workuperlimbdisorder jueves

8/6/2019 workuperlimbdisorder JUEVES

1/117

R E S E A R C H

European Agency f orSafety and Health atWorkN

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

w o r k - r e l a t e d

neck and

u p per l i m b


2/117


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

musculoskeletal

disorders

R E S E A R C H

European Agency f orSafety and Health atWork

Report prepared by

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

European Institute of Health & Medical SciencesUniversity of Surrey

Guildford, Surrey, U.KGU2 5XH


3/117

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


4/117


3n

Following a request from the European

Commission (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 problem

within 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 Robens

Centre 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 review

process. 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


5/117

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


6/117


5n

C o n t e n t s

FOREWORD 3CONTENTS 5

WORK-RELATED NECK AND UPPER LIMB MUSCULOSKELETAL

DISORDERS - Summary 7

Introduction 7

Assessment of work-related neck and upper limb musculoskeletal

disorders (WRULDs) 7

Size of the WRULDs problem 7

Biological mechanisms 8

Work-relatedness of WRULDs 8

Scope for prevention 9 1. INTRODUCTION 11

1.1 Approaches used to prepare the report 12 2. THE NATURE OF THE DISORDERS 15

2.1 How are the disorders measured? 16

2.2 How many experience these disorders in the EU? 18

2.3 The cost of the problems 23

2.4 Scientific basis for prevention 25

2.5 Summary - The Nature of the Disorders 28 3. THE RELATIONSHIP BETWEEN WORK AND NECK AND UPPER LIMB

DISORDERS 29

3.1 Models for the pathogenesis of the disorders 30

3.2 Biological responses and pathology 33

3.3 The epidemiological evidence of work-relatedness 39

3.4 Interventions in the workplace 43

3.5 Summary - The Work-relatedness of neck and upper limb

disorders 46 4. STRATEGIES FOR PREVENTION 47

4.1 Introduction 48

4.2 Health and work system assessment 52 4.3 Definition of risk and concept of action zones 53

4.4 Assessment of risk: work system assessment 55

4.5 Definitions of work system factors to be assessed 56


7/117

5. RISK FACTORS REQUIRING ASSESSMENT 59

5.1 General aspects of posture 60

5.2 Neck 61

5.3 Shoulders and arms 63 5.4 Wrists 65

5.5 Interactions 68

5.6 Hand Arm Vibration (Hand-Transmitted Vibration) 69

5.7 Work organisation and psychosocial factors 716. HEALTH AND RISK SURVEILLANCE 75

7. DEVELOPMENTS IN THE CONTEXT OF OTHER EUROPEAN UNION

INITIATIVES 77

8. SUMMARY - STRATEGIES FOR PREVENTION 78

9. CONCLUSIONS 83

9.1 Diagnostic criteria 84 9.2 Size of the problem 85

9.3 Pathogenesis 86

9.4 Work-relatedness 87

9.5 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 107

Appendix 3. Literature search terms and databases 108

Appendix 4. Summary tables of postural risk factors 110

Appendix 5. Annex I of the Minimum health and safety requirements

for themanual handling of loads 113


n6


8/117


7n

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 invited

Professor 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. These

include 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, but

rather utilises authoritative reviews of suchsources, where appropriate. Emphasis hasbeen placed on those reviews that wereagreed to be acceptable to the expertpanel of scientists.

A ss e ss m e n t o f 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 cu 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.

Si z e o f t h e W RU 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 will

increase 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


9/117

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 workplace

across 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 have

found 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 of

such 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 work

factors). 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.


n8


10/117


Sc o p e f o r p r e v e n t i o n

The report has not identified a specific

form 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 intervention

on workplace risk factors for any sin-

gle specific disorder is likely to help

prevent other disorders. For example,

reducing the exposure to hand-armvibration will not only reduce the like-

lihood of the development of

Raynaud's disease, but may also

reduce the need for high force exer-

tion at the hand and, thus, reduce the

risk for hand/wrist tendinitis. Such

benefits arise because of the commonbiological pathways involved in 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 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 such

restrictions, 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.

9n


11/117



12/117


11n

R

E

S

E

A

R

C

H

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 evidence

regarding 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 and

other 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


13/117


n12

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

PREPARE THE REPORT

This information has been collected from

an 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 at

Work). 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 Ex 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 was

agreement 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 Li 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 articlesl Reports not yet submitted or papers in

press to scientific peer reviewed jour-


14/117


13n

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). It

is 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.


15/117



16/117


15n

R

E

S

E

A

R

C

H

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 as

the 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 sole

determinant 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


17/117


n16

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 Europeare 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 cases

that present with upper limb pain are clas-sified as a non-specific upper limb condi-tions (Cooper and Baker, 1996).

Ta b l e 1 . Cl 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 cc 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-related

disorders 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 syndrome

l tenosynovitis/ l Cubital tunnel l Muscle sprain l Raynauds

l synovitis l syndrome l and strain l syndrome

l Epicondylitis l Guyon canal l Myalgia and

l De Quervains l syndrome l myositis

l disease l Pronator teres

l Dupuytrens l syndrome

l contracture l Radial tunnel

l Trigger finger l syndrome

l

Ganglion cystl

Thoracic outletl syndrome

l Cervical syndrome

l Digital neuritis


18/117


17n

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 or

pathology be considered in health

monitoring 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 shown

to 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 disability

remain unclear. A greater understandingof these relationships, along with the clin-ical natural history of these disorderswould be beneficial (National ResearchCouncil, 1999).


19/117


n18

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 verifiable

neck 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 be

derived 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 of

work-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 approximate

size 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 of

both 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 and

method 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.


20/117


19n

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 in

the 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

Ta b l e 2 . Th 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 cu 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 Outcome

Organisation 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 work

the 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 monthsDenmark National Institute of General industry 29% of men, Neck musculoskeletal

Occupational Health 46% of woman problems

Borg & Burr, 1997 26% of men, Shoulders musc.

44% of woman problems

14% 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


21/117


22/117


21n

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 reported

musculoskeletal 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 demonstrated

that 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). In

the 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 Scurit (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 that

affected 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.


23/117


n22

carpal tunnel syndrome, frozen shoulder,tenosynovitis, tennis or golfers 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 the

survey (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 Britain

suggests that 20000 cases ofw o r k - r e 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 the

number 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 and

carpal 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 for

upper 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

Denm

ark

FormerW

estGe

rmany

Greece Ita

lySpa

inFra

nceIre

land

Luxem

bourg

Nethe

rlands

Portua

l UK

Former

EastG

ermany

Finlan

dSw

eden

Austri

a

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 Eu 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 .

Percentageofrespondents

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


24/117


23n

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 collects

information 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 neck

and upper limb musculoskeletal disorders

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

Jensen, 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 only

a 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 significant

problem within the European Union.

Some member states have identified a

major ill-health and financial burden

associated 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.)


25/117


n24

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 and

the 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 and

personnel 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 important

than 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 surveys

conducted by trade unions in France,Spain, the United Kingdom and Denmark(TUTB, 1996).

This review suggests that neck and

upper limb musculoskeletal disorders

are increasingly recognised as a signif-

icant occupational health problem by

occupational doctors, employers, aca-

demia, trade unions and governments.

There are data that support the need

to address these disorders within the

European Union.


26/117


25n

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 the

occurrence 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 one

preventative strategy might com-

mence by identifying groups that are

highly exposed to risk factors for neck

and upper limb musculoskeletal disor-

ders. They considered that the great-est benefits, relative to the resources

required, 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 on

Working 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 tasks

l 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


27/117


n26

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 annual

prevalences 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 a

job 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 is

important 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 Working

Conditions in Europe, the percentage ofworkers exposed for greater than 50% ofthe working time increased for the follow-ing:

l Working in painful postures

l Handling heavy loads

l Working at high speed

l Working with deadlines

It would seem, therefore, that there is

considerable potential for reducing

the 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


28/117


29/117


n28

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 the

EU 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 to

the 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. This

report 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 rates

between 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.


30/117

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

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


29n

R

E

S

E

A

R

C

H

3.


31/117


n30

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 other

various 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 pathways

not consideredin this model.Other models(Van der Beekand Frings-Dresen, 1998;Winkel andM a t h i a s s e n ,1994) suggest

that 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 activity

produces 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 ck 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 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 e

p 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


32/117


31n

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 and

job decision latitude.The latter is defined asthe extent of autono-my and opportunitiesfor workers toimprove (or to make

worse) 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 way

a 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). Whilst

not 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 of

objects, 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 e

b o x sh o w n i n f i g u r e 2 . A d a p t e d

f r o m Va 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

Posture

Movement

Exerted forces

Internal factors shown in figure 2

Exposure


33/117


n32

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 . Co 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 t

p 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 hCo u n c i l , 1 9 9 9 ) .

Load

Response

Physiological

pathways

Impairment

Disability

Symptoms Adaptation

Work procedures,

equipment and

environment

Organisational

factors

Social context

Individual, Physical

and Psycho-logical

Factors and

Non-work related

activities


34/117


33n

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 Council

review 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 that

there 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 body

that 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 or

repetitive 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 of

other plausible explanations for theobserved effect, temporal contiguity; andcongruity between the cause and effect.


35/117


n34

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. It

should 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),Hgg (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

Hgg (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 that

problems of myalgia can occur at very lowcontraction levels. This, and otherresearch, led Hgg (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 (Waersted

and 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. Hgg (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. Hgg (1998) hasindicated that these types of muscleabnormalities may be a necessary but not

sufficient condition for pain perception.Of further interest, is the observation thattype I muscle fibres show mitochondrialdisturbances - type I fibres being those


36/117


35n

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 Te n d o n / l i g a m e n t

Tendons, mainly formed of collagenous

tissue, 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 friction

has 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 hours

initiated 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


37/117


n36

out that whilst a dose-response relation-ship with pressure occurs, the critical pres-sure/duration values for nerve injury are

unknown. 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.

Strmberg 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; Pyykk,1986). In animal models, structural

changes 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

(Strmberg 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 Ci 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 ca l M e ch a n i c a l P r e s su r e

Hagberg et al. (1995) have considered the

possible relationship between localmechanical pressure and the onset ofmusculoskeletal problems. Directmechanical pressures on tissues can occur


38/117


37n

with, for example, poorly designed toolsand handles. Thus, pressure from metaltools, such as scissors can lead to digital

neuritis 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 Co 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 may

act 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 by

Sunderlin 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(Sjgaard, 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 the

release 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-


39/117


40/117


39n

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 -

RELATEDNESS

The National Institute of Occupational

Safety 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 studiesl The temporal effect between becoming

exposed 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 combination

with 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 individual

factors (e.g. previous medical history)

may influence the degree of risk fromspecific exposures and it is likely that

the reviewed disorders may also be

caused by non-work factors. This did

not substantially alter the association

with work factors.

Psychosocial work factors were consideredwithin the NIOSH review and, despite the

evidence 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 steering

committee and scientists (NationalResearch Council, 1999). This review,approved by the Governing board of theNational Research Council, U.S.A., exam-


41/117


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 a

positive 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 of

musculoskeletal disorders. This evidencefurther supports the relationship betweenwork activities and the occurrence of mus-culoskeletal disorders.

Ta 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 no

Risk factor effect

Neck and Neck/shoulder

Repetition

Force

Posture

Vibration

Shoulder

Repetition

Force

Posture

Vibration

Elbow

Repetition

Force

Posture

Combination

Hand/wrist

Carpal tunnel syndrome

Repetition

Force

Posture Vibration

Combination

Tendinitis

Repetition

Force

Posture

Combination

Hand-armvibration syndrome

Vibration


42/117


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 recognised

that 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 task

identity) 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 on

the 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 the

causal 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-


43/117


n42

opment of these disorders were postulat-ed. This contrasts with the findings of theNIOSH (1997) review where considerable

evidence 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 of

the 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 concluded

from 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 of

digital vasospastic disorders, known asvibration-induced white finger.


44/117


43n

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 limb

musculoskeletal 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 the

subsequent incidence of any upper

limb 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 Research

Council, 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 pattern

training 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, Aars 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).Aars et al. (1999) then introduced thenew mouse design to a group of officeworkers. The subjects were randomlyassigned to an intervention or control

group. Six months after the intervention asignificant reduction in the intensity andfrequency of wrist/hand, forearm, shoul-der and neck pain was observed in the


45/117


n44

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 exposure

directly (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 achieved

a reduction in musculoskeletal problemsincluding those of the neck and upperlimbs.

The conclusions from this contemporaryand authoritative review were to focusinterventions on factors within the

work organisation, not solely on the

worker (e.g. training/work hardening). It

was also emphasised that the active sup-port and involvement of the individuals atrisk and other stakeholders in the organi-sations was highly recommended.

Hkknen 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 for

upper 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.


46/117


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 to

reduce 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.


47/117


n46

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

workuperlimbdisorder jueves

Documents