to direct observational techniques.

Li and Buckle (1999) have shown thatpractitioners have great difficulty inassessing some aspects of wrist posture.This is important because some methodspropose the use of precise set boundariesbetween a ‘good’ and ‘bad’ wrist posture(e.g. RULA (McAtamney and Corlett,1993.)) The epidemiological basis for thisis unclear, but it is evident (Li and Buckle,


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1999) that it is difficult for an observer to‘measure’, through observation, whetherthe wrist is within, or beyond, 15º or 20ºfrom its neutral position, during work.

An alternative approach, that has beenfound acceptable to practitioners, hasbeen to assess wrist posture using descrip-tive terms. The descriptors used arederived from studies that have used ‘thinkaloud’ protocols (Li and Buckle, 1998).

Repetition has been widely recognised asa risk factor associated with bothhand/wrist tendinitis and carpal tunnelsyndrome, especially when in combinationwith other task factors such as force andposture.

In some studies (e.g. Silverstein et al.,1986) high-repetitive tasks have beendefined as those with a work cycle time ofless than 30 seconds or with more than50% of the cycle time involved in per-forming the same motion pattern.However, in many work situations, a workcycle may not exist, or if it does, workcycle time may vary periodically. Thismakes it difficult to assess within a limitedobservation period.

Recent research (Latko et al., 1997) hasused verbal descriptors in conjunctionwith visual analogue scales to enableexposure assessments to be made.Extreme exposures for hand/wrist repeti-tive movement have therefore beendefined using such descriptors (i.e. Workinvolving rapid and steady hand move-ments that are almost continuous). Suchexposures may place the worker in thehigh risk zone.

Some authors have also identified theimportance of high wrist velocities andaccelerations (e.g. Marras andSchoenmarklin, 1993; Malchaire andCock, 1996). Further research on thesefactors is required to enable guidance tobe developed.

The importance of force as a risk factorassociated with hand/wrist musculoskele-tal disorders has been recognised byNIOSH (1997). The consistency of the rela-tionship is reflected in the criteria used toassess the strength of the evidence(described earlier in this report).Nevertheless the exposure response rela-tionship is complex as other risk factorsare likely to be present in any study group.

These problems are also recognised in adraft CEN standard "Safety of machinery -Human physical performance - Part 3Recommended force limits for machineryoperation (prEN 10005-3)". Whilst forcelimits have been proposed they requirecareful use of factors such as the velocity,the frequency and the duration of action.Further modifications are suggested forthe tolerability of body tissues as well as asafety margin addressing acceptability. Ithas also been recognised that the guid-ance given in this draft standard assumesthat an optimal posture can be achievedfor the force exertion.

The scientists agreed that there was aneed to combine and then synthesise bothepidemiological and experimental data inthis area.

The assessment of force at the hand isaccepted as being methodologically diffi-cult. It should be recognised that the


67n

actual load or mass handled can be differ-ent from the force exerted by hand. Forexample, the mass of a power tool may be3 kg, but the effective load at thewrist/hand will also depend on the centreof gravity with respect to the hand whenthe tool is in use. Similarly, the force onthe hand is also influenced by the forceexerted on the tool when in use. Thus theforce, which is a risk factor for thehand/wrist, cannot necessarily be record-ed directly from the weight/mass of theexternal load.

It has therefore proved scientifically diffi-cult to evaluate the forces required tocarry out tasks at the workplace. Thus,surrogates for these values have frequent-ly been sought (e.g. the perceived effortreported by the worker or estimates pro-vided by observers).

For action to be effective it was consideredunfeasible, in most instances, to expectassessors in the workplace to measure theactual forces required. Therefore, guid-ance would be needed on how to obtainsuitable force estimates based on workerperceptions or observer estimates.Similarly, it was recognised by the expertpanel that guidance might be required forupper and lower limits of force applica-tions on typical jobs. These may have tobe industry or sector specific.

The Swedish ordinance (Ergonomics forthe Prevention of MusculoskeletalDisorders, AFS 1998:1), which has a three-zoned system, was considered as a possi-

ble model, although some additionalparameters (e.g. mechanical pressure onthe wrist) might be used to further thismodel.

Some epidemiological reports have sug-gested that, for the hand/wrist exposure,high-force jobs are those with estimatedaverage hand force requirements of morethan 4 kilogrammes of force (kgf) andlow-force jobs are those with hand forcerequirements below 1 kgf (Silverstein etal., 1986). Chiang et al. (1993) used alower force cut off (3kgf) for defining theirhigh force exposure groups and showedsignificant associations with hand/wristmusculoskeletal disorders. Silverstein etal. (1986) reported substantially greaterodds ratios than did Chiang et al. (1993)with respect to force.

The TUTB (Ringelberg and Voskamp,1996) advanced a set of proposals forintegrating ergonomic principles into C-standards for machinery design. Theysuggested that operators who have to liftitems of more than 3 kg and/or operatorshaving to exert a hand-arm force of morethan 20 Newtons should have a risk eval-uation (see also prEN 1005-2)

It is considered that the setting of a 4kgf high risk action zone would beappropriate to ensure that those atgreater risk were identified, althougha lower force (as suggested by Chianget al. 1993) might be considered pru-dent.


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5.5I N T E R A C T I O N S

The need to consider the interactionsbetween potential risk factors wasreferred to frequently throughout the dis-cussions with the expert panel. For exam-ple, whilst force and posture are likely tobe assessed separately in the workplace,their interactions are undoubtedly ofimportance (Haselgrave, 1992; Silversteinet al., 1986) Nevertheless, their separateassessment in the workplace may wellprovide important pointers for potentialareas of intervention.


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5.6H A N D A R M V I B R A T I O N

( H A N D - T R A N S M I T T E D

V I B R A T I O N )

A s s e s s m e n t o f V i b r a t i o n a t t h e H a n d

The CEN report entitled "Mechanicalvibration - Guide to the health effects ofvibration on the human body" (see CR12349, 1996) found that poweredprocesses and tools that expose the oper-ator to hand/arm vibration were wide-spread. Exposure can arise from rotatingand percussive tools as well as vibratingwork pieces and controls. It is estimatedthat 1.7 % to 3.6% of the work force inEurope and in the USA are exposed topotentially harmful hand transmittedvibration.

The knowledge base relating to the expo-sure to vibration at the hand interface andits effects on biological tissues is wellestablished and it is generally recognisedthat excessive exposure may result indisturbances to finger blood circula-

tion and also in neurological and loco-motor functions of the hand and arm(Bovenzi, 1998). The potential disordersresulting from exposure to vibration,therefore, are not only musculoskeletal innature.

It was noted that whilst the draft ISOstandard for Vibration should pertain to allbiological effects of exposure, in realitythe data are only satisfactory for vasculardisorders. For vascular disorders well-defined acute and long-term outcomesare apparent (see table 6) and both epi-demiological and laboratory data arecoherent with regard to this.

Dose-response relationships have beenestablished which are now embodied inthe draft ISO/CEN Standards. The expo-sure to vibration is further to be consid-ered under the draft proposal from theEuropean Union on Physical agents

T a b l e 6 . T h e S t o c k h o l m W o r k s h o ps c a l e f o r s t a g i n g c o l d - i n d u c e dR a y n a u d ' s p h e n o m e n o n i n t h e

h a n d - a r m v i b r a t i o n s y n d r o m e . I nC E N C R 1 2 3 4 9 : 1 9 9 6 E .

Stage Grade Symptoms

0 - No attacks

1 Mild Occasional attacks affecting onlythe tips of one or more fingers

2 Moderate Occasional attacks affecting distaland middle (rarely also proximal)phalanges of one or more fingers

3 Severe Frequent attacks affecting all pha-langes of most fingers

4 Very severe As in stage 3, with trophic skinchanges in the fingertips


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(Council of the European Union, 94/C230/03, 1994).

The relationship between vibration andother physical risk factors was considered.For carpal tunnel syndrome the combi-nation of vibration with some otherphysical factors may lead to a dou-bling of the risk. The CEN (CR12349:1996 E) suggests that physicalstressors acting on the hand and wrist(repetitive movements, forceful gripping,awkward postures), in combination withvibration may cause carpal tunnel syn-drome in workers handling vibrating tools.

G u i d a n c e i s n e e d e d f o r p r a c t i -t i o n e r s o n t h e v i b r a t i o n c h a r -a c t e r i s t i c s o f t o o l s .

Databases are currently being establishedthat will make available both manufactur-er data and field data (e.g. Sweden,http://umetech.niwl.se/Vibration/HAVHome.html). Thus, the daily energy-equiva-lent total vibration values will be providedfor practitioners.

It was further recognised that the methodof use of a tool, the piece that the toolwas working on and issues of mainte-nance may all significantly affect theextent of risk associated with those tasks.

Methods for assessing human exposure tomechanical vibration and shock are con-

tained in ISO/CD 5349-2 (1999). This pro-vides appropriate advice regarding the useof accelerometers to assess vibration char-acteristics at the "hand", methods ofmounting the accelerometers on thevibrating equipment or surface, problemsof processing the data and evaluation ofuncertainties. It also details the calcula-tion of daily vibration exposure (8 hourenergy equivalent acceleration of vibra-tion) and estimated daily vibration expo-sure with respect to risk of finger blanch-ing (based on ISO/CD 5349-1).

Assessment of the workers exposure tohand/arm vibration requires considerablepractitioner expertise and access to tech-nical equipment. It is difficult or impossibleto gain any meaningful ‘measure’ of theexposure to vibration or the characteristicsof the vibration through observationalmethods. Therefore, in the absence ofappropriate direct measurement devices(accelerometers) and technical knowl-edge, subjective judgements may beneeded.

The need to include vibration as a riskfactor for upper limb musculoskeletaldisorders, to assess exposure and takeappropriate action is convincing basedon the evidence. However, difficultiesexist with the application of riskassessment amongst practitionergroups without access to appropriateequipment.


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5.7W O R K O R G A N I S A T I O N A N D

P S Y C H O S O C I A L F A C T O R S

Whilst other areas of action have beenconsidered with reference to body loca-tion, the final section is of a generic natureand has been considered separately. Bothwork organisation and psychosocial workfactors are recognised as associated withthese disorders (Devereux and Buckle,1998; Smith and Carayon, 1996).However, the lack of standardisation ofboth concepts and terminology has gener-ated difficulties when seeking to interpretresearch findings and to generate actionlimits. Hagberg et al. (1995) have dis-cussed the meaning of work organisation-al and psychosocial work:"Psychosocialfactors at work are the subjective aspectsas perceived by workers and the man-agers. They often have the same namesas the work organisation factors, but aredifferent in that they carry ‘emotional’value for the worker. Thus, the nature ofthe supervision can have positive or nega-

tive psychosocial effects (emotionalstress), while the work organisationaspects are just descriptive of how thesupervision is accomplished and do no notcarry emotional value. Psychosocial fac-tors are the individual subjective percep-tions of the work organisation factors."

It must be noted that this is not a globallyaccepted definition but is considered to besuitable for the purposes of this report.

Theorell (1996) considered the possiblemechanisms behind the relationshipbetween the demand-control-supportpsychosocial model of Karasek (1979) andKarasek and Theorell (1990) and disordersof the musculoskeletal system. In thismodel, both quantitative and qualitativepsychological demands have greateradverse consequences if they occur jointlywith low decision latitude (i.e. little oppor-tunity to influence decisions in the job).He identified three different kinds ofmechanisms that might relate psychoso-cial factors to musculoskeletal disordersymptoms. The three mechanisms postu-lated are physiological, leading to organicchanges; physiological mechanisms thatinfluence pain perception; and sociopsy-chological conditions that are of signifi-cance to the individual's possibility of cop-ing with the illness. The latter are of par-ticular importance in rehabilitation. Healso identified a further complication tounderstanding in that the mechanismsgenerating acute conditions are often dif-ferent to those perpetuating pain and cre-ating chronic conditions. It would appearthat more physiological studies are need-ed in the exploration of possible path-ways.


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The International Labour Office (ILO) 1998publication "Work Organization andErgonomics" emphasised the potentialimportance of integrating ergonomics andwork organisation to achieve better phys-ical conditions, better social relationshipsand equipment and better work organisa-tion practices (Buchanan et al., 1998). Theapproach advocated requires furtherdebate, particularly with regard to its rolein preventive strategies.

As noted earlier (see section on workrelatedness and epidemiology) there islimited research on the relationshipbetween work organisation and neck andupper limb musculoskeletal disordersalthough there is plausibility in such a rela-tionship. For example, the effect of anorganisation downsizing has been shown,in a follow-up study in Finland, to increasethe risk substantially for sick leave due tomusculoskeletal disorders. The disorders inthis study were classified under theInternational Classification of Diseases(1977 revision) (Vahtera et al., 1997).

It has been postulated that work organisa-tional factors may affect short and longterm reactions to mental stress(9). Thesemay subsequently affect the developmentof upper limb disorders. In addition, workorganisation factors may directly influencephysical work risk factors for neck andupper limb disorders such as posture andduration of repetitive movements(Bongers et al., 1993; Smith and Carayon,1996).

A report aimed at investigating time con-straints and autonomy at work in theEuropean Union has shown that time con-straints are clearly rising (Dhondt, 1998).Less firm judgements can be made regard-ing job autonomy due to differences indefinitions and instruments used in sur-veys. It is concluded that high strain work-ing conditions are increasing in theEuropean Union but that further researchis required to clarify the observed trends.

An EU community action (Council direc-tive 93/104/EC on Working Time) drawsattention to alleviating monotonous workand work at predetermined work-rates,and thus has a direct bearing on exposureto the risk factors described in this report.

An ergonomics approach to work(re)design on organisational factors hasbeen shown to be effective when there isa high commitment from stakeholders,and when multiple strategies are used toreduce identified risk factors (Westgaardand Winkel, 1997). This strategy isechoed by the International LabourOrganisation (1998) who states that"problems are interrelated – solutions aremultiple". Participatory ergonomics offersthe potential for developing such an inte-grated approach (for a review, see Hainesand Wilson, 1998). It is recommendedthat future interventions consider the ben-efits of such a strategy.

A recent report (Parkes et al., 1998) by theU.K. Health and Safety Executive includesindustrial case studies. These have

(9) Mental stress has been defined under ISO 10075:1991(E) as "The total of all assessable influences impinging upona human being from external sources and affecting it mentally".


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demonstrated the value of work redesignby organisational interventions. Thisenabled improved management of risk forpsychosocial work factors.

The NIOSH (1997) and National ResearchCouncil (1999) reviews on work-relatedmusculoskeletal disorders provide sup-porting evidence for a relationshipbetween psychosocial work factors andneck and upper limb musculoskeletal dis-orders. There is, however, a re-iteration ofthe need for agreed definitions withrespect to psychosocial factors.

Subjective, perceived workload is associat-ed with a variety of disorders. However,mental workload cannot easily be meas-ured and workload can mean differentthings to different people. That is, work-load is not merely a property of the task,but of the task, the human and their inter-action (Tulga and Sheridan, 1980).Although no single psychosocial or workorganisational factor is the predominantcause of disorders (Hales et al., 1994),based on the current knowledge, somepsychosocial work factors should still beassessed.

Their importance in the current EuropeanDirectives has already been identified. Forexample:

"Manual Handling of Loads

1. Requirements of the activity

The activity may present a risk particularlyof back injury if it entails one or more ofthe following requirements: - over-fre-quent or over-prolonged physical effortinvolving in particular the spine, - an insuf-ficient bodily rest or recovery period, -

excessive lifting, lowering or carrying dis-tances, - a rate of work imposed by aprocess which cannot be altered by theworker."

Existing Council Directive 93/104/EC (23November 1993) concerning certainaspects of the organisation of workingtime, has also identified psychologicalaspects of work as issues to be addressed:

"Article13

Pattern of work

Member States shall take the measuresnecessary to ensure that an employer whointends to organize work according to acertain pattern takes account of the gen-eral principle of adapting work to theworker, with a view, in particular, to allevi-ating monotonous work and work at apredetermined work-rate, depending onthe type of activity, and of safety andhealth requirements, especially as regardsbreaks during working time."

Bongers et al. (1993) and Lindström(1994) have provided criteria for goodwork organisation and psychosocial fac-tors. These may form the basis for furtherconsultation on these issues.

In this report, it is suggested that anyguidance should be limited to the fac-tors of job decision latitude, jobdemands and social support. A similarapproach has been taken in the SwedishOrdinance on Ergonomics for thePrevention of Musculoskeletal DisordersAFS 1998:1 (Statute Book of the SwedishNational Board of Occupational Safety andHealth).


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It is recognised that assessment of psy-chosocial work factors is subjectiveand contextual. However, these fac-tors have been associated with the dis-

orders under review here and, thus,should be addressed. It is suggestedthat further consultations are held onthis topic.

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6.The importance of health and risk surveil-lance is both recognised and establishedin some existing directives. For example,Council Directive 89/391/EEC on the intro-duction of measures to encourageimprovements in the safety and health ofworkers at work has:

"Article 14

Health surveillance

1. To ensure that workers receive health

surveillance appropriate to the healthand safety risks they incur at work,measures shall be introduced in accor-dance with national law and/or prac-tices.

2. The measures referred to in paragraph1 shall be such that each worker, if heso wishes, may receive health surveil-lance at regular intervals.

3. Health surveillance may be provided aspart of a national health system. "

The major goals of any surveillance system(Hagberg et al., 1995) are to achieve earlyidentification of work related muscu-loskeletal disorders and symptoms as wellas their risk factors. Additional goalsinclude:l Determination of the size of the prob-

lem l Identifying those at most risk l Identifying those at least risk (to help

inform the change process) l Systematic description of the risk fac-

tors to inform change and prioritiseneeds

l Assessment of change over time andsuccess of preventative changes andactions

Surveillance data collection methods mustbe practical, uniform and be able to beused rapidly, even if this has some effecton their accuracy (see also Last, 1983).Surveillance methods are characterised aseither passive or active. Passive methodsusually rely on existing data sources (e.g.occupational health records, sicknessabsence records, routine risk assessments).Active methods may also include specifi-cally designed methods and tools with


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information being collected from, forexample, particular sections of a work-force.

One example of this approach already inaction comes from the EuropeanCommittee for Standardization (CEN).They have identified the need for healthsurveillance with regard to hand armvibration exposure and the associatedinjuries or disorders (see CEN CR 12349,1996). A handbook on surveillance forwork-related musculoskeletal disorders iscurrently being developed by theInternational Commision on OccupationalHealth (ICOH) and the InternationalErgonomics Association (IEA.)

It should be noted, however, that whilstthe potential benefits of health and risksurveillance programmes for these disor-ders are considerable, the actual benefitsare largely unknown. An evaluation pro-gramme is therefore warranted.

It is suggested that any preventivestrategy relating to neck and upperlimb musculoskeletal disorders makesfull reference to an appropriateapproach to surveillance.

The process of consultation has enabledviews to be gathered from a wide range of

experts and organisations. The feedbackhas been highly supportive of the meth-ods and findings of this report. However,there is a growing belief that the socialdimension to these problems may requireadditional strategies for prevention. Inparticular the recognition that, withrespect to public health, general social fac-tors (e.g. poor economic circumstances,low levels of education, poor connectionswith the labour market) contribute to ill-health by increasing the vulnerability oflarge populations. This happens independ-ently of the working conditions and willlimit the potential effectiveness of inter-ventions directed specifically at the workplace.

Similarly, within organisations the abilityto recognise, adopt and implement theavailable ergonomics advice also requiresfurther consideration. For example, thebalance between analysis and actionwhen limited resources are available or thepotential for incorporating approachesinto existing management and organisa-tional thinking have not been discussedwithin this report, yet they remain vitalcomponents if prevention strategies are tobe optimised.

D E V E L O P M E N T S I N T H E

C O N T E X T O F O T H E R

E U R O P E A N U N I O N

I N I T I A T I V E S


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7.Finally, the complex nature of existingdirectives, member state regulations andguidance and current standards has high-lighted the need for further harmonisa-tion. Whilst these have been recognised,it is considered outside of the scope of thisreport to resolve these issues.


S U M M A R Y - S T R A T E G I E S F O R

P R E V E N T I O N


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8.This section has focussed on the assess-ment of risk factors, preventive and pro-tective measures and the provision ofappropriate surveillance. It recognises theneed to provide appropriate informationand training.

The report has considered the ability ofthose at the workplace (e.g. practitioners,worker representatives) to make riskassessments. Advice has been provided asto how such assessments could be made.

Consistently reported risk factors requiringconsideration in the work system are pos-tural (notably relating to the shoulder andwrist), force applications at the hand,hand arm exposure to vibration, directmechanical pressure on tissues, effects ofa cold work environment and work organ-isational and psychosocial issues. The lim-ited understanding of interactionsbetween these variables mean that expo-sure-response relationships are difficult todeduce. However, those workers at highrisk can be identified using the currentknowledge base.

Scientists with experience of policy settingaffirmed their belief that it was prudent toconsider fatigue as a potential precursorto some of the disorders. Its use in surveil-lance programmes was also suggested.The role of fatigue is evident in some exist-ing European health and safety directivesand standards.

General Issues of Exposure: Althoughthere was some research evidence in sup-port of a duration of exposure(s) of fourhours placing work tasks in the high"action" zone, further debate on thisissue is required. A distinction betweenrepetitive work and work recovery isrequired when interpreting data and inproviding recommendations.

Neck: The expert panel agreed that theepidemiological data were not conclusivewith regard to specific neck postures andthe risk of developing the disorders underconsideration in this report. The uncer-tainty over the epidemiological data ledthe group to recommend that a further


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consideration of the current experimentaldata should be undertaken.

Shoulders: Working above shoulderheight is widely recognised as a risk factorfor shoulder musculoskeletal disorders.Recommendations for action on posturehave been made. Epidemiological studieshave not yet provided sufficient informa-tion to define the exposure-response rela-tionship regarding the frequency of repet-itive shoulder movements or for forceexertions at the shoulder.

Wrists: The expert panel agreed thatextremes of wrist movement should beincluded in risk assessments and that anyintervention on this risk factor is likely tohave benefits for other upper limb muscu-loskeletal disorders. Biomechanical andepidemiological data support each otherwith regard to hand/wrist tendinitis.However, whilst the epidemiological andbiological evidence in support of the needfor action is strong, there are difficulties inproviding suitable tools to allow riskassessment to be made in the work place.The importance of force as a risk factor forhand/wrist musculoskeletal disorders wasrecognised and the setting of a high-riskaction zone for force at the wrist was seenas feasible.

Hand Arm Vibration: The knowledge baserelating to the exposure to vibration at thehand interface and its effects on biologicaltissues is substantial. Excessive exposuremay result in disturbances to finger bloodcirculation and also in neurological andlocomotor functions of the hand and arm.Guidance is needed for practitioners onthe vibration characteristics of tools. The

inclusion of vibration as a risk factor forupper limb musculoskeletal disorders andthe need to assess exposure and seekappropriate action is convincing, based onthe current evidence. Some difficultiesexist with the availability of specialistequipment required for risk assessment,although newly developed databases pro-vide a good source of information for thevibration characteristics of powered tools.

Organisational and Psychosocial work fac-tors: Assessment of psychosocial workfactors is subjective and contextual.However, these factors are associated withthe disorders and should be addressed.The importance of work organisationalfactors is evident in a number of EUDirectives and their relationship with thesedisorders has been demonstrated in anumber of epidemiological studies.Plausible hypotheses and mechanismsexist to explain these relationships but fur-ther research and wider consultation onpreventive strategies are required.

Interventions: The report has found goodevidence in support of an ergonomicswork system approach. This is harmoniouswith a number of European Union direc-tives and standards. Such an approachmust take due regard of the work systemrisk factors identified in this report.Participatory ergonomics offers the poten-tial for developing an integratedapproach.

Appropriate ergonomics intervention onthe work system risk factors for any singlespecific disorder is also likely to conferbenefits with regard to other disorders.For example, reducing the exposure to


81n

hand arm vibration will not only reducethe likelihood of the development ofRaynaud's disease, but also may alsoreduce the need for high force exertion atthe hand and, thus, reduce the risk forhand/wrist tendinitis. Such benefits arisebecause of the common pathways leadingto some of the disorders.

The importance of a health and risk sur-veillance programme has been empha-sised, and is supported by both existingEuropean Union directives and a numberof internationally recognised professionalcommissions and associations. The provi-sion of methods to enable organisationsto undertake such surveillance is consid-ered to be an additional and importantfactor in determining both the nature andscope of any preventive strategies.

Many organisations have sought to imple-ment ergonomic programmes and inter-ventions aimed at primary prevention ofthe problems. This would suggest thatthey already believe in the effectiveness ofergonomic and occupational health strate-gies aimed at preventing the developmentof this group of disorders. Organisationsinvolved in such programmes provideimportant role models for others wishing

to initiate preventive programmes. It is lessclear how beneficial such approaches havebeen although there are a number ofstudies that demonstrate the cost-effec-tiveness of an ergonomics approach.Within organisations the ability to recog-nise, adopt and implement the availableergonomics advice also requires furtherconsideration.

The process of dissemination might beenhanced through appropriate use of thenewly established Topic Centre on GoodSafety and Health Practice concerningMusculoskeletal Disorders. This is a recentinitiative from the European Agency forSafety and Health at Work.

There is a growing belief that the socialdimension to these problems may requireadditional strategies for prevention. Inparticular, the recognition that generalsocial factors (e.g. poor economic circum-stances, low levels of education, poor con-nections with the labour market) con-tribute to ill-health by increasing the vul-nerability of large populations. This hap-pens independently of the working condi-tions and may limit the potential effective-ness of interventions directed specificallyat the work place.


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9.


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9.1D I A G N O S T I C C R I T E R I A

There is little evidence of the use of stan-dardised criteria across member states.This is reflected in the nationally reporteddata as well as the research literature andmakes comparison between memberstates difficult. Current studies that havereached consensus diagnostic criteriashould be disseminated widely for furtherconsultation, with a view to standardisa-tion. This report recognises that the crite-ria for primary preventative use in work-place surveillance and occupational healthwill be different from the criteria used forsome clinical interventions.


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9.2S I Z E O F T H E P R O B L E M

There is substantial evidence within the EUmember states that neck and upper limbmusculoskeletal disorders are a significantproblem with respect to ill health andassociated costs within the workplace. It islikely that the size of the problem willincrease as exposure to work-related riskfactors for these conditions is increasingwithin the European Union.

Estimates of the cost of these problemsare limited. Where data do exist (e.g. theNordic countries and the Netherlands) thecost has been estimated at between 0.5%and 2% of GNP.

The lack of standardised diagnostic criteriamakes comparison of data between mem-ber states difficult and little is known ofthe validity of the reported data. This alsomakes it difficult to assess the extent of illhealth and associated costs within theworkplace. Those studies that have used

the same methodological criteria havereported large differences in prevalencerates between member states. The rea-sons for this require further investigation.

A number of epidemiological studies havefound that women are at higher risk forwork related neck and upper limb disor-ders, although associations with work-place risk factors are generally found to bestronger than gender factors. The impor-tance of gender differences, and theirimplication for work system design, islargely outside the scope of this report butrequires more substantial debate.


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9.3P A T H O G E N E S I S

Understanding of the pathogenesis ofthese disorders varies greatly with regardto the specific condition in question. Formany of the disorders, (e.g. carpal tunnelsyndrome) the body of knowledge isimpressive, bringing together biomechan-ics, mathematical modelling and directmeasurement of physiological and soft tis-sue changes. These form a coherent argu-ment that is persuasive of the biomechan-ically induced pathogenesis of such condi-tions. For those conditions where theknowledge base is smaller, plausiblehypotheses do exist and are currently thesubject of much research interest.


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9.4W O R K - R E L A T E D N E S S

The scientific reports, using defined crite-ria for causality, established a strong posi-tive relationship between the occurrenceof some neck and upper limb muscu-loskeletal disorders and the performanceof work, especially where high levels ofexposure to work risk factors were pres-ent. Thus the identification of workers inthe extreme exposure categories shouldbecome a priority for any preventativestrategy.

Consistently reported risk factors requiringconsideration in the work system are pos-tural (notably relating to the shoulder andwrist), force applications at the hand,hand arm exposure to vibration, directmechanical pressure on tissues, effects ofa cold work environment and work organ-isational and psychosocial issues. The lim-ited understanding of interactionsbetween these variables means that expo-

sure-response relationships are difficult todeduce. However, those workers at highrisk can be identified using the currentknowledge base.


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9.5S C O P E F O R P R E V E N T I O N

The expert panel concluded that existingscientific knowledge could be used in thedevelopment of preventative strategies.These will be acceptable to many stake-holders and are practical for implementa-tion. There is limited but persuasive evi-dence on the effectiveness of work systeminterventions incorporating ergonomics.The ergonomics work system approachmust take due regard of the work systemrisk factors identified in this report and athree level model of risk assessment hasbeen proposed.

Appropriate ergonomics intervention onthe work system risk factors for any singlespecific disorder is also likely to conferbenefits with regard to other disorders.For example, reducing the exposure tohand arm vibration will not only reducethe likelihood of the development ofRaynaud's disease, but also may also

reduce the need for high force exertion atthe hand and, thus, reduce the risk forhand/wrist tendinitis. Such benefits arisebecause of the common pathways leadingto some of the disorders.

Scientists with experience of policy settingaffirmed their belief that it was prudent toconsider fatigue as a potential precursorto some of the disorders. Its use in surveil-lance programmes was also suggested.The role of fatigue is evident in some exist-ing European health and safety directivesand standards.

Many organisations have sought to imple-ment ergonomic programmes and inter-ventions aimed at primary prevention ofthe problems. This would suggest thatthey already believe in the effectiveness ofergonomic and occupational health strate-gies aimed at preventing the developmentof this group of disorders. Organisationsinvolved in such programmes provideimportant role models for others wishingto initiate preventive programmes. Thatsaid, it is less clear how beneficial suchapproaches have been. Within organisa-tions the ability to recognise, adopt andimplement the available ergonomicsadvice also requires further consideration.

The importance of a health and risk sur-veillance programme has been empha-sised, and is supported by both existingEuropean Union directives and a numberof internationally recognised professionalcommissions and associations.

The report has considered the ability ofthose at the workplace (e.g. practitioners,worker representatives) to make riskassessments. Advice as to how such


89n

assessments could be made, given theserestrictions, has been provided. The agree-ment of valid, standardised methods forthe evaluation of working conditions andassessment of risk factors is required.

The report has not identified a specificform of action. However, the report hasprovided a basis on which action could beformulated and existing European direc-tives on health and safety issues are con-sistent with the recommendations made.Those organisations that have implement-ed ergonomic programmes for preventionshould be encouraged to help promoteany future action.

The process of dissemination might beenhanced through appropriate use of the

newly established Topic Centre on GoodSafety and Health Practice concerningMusculoskeletal Disorders. This is a recentinitiative from the European Agency forSafety and Health at Work.

Finally, there is a growing belief that thesocial dimension to these problems mayrequire additional strategies for preven-tion. In particular, the recognition thatgeneral social factors (e.g. poor economiccircumstances, low levels of education,poor connections with the labour market)contribute to ill-health by increasing thevulnerability of large populations. Thishappens independently of the workingconditions.


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A P P E N D I C E S


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RE

SE

AR

CH

11.


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A.1A P P E N D I X 1 .

P R O J E C T O R G A N I S A T I O N

S t e e r i n g c o m m i t t e e

Dr. M. Aaltonen, Project Manager,ResearchEuropean Agency for Safety and Health atWorkGran Via, 33 E-48009 Bilbao SPAIN

Dr. G. Aresini, Dr. C. Martin, Dr. F.AlvarezEuropean Commission, Directorate-General VEmployment, Industrial Relations andSocial AffairsPublic health and safety and at workHealth, safety and hygiene at workRue Alcide de GasperiEUFO 4270L-2920 Luxembourg

Prof. P. Buckle, (project leader), Dr. J.Devereux (technical secretariat)

Robens Centre for Health Ergonomics

European Institute of Health & MedicalSciences

University of Surrey, Guildford, Surrey,U.K. GU2 5XH

C o m m i t t e e o f s c i e n t i f i c e x p e r t s

Professor Tom Armstrong, Centre forErgonomics, University of Michigan, AnnArbor, Michigan 48109-2029, U.S.A.

Dr. Massimo Bovenzi, Institute ofOccupational Health, University of Trieste,Centro Tumori, I-34129 Trieste, Italy.

Professor Asa Kilbom, Centre forErgonomics, National Institute of WorkingLife, S-171 84 Solna, Sweden.

Professor Monique H.W. Frings-Dresen, Coronel Institute forOccupational and Environmental Health,Academic Medical Center, Meibergdreef15, 1105 AZ Amsterdam, The Netherlands

Dr. Larry Fine, National Institute ofOccupational Safety and Health, ColumbiaParkway, Cincinnatti, Ohio, U.S.A.

Dr. Paulien Bongers TNO Work andEmployment, Polaris Avenue 151, 2132 JJHoofddorp, The Netherlands

Professor Peter Buckle and Dr. JasonDevereux, Robens Centre for HealthErgonomics, European Institute of Health& Medical Sciences, University of Surrey,Guildford, Surrey, U.K. GU2 5XH


107n


S U M M A R Y O F C O N S U L T A T I O N

These included meetings with representa-tives from the National Institute forWorking Life, Sweden; the University ofGothenburg, Sweden; the University ofMilan, Italy; the Health and SafetyExecutive in the UK, consultation withtrade union bodies, NIOSH in the UnitedStates, consultation with DG V and somedissemination of key information toappropriate member states.

Meetings have been held with the TradeUnion Technical Bureau for Health andSafety in Brussels, Belgium and the Frenchemployer's federation CNPF.

There has also been liaison with theCoronel Institute, Amsterdam who aredeveloping diagnostic criteria for upperlimb disorders and with TNO Work andEmployment, Hoofddorp, who areinvolved with other European researchprojects investigating work-related neck

and upper limb disorders under the SAFEprogramme.

The approach has been presented and/ordiscussed at the following meetings:

l Organisational Design andManagement 6 , The Hague,Netherlands, August 1998

l PREMUS-ISEOH, Helsinki, Finland,September, 1998

l Occupational Disorders of the UpperExtremities, Universities of Berkeley,UCLA and University of Michigan,December 1998

l New Perspectives in OccupationalMedicine Meeting, School of PublicPolicy, University College London,March 1999

l Contemporary Ergonomics, ErgonomicsSociety Annual Conference, Universityof Leicester, England, April 1999

l RSI, Law and Medicine Trades UnionCongress (TUC) Meeting , London,England, April 1999

These conferences provided a forum fordiscussion and feedback on the approachtaken.

The special consultation process was car-ried out in the summer of 1999 by send-ing the manuscript to the members of theThematic Network Group on Research -Work and Health, DGV, European socialpartners (ETUC, UNICE) and other interna-tional experts on the topic.


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L I T E R A T U R E S E A R C H T E R M S

A N D D A T A B A S E S

D a t a b a s e s s e a r c h e d

BIDS-ONLINENIOSHTICMEDLINEHSELINECISDOCOSH-CD

K e y w o r d s f o r s e a r c h

M E S H t e r m s

Arm-injuries-epidemiologyArm-injuries-etiologyCumulative-trauma-disorders-epidemiolo-gyCumulative-trauma-disorders-etiologyHand-injuries-epidemiologyHand-injuries-etiologyCumulative-trauma-disorders-prevention& controlMusculoskeletal diseases

Cumulative trauma disorders Musculoskeletal system disorders

N o n - M E S H t e r m s

RSI or repetitive strain injur* WRULD* work related upper limb disorder* WRUED* work related upper extremity disorder*repetition strain injuryepidemiologyetiologycumulative trauma disordersnecktension neck syndromeshoulderrotator cuffelbowepicondylitistendinitistenosynovitiscarpal tunnelde Quervain’snerve entrapment syndromevibrationhand arm vibration syndromevibration white fingerRaynaud’s phenomenonDupuytren’s contractureTrigger fingerCubital tunnel syndromeGuyon canal syndromePronator teres syndrome Radial tunnel syndromeThoracic outlet syndromeCervical syndromeDigital neuritisHypothenar hammer syndrome


109n

Adverse mechanical tensionMyotherapy –trigger pointsFibrositisMyofascial syndromeChronic painmyalgiaReviewsOccupational Diseases physiopathologyPain physiopathologymechanismsMyofascial Pain Syndromes etiologyMyofascial Pain Syndromes physiopathol-ogyNeck physiopathologyCumulative Trauma Disorders complica-tions

Shoulder physiologyFatigue physiopathologyMicrocirculation physiologyNeck physiopathologySoft Tissue Injuries physiopathologyPain physiopathologychronic painMuscles physiopathology InterventionReview

N o t e :

Additional Mesh and Non-mesh termshave been included during the iterative lit-erature search process.


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S U M M A R Y T A B L E S O F

P O S T U R A L R I S K F A C T O R S

(Hagberg et al., 1995)

P o s t u r a l r i s k f a c t o r s r e p o r t e d i nt h e l i t e r a t u r e f o r t h e s h o u l d e r s .

Risk factor Results: ReferencesOutcome and details

More than 60° Acute shoulder Bjelle et al., 1981abduction or flexion and neck painfor more than 1 hour/day

Less than 15° Increased sick Aaras et al.,median upper arm leave due to 1988flexion and 10° musculoskeletal abduction for problemscontinuous work with low loads

Abduction greater Rapid fatigue at Chaffin, 1973than 30° greater abduction

angles

Abduction greater Rapid fatigue Herberts et al.,than 45° at 90° 1980


Abduction greater Hyperabduction Beyer and than 100 syndrome with Wright, 1951

compression of blood vessels

Shoulder forward Impairment of Järvholm et al.,flexion of 30°, blood flow in the 1988Abduction greater supraspinatus Järvholm et al.,than 30° muscle 1990

Hands no greater Onset of local Wiker et al.,than 35° above muscle fatigue 1989shoulder level

Upper arm flexion or Electromyo- Hagberg, 1981aabduction of 90° graphic signs of

local muscle fatigue in less than one minute

Hands at or above Tendinitis and Bjelle et al., 1979shoulder height other shoulder Herberts et al.,

disorders 1981Herberts et al.,1984

Repetitive shoulder Acute fatigue Hagberg, 1981bflexion

Repetitive shoulder Neck/shoulder Kilbom et al.,abduction or flexion symptoms 1986

negatively related to movement rate

Postures invoking Tendinitis and Luopajärvi et al.,static shoulder loads other shoulder 1979

disorders

Arm elevation Pain Sakakibara et al.,1987

Shoulder elevation Neck/shoulder Jonsson et al.,symptoms 1988

Shoulder elevation Neck/shoulder Kilbom et al.,and upper arm symptoms 1986abduction


111n


Abduction and Shoulder pain Aarås and forward flexion and sick leave Westgaard, 1987invoking static due to Aarås et al.,shoulder loads musculoskeletal 1987

problems

Overhead reaching Pain Bateman, 1983and lifting

P o s t u r a l r i s k f a c t o r s r e p o r t e d i nt h e l i t e r a t u r e f o r t h e n e c k .


Static flexion No pain in the Chaffin, 1973neck or EMG changes at 15°flexion for 6 hours. At 30°flexion, it took 300 mins for severe pain to occur. At 60°flexion, the corresponding time was 120 mins

Flexion Head inclination Hünting et al.,more than 56° 1981pain and tenderness in medical examination in 2/3 of the cases

Dynamic flexion Median flexion of Aaras et al.,between 19° and 198839° resulted in low sick leave due to musculoskeletal problems

Maximum static Rapid Harms-Ringdahl flexion development of and Ekholm,

pain at end of 1986 range of motion


n112


Deviated wrist Workers with Armstrong and positions carpal tunnel Chaffin 1979

syndrome used these postures more often

Hand manipulations More than Hammer 1934500-2000 manipulations per hour led to tenosynovitis

Wrist motion 1276 flexion Bishu et al.,extension motions 1990lead to fatigue

Wrist motion Higher wrist Marras and accelerations and Schoenmarkin velocities in 1993high-risk wrist WMSD jobs

P o s t u r a l r i s k f a c t o r s r e p o r t e d i nt h e l i t e r a t u r e f o r t h e h a n d a n d

w r i s t .Risk factor Results: References

Outcome and details

Wrist flexion CTS. Exposure of de Krom et al.,20-40 1990hours/week

Wrist flexion Increased median Smith et al.,nerve stresses 1977(pressure)

Wrist flexion Increased finger Moore et al.,flexor muscle 1991activation for grasping

Wrist flexion Median nerve Armstrong and compression by Chaffin, 1978;flexor tendons Moore et al.,

1991

Wrist extension Median nerve Keir and Wells,compression by 1992flexor tendons

Wrist extension CTS. Exposure of de Krom et al.,20-40 1990hours/week

Wrist extension Increased Gelberman et al.,intra-carpal 1981tunnel pressure for extreme extension of 90

Wrist extension Increased median Smith et al.,nerve stresses for 1977extension of 45-90

Wrist ulnar deviation Exposure Hunting et al.,response effect 1981found: if deviation greater than 20 increased pain and pathological findings


113n


A N N E X I

O F T H E M I N I M U M H E A L T H

A N D S A F E T Y R E Q U I R E M E N T S

F O R T H E M A N U A L H A N D L I N G

O F L O A D S

Council Directive 90/269/EEC of 29 May1990 on the minimum health and safe-ty requirements for the manual han-dling of loads where there is a risk par-ticularly of back injury to workers(fourth individual Directive within themeaning of Article 16 (1) of Directive89/391/EEC)

Official journal NO. L 156 , 21/06/1990 P.0009 - 0013

A N N E X I

(*) REFERENCE FACTORS (Article 3 (2),Article 4 (a) and (b) and Article 6 (2))

1 . C h a r a c t e r i s t i c s o f t h e l o a d

The manual handling of a load may pres-ent a risk particularly of back injury if it is: - too heavy or too large, - unwieldy or difficult to grasp, - unstable or has contents likely to shift, - positioned in a manner requiring it to be

held or manipulated at a distance fromthe trunk, or with a bending or twistingof the trunk,

- likely, because of its contours and/orconsistency, to result in injury to workers,particularly in the event of a collision.

2 . P h y s i c a l e f f o r t r e q u i r e d

A physical effort may present a risk partic-ularly of back injury if it is: - too strenuous, - only achieved by a twisting movement of

the trunk, - likely to result in a sudden movement of

the load, - made with the body in an unstable pos-

ture.

3 . C h a r a c t e r i s t i c s o f t h e w o r k i n ge n v i r o n m e n t

The characteristics of the work environ-ment may increase a risk particularly ofback injury if: - there is not enough room, in particular

vertically, to carry out the activity, - the floor is uneven, thus presenting trip-

ping hazards, or is slippery in relation tothe worker's footwear,


n114

- the place of work or the working envi-ronment prevents the handling of loadsat a safe height or with good posture bythe worker,

- there are variations in the level of thefloor or the working surface, requiringthe load to be manipulated on differentlevels,

- the floor or foot rest is unstable, - the temperature, humidity or ventilation

is unsuitable.

4 . R e q u i r e m e n t s o f t h e a c t i v i t y

The activity may present a risk particularlyof back injury if it entails one or more ofthe following requirements: - over-frequent or over-prolonged physical

effort involving in particular the spine, - an insufficient bodily rest or recovery

period, - excessive lifting, lowering or carrying dis-

tances,

- a rate of work imposed by a processwhich cannot be altered by the worker.

(*) With a view to making a multi-factoranalysis, reference may be made simulta-neously to the various factors listed inAnnexes I and II.

A N N E X I I

(*) INDIVIDUAL RISK FACTORS (Articles 5and 6 (2)) The worker may be at risk ifhe/she:

- is physically unsuited to carry out thetask in question,

- is wearing unsuitable clothing, footwearor other personal effects,

- does not have adequate or appropriateknowledge or training.

(*) With a view to multi-factor analysis,reference may be made simultaneously tothe various factors listed in Annexes I andII.


Work-related neck and upper limb musculoskeletal disorders

Luxembourg: Office for Official Publications of the European Communities

1999 — 114 pp. — 14.8 x 21 cm

ISBN 92-828-8174-1


R E S E A R C H

work-related neck and upper limb

European Agency for Safety and Health at WorkENEN

OFFICE

L-2985

OF THEFOR OFFICIAL PUBLICATIONSEUROPEAN COMMUNITIES

Luxembourg

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ntIn order to encourage improvements,

especially in the working environment, as

regards the protection of the safety and

health of workers as provided for in the

Treaty and successive action programmes

concerning health and safety at the

workplace, the aim of the Agency shall be

to provide the Community bodies, the

Member States and those involved in the

field with the technical, scientific and

economic information of use in the field of

safety and health at work.

54 A

S-24-99-712-E

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Gran Vía 33. E-48009 Bilbao Spain

Tel: +34 94 479 4360 . Fax: +34 94 479 4383

wo rk - r e l a t ed ne ck and

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Documents

Work Related Neck and Uper Limb Musculoeskeletal Disorders