Research on work-related - Fedris

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R E S E A R C H

European Agencyfor Safety and Healthat Work

Research onwork-related

low back disorders

REPORT PREPARED BY

Lic. Rik Op De BeeckDr. Veerle Hermans

Prevent

Institute for Occupational Safety and HealthGachardstraat 88, P.O Box 4

B - 1050 BrusselsBelgium

Low back disorders 30/10/00 14:22 Página 1

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, 2000

ISBN 92-95007-02-6

© European Agency for Safety and Health at Work, 2000Reproduction is authorised provided the source is acknowledged.

Printed in Belgium


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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3.3 Prognosis of low back disorders and return to work 323.4 Assessment techniques and risk factors 33

4. STRATEGIES AND EFFECTIVENESS OF PREVENTION 354.1 Prevention stages 364.2 Primary prevention strategies 36

4.2.1.Types of interventions to reduce work place risks 36

4.2.2. Work-organisational factors 424.3 Secondary prevention strategies 44

4.3.1 Assessment of the worker with low back disorder 44

4.4 Guidelines and standards related to prevention of low back disorders 47

4.5 Conclusions on effectiveness of prevention 485. RISK ASSESSMENT METHODS 51

5.1. Methods for use in the workplace 525.2. Additional laboratory methods 54

6. FUTURE RESEARCH TOPICS 557. CONCLUSIONS 57

The extent of work-related low back disorders within European Member States 57

Current knowledge of the origin of low back disorders 57

Epidemiological evidence regarding risk factors 58Strategies for prevention of work-related

low back disorders and knowledge about their effectiveness. 58

Risk assessment methodology for work-related low back disorders 58

Future research topics 598. REFERENCES 619. APPENDICES 65

Appendix 1. Project organisation 66Appendix 2. Council Directive 90/269/EEC:

Minimum health and safety requirements for the manual handling of loads (Annex I and II) 68

Appendix 3. Overview of secondary/tertiary interventions. 691. Interventions for acute Low

Back Disorders 692. Interventions for chronic Low

Back Disorders 703. Cognitive and behavioural strategies 70

CONTENTS 3FOREWORD 4EXECUTIVE SUMMARY 5Size of the problem 5Origin of low back disorders 5Work-related risk factors 6Strategies and effectiveness of prevention 6Need for research and consensus 71. INTRODUCTION 9

Approaches used to prepare the report 9Information retrieval from databases 9Expert Workshop 10Consultation and liaison 10

2. THE NATURE OF WORK-RELATED LOW BACK DISORDERS 112.1 Introduction: low back disorders and

work-related low back disorders 122.2 Prevalence of low back disorders 122.3 Duration of the problem 152.4 Cost to society 162.5 Origin 17

2.5.1 Intervertebral disc-related disorders 172.5.2 Soft tissue related disorders 182.5.3 Psychosocial mechanisms 19

3. RISK FACTORS 213.1 Models for pathogenesis 223.2 Risk factors 24

3.2.1 Physical risk factors 253.2.2 Psychosocial factors 283.2.3 Individual risk factors 29

C o n t e n t s


R e s e a r c h o n w o r k - r e l a t e d l o w b a c k d i s o r d e r s

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F O R E W O R D

One of the aims of the European Agency forSafety and Health at Work is to assist in thedevelopment of common research programmesand the sharing of research information in thefield of Occupational Safety and Health (OSH).Work-related lower back disorders are one ofvarious work-related musculoskeletal disorders(MSD). MSD are a designated priority work areafor the Agency. Due to the prevalence of work-related back disorders, and in order tocompliment a previous Agency research report onneck and upper limb disorders it was decided tomake a research report into work-related lowback disorders. This also supports the researchpriority of ergonomics, particularly in regard tomanual handling, that has been indicated by theMember States.

Furthermore, a European Week for Safety andHealth at Work has been organised for October2000 to promote both awareness raising andprevention activities across the Member States onmusculoskeletal disorders at work. “Turn yourback on work related musculoskeletal disorders” isthe message to all European workplaces. One ofthe aims is that European Week’s focus on MSDwill promote the sharing and exchange of goodpractice solutions to prevent work related MSDs. It

is hoped that this report too will play its role to helpfurther knowledge on work-related back disordersand their prevention.

The work to facilitate this report on work-related low back disorders for the Agency wascarried out by Prevent ( Institute forOccupational Safety and Health, Belgium)within the framework of the Agency’s TopicCentre on Research - Work and Health. ThisTopic Centre consists of a consortium of 10major OSH research institutes in Europe. Thereport was prepared by Lic. Rik Op De Beeck andDr. Veerle Hermans. A workshop of experts wasused to provide input into the report andcomment on an early draft. A consultationprocess was carried out by sending themanuscript to members of the Agency ThematicNetwork Group on Research-Work and Health,which includes European social partners and theEuropean Commission. Further input fromexperts was also sought. After the consultationprocess the final report was prepared andpublished.

The Agency wishes to thank all those whocontributed to the report and especially Preventfor drafting the report.

Bilbao, October 2000

European Agency for Safety and Health at Work



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Work-related low back disorders, covering bothlow back pain and low back injuries, are asignificant and increasing problem in Europe.This report covers the prevalence, origin, work-related risk factors and effective preventionstrategies for low back disorders. The report islimited to low back disorders although some ofthe findings may be applicable to other types ofwork-related back problems.

S i z e o f t h e p r o b l e m

Studies suggest that between 60% and 90% ofpeople will suffer from low back disorders at somepoint in their life and that at any one timebetween 15% and 42% of people are suffering(depending on the study population and thedefinition of back pain used). Data from theEuropean survey on working conditions revealthat 30% of European workers suffer from backpain, which tops the list of all reported work-related disorders. In a recent report on the Stateof Occupational Safety and Health in the MemberStates (European Agency, 2000b) some MemberStates of the European Union have reported an

increase in manual handling injuries and backinjuries.

Although in most cases patients make a fullrecovery from an episode of low back pain (60-70% recover within 6 weeks, 70-90 % within12weeks) this still adds up to a very large amount oflost time from work. In addition the recurrencerate for low back disorders is very high. In oneyear the recurrence rate is between 20% and44% and over a lifetime recurrences of up to85% are reported. It is important to rememberthat once injured, the back can becomesusceptible and re-injury is more likely if there arerisk factors in the work place that are notcorrected.

Although very common across all types ofindustries and jobs, several studies havedemonstrated that low back disorder rates areparticularly prevalent in certain types of industriesand within certain occupations. Particularly highprevalence rates are found for example among:agricultural workers; construction workers;carpenters; drivers including truck and tractoroperators; nurses and nursing assistants;cleaners, orderlies, domestic assistants. It appearsthat the prevalence of low back disorders in theEuropean Union is similar among men andwomen.

Although precise figures do not exist, estimatesfrom Member States of the economic costs ofall work-related ill health have been estimatedto range from 2.6 to 3.8% of Gross NationalProduct. However the figures maybe higher asthe true social costs are difficult to estimate. Astudy from the Netherlands estimated the totalcost of back pain to society to be 1.7% of thegross national product in 1991.

O r i g i n o f L o w B a c k D i s o r d e r s

Low back disorders include spinal disc problemssuch as hernias and spondylolisthesis, muscleand soft tissue injuries. In addition to the normaldegenerative aging process, epidemiologicalstudies reveal that poor ergonomic factors inthe workplace contribute to low back disordersin a healthy back or accelerate existing changes

E X E C U T I V E S U M M A R Y



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in an already damaged back. Poor ergonomicwork factors increase the load or strain on theback. This may arise from many situations, forexample lifting, twisting, bending, awkwardmovements, stretching, and static postures.Tasks include physical work, manual handlingand vehicle driving (where whole body vibrationis known to be another contributing factor).

Although spinal disc related problems maybedetectable by x-rays or bone scans, otherabnormalities, such as muscular and other soft-tissue injuries, can often not be detected in thisway. In fact, 95% of low back disorders are termed“non-specific”. Evidence suggests that thecommon approach suggested below can be takento prevent and reduce all types of work-related lowback disorders.

W o r k - r e l a t e d r i s k f a c t o r s

Many reviews have been published of studiesconcerning the risk factors of low back disorders,including a multitude of physical, psychosocialand/or personal risk factors. The number ofepidemiological studies addressing psychologicalrisk factors during work is considerably smallerthan studies focussing on physical load. Inaddition, the strength of the association isgenerally higher for biomechanical factors.However, the evidence to link psychosocialfactors with low back disorders is growing,especially where they occur at the same time as

the physical factors. The incidence of low backdisorders has also been strongly associated withlow job content and poor work organisation.The main work-related risk factors are given inBox 1.

S t r a t e g i e s a n d e f f e c t i v e n e s s o fp r e v e n t i o n

Strategies to prevent low back disorders includeboth workplace based and health care basedinterventions. Increasingly there is recognitionthat an integrated approach including bothtypes of intervention is needed to really tacklethe problem effectively. Prevention, training,health surveillence, rehabilitation etc. should allbe approached together. In the workplace thereis growing support for the effectiveness ofergonomic interventions. Ergonomicsinterventions are based on a “holistic” orsystems approach that considers the effect ofthe equipment, the work environment and thework organisation as well as the worker. The fullparticipation of workers in the ergonomicsapproach is important for its effectiveness.

A summary of the main prevention strategies isgiven in Box 2. These cover both strategies forboth primary prevention (eliminating thecauses) and secondary prevention (treatmentand rehabilitation). Again expert opinion is thatalthough the focus should be strongly onprimary prevention, all these factors need to belooked at together. For example studies showthat training alone is unlikely to be effective ifthe ergonomic factors in the work remain poorand basic training, for example, needs toinclude how to spot potential risks and what todo if found as well as safe physical handlingtechniques. Finally, prevention of low back andother work-related musculoskeletal disordersshould form part of employers overallprevention plan for all health and safety risks.

European employers are already provided withimportant information to protect workers fromback injury from manual handling work in the“Manual Handling Directive” (Council Directive90/269/EEC), which was made with theparticular goal of preventing risks of back injury

B o x 1 : W o r k f a c t o r s t h a t i n c r e a s et h e r i s k o f l o w b a c kd i s o r d e r s

Physical aspects of work • Heavy physical work• Lifting and handling of loads; • Awkward postures (for example: bending;

twisting; static postures)• Whole body vibration (for example truck driving)

Psychosocial work-related factors• Low social support• Low job satisfaction

Work organisation factors• Poor work organisation• Low job content



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during the manual handling of loads. Based oncurrent knowledge, it includes minimum healthand safety requirements that fol low anergonomic approach, with a list of risk factorsprovided in the schedule to the directive.Employers should to pay attention to these riskfactors when making an assessment andselecting prevention measures. They include:

• Characteristics of the load (for example: is itheavy or difficult to hold);

• Physical effort required (for example:strenuous; twisting; body in an unstableposition);

• Characteristics of the working environment(for example: not sufficient room or otherconstraints on the posture of worker such asworking height too high or low; uneven orslippery flooring);

• Requirements of the activity (for example:prolonged activity or effort; insufficient restperiods; excessive distances to move loads;imposed work rate)

• Individual factors (for example: clothing etc.restricting movement; inadequateknowledge or training)

It is thought to be somewhat artificial toseparate out low back disorders from otherwork-related back problems as there is no strictdivide between back problems and othermusculoskeletal disorders. A common approachis needed to all musculoskeletal problems in thework place. In this context it is helpful to viewthe risks in terms of combined “overload” onthe musculoskeletal system (for example the

combination effect of force, sustained force,static force, work organisation, stress etc).

N e e d f o r r e s e a r c h a n d c o n s e n s u s

There is support in the literature for theergonomics approach, contained in the“Manual Handling Directive”, as the basis foremployers to take action. To assist its applicationthe report suggests that the main focus offuture research should be on how theergonomics approach can be used mosteffectively in practice. Such research mayinclude:

• Satisfactorily evaluated studies of “holistic”intervention strategies (for example:application of ergonomics; ergonomicsintegrated with rehabilitation and healthsurveillance)

• Studies to develop and evaluate practical riskassessment methods for use in the workplace

• Studies of the effect of combinations offactors and their practical assessment

Although it is proposed that the main focus offuture research be on strategies to preventinjury in the work place, a number of areasconcerning laboratory analysis of the problemare suggested (for example: exposuremeasurement techniques; joint movementmeasurement methods and studies to furtherunderstand the biochemical andbiomechanical properties of the vertebra, discand ligaments).

B o x 2 : S t r a t e g i e s t o p r e v e n t l o wb a c k d i s o r d e r s i n t h ew o r k p l a c e

• Reduction of physical demands • Improvements in work organisation• Education/training (as part of an integrated

approach)• Medical treatment and rehabilitation (as part of

an integrated approach)• Cognitive and behavioural strategies (for

example coping strategies)



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

There is a growing interest in the subject ofmusculoskeletal disorders (MSDs) related to theworkplace, due to the increasing amount ofworkers suffering from these disorders. Alsowithin the European Agency for Safety andHealth at Work, documents on this subject havebeen published recently:

• Repetitive Strain Injuries in the Member Statesof the European Union: the results of aninformation request (European Agency, 2000a)

• Work related neck and upper l imbmusculoskeletal disorders (European Agency,1999 - Buckle and Devereux)

With the current publication, the focus isentirely on the low back and the reportedfindings should not be related as beingapplicable to all types of disorders. Nevertheless,work-related upper limb disorders and backdisorders should be seen on a continuum, sincethe same general prevention approach appliesto both.

This report has addressed the following questions:

What is the extent of work-related low backdisorders within European member states?

What is the current knowledge on the origin oflow back disorders?

What is the epidemiological evidence regardingrisk factors?

Which strategies for prevention of low backdisorders are present and what do we knowabout the effectiveness of these interventionstrategies?

Which risk assessment methodology can beused for the prevention of low back disorders?

What are the most important future researchtopics?

Non-occupational back disorders such asinfectious diseases, inflammatory disease,tumours, metabolic disorders or other non-mechanical disorders will not be included in thisdocument. Also primary psychiatric disorderswith psychosomatic low back pain are not thefocus of this report.

A p p r o a c h e s u s e d t o p r e p a r e t h er e p o r t

I n f o r m a t i o n r e t r i e v a l f r o m d a t a b a s e s

To write this status report, a thorough literatureexamination was performed, concentrating onscientific peer-reviewed epidemiological reviewjournal articles, but including individual articleswith specific additional value. Individual studiesincluded in the review articles were acceptedafter passing a thorough selection regarding

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C o n s u l t a t i o n a n d l i a i s o n

The second draft report was sent for comment tothe members of the Thematic Network Group onResearch - Work and Health. This group consistsof research experts from the Member States andobservers from the European Social Partners andEuropean Commission. Also the draft report wassent to the European Agency’s Topic Centre onGood Practice - Musculoskeletal Disorders andother experts in the field. Based on the commentsreceived and additional information, the finalreport has been prepared.

It is recognised that the opportunities andresources available for this process have beenlimited. It is hoped that wider consultation andmore extensive views will be gathered followingfinal publication of the report.

methodological issues. Attention is given toreview studies addressing cohort or case-controlstudies. Papers submitted or in press to scientificpeer reviewed journals and providing additionalimportant information are also mentioned. Theindividual researchers provided these papers.Furthermore, recent textbooks, reports of theEuropean Agency for Safety and Health at Workand other documents or government reportswere consulted. Searches were carried out oncomputer-based bibliographic databases:Medline® , NIOSHTIC® (a database of theNational Insitute of Occupational Safety andHealth, USA), and HASTE (the European Healthand Safety Database).

The l iterature search focused upon thefollowing areas:

• Prevalence of disorders

• Origin

• Work-related risk factors

• Strategies and effectiveness of prevention

Most important keywords were: (low) backpain, (low) back disorder, origin, aetiology,work, risk factors, epidemiology, prevention,strategies, interventions, methods, assessment,statistics, prevalence, review.

E x p e r t W o r k s h o p

An expert workshop (see appendix 1 formembership of the panel and summary of thediscussion and conclusions) was held in Brussels21 June 2000. The aims of the meeting were todiscuss: the proposed structure and keyelements of the document; sources ofinformation and definitions; the contents of thedocument, including what conclusions could bedrawn from the l iterature survey; andrecommendations for future research andregarding prevention of low back disorders. Theworkshop resulted in an action plan for theauthors with a summary of information how todevelop the report further.



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2.T H E N A T U R E O F W O R K -

R E L A T E D L O W B A C K

D I S O R D E R S

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2.2P R E V A L E N C E O F L O W B A C K

D I S O R D E R S

Back pain is a major health problem in theWestern world. The lifetime prevalence hasbeen estimated at 59% to 90%, and the pointprevalence varies between 15% and 42%,depending on the study population and thedefinition of back pain. The annual incidence ofback pain has been reported to beapproximately 5% (Andersson, 1999;Hoogendoorn et al., 1999). For instance, in theUK, the annual incidence of low back pain in thegeneral population is 4.7%, the pointprevalence 19%, the prevalence during the last12 months 39% and the lifetime prevalence59% (Hillman et al. 1996). In a recent study ofthe general population in The Netherlands, theprevalence during the last 12 months was foundto be 46% for men and 52% for women. Thisstudy also showed that the high prevalence ofback pain has important consequences in termsof disability, the utilisation of health services,and sick leave. 28% of the people with low-back pain were restricted in their daily activities,42% underwent medical treatment, 23% tooktime off work, 8% received a (partial) disabilitypension, and 6% changed jobs or hadadaptations in the workplace (Picavet in


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2.1I N T R O D U C T I O N : L O W B A C K

D I S O R D E R S A N D W O R K -

R E L A T E D L O W B A C K

D I S O R D E R S

In a systematical review of the availablescientific evidence on the causes of low backpain and the effectiveness of interventions toprevent it, Frank et al. (1996) mention twoterms that are usually used to describe thephenomenon of low back pain. Low back painis any back pain between the ribs and top of theleg, from any cause. Work-related low backpain, is any back pain originating in the contextof work and considered clinically to have beenprobably caused, at least in part, or exacerbatedby the claimant’s job. However in practice it isoften impossible to distinguish back pain“caused” by work from pain of uncertain originthat makes the patient’s work impossible tocarry out. This report is limited to low back-painand injuries although some of the findings maybe applicable to other types of work-relatedback disorders.



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Also other recent studies have demonstratedthat low back disorders rates vary substantiallyby industry, occupation, and by job within givenindustries of facilities. High prevalence rates arefound, in particular, for non-sedentaryoccupations (Hoogendoorn et al., 1999). Thiscorresponds with a Finnish study where forfarmers the odds ratios (OR: proportion of casesexposed to the risk factor versus the proportionof non cases exposed) were 2.1, for manualworkers 1.8 and for white-collar workers 1.4(Leino-Arjas et al., 1998). A German study evenmentions an odds ratio of 0.59 for “desk work”(Latza et al., 2000).

European Agency for Safety and Health at Workhas published a report on the “State ofOccupational Safety and Health in the EuropeanUnion” (European Agency, 2000b). Thisdocument provides an overview of the currentsafety and health situation in the EuropeanUnion with the aim of supporting theidentification of common challenges and

T a b l e 1 . : P e r c e n t a g e s o f w o r k e r s r e p o r t i n g b a c k p a i n r e l a t e d t o w o r k a c r o s st h e m e m b e r s t a t e s ( P a o l i 1 9 9 7 )

B DK D EL I E F IRL L NL P UK FIN S A EU

21 30 30/37 44 32 35 29 13 32 17 39 23 33 31 31 30

A – Austria, B – Belgium, DK – Denmark, FIN – Finland, F – France, D – Germany, EL – Greece, NL – Netherlands,IRL – Ireland, I – Italy, L – Luxembourg, P – Portugal, E – Spain, S – Sweden, UK - United Kingdom

Hoogendoorn et al., 1999). Also other studiesmentioned that only half of the low back painproblems are followed by medical advice (Hillmanet al., 1996; Ozguler et al. 1999).

Regarding the relationship with work, in theSecond European Survey on WorkingConditions (Paoli, 1997) 30% of Europeanworkers reported that their work causes backproblems. Table 1 represents the percentages ofeach country.

Workers in agriculture and construction areparticularly concerned, whereas for the morewhite-collar workers (e.g. clerks) thepercentages are much lower. In addition, 34%of the European workers are required to handleheavy loads in the work (Table 2). Also for thisfactor workers in the agriculture andconstruction sectors were more exposed. Theleast exposed were the more white-collarworkers (Paoli, 1997). These results arepresented in Table 3.

T a b l e 2 . : P e r c e n t a g e s o f w o r k e r s w h o s e j o b i n v o l v e s c a r r y i n g o r m o v i n gh e a v y l o a d s a c r o s s t h e m e m b e r s t a t e s ( a d a p t e d f r o m P a o l i , 1 9 9 7 ) .

Time PeriodTotal Member State

(%) A B DK FIN F D EL NL IRL I L P E S UK

①All or almost all the time 11 11 8 6 6 16 9 15 8 8 6 8 12 16 8 10

②Around 3/4 or 1/2 the time 9 12 11 11 12 10 8 15 6 12 7 8 7 8 10 10

③Around 1/4 of the time 14 13 13 18 21 14 15 9 10 15 10 8 8 11 17 17

Total ①+②+③ 34 36 32 35 39 40 32 39 24 35 23 24 27 35 35 37

A – Austria, B – Belgium, DK – Denmark, FIN – Finland, F – France, D – Germany, EL – Greece, NL – Netherlands,IRL – Ireland, I – Italy, L – Luxembourg, P – Portugal, E – Spain, S – Sweden, UK - United Kingdom



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priority areas for preventive actions. Regardingthe question lifting/moving heavy loads,comparable results with the Second EuropeanSurvey were found. The main causes foraccidents identified in the report are “slip/tripsand falls” and “manual handling”. The mostidentified sectors were construction andmanufacturing. Mainly male operators wereinvolved (on average 79%).

Heliövaara et al. (in Lagasse, 1996) reported onthe frequency in percentage terms of differentindicators of low back pain (See Table 4).

T a b l e 3 . : P e r c e n t a g e s o f w o r k e r s w h o s e j o b i n v o l v e s c a r r y i n g o r m o v i n g h e a v yl o a d s a c r o s s t h e d i f f e r e n t j o b s e c t o r s ( a d a p t e d f r o m P a o l i , 1 9 9 7 )

Time PeriodTotal Sector

(%) A-B C-D E F G H I J K L M-Q

①All or almost all the time 11 22 11 15 24 12 8 12 3 5 4 7

②Around 3/4 or 1/2 the time 9 21 9 10 17 10 12 8 2 3 5 7

③Around 1/4 of the time 14 18 15 11 16 17 16 12 5 12 10 12

Total ①+②+③ 34 61 35 36 57 39 36 32 10 20 19 26

A-B: Agriculture, Hunting, Forestry and Fishing C-D: Mining, Quarrying and ManufacturingE: Electricity, Gas and Water Supply F: ConstructionG: Wholesale and Retail Trade; Repair of Motor Vehicles, Motorcycles and Personal and Household GoodsH; Hotels and Restaurants I: Transport, Storage and CommunicationsJ: Financial Intermediation K: Real Estate, Renting and Business ActivitiesL: Public Administration and Defence; Compulsory Social Security M-Q: Other Services

T a b l e 4 . : F r e q u e n c y i n % o f d i f f e r e n t i n d i c a t o r s o f l o w b a c k p a i n ( L B P )( H e l i ö v a a r a e t a l . , i n L a g a s s e , 1 9 9 6 )

Question Men (age standardised) Women (age standardised)

LBP ever 76.3 73.3

6 or more episodes 45.3 44.6

LBP continuously 9.4 8.5

LBP during the previous month 19.4 23.3

Number of subjects 3322 3895



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2.3D U R A T I O N O F T H E P R O B L E M

Although the literature is filled with informationabout the prevalence of back pain in general,there is less information about chronic backpain, partly because of a lack of agreementabout the definition. Chronic low back pain issometimes defined as back pain that lasts forlonger than 7-12 weeks. Others define it as painthat lasts beyond ‘the expected period of healing’(Andersson, 1999). Overall, most patients withback pain recover quickly and without residualfunctional loss, 60-70 % recovers by 6 weeks,80-90 % by 12 weeks. Fewer than half of thoseindividuals disabled for longer than 6 monthsreturn to work and, after 2 years of absence fromwork, return-to-work rate is close to zero.

A survey in the UK estimated that each suffererof low back pain took 11 days off work in 1995because of his or her complaint (HSE 1995).

Several models have been developed to predictthe return to work after a period of low backpain. However, the differences in the populationstudied, time of the evaluation, workingconditions and socio-economic differencesmake these studies difficult to compare. Somestudies mention age and location of the

symptoms as the most predictive factors,whereas others mention work environment andpsychosocial factors.

In addition to the duration of the problem, itshould be mentioned that the recurrence rate oflow back disorders is very high, seeming to bepart of its natural history. Lifetime recurrences ofup to 85% are reported, one year recurrencebetween 20 and 44% (Andersson, 1999). Vanden Hoogen et al. (1997) mention that thereappearance of low back pain can even rise to75% in the first following year, without absencefrom work.


2.4C O S T T O S O C I E T Y


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2000). The differences in these data areattributed to the different organisation ofinsurance systems. Data from the USA revealsthat low back disorders significantly increaseworkers compensation costs. For example, lowback disorders account for only 16-19% of allworker compensation claims, but 33-41% ofthe total cost of all work compensation costs(Marras 2000).

In the UK, 12.5% of all sick days are related tolow back disorders, this corresponds with datafrom Sweden, where 13.5% of sick days arereported (Andersson, 1999). A survey from theHSE estimated 4.8 million working days lost inBritain in 1995 due to back disorders (HSE1995). Calculations based on a HSE report(1997) have estimated that back disorders costemployers between £315 million and £335million. The Clinical Standards Advisory Groupin the UK (Rosen, 1994) crudely estimated thelost production costs to be approximately £3.8billion and social security benefits £1.4 billion. Astudy by the Trade Union Congress (1998)reported that only 17% of employers hadactually calculated the costs of low backdisorders, only a third provided treatment,physiotherapy or rehabilitation and fewer thanhalf monitored the number of workers sufferingfrom and the number of days lost due to lowback disorders.

Lombaert et al. (1996) studied the cost ofdifferent illnesses of Belgian employees: colds,flu, of low back pain and psychosocial stress.The average duration of the total sick leave wassignificantly higher in the case of low back painand psychosocial stress. Furthermore themedical costs were the highest in the case oflow back pain diagnosis (costs of radiology,treatment by physiotherapists and specialists).

Although precise figures do not exist, estimatesfrom Member States of the economic costs ofall work related ill health range from 2.6 to3.8% of Gross National Product (EuropeanAgency, 1998).

In 1991, the total cost of back pain to society inThe Netherlands was estimated to be 1.7% ofthe gross national product (Van Tulder et al.,1995). The costs were estimated as follows:

All these costs can be attributed to lostproduction, staff sickness, compensation andinsurance costs. Indirect costs such as losingexperienced staff and costs of recruiting andtraining new staff, are not included. It is difficultto compare direct and indirect costs of low backdisorders between countries, e.g. the averageannual cost per worker varies between FRF100-150 in France, the Netherlands and in the UK,whereas the cost is FRF 600 in the USA. The datafrom Germany is somewhere between (Inserm

• Total direct medical costs: US $367.6 million(total costs of hospital care: US$ 200 million)

• Costs due to absenteeism: US $3.1 billion• Costs due to disablement: US $ 1.5 billion



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other disorders (e.g. psychiatric disorders) arenot the purpose of this report. Furthermore, theknowledge on the relation between low backpain and psychosocial aspects is mentioned.

2 . 5 . 1 I n t e r v e r t e b r a l d i s c - r e l a t e dd i s o r d e r s

The lumbar back is subjected to highcompressive loads during normal activities. Themain function of the intervertebral disc, locatedbetween two vertebrae, is to resist thiscompression. Therefore, the three anatomicalstructures that make up the disc are veryimportant. The nucleus pulposus is a viscous gel,which transforms compressive loading intohydrostatic pressure, which is directed as tensilestress in the annulus fibrosus, constituted ofconcentric lamellae. The carti laginousendplates, the layer between the annulus andthe vertebral body, is important for the diffusionof nutrients to the intervertebral disc (Goel etal., 1999).

Degeneration of the lumbar discs reduces thestabil ity of the lumbar spine. A highbiomechanical demand on such an unstablelumbar spine leads to a high demand on theligamental, capsular and muscular structuresand the facets. The disc degeneration process isslow and is the cumulative effect of manyfactors over time. The proportion of people withdegenerated discs at the age of 40-60 isbetween 40 and 60% (Lawrence, 1969). In amagnetic resonance imaging study theprevalence of disc degeneration among 20-39,40-59 and 60-80-year old persons was 34, 59and 93% respectively (Boden et al., 1990). Formany patients, physiological ageing of thespinal elements – the vertebra, discs, andligaments – is a potential source of backproblems.

In addition to the age-related naturaldegenerative process, epidemiological studieshave revealed that ergonomic factors in theworkplace can lead to accelerated degenerativechanges in the discs and other structures(Riihimäki, 1991; Luoma et al., 1998).Understanding the role of mechanical factors in

The exact origin (or aetiology) of low backdisorders are often not clear. Currentknowledge cannot always determine the exactmedical cause of low back pain by clinicalexamination or laboratory tests. While there issometimes a relationship between pain andfindings on magnetic resonance imaging of discabnormalities (such as with a herniated disc orclinical findings on nerve compression), themost common form of back disorders is “non-specific symptoms” (Bernard et al., 1997). Onaverage 95% of low back disorders are called“non-specific” or “strain/sprain” because thesource of the pain is unknown. Furthermore,the pain may arise from any of the spinalstructures - disc, facets, ligaments, vertebrae,tendons and muscles – and a differentiationbetween the multiple causes is often impossible(Frank et al., 1996a). Conventionally, the originsof low back pain are grouped under fourcategories: discogenic/neurological,muscular/ligamentous, structural, and otherdisorders (Khalil et al., 1993). In this review, thefirst two main categories of disorders arediscussed, since structural disorders are oftenmentioned together with the first category and

2.5O R I G I N



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producing disc degeneration is essential forcomprehension of low back pain aetiologiesand preventive measures. The degenerativeprocess is hypothesised to result fromcumulative damage to the spinal componentsinduced by acute or chronic loading. Thisloading can be caused by many situations, e.g.lifting, twisting and bending the trunk duringheavy physical work, or postures with sustainedstatic loading, or vibration from activities likevehicle driving. It has been commonly acceptedthat compressive loads on the vertebral endplate of 3400 Newton represent the level atwhich vertebral end plate micro-fractures beginto occur. Marras (2000) mentions that thiscompression tolerance to spinal loading appearsto be modulated by additional factors. Firstly,spine tolerance is reduced as the frequency ofloading increases and it is known that a dischernia from a single application of force is rare.The risk increases significantly when the disc issubjected to repeated loading. Secondly, therelative position or posture of the spine whenthe load is applied appears to be of greatsignificance to the tolerance of the spine. Finally,hydration is important and related to the time ofday: tolerance would be expected to varythroughout the working day.

How can these types of loads lead todegeneration of the lumbar disc? During axialcompression on the vertebral spine, the discsbear most of the load. Experimental studiesrevealed that failure occurs first in the endplate,where micro-fractures are caused (van Dieën etal., 1999). In many cases these fractures willheal and the associated pain will disappear aftera limited period. However, further damage mayoccur and this may lead to a decrease in thediffusion area for the nutrition of the disc. As aresult, the chemistry of the disc and themechanical behaviour of the constituents maybe altered, a rupture in the annulus occurs andthe nucleus pulposis bulges (Goel et al., 1999).This may lead to spinal cord or nerve rootcompression, resulting e.g. in sciatica in whichpain radiates into one or both legs (Scheer et al.,1996). Other indications of disc degenerationare separation of the laminae of the annulusand rupture of ligaments and facets during

higher than normal loads. Spinal osteoarthritisrefers to an accelerated and increased level ofdegeneration, which affects discs, facet jointsand vertebrae. With spondylolisthesis, aforward subluxation of the fifth (and sometimesthe fourth) lumbar vertebra is mentioned (Goelet al., 1999).

Regarding the aetiology of chronic low backpain, Freemont et al. (1997) mentioned theimportance of nerve growth into theintervertebral disc. In the healthy back, only theouter third of the annulus fibrosus of the disc isinnervated. Among the patients with chroniclow back pain, nerves extended into the innerthird of the annulus. Often isolated nerve fibreswere found, nerves not accompanied by bloodvessels. Since these findings were associatedwith pain, this suggests an important role fornerve growth into the intervertebral disc in thepathogenesis of certain types of chronic lowback disorders.

2 . 5 . 2 . S o f t t i s s u e r e l a t e d d i s o r d e r s

Although it is not possible at this time to identifydefinitively paraspinal muscles as an etiologicalsite of low back pain, muscular and other soft-tissue injuries are suspected when no otherstructural or neural abnormalities can beidentified on the basis of radiographs or bonescans. Both injuries are sometimes related: if thelumbar spine is unstable because of thedegeneration of the discs, soft tissues areexposed to a high mechanical burden. Sincethese structures contain a lot of pain receptors,low back pain may result (Krämer 1994).

Roy and De Luca (1996) consider muscleimpairment as two types of disorders, primaryand secondary disorder. Primary disorders resultfrom direct muscle injury, most commonly as theresult of muscle strain injuries than directtrauma. Few experimental studies investigatedthe cause of strain. Garret et al. (in Roy and DeLuca, 1996) indicated that injuries usually occuras a response to excessive load or stretch andare most common during eccentriccontractions, e.g. forward bending of the spine.Furthermore, prolonged activation of motor



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people might be more sensitive to pain and morelikely to report injury or pain.

Recently, the European Agency published areview “Research on Work-Related Stress”(European Agency, 2000c) where themechanisms of stress-related physio-pathologyare further explained.

units in the muscle may lead to localised muscletension, due to the continuous and relativelyhigh activity of some type I motorunits (e.g.Hägg et al., 1991). This could lead to strains orfatigue and other soft-tissue damage. Indeed,work characterised by prolonged isometriccontractions of the back muscles has beenlinked with elevated rates of disorders (Videmanet al., in MacGill et al., 2000). The paraspinalmuscle fatigue can decrease the muscularsupport to the spine, causes impairment ofmotor co-ordination and control and may resultin increased mechanical stress to its functionalcomponents. The occurrence of muscle fatigueis often examined by evaluating the changes inthe electromyographic signal of the muscleduring sustained or intermittent work (Hermanset al., 1997).

With secondary disorders, the onset of paininitiates neuromuscular and behaviouralresponses to prevent or reduce further pain. Thebody responds involuntarily to pain by theproduction of a muscle spasm that immobilises orprotects the painful area to allow for recovery. Thismay even aggravate the sensation of pain byrestricting circulation and promoting theaccumulation of muscle metabolites that areirritants to nerve endings.

2 . 5 . 3 P s y c h o s o c i a l m e c h a n i s m s

Regarding the relationship between psychosocialfactors and low back pain, Davis and Heany(2000) summarised the different mechanisms thathave been hypothesised. First, psychosocialfactors are directly related to low back pain byinfluencing the loading on the spine. This meansthat jobs with high biomechanical demands areassociated with high psychosocial demands (highstress, low job satisfaction). Second, psychosocialfactors influence various chemical reactions in thebody during the performance of job tasks. Anincreased muscle tension is found with poorpsychosocial factors, this may reduce blood flowresulting in the accumulation of metabolites thatresult in muscle pain. A third potential mechanismlinks the presence of psychosocial factors with areduced pain tolerance. In a stressful environment



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3.R I S K F A C T O R S

There are several epidemiological studiesinvestigating risk factors of low back disorders.Epidemiology is the study of the distribution anddeterminants of health problems in specifiedpopulations and the application of the study tothe control of the problems (Last, 1995). Studiesin epidemiology seek to find associationsbetween exposure and disease (or cause andeffect). Conceptual models are used to representthe relation between these two factors. Themultifactorial nature of low back disordersnecessitates the presentation of differentcategories of risk factors in these models.

RE

SE

AR

CH



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The authors explain the model as follows. Thecentral physiological pathway shows, firstly, thebiomechanical relationship between load andthe biological response of the body. Loadswithin a tissue can produce several forms ofresponse. If the load exceeds a mechanicaltolerance or the ability of the structure towithstand the load, tissue damage will occur.For example, damage to a vertebral end platewill occur if the load borne by the spine is largeenough. Other forms of response may entailsuch reactions as inflammation of the tissue,oedema, and biochemical responses. However,imposing a certain biomecanical load onmusculoskeletal tissues may also have astrengthening effect and adaptation may occur.

Biomechanical studies can elucidate some ofthese relationships. Biomechanical loading canproduce both symptomatic and asymptomaticreactions. Feedback mechanisms can influencethe biomechanical loading and responserelationship. For example, the symptom of painmight cause an individual to use his or hermuscles in a different manner, thereby changingthe associated loading pattern. Adaptation to aload might lead individuals to exposethemselves to greater loads, which they mightor might not be able to bear.

The responses, symptoms and adaptations canlead to functional impairment. In the workplacethis might be reported as a work-relatedmusculoskeletal disorder. If severe enough, theimpairment would be considered a disabilityand lost or restricted workdays would result.

The left part of the framework showsenvironmental factors that might affect thedevelopment of musculoskeletal disorders,including work procedures, equipment, andenvironment, organisational factors and socialcontext.

The right part of the framework shows theinfluence of individual physical andpsychological factors, as well as non-work-related activities, which might affect thedevelopment of musculoskeletal disorders.

3.1M O D E L S F O R P A T H O G E N E S I S

Several models have been developed to presentthe possible pathways that could lead to thedevelopment of musculoskeletal disorders. Somemodels focus on mechanical exposure (e.g. Vander Beek and Frings-Dresen, 1998), whereasother authors focus on psychosocial aspects (e.g.Hurrell and Murphy, in Hales and Bernard, 1997).Recently The National Research Council (1999)outlined a broad conceptual framework (figure1), indicating the roles that various work andother factors may play in the development ofmusculoskeletal disorders. This framework servesas a useful tool to examine the diverse literaturesassociated with musculoskeletal disorders,reflecting the role that various factors can play inthis development - work procedures, equipmentand environment; organisational factors; physicaland psychological factors of individuals; non-work-related activities; organisational factors;and social factors-. Its overall structure suggeststhe physiological pathways by whichmusculoskeletal disorders and thus low backdisorders can occur or, conversely, can beavoided.



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This framework can accommodate the diverseliterature regarding musculoskeletal disordersby characterising the pathways that each studyaddresses. For example, an epidemiologicalinvestigation might explore the pathwaysbetween the physical work environment andthe reporting of impairments or the pathwaybetween organisational factors and thereporting of symptoms. An ergonomic studymight explore the pathways between workprocedures and equipment and thebiomechanical loads imposed on a tissue. Thisframework also focuses attention on theinteractions among factors.

To understand more about the concept of painsee the publication of Johansson and Sojka(1991). The authors introduced a patho-physiological model for the cause of musculartension and pain in occupational painsyndromes and chronic musculoskeletal painsyndromes. This model may be important toexplain that not only muscles but also thecentral nervous system is involved in the

development and perpetuation of painsyndromes.

Physiologicalpathways

Work procedures,equipment andenvironment

Organisationalfactors

Social context

Individual, Physicaland Psychological

Factors andNon-work related

activities

Load

Response

Symptoms Adaptation

Disability

Impairment

F i g u r e 1 : C o n c e p t u a l f r a m e w o r k ( T h e 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 )


3.2R I S K F A C T O R S


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Many review articles have been publishedinvestigating the risk factors of low backdisorders on the physical, psychosocial andpersonal domains. These factors may interact indifferent ways to cause low back disorders. Inone situation the psychosocial risk factor may bethe main contributor, whereas in other cases itmay be the physical risk factors that are theprimary causes. Thus, in every situation the riskfactors would interact in a different manner toreach a critical tolerance level unacceptable tothe person, and resulting in reporting of lowback pain. The comparison of the differentstudies is not always easy, due to differentdefinitions of risk factors or categories of riskfactors. Especially in the non-biomechanicaldomain, as the terms such as psychological,psychosocial, psychic, individual and personalare often used with overlapping meanings.Hagberg et al. (1995) have discussed themeaning of work organisational andpsychosocial work: “Psychosocial factors at workare the subjective aspects as perceived byworkers and the managers. They often have thesame names as the work organisation factors,but are different in that they carry ‘emotional’

value for the worker. Thus, the nature of thesupervision can have positive or negativepsychosocial effects (emotional stress), while thework organisation aspects are just descriptive ofhow the supervision is accomplished and do notcarry emotional value. Psychosocial factors arethe individual subjective perceptions of the workorganisation factors.” With individual factors,factors related to the subject but outside thework organisational context are stressed.

It should be mentioned that a combination ofpossible risk factors might increase thedevelopment or occurrence of low backdisorders. Vingard et al. (2000) reported that acombination of high physical and psychosocialload increased the care seeking for low backpain in working men and women.

Below is a brief discussion of some of the mostimportant risk factors of the different domains,based on several review studies that use thoroughselection criteria to identify relevant articles (e.g.Riihimäki, 1991; Hales and Bernard, 1996;Bernard et al., 1997; Burdorf and Sorock, 1997;Ferguson and Marras, 1997; Frank et al., 1996aand 1996b; Bongers et al., 2000; Hoogendoornet al., 2000). Emphasis is laid on risk factorsrelated to the working environment, althoughsome information on personal risk factors isprovided.

An effort is made to summarise the relationshipbetween low back disorders and the risk factors(Table 5). The classification system of Bernard etal. (1997) and the classif ication ofHoogendoorn et al. (2000) was used tocharacterise the strength of evidence for work-relatedness, examining the contribution of eachphysical risk factor to low back disorders.

The evidence for a relationship is classified intoone of the following categories:

• Strong evidence of work-relatedness (+++):provided by generally consistent findings inmultiple high quality studies.

• Evidence (++): provided by generallyconsistent findings in one high quality studyand one or more low quality studies, or inmultiple low quality studies



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biomechanical studies interpret heavy work asjobs that impose large compressive forces onthe spine (Marras et al., 1995). In this review,the definition for heavy physical work includesthese concepts, along with investigators’perceptions of heavy physical workload,which range from heavy tiring tasks, manualmaterials handling tasks, and heavy, dynamic,or intense work.

Conclusions

A general consensus has been found on theassociation of low back disorders and heavy

• Insufficient evidence (+/0): only one studyavailable or inconsistent findings in multiplestudies.

3 . 2 . 1 P h y s i c a l r i s k f a c t o r s

3 . 2 . 1 . 1 H e a v y m a n u a l l a b o u r

DefinitionIn the NIOSH-review (Bernard et al, 1997)heavy physical work has been defined as workthat has high energy demands or requiressome measure of physical strength. Some

T a b l e 5 . T h e w o r k r e l a t e d n e s s o f l o w b a c k d i s o r d e r s : o v e r v i e w o f t h e r i s kf a c t o r s .

Category of risk factor Risk factor evidence

Physical factors

Heavy manual labour ++

Manual material handling +++

Awkward postures ++

Static work +/0

Whole-body-vibration +++

Slipping and falling +

Psychosocial/work-organisational factors

Job content +/0

Work/time pressure +/0

Job control +/0

Social support +++

Job dissatisfaction +++

Individual factors

Age +/0

Socio-economic status +++

Smoking ++

Medical history +++

Gender +/0

Anthropometry +/0

Physical activity +/0



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manual work (Bernard et al., 1997). Evidencefor a positive association was provided, despitethe fact that the studies included defineddisorders and assessed exposures in many ways.

3 . 2 . 1 . 2 M a n u a l m a t e r i a l s h a n d l i n g

DefinitionManual materials handling include lifting,moving, carrying and holding loads. Bernard et al.(1997) defined lifting as moving or bringingsomething from a lower level to a higher one. Theconcept encompasses stresses resulting fromwork done in transferring objects from one planeto another as well as the effects of varyingtechniques of patient handling and transfer.Forceful movements include movement of objectsin other ways, such as pulling, pushing, or otherefforts.

ConclusionsThere is strong evidence that low-back disordersare associated with work-related lifting andforceful movements (Marras et al., 1995; Bernardet al., 1997; Hoogendoorn et al., 1999).

In some studies where no association wasfound, it is reported that this is probably due tosubjective measures of exposure. Whenobjective measures are used to examine specificlifting activities, the risk estimates even increase.The magnitude of risk estimates or odds ratio’s(Odds Ratio-OR is the proportion of casesexposed to the risk factor versus the proportionof non-cases exposed) range from 1.5 to 3.1(Hales and Bernard, 1997; Hoogendoorn et al.,1999).

The extent of spinal loading during manual loadhandling can be modified by (Karwowski et al.,1992).

• load dimensions, shape and weight• horizontal and vertical patterns of dynamic

lifting motions• degree of flexion and rotation of the spine• task frequency• environmental factors

Also Marras (2000) demonstrated the importanceof frequency of loading and the relative positionof the spine with his laboratory experiments.

3 . 2 . 1 . 3 B e n d i n g a n d / o r t w i s t i n g( a w k w a r d p o s t u r e s )

DefinitionBending is defined as flexion of the trunk, usuallyin the forward or lateral direction (Bernard et al,1997). Twisting refers to trunk rotation or torsion.Awkward postures include non-neutral trunkpostures (related to bending and twisting).

ConclusionsResults are consistent in showing positivebetween low-back disorders and work-relatedawkward postures association (Bernard etal.,1997; Hoogendoorn et al. 1999). There is anincreased risk of back disorder with exposure,despite the fact that studies defined disordersand assessed exposures in many ways. Severalstudies found risk estimates above an odds ratioof 3 and dose-response relationships betweenexposures and outcomes.

3 . 2 . 1 . 4 S t a t i c w o r k , s i t t i n g a n ds t a n d i n g

DefinitionStatic work postures include positions wherevery l itt le movement occurs, along withcramped or inactive postures that cause staticloading on the muscles (Bernard et al, 1997).This includes prolonged standing or sitting andsedentary work. In many cases the exposurewas defined subjectively and/or in combinationwith other work-related risk factors.

ConclusionsDue to the technological innovations, thenumber of static work has increasedtremendously (e.g. office/VDT work, controltasks). Hales and Bernard (1996) concluded intheir review that prolonged sitting is a potentialrisk factor for the development of low backpain. During sitting, a prolonged compressionforce may increase the risk of disc problems(Videman et al., 1990), or the continuousactivity of some type I motor units of (back)muscles may contribute to the development offatigue (Hägg et al., 1991). The fact that severalinvestigations mention an increased risk for lowback disorders when jobs have to be performed



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sitting, compared with jobs where frequentchanges in posture are adopted, increased thedevelopment of new types of chairs to promote“dynamic sitting”. By allowing movement ofthe back support and/or chair seat, a dynamicsitting pattern is created which could have apositive prevention effect. However, Jensen andBendix (1992) found in their experimental studyno effect of a movable chair seat. Moreover, inseveral reviews conflicting results are mentioned(Bernard et al., 1997; Hoogendoorn et al., 1999).Recently, van Dieën et al. (2000) found thatdynamic office chairs offer a potential advantageover fixed chairs, but the effects of the specifictask that a subject has to perform (e.g. reading orworking with a computer) appeared to be morepronounced. Regarding prolonged standing as apossible risk factor, inconsistent results arementioned, no evidence for an effect ofprolonged standing can be found (Hoogendoornet al., 1999).

3 . 2 . 1 . 5 V i b r a t i o n a n d d r i v i n g

DefinitionWhole-body-vibration (WBV) refers tomechanical energy osci l lations that aretransferred to the body as a whole (in contrastto specific body regions), usually through asupporting system such as a seat or platform.Typical exposures include driving cars andtrucks, and operating industrial vehicles, such asforklifts.

ConclusionsThere is agreement among internationalinvestigators that long-term whole-body-vibration from engines and vehicles is animportant mechanical stress factor contributingto early and accelerated degenerative spinediseases, leading to back pain and prolapseddiscs. Poor body posture, inadequate seatsupport and fatigue of back muscles have beendescribed as co-factors in the pathogenesis ofmusculoskeletal disorders of the spine inoperators/drivers (Hulshof ,1998; Johanning,2000). Two principal pathological mechanisms ofvertebral damage due to whole-body-vibrationhave been suggested. Firstly, induction of micro-fractures at the endplates, with callus formation

during healing and the altered disc dimensionunder the load, may reduce the rate of nutrientdiffusion. Secondly, vibration-inducedmechanical overload, causing continuouscompression and stretching of the spinalstructures, may result in tissue fatigue. Spinalmuscle fatigue can increase the effect(Johanning, 2000).High prevalence of low back disorders has beenconsistently reported among vibration-exposedoccupational groups, i.e. tractor drivers,truckers and bus drivers, crane or earth movingequipment operators and helicopter pilots(Hulshof, 1998). Also among operators of rail-vehicles with relatively low vertical but highlateral vibration, the prevalence is high. Thehighest levels of vertical vibration were found inoff-road vehicles and forklifts (Johanning,2000).

3 . 2 . 1 . 6 S l i p p i n g a n d f a l l i n g

Khalil et al. (1993) reported that the mostimportant and detrimental factor in the onset oflow back disorders appears to be related to theway in which work activities are performed. Themost common event leading to low back pain andinjury in their study was slipping and falling, whichis an unexpected, uncontrolled event. Slipping andfalling on wet surfaces was an especially importantrisk factor. Although often mentioned as animportant risk factor, few studies can be foundthat investigated its importance. In the review ofFerguson and Marras (1995) only one studymentioned. In this study a positive associationbetween low back pain and slipping/falling wasfound.

3 . 2 . 1 . 7 C o n c l u s i o n s o n p h y s i c a l r i s kf a c t o r s

Bernard et al. (1997) report that several studiesuse indices of physical workload combiningseveral physical risk factors (e.g. lifting and heavyphysical work). Frank et al. (1996a) mention thatthe ability of a study to identify relevantassociations is reduced when non-validatedmeasurement instruments are used. Poormeasurements of exposure may result in lower



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risk estimation and important risk factors will beoverlooked. This is confirmed by the NIOSHreview, were often higher associations or riskestimates were found when objective measureswere used. Nevertheless, two observationssupport the conclusion that there is reasonablygood evidence for a causal relationship betweenlow back disorders and workplace biomechanicalexposures:

(1) the consistency of the reports on certainvariables (lifting, driving and whole-body-vibration); and

(2) the strength of the associations of certaingeneral characteristics measured objectively(high spinal loading and awkward postures).

Bongers et al. (2000) performed a prospectivelongitudinal study to analyse possible riskfactors that induce low back disorders. Strongbending of the trunk and heavy lifting wherethe most important physical risk factors.

3 . 2 . 2 P s y c h o s o c i a l f a c t o r s

Burdorf and Sorock (1997) report that thenumber of epidemiological studies addressingpsychosocial r isk factors during work isconsiderably smaller than the studies focusingon physical load. In addition, the strength of theassociation is generally higher forbiomechanical factors. However, the empiricalevidence linking these factors with low backdisorders is growing. Bongers et al. (1993) werethe first to perform a thorough review of theliterature on this topic. Recently, Hoogendoornet al. (2000) reviewed the relationship betweenpsychosocial factors and back pain.

3 . 2 . 2 . 1 J o b c o n t e n t

Poor job content includes monotonous work, fewpossibilities to learn new things and to developknowledge and skills at work (Hoogendoorn etal., 2000). Several studies (Heliovaara et al., 1991;Houtman et al. in Bernard et al, 1997; Burdorf andSorock, 1997) have reported associationsbetween monotonous work and reports of backcomplaints. However, Hoogendoorn et al. (2000)mention that there is insufficient evidence of an

effect. In addition, in the NIOSH review,inconsistent findings are reported.

3 . 2 . 2 . 2 I n c r e a s i n g w o r k / t i m ep r e s s u r e o r i n t e n s i f i e d w o r kl o a d

A number of studies have reported associationsbetween perceptions of intensified workload, asmeasured by reports of time pressure and highwork pace, and self-reports of back pain(Heliövaara et al. and Lundberg et al. in: Bernardet al.,1997). However, Hoogendoorn et al.(2000) mention insufficient evidence of aneffect of a high work pace, due to inconsistentfindings.

3 . 2 . 2 . 3 J o b c o n t r o l

Job control includes aspects as autonomy andinfluence. Hoogendoorn et al. (2000) found onehigh quality study where an effect between lowwork control and low back pain was found butonly for manual women workers. In anotherhigh quality study an effect between low jobcontrol and absences due to low back pain wasfound, except in lower grade men and highergrade women where the effect was reserved.The authors concluded that there wasinsufficient evidence of any effect.

3 . 2 . 2 . 4 S o c i a l s u p p o r t i n t h ew o r k p l a c e

Social support in the workplace includes socialsupport of co-workers and supervisors,relationships at work and problems with workmates and superiors. Strong evidence for lowsocial support in the workplace as a risk factor forlow back pain has been found (e.g.Hoogendoorn et al., 2000).

3 . 2 . 2 . 5 J o b s a t i s f a c t i o n

For low job satisfaction as a risk factor, strongevidence has also been found (Hoogendoorn etal., 2000). Burdorf and Sorock (1997) alsoreport this relation.



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3 . 2 . 2 . 6 C o n c l u s i o n s o n w o r k - r e l a t e dp s y c h o s o c i a l f a c t o r s

Based on the review studies, low job satisfactionand low social support were found to have amajority of positive associations with theoccurrence of low back pain. These factors increaseperceived stress in the working environment. Intheir prospective longitudinal study, Bongers et al.(2000) report high workload and decreased socialsupport from colleagues or supervisors as being themost important psychosocial prognosis factors.

Inconsistent results for the other psychosocialfactors may be attributed to methodologicalissues, e.g. lack of controlling for potentialconfusing factors (age, gender, biomechanicalfactors) or different timing of the exposure andoutcome variables (Davis and Heany 2000).

3 . 2 . 2 . 7 P s y c h o s o c i a l f a c t o r s i n t h ep e r s o n a l s i t u a t i o n

Bongers et al. (1993) reported several factorsassociated with the individual worker (e.g.personality) and extra-work environment (e.g.living alone) that have been linked to back painand disabil ity. In their recent review,Hoogendoorn et al. (2000) studied theinfluence of family support, having friends orneighbours, social contact, social participation,instrumental support and emotional support.The only effect found was that high emotionalsupport had a positive effect in an elderlypopulation.

3 . 2 . 3 I n d i v i d u a l r i s k f a c t o r s

Although this report is not focused on individualrisk factors, it is important to mention thesignificant relationships between some factorsand low back disorder occurrence. Howeversome of these factors are confounded withemployment history (length and type of work).

3 . 2 . 3 . 1 A g e / y e a r s o f e m p l o y m e n t

It is agreed that the prevalence of low backdisorders increase as people enter their workingyears: by the age of 30, most people have had their

first episode of back pain. It would be incorrect toinclude that low back disorders are a healthproblem only for older workers, since prevalencerates are also found in younger age groups. In theEuropean study, a prevalence of 25% was foundbefore 25 years and 35% at 55 years and older(Paoli, 1997). Leboeuf-Yde and Kyvik (1998) evenmention that by the age of 20 years, more than50% of young people have had experienced atleast one low back pain episode. Burdorf andSorock (1997) mention twelve studies reporting apositive association between low back disordersand increasing age, but also 15 studies where noassociation is mentioned.

It is important to investigate also the years ofemployment. Age and years of employment areoften strongly correlated which makes it difficultto disentangle their effects on the occurrence oflow back disorders. They both can confound eachother’s effect. A person of 30 years for instancemay experience low back pain but alreadyperforms lifting tasks for 10 years. However, alsoyoung people with little experience often reportlow back pain due to unadjusted postures orbecause they are placed in jobs that require moremanual material handling because of their lowerseniority.

3 . 2 . 3 . 2 S o c i o - e c o n o m i cs t a t u s / e d u c a t i o n

Lower socio-economic status employees reportlow back pain more frequently. However, it isargued that this can be caused by the morephysically demanding occupations oftenperformed by people with lower educationlevels. Luoma et al. (2000) investigated theinfluence of type of work on low back painfrequency. The authors concluded in bothstudies that machine operators and carpentersreported more sciatic pain than office workersand the latter were indeed more highlyeducated subjects and the majority of thembelonged to a higher social class than themanual workers. Also Leino-Arjas et al. (1998)found higher prevalence of low back pain infarmers and manual workers as compared withoffice and administrative etc. workers. This



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corresponds to the European study where theprevalence of low back pain in office/administrative workers was on average 20%,compared with 49% in agriculture and 44% inconstruction (Paoli, 1997). The findings of Latzaet al. (2000) support the hypothesis that severeback pain is less prevalent among adults ofhigher socio-economic status.

3 . 2 . 3 . 3 S m o k i n g

Most studies reviewing the influence of smokingreport a relation with low back pain. Severalpapers have presented evidence that a positivesmoking history is associated with low back pain,sciatica, or intervertebral herniated disc (Bernardet al., 1997), whereas in others the relationshipwas negative (Bongers et al. 2000).

As the postulated mechanisms are mentioned: adecreased blood flow, induced by the nicotine;smoking-induced diminished mineral content ofbone causing micro-fractures and the smokinginduced coughing that increases abdominal andintradiscal pressure (Hales and Bernard, 1996). Ina review of 47 studies, Leboeuf-Yde (1999)concluded that smoking should be considered aweak risk indicator but not a cause of low backpain. There must also be the strong confoundinginfluence of socio-economic status and thereforetype of job (manual workers smoke more thannon-manual workers) and the link between stressand higher smoking could be a bias.

3 . 2 . 3 . 4 M e d i c a l h i s t o r y

A general consensus has been found on previoushistory of low back pain as one of the mostreliable predictive factors for subsequent work-related low back pain (e.g. Lagerstrom et al.,1998). Luoma et al. (1998) found in their study onrisk factors of lumbar disc degeneration that allsigns of degeneration were related to a history ofback accidents. In some studies, a previous historyhas been interpreted as representing anunderlying personality trait (“complainer”),although it could also be indicative of a reducedthreshold for injury or pain in spinal tissues (Franket al., 1996a). Some studies mention the relation

between births or final stage pregnancies and lowback pain.

3 . 2 . 3 . 5 G e n d e r

It is mentioned that the prevalence of low backdisorders in the European Union is equal amongmen and women (Paoli, 1997). However, somestudies report higher rates of severe disordersamong the male population, especially for sciatica(Lagasse, 1996). It is important in these studies toconsider the possible different types ofoccupation (Burdorf and Sorock, 1997). In aEuropean Agency study (2000b) it was found thataccidents in the workplace were mainly attributedto “slip/trips and falls” and “manual handling”,which occurred more in the construction andmanufacturing sectors. Mainly male operatorswere involved (on average 79%).

Recently, Vingard et al. (2000) found thatcurrent and past physical and psychosocialoccupational factors seemed to be gender-specific. Psychosocial factors alone seemed tobe of less importance in women, but “poor jobsatisfaction” and “mostly routine work withoutpossibilities of learning” increased in men.

3 . 2 . 3 . 6 A n t h r o p o m e t r y : w e i g h t a n dh e i g h t

Although Leino-Arjas et al. (1998) found that thebody mass index was associated with back painamong women, most of the evidence in literatureappears to be negative. Also for stature andbuild, in general no strong correlation with lowback disorders is found (Bernard et al., 1997;Burdorf and Sorock, 1997). From a review of 65epidemiologic studies, Leboeuf-Yde (2000)concluded that due to lack of evidence, bodyweight should be considered only as a possibleweak risk indicator, but there is insufficient datato assess if it is a true cause of low back pain.

3 . 2 . 3 . 7 P h y s i c a l a c t i v i t y : f i t n e s s a n ds t r e n g t h

Regarding the preventive effect of physical fitnesson low back disorders, no conclusions can bedrawn from the literature. The level of general



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(cardio-respiratory) fitness has no predictive valuefor future low back disorders (Carter and Birrell,2000). Furthermore, strong spinal and abdominalmuscles are not considered as significant factorsfor the prevention of work-related low backdisorders. Weaker muscles may in fact be theresult of low back pain, not the cause of it.According to the review study of Hoogendoornet al. (1999), no evidence was found for an effectof sports activities or total physical activity duringleisure time. Furthermore, no evidence was foundfor participation in specific sports or driving a carduring leisure time. The authors mention that theapplication of physical activity types was differentin the different studies and in general not veryspecific. It may be worthwhile to develop newmethods to measure and evaluate this factormore adequately in the future. Westgaard andWinkel (1997) concluded that interventions thatactively involved the worker (e.g. physical trainingor active training in work technique) oftenachieved positive results, whereas more passivemeasures (e.g. health education) did not appearto be equally successful.

3 . 2 . 3 . 8 P s y c h o l o g i c a l f a c t o r s

Andersson (1999) mentions in his review variousstudies where an association between low backpain and psychological factors is found (e.g.anxiety, depression, stress). The experience ofthese factors is sometimes, but not always,secondary to back pain. In a few prospectivestudies, various symptoms that indicatepsychological distress predicted thedevelopment of low back pain in people who didnot have previous back disorders. In a study ofPolatin (in Andersson, 1999) the possibleetiological importance of psychiatric disorderswas investigated. It was concluded from a groupof 200 patients that substance abuse (94 %) andanxiety disorders (95 %) precede chronic lowback pain, whereas depression (54 %) maydevelop before or after the onset of chronic lowback pain.

However, the relationship between psychologicalfactors and musculoskeletal disorders remainsunclear (Feyer et al., 1992). One possibility is thatpsychological distress is simply a consequence of

chronic low back pain, with no etiologic role in thedevelopment of the disorder. Alternatively, it ispossible that psychological factors may have someetiologic role in the transition from an employeewith a history of back pain to the status of anunemployed patient with chronic back pain, dueto fear of re-injury, or other factors which wouldmake job performance impossible

3 . 2 . 3 . 9 C o n c l u s i o n s o n i n d i v i d u a lr i s k f a c t o r s

The most consistent associations have been foundbetween low back disorders and socio-economicstatus or medical history, whereas for theassociation between low back disorders andfitness, many conflicting results are reported.However, this factor may contribute to generalhealth benefits, e.g. by organising fitnessprograms. Also anti-smoking campaigns orhealthy food provision may have this beneficialgeneral health effect.

It is often mentioned that prevention of severalof the individual risk factors is not possible: age,gender and medical history cannot be changed.However, the sooner prevention is induced, themore probable it is that a medical history for lowback disorders will not develop or even exist.When considering age as a risk factor, the“healthy worker effect” often causes bias: ifworkers who have health problems leave theirjobs, or change jobs to one with less exposure,the remaining population includes only thoseworkers whose health has not been adverselyaffected by their jobs.



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Carter and Birell (2000) reviewed pre-placementassessment. They concluded that examinationfindings, including in particular height, weight,lumbar flexibility and straight leg raising, havelittle predictive value for future low backdisorders or disability. Also the level of generalfitness (cardio-respiratory), X-ray and magneticresonance imaging findings have no predictivevalue for future low back disorders or disability.Furthermore, back-function-testing machines(isometric, isokinetic or isoinertialmeasurements) have no predictive value.

They also state that low back disorders arecommon and recurrent and is not a reason fordenying employment in most circumstances.However, care should be taken when placingindividuals with a strong history of low backdisorders in physically demanding jobs. Attentionshould be given to adapt work organisationalfactors.

Verbeek et al. (2000) recently performed anextensive search on articles that dealt withprognosis on low back disorders. Theyconcluded that increased time to return to workis predicted by older age, a higher degree of

disability and a specific diagnosis. It is not clearby what mechanism these factors worsen theprognosis of return to work, but the authorssuggest the following: for age, the increasingage itself makes it more difficult to resume worktasks. A high level of disability takes more timeto resolve and leads consequently to a longertime off work. That a specific diagnosis predictsa late return to work may be caused by theseriousness of the disease and/or by thebehaviour of doctors being more cautious inadvising return to work. Regarding the workingconditions, the authors mentioned that heavyphysical work is not a predictor of longer delayuntil return to work. Other work-related factorssuch as the possibility of taking breaks andsocial support were of more importance inpredicting a shorter time. However, Meyer et al.(1998) found that workers involved in manualhandling had higher frequency and severity oflow back disorders than a reference population.The authors state that individual factors areoften decisive in the onset of low backdisorders, but in the more serious cases materialhandling is an aggravating factor.

Loisel et al. (1997) developed and tested amodel of management of sub-acute back painto prevent prolonged disability. Workers wereplaced in one of four treatment groups. It wasfound that the group receiving full intervention(clinical and occupational intervention) returnedto regular work 2.4 times faster than the usualcare intervention group. There is preliminaryevidence that educational programmes whichspecifically focus on beliefs and attitudes mayreduce future work loss due to low backdisorders (Carter and Birrel, 2000).

3.3P R O G N O S I S O F L O W B A C K

D I S O R D E R S A N D R E T U R N T O

W O R K



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Ferguson and Marras (1997) hypothesised thatcertain risk factor categories may influencedifferent events in the progression of low backdisorders in different ways. For each step in thetime progression of low back disorders, specificanalysis techniques can be used. The authorsperformed a careful examination of the existingliterature (articles were only included when atleast one technique was used, at least one riskfactor was analysed, and certainmethodological issues were respected).Conclusions were made based on 57 studiesthat fulfilled the above-mentioned criteria:

• Using incidence as analysis techniques resultsin more positive findings with exposure riskfactors

• Analysis techniques indicating moreadvanced stages of low back disorders (e.g.lost time) had more positive findings withpsychosocial risk factors. This suggests that aslow back disorders disorders progress todisability, the psychosocial risk factors play amore prominent role.

• The precision of measurement is veryimportant in the attempt to distinguish

symptomatic and asymptomatic subjects.Strength measures that require higher levelsof motor control were better indicators of lowback disorders (e.g. weight-handling skillsinstead of isometric or isokinetic strengthmeasures).

In their recent review, Davis and Heaney (2000)found that the association betweenpsychosocial work characteristics and low backpain differed by the type of outcome measureused. More posit ive associations withpsychosocial work characteristics were foundwhen self-reports of symptoms or injuries wereused than when low back disorders wasdetermined by physical examination.

3.4A S S E S S M E N T T E C H N I Q U E S

A N D R I S K F A C T O R S



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RE

SE

AR

CH

4.S T R A T E G I E S A N D

E F F E C T I V E N E S S O F

P R E V E N T I O N


4.2


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P R I M A R Y P R E V E N T I O N

S T R A T E G I E S

4 . 2 . 1 . T y p e s o f i n t e r v e n t i o n s t or e d u c e w o r k p l a c e r i s k s

Elimination of lifting or other types of physical“overload” on the body in the first placeshould be the first priority for prevention andreduction of work-related disorders. Formanual handling tasks this can be achievedthrough task automation so that the workeronly performs a control task (e.g. in carassembly). This solution is very radical andoften not practical to establish, and can alsolead to the introduction of other work-relatedproblems for example from a change to morerepetitive tasks. Therefore other preventionstrategies also have to be considered toreduce the amount and physical demands ofmanual handling tasks. Several strategies arepossible (Frank et al., 1996a): adjustments tothe work to reduce the physical demands (e.g.using material handling devices) or changes toorganisational factors (e.g. organising breaksand job rotation) and training workers toincrease their ability to recognise and avoidunsafe lifting situations.

4.1P R E V E N T I O N S T A G E S

In general, three prevention stages can bedescribed. With primary prevention, the goal is toavoid low back disorders in the first place, toprevent the onset of low back disorders. The goalof secondary prevention is to halt the furtherdevelopment of low back disorders, to preventthe onset of chronic pain and recurrence of a lowback disorder. Studies to determine effectiveinterdisciplinary approaches to the identificationof workplace risk factors. In the tertiary preventionstage, the goal is to reduce disability or handicapand a more specific individual approach isnecessary, which goes beyond the scope of thisreport.

Emphasis is placed on primary prevention in theworkplace. However, due to the high prevalenceof low back disorders in the working environmenttoday and therefore the need to address return-to-work and rehabilitation issues strategies ofsecondary prevention are also covered. Inimplementing the secondary and tertiarymeasures an integrated work-place approach isrecommended, with treatment and rehabilitationtaking place within the context of a clear focus oneliminating and reducing the work-related risksgiving rise to the problems. Details on the possiblecontents of secondary/tertiary strategies are givenin appendix 3.



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not always reduce risk for all workers in therotation. The effects are not always intuitivelypredictable because of the complex effect ofmixes of tasks that influence both peak andcumulative loading on tissues. It is not only highpeak compression and sheer force on spinaltissues that are problematical, but also highaccumulation of these forces over the course of awork shift, regardless of whether they are high ornot. Again, this necessitates the reduction ofrepetitive lifting.

• Material handling devices

Mechanical lifting and carrying devices arebecoming increasingly important in the workingenvironment, with the aim of reducing thestresses imposed on the musculoskeletal systemduring manual handling work. By introducing ahandling device in the workplace, the weight ofan external load is reduced and extreme flexionand rotations of the trunk are avoided. Whenimplementing these tools in the workplace, it isimportant to take into account several otherfactors:

• T ime: it has been found that using amechanical device sometimes takes longerthan manual lifting and may be a reason whydevices are not used (Mathisson et al., 1994,Hermans et al., 1999a).

• Work space: manipulating an object with amechanical device may require more space,which is often very limited. This may influencealso the safety of the working environment(Hermans et al. 1999a).

• Instruction: High biomechanical stress on theback can still be a problem, primarily due tothe inertia of the device, which produces highacceleration and deceleration phases whenutilising the device (Chaffin et al., 1997). Infurther experiments, Chaffin et al. (1999)found that when subjects were instructedand controlled to keep a comfortable speed,material handling devices had a particularlybeneficial effect on reducing the compressionforces in the lower back during loweringactivities. Training to work efficiently with thedevice should be provided.

4 . 2 . 1 . 1 R e d u c i n g t h e p h y s i c a ld e m a n d s

• Optimisation of workplace factors

Several general ergonomic solutions can be madeto reduce the physical demands of the task:

• design of the work task: reduction of thenecessity to handle a load, reduction of theweight of the load, reduction of the shapeand size of the load, reduction of the numberof moves and the distance of moves.

• design of the work place: allow enough spacefor body movement, avoid bending of thetrunk and optimise the working level.Furthermore, create safe workingenvironments for the prevention of accidentalinjuries, avoid the risks for slipping or falling.

• design of the work organisation: adequaterelation between demands and rests,duration and frequency of lifting.

From a recent prospective longitudinal study,Bongers et al. (2000) mentioned the followingrecommendations:

• Reduction of physical load at work to helpreduce the number of low back problems andabsence from work. Attention should be onreduction of high exposure and repetitivelifting: Lifting of 25 kg or more has to beavoided, especially when lifting more than 15times per day.

• Work situations with trunk bending have tobe avoided (especially when bending 60° ormore).

• Work situations with trunk rotation duringmore than 10% of the work time have to beavoided.

A commonly used practice to change workorganisational design is job rotation: to moveworkers from work station to station or tochange tasks within one work station on someorganised schedule (e.g. every two hours). Jobrotation is used for a variety of reasons: toincrease motivation; to train a more versatilework force; to reduce fatigue and risk ofmusculoskeletal disorders. However, Frazer et al.(2000) recently showed that job rotation does



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• Total physical load: when implementing thedevice in the workplace, attention must begiven to ensure that no shift of static load toother body regions occurs, e.g. to the upperlimbs (Hermans et al., 1999a).

Carter and Birrell (2000) advise on current goodpractices such as specified in the Manual HandlingDirective and associated guidance. Furthermore, itis expected that still more and better mechanicallifting aids will be developed in the future. Theintroduction of CEN Standards, among otherthings, including the requirements for ergonomicsand safety of machinery, will promote thisdevelopment (e.g. EN 894-1, EN 894-3, EN 614-1, EN 547-1, EN 547-2, EN 1005-3).

• Back belts

Back belts were initially used in medical settingsto provide additional support duringrehabilitation of back injuries. Later, weightlifting athletes began using leather belts. Today,more than 70 types of industrial back belts exist,usually a lightweight, elastic belt, often called‘back belt’, ‘back supports’ or ‘abdominal belts’.The advantages of using a belt are mentionedby (Carter and Birrell, 2000):

• the internal forces on the spine are reducedduring forceful exertions of the back

• the intra-abdominal pressure increases,which may counter the forces on the spine

• the spine stiffens, which also decreases theforces

• the wearer is reminded to lift properly

Van Poppel et al. (1999) evaluated the evidencefor the hypothesis that trunk motion is affectedwearing a belt so that extreme postures areobstructed. A positive association was found in8 out of 13 studies in the literature. The trunkmotion was at least in one of the motion planesdecreased, mainly flexion/extension and lateralbending were reduced. No statistical significanteffect was found for rotation, which possiblycan be explained by the large variation amongsubjects. Regarding a second hypothesis thatintra-abdominal pressure increases wearing abelt without increase of muscle activity so thatthere is less muscle loading, conflicting results

were found in the studies. Also other studiesquestioned the effectiveness of back belts (e.g.Op De Beeck and Vertongen, 1995; NIOSH1994). NIOSH concluded from their review thatthe results can not be used to either support orto refute the effectiveness in injury reduction. Inaddition, workers wearing back belts mayattempt to lift more weight than they wouldhave without a belt. A false sense of securitymay subject workers to greater risk of injury.

In conclusion, there seems to be strong scientificevidence that lumbar back belts or supports donot reduce low back disorders and work loss(Carter and Birrell, 2000).

• Chairs

Harrison et al. (1999) conclude in their reviewthat sitting causes the pelvis to rotate backwardand causes reduction in lumbar lordosis, trunk-thigh angle, knee angle and causes an increasein muscle effort and disc pressure. Subjects inseats with backrest inclinations of 110 to 130degrees, with concomitant lumbar support,have the lowest disc pressures and lowest spinalmuscle activity. To reduce forward translatedhead postures, an incl ination of 110 ispreferable over higher inclinations. A seat-bottom posterior inclination of 5 degrees andarmrests can further reduce the pressures andactivity. Subjects give the highest comfortratings to adjustable chairs, which allowchanges in position. Nevertheless, it should bementioned that in several reviews still noassociation between low back disorders andprolonged sedentary mentioned was found(Burdorf and Sorock, 1997).

• Vibration limits

According to ergonomics recommendations,tractors, heavy vehicles and constructionsmachinery with frequencies most oftenbetween 2 and 5 Hz and operating for an 8hours day, require a l imit of osci l lationacceleration of 0.3 – 0. 45 m/s2. These limits areoften exceeded but technically they can beachieved by jointly engineering the suspensionof the vehicle’s axles and the driver’s andpassengers’ seats (Kroemer and Grandjean,



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1997). In many studies investigating therelationship between low back disorders andwhole body vibration, an action level of 0.5m/s2 is often mentioned (Hulshof, 1998). TheEuropean Union Directive for physical agentsproposes an exposure limit figure of 0.7 m/s2(Johanning, 2000).

Besides considering the acceleration exposurelimits, attention should also be given to otherwork-related factors, including prolongedsitting, lifting and awkward postures. Thesefactors may act in combination with whole bodyvibration to cause back problems.

4 . 2 . 1 . 2 E d u c a t i o n / t r a i n i n g

Information and training activities can play animportant role, when part of a generalprevention strategy focused on reduction ofrisks in the work place. Previous training effortshave generally fallen into three areas: (1)training of specific lifting techniques; (2)teaching biomechanics-thus increasing theunderstanding and awareness of back injuriesso safe approaches towards lifting are adopted;and (3) training the body via physical fitness sothat it is less susceptible to injury.

• Lifting techniques

In several reviews, emphasis is laid on manualhandling as the most important risk factor.Consequently, in many companies and in liftingschools, the importance of a good liftingtechnique is emphasised. The most commonlyadvised technique, dating from the 1940s, issquat or leg lifting: flexing the knees whilekeeping the back as straight as possible (Kroemer,1992). This technique has several advantagescompared with the opposite technique, calledstoop or back lifting where the back is flexed andthe legs extended. Although the leg liftingtechnique has been introduced and appliedworld-wide, several studies have revealednumerous comments on this technique, e.g. ahigher energetic physiologic cost (Kumar, 1984),awkward postures when lifting larger volumes(van Dieën, 1999a) or more balance loss(Toussaint et al., 1997).

Information on the advantages anddisadvantages of the leg lift and the back lift issummarised in table 6 (Hsiang et al., 1997).Some of the advantages/disadvantages are inparentheses, indicating that contradictoryresults are found in some studies. Furthermore,information is given on lifting with the back in alordosis or kyphosis posit ion, twistingmovements and the influence of fast lifting.

Though little scientific evidence of a directrelationship between low back disorders andlifting technique exists, there are certainworkplace realities that cannot be ignored(Hsiang et al, 1997):

1. Those responsible for improvingoccupational safety will continue to trainindustrial workers in some form of liftingtechnique,

2. Industrial workers will continue to lift objectsas part of their jobs, and

3. For some workers, the way in which theyaccomplish the lifting task will be related tothe techniques they have been taught.

Therefore it is important to understand thatfocusing only on the position of the back duringlifting is not sufficient.

Van Dieën et al. (1999a) advise that for theprevention of low back disorders, trainingshould also be focused on other aspects oflifting: asymmetry, speed of lifting, position ofthe load, position of the grips of the load, loadmass). This is demonstrated by Marras (2000)who found five factors in combination thatdescribed very well the relationship with risk ofreporting disorders and lost or restricted timefrom low back disorders. These factors are liftfrequency, sagittal torso bending angle, lateralvelocity, twisting velocity and external loadmoment.

• Broader information and trainingapproaches

As it is clear from the previous section thattraining in specific lifting techniques alone doesnot appear effective. Kroemer (1992) suggeststhat one reason for this is probably because there



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T a b l e 6 . A d v a n t a g e s a n d d i s a d v a n t a g e s o f t h e l e g l i f t o r t h e b a c k l i f t( a d a p t e d f r o m H s i a n g e t a l . 1 9 9 7 ) . P i c t u r e s f r o m I N R S ( I n s t i t u tN a t i o n a l d e R e c h e r c h e e t d e S é c u r i t é ) .

1. Leg lift (squat)

Advantages• (Small peak compressive on L5/S1)• Load closer to the body• Less strain on the low back ligaments• (Minimises disc compression)• (Minimises overall strength requirements)• (Mechanical advantage)

Disadvantages• Knee muscles not well-suited to prolonged lifting• Fatigue of quadriceps• High integral of compression over time at the L5/S1 disc• Diminishes mechanical advantage of the long moment arm when the hip falls below the knees• Higher oxygen consumption• High inspiratory ventilation volume• Subjectively the most tiring

2. The back lift (stooped)

Advantages• Produces a relatively small integral of compression over time at the L5/S1 disc• May result in lower compressive force• Allows better body control • Provides better balance • Allows better knee clearance • Lowers the estimated energy expenditure rate• Superior from an effectiveness standpoint because it minimises the change in potential energy of the lifter’s

body • Utilises the hip and trunk muscle groups, which are better suited to prolonged lifting than the knee muscles

Disadvantages:• Produces relatively high peak compressive force on L5/S1 disc• Produces relatively high shear forces

3. Lordosis (accentuation of the inward lumbar curvature)

Advantages• Results in more even distribution of stresses on the lumbar disc• May minimise the hydrostatic pressure in the disc, in contrast to kyphosis• Provides greater muscle control of the trunk • Minimises strain on posterior spinal ligaments

Disadvantages• Forces all torso flexion to be accomplished at the hip joints because lumbar lordosis is maintained by holding

the trunk rigid• Requires greater activity of the erector spinae when the load lifted increases• Decreases lumbar moment arm• Increases compressive stress on the posterior annulus when the weight is heavy• (Results in less compressive strength of the lumbar intervertebral joints)• (Does not allow posterior spinal ligaments to bear some of the load )



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is no one technique that is appropriate for all lifts.Increasing the knowledge of risks and how toavoid them and promoting good practicenecessitates determining what should be taught,how much knowledge is needed and tailoringthis to the particular work and type of workplace. Scheer et al. (1995) investigated theefficacy of “back schools”, which represent acollection of educational processes for back care.

They generally consist of a series of discussionsabout anatomy, biomechanics, lifting andmaterial handling and exercise instruction. Manytraining programmes now also include how tospot risks in the work place and what to do in thecircumstances as well as lifting techniques.Training is also required to effectively use liftingdevises for example (see section on mechanicaldevises).

A d v a n t a g e s a n d d i s a d v a n t a g e s o f t h e l e g l i f t o r t h e b a c k l i f t ( a d a p t e d f r o mH s i a n g e t a l . 1 9 9 7 ) . ( c o n t . )

4. Kyphosis (lumbar curvature towards more flexion of the spine)

Advantages• Allows sharing of muscle group distribution of work• Requires less activity of the erector spinae (than lordosis) when the load lifted increases • (Increases lumbar moment arms)• Reduces the compressive stress on the posterior annulus when the weight is heavy• Improves transport of metabolites in the intervertebral discs when the weight is heavy• (Results in greater compressive strength of the lumbar intervertebral joints)• Allows posterior spinal ligaments to bear some of the load • Reduces the stresses at the apophyseal joints

Disadvantages• (Results in uneven distribution of stresses on the lumbar disc)• May increase the hydrostatic pressure in the disc in contrast to lordosis• Provides less muscle control of the trunk• Increases the compressive stress on the anterior annulus

5. Twisting

Advantages• Faster than sagittal lifting • May allow people to fully utilise the different forces generated from the dominant and non-dominant hands.• For certain tasks, may involve less energy expenditure than lifting, carrying, and lowering a load

Disadvantages• Considered damaging to the spine since the annulus fibrous is maximally stressed while least protected by

the posterior elements during flexion-rotation• Increases intradiscal pressure • Intra-abdominal pressure increases when the trunk is loaded in rotation

6. Fast lifting speed

Advantages• With sufficient speed at an early phase of lifting, can provide enough kinetic energy to take the load past the

individual’s weaker lifting levels• For heavy loads, may reduce stress on the annulus because the amount of load that the annulus can safely

transmit decreases with time and time is limited with fast lifting

Disadvantages• Produces marked increases in compressive force.• Significantly decreases torque producing capability of the trunk muscles• Reduces peak dynamic strength



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Practitioners have to be aware of possiblereasons for disappointing results, which include:

• people tend to revert to previous habits andcustoms if training in practices to replaceprevious ones are not reinforced andrefreshed

• in emergency situations a sudden quickmovement of weight increase may overlystrain the body

• if the job requirements are physically stressful,the behaviour modification will not eliminatethe inherent risk. Therefore designing a safejob is fundamentally better than trainingpeople to behave safely.

Furthermore, it is important to consider theinfluence of instruction style and media oncewhat should be taught has been determined.Questions such as “Where should the sessions beheld?” should be addressed. At the work site hasto be preferable to classroom-type instruction,except when emphasis is laid on knowledge andinstructional purposes. Or “Is it best to trainemployees working together as a group, orshould the group be split up?” Currently,information is not available on which to basesound judgement. But it is known that materialshandling task characteristics and requirementsdiffer considerably even between industries orbetween tasks/jobs in one industry so customisedtraining to small groups is often recommended(Kroemer, 1992).

In summary reliance on training alone, especiallyon lifting techniques, is likely to be misleading,particularly where the realities of the workingenvironment prevent or hinder the adoption ofsafe postures and the use of ideal liftingtechniques. In addition frequent manualhandling of loads even in ideal conditions willput a strain on the back.

• Physical training

There are several types of physical trainingprograms: spinal flexion exercise, extensionexercise, isometric strengthening exercise forabdominal and lumbar muscles and aerobicexercise (Scheer et al., 1995). The rational forperforming exercises as a prevention method

includes strengthening of weak muscles and oftight muscles and ligaments, stabilisation ofhypermobile segments, correcting poor posture;decompressions of radicular structures, bony lockor of bulging annulus. In their review of theliterature on low back disorder prevention, Scheeret al., (1995) found four studies that were eligiblefor analysis (after passing a thorough selectionregarding methodological issues). A picture of theefficacy of physical training exercise for acute lowback pain begins to emerge from the availabledata. Long-term exercise, particularly whenreinforced at work, appears to be beneficial forprevention of backache. Also Westgaard andWinkel (1997) concluded that interventions thatactively involves the worker (e.g. physical trainingor active training in work technique) often achievepositive results, whereas more passive measures(e.g. health education) do not appear equallysuccessful.

Frank et al. (1996a) report two importantremarks on this type of intervention:

Firstly, the underlying assumption of this type ofintervention is that better conditioning and careof the back will translate into a reduced risk of lowback pain onset. However the underlyingassumption can be perceived negatively, as a formof victim blaming. The interventions imply that theproblem of low back disorders are not so much asa result of the work being done as of the workerswho are doing it. It should be mentioned thataccording to the Manual Handling Directive (seeAppendix 2), employers are obliged to provide ahealthy and safe working environment.Therefore, appropriate working conditions shouldbe developed and not only providing physicaltraining that focuses only on the individual.

Secondly, these interventions can also beconsidered as a controversial form of pre-placement screening of individuals for job fitness.However, most of the screening efforts (e.g.radiological examinations, pre-employmentstrength tests) have been ineffective in predictingwho will subsequently develop disabling low backpain. Also in the “Occupational Health Guidelinesfor the Management of Low Back Pain at Work”produced by the Faculty of Occupational Medicine



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in London (Carter and Birrell, 2000) the advice isnot to routinely include clinical examination of theback, lumbar x-rays, back function testing, generalfitness or psychosocial factors in the pre-placementassessment.

4 . 2 . 2 . W o r k - o r g a n i s a t i o n a l f a c t o r s

Giving attention to the job design and workorganisation can contribute to prevention ofwork-related low back disorders. Westgaardand Winkel (1997) concluded from their reviewthat regarding organisational cultureinterventions, a possible distinguishing featureof successful interventions relative to those thatfailed is the extent to which interventionownership is embedded in the company,including company management. Therefore,the authors suggested that the followingintervention strategies have the best chance ofsuccess:

• Organisational culture interventions withhigh commitment of stakeholders, utilisingmultiple interventions to reduce identifiedrisk factors

• Modifier interventions, especially those thatfocus on workers at risk, using measures thatactively involve the worker

Carter and Birell (2000) mention that there islimited evidence but general consensus thatjoint employer-worker initiatives can reduce thenumber of reported back ‘injuries’ and sicknessabsences, but there is no clear evidence as tothe optimum strategies and inconsistentevidence on the size of the effect. In general,these initiatives should involve organisationalculture and high stakeholder commitment toidentify and control occupational risk factorsand improve safety, surveillance measures andthe ‘safety culture’. Active health surveillance(e.g. symptom surveys, physical examinations)at the workplace prior to back disorderdevelopment is not sufficiently developed(Hagberg et al. 1995). Volinn (1999) mentionstwo studies focusing on managementawareness and commitment with successfuloutcomes: a reduction in the rate of lost timedue to low back pain was found after the

intervention. Also Bongers et al. (2000)mentioned in their study that an optimalcollaboration with colleagues improves thereduction of low back pain.

Carter and Birell (2000) advise employers thathigh job satisfaction and good industrialrelations are the most important organisationalcharacteristics associated with low back painand sickness absence rates. So employersshould be encouraged to:

• consider joint employer –worker initiatives toidentify and control occupational risk factors

• monitor back problems and absence due tolow back disorders

• improve safety and develop a ‘safety culture’.



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This section covers interventions following theoccurrence of a work-related low back disorder.The interventions are therefore aimed atpreventing reoccurrence and reduction of effects.Given that previous medical history of a low backdisorder is linked to the (re)occurrence of a lowback disorder, this emphasises the necessity ofpreventing the on-set of work-related disorders inthe first place through primary prevention.Nevertheless an integrated approach to removal ofrisks and supporting injured workers return towork through treatment and rehabilitation is veryimportant.

Burton and Erg (1997) mention thatbiomechanic/ergonomic considerations may berelated to the first onset of low back pain, butthere is little evidence that secondary controlbased solely on these principles will influencethe risk of recurrence or descent into chronicdisability. According to the authors, morepromising in this respect are programmes thatalso take account of the psychosocial influencessurrounding disability. Work organisationalissues are clearly important, but so is thebehaviour of clinicians. A proactive approach to

rehabil itation should be adopted byrecommending, when possible, early return tonormal duties as well as complementarypsychosocial advice.

One of the important treatment goals should bethe carefully guided return-to-work of thepatient with a back disorder. A well-plannedreturn-to-work programme should incorporatea risk assessment and a control of hazardous jobtasks or conditions to prevent re-injury andcontinued harm. Both workplace-based andhealthcare-based interventions are important.

When looking at treatment and rehabilitationissues it is important to distinguish between thedifferent stages of the development of low backdisorders as the recommended interventiondiffers according to the specific stage (acute orchronic low back disorders). The current state-of-the-art effectiveness of conservativetreatments for acute and chronic low back painwas evaluated by van Tulder et al. (1999). Theresults of their review are summarised in Table 7below. More specific information on thesestrategies is presented in appendix 3.

4 . 3 . 1 A s s e s s m e n t o f t h e w o r k e r w i t hl o w b a c k d i s o r d e r

As with primary prevention it is necessary toassess the situation and match the interventionto the situation, being aware of the all therelevant factors. For example whilst there aregeneral recommendations such as “keepactive” this can not be recommended in everycase.

In his review on occupational back disorders,Johanning (2000) mentions many factors thathave a strong influence on the success rate ofreturn to work outcome and the developmentof chronic low back disorders:

• Job demands, control and satisfaction• Employer/employee motivation/practice• Employee age• Benefit structure/disability case management• Contractual labour – management

arrangement

4.3S E C O N D A R Y P R E V E N T I O N

S T R A T E G I E S



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• Insurance carrier case management problems• Adversarial medico-legal (worker’s

compensation) relationship and management• Previous history of low back disorders• Total work loss in past twelve months (low

back disorder related)• Radiating leg pain, nerve root involvement• Reduced trunk muscle strength and

endurance• Poor physical fitness• Heavy smoking• Psychological complications

Loisel et al. (1997) concluded from their studythat receiving full intervention (clinical andoccupational intervention) resulted in fasterreturn to regular work than a usual careintervention.

Concerning the assessment of the workerpresenting back pain, the following should beconsidered (Carter and Birrell 2000):

• Screen for serious spinal diseases and nerveroot problems

• Clinical examination may aid cl inicalmanagement, but is of limited value in

planning occupational health management orin predicting the vocational outcome.• Take a clinical, disability and occupational

history, concentrating on the impact ofsymptoms on activity and work, and anyobstacles to recovery and return to work

• Consider psychosocial ‘yellow flags’ toidentify workers at particular r isk ofdeveloping chronic pain and disability. Usethis assessment to instigate active casemanagement at an early stage.

• X-rays and scans are not indicated for theoccupational health management of thepatient with low back disorders.

• Ensure that any incident of low back disorderswhich may be work-related is investigatedand advice given on remedial action. Ifappropriate, review the risk assessment.

The authors also formulated managementprinciples:

Clinical recommendations:• Advice to continue ordinary activities of daily

living as normally as possible if pain istolerable. This can give equivalent or fastersymptomatic recovery from acute symptoms,and leads to shorter periods of work loss,

T a b l e 7 . : E f f e c t i v e n e s s o f c o n s e r v a t i v e t r e a t m e n t f o r a c u t e a n d c h r o n i c l o wb a c k d i s o r d e r s ( L B D ) ( v a n T u l d e r e t a l . , 1 9 9 9 )

Acute LBD Chronic LBD

Strong evidence for NSAIDs (non-steroidal anti- Exercise therapyeffectiveness inflammatory drugs) Multidisciplinary programs

Muscle relaxantsAdvice to stay active

Moderate evidence Analgesics Analgesicsfor effectiveness Antidepressants Antidepressants

Facet joint, trigger point, or Colchicineligamentous injections Epidural corticosteroïd, triggerAcupuncture point, or ligamentous injectionsBack schools Muscle relaxantsBehavioural therapy Advice to stay activeMultidisciplinary programs Bed restEMG biofeedback Lumbar supportsLumbar supports Physical modalitiesPhysical modalities Spinal manipulationSpinal manipulation Transcutaneous electricalTranscutaneous electrical nerve stimulationnerve stimulation

Strong evidence for Bed rest Tractionineffectiveness



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packages, but there is generally consistentevidence on certain basic elements. Suchinterventions are more effective in anoccupational setting than in a health caresetting.

• The temporary provision of l ighter ormodified duties facilitates return to work andreduces time off work.

A combination of optimum clinicalmanagement, a rehabilitation programme, andorganisational interventions designed to assistthe worker with a low back disorder return towork is more effective than single elementsalone.

fewer recurrences and less work loss over thefollowing year than ‘traditional’ medicaltreatment (advice to rest and ‘let pain be yourguide’ for return to normal activity).

• The above advice can be usefullysupplemented by simple educationalinterventions specifical ly designed toovercome fear avoidance beliefs andencourage patients to take responsibility fortheir own self-care.

Occupational recommendations:• Communication, co-operation and mutually

agreed goals between the worker with lowback disorders, the occupational health team,supervisors, management and primary healthcare professionals is fundamental forimprovement in clinical and occupationalhealth management and outcomes.

• Most workers with low back disorders areable to continue working or to return to workwithin a few days or weeks, even if they stillhave some residual or recurrent symptoms,and they do not need to wait till they arecompletely pain free.

• Advice to continue ordinary activities, if painis tolerable, as normally as possible, inprinciple applies equally to work. Thescientific evidence confirms that this generalapproach leads to shorter periods of workloss, less pain recurrences and less work lossover the following year, although most of theevidence comes from intervention packagesand the clinical evidence focusing solely onadvice about work is limited.

• There is general consensus but limitedscientif ic evidence that workplaceorganisational and/or management strategies(generally involving organisational cultureand high stakeholder commitment toimprove safety, provide optimum casemanagement and encourage and supportearly return to work) may reduce absenteeismand duration of work loss.

• Changing the focus from purely symptomatictreatment to an ‘active rehabil itationprogramme’ can produce faster returns towork, less chronic disability and less sicknessabsence. There is no clear evidence on theoptimum content or intensity of such



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Regulatory actions are based on two distinctelements - risk assessment and risk management.In the former, facts are used to define the healtheffects of the exposure of individuals orpopulations to hazardous situations. The latter is aprocess of integrating the results of riskassessment with engineering data and with social,economic, and political concerns to select themost appropriate regulatory action. For these twoelements, a scientific basis of risk assessment isnecessary, and therefore both epidemiologicalstudies on human populations and experimentalstudies have considerable importance (NationalResearch Council in Viikari-Juntura, 1997).

The Manual Handling Directive (CouncilDirective 90/269/EEC) is made with the primarygoal of preventing back injury during themanual handling of loads. Minimum health andsafety requirements are given for the manualhandling of loads and a series of relevant factorsare listed in annexes to the directive (SeeAppendix 2). Employers should to pay attentionto these risk factors when making assessmentsand selecting preventive measures. Theyinclude:

• Characteristics of the load (for example: is itheavy or difficult to hold);

• Physical effort required (for example:strenuous; twisting; body in an unstableposition);

• Characteristics of the working environment(for example: insufficient room or otherconstraints on the posture of worker such asworking height too high or low; uneven orslippery flooring);

• Requirements of the activity (for example:prolonged activity or effort; insufficient restperiods; excessive distances to move loads;imposed work rate)

• Individual factors (for example: clothing etc.restricting movement; inadequateknowledge or training)

ISO ergonomic standards are developed withthe aim of standardising for exampleterminology, methodology, and human factorsdata in the field of ergonomics. In the ISO /TC159 / SC3 group the following items areaddressed: anthropometry, evaluation ofworking postures and human physical strength.The draft standards that are being prepared willbe of importance with regard to the physicalaspects during work and the occurrence of lowback disorders. Until now, the followingstandards have been developed:

• ISO 7250:1996: basic human bodymeasurements for technological design

• ISO 15534-1:2000: Ergonomic design for thesafety of machinery – Part 1: principles fordetermining the dimensions required foropenings for whole-body access tomachinery

• ISO 15534-2:2000: Ergonomic design for thesafety of machinery – Part 2: principles fordetermining the dimensions required foraccess openings

• ISO 15534-3:2000: Ergonomic design for thesafety of machinery – Part 3: anthropometricdata.

Other guidelines relevant to the prevention oflow back disorders include ISO 2631-1 and ISO5349.

4.4G U I D E L I N E S A N D S T A N D A R D S

R E L A T E D T O P R E V E N T I O N O F

L O W B A C K D I S O R D E R S



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Also working group 4: Biomechanics of theTechnical Committee CEN/TC 122 –“Ergonomics” is further developing a Europeanstandard prEN 1005 2: “Safety of machinery-Human physical performance-part 2: Manualhandling of machinery and component parts ofmachinery”. This European standard has beenprepared under a mandate from the EuropeanCommission and the European Free TradeAssociation and supports essential requirementsof the Machinery Directive 98/37/EC.

To evaluate lumbar load with respect to the riskof overexertion during manual materialhandling, the National Institute of OccupationalSafety and Health introduced the ‘NIOSH’method. A l ift ing formula (equation), amultiplication model with six task variables, hasbeen proposed to protect healthy workers (seealso 5.5).

To obtain more information on the risks ofvibration and to calculate an occupationalvibration-exposure dose, recommendations andreferences are given by Johanning (2000). The demand for workplace interventions to

prevent low back disorders has increased inrecent years. Strategies to prevent low backdisorders include both workplace based andhealth care based interventions. Increasinglythere is recognition that an integrated approachincluding both types of intervention is neededto really tackle the problem effectively.Ergonomics interventions are based on a“holistic” or systems approach that considersthe effect of the equipment, the workenvironment and the work organisation as wellas the worker. The full participation of workersin the ergonomics approach is important for itseffectiveness.

There are dissenting views in the literature onwhether or not the programmes work. Thediscrepancies are often attributed to thedifferent methodological quality of the studies:lack of control groups, lack of randomisation,lack of a placebo group, small number ofsubjects, no standardisation of theenvironment, (Nordin, 1997; Volinn, 1999).Other negative factors are high costs ofinterventions, lack of underlying commitment

4.5C O N C L U S I O N S O N

E F F E C T I V E N E S S O F

P R E V E N T I O N



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prevention in the work place is also important inthis stage-for example increasing workorganisational awareness by actively involvingworkers and management or reducing thephysical demands of the work task.

Expert opinion is that although the focus shouldbe strongly on primary prevention, all thesefactors need to be looked at together. Forexample, studies show that training alone isunlikely to be effective if the ergonomic factorsin the work remain poor and basic training, forexample, needs to include how to spot potentialrisks and what to do if found, as well as safephysical handling techniques.

Based on the current knowledge on theeffectiveness of prevention strategies,employers are provided with information toprotect the workers. Guidelines andstandardised criteria have been and are beingdeveloped to increase the awareness of allpossible problems associated with low backdisorders, to increase the use of a standardisedapproach regarding risk assessment and toincrease the application of primary prevention inthe workplace.

from workers or management (Frank et al.,1996a). Furthermore, the presence of severalrisk factors and the question of the causal effectof the factors, increase the problems forprevention strategies. Volinn (1999) concludedthat many studies report a positive effect of theprevention strategies, but the report is mainlypragmatically oriented. It is often mentionedthat workplace interventions may have an effecton low back disorders.

However, from the previous chapter it is clearthat there are strong work-related risk factorsthat can be related to the occurrence of lowback disorders, so it is necessary to modify thesefactors where possible using preventionstrategies. More conclusive studies arenecessary to investigate thoroughly theeffectiveness of prevention, taking into accountthe methodological quality. In these studies it isimportant to use the global participatoryergonomics approach. This approach focuses onthe identification and evaluation of risk factorsin the task, the equipment, the workenvironment and the work organisation. Thiswill be further explained in the chapter on riskassessment.

Regarding the reduction of physical demands ofthe tasks, suitable material handling devices orother workplace aids can be selected and used.Practitioners must be aware of the advantagesand disadvantages of these devices.Furthermore, education or training may help toprevent low back disorders. This may beaccomplished by teaching the principles of backfunctioning, training in lifting techniques andtraining the body via physical fitness. Achievingsuccessful intervention is often related to theextent to which intervention philosophy isembedded in the company, including companymanagement.

To halt the further development of low backdisorders or to prevent the onset of chronic painand recurrence once pain has started, severalstrategies are also possible. As well as the so-called conservative treatment for low backdisorders (e.g. medication, bed rest, exercisetherapy) and health-care-based intervention,



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5.R I S K A S S E S S M E N T M E T H O D S

Since the exact origin or aetiology of the disorder

is often not evident and the effect of prevention

is not always positive, more research into work-

related low back disorders is necessary, both in

laboratory studies to reveal more scientific

background but also in the working environment

itself to quantify specific risks. This scientific

knowledge could be used in the development of

prevention strategies, so that these will be

acceptable to companies and practical for

implementation so that practitioners are able to

perform effective risk assessments. Buckle and

Devereux (European Agency, 1999) report themain criteria for exposure assessment methods.

In this chapter, the focus is mainly on methodsrelated to the work environment. For moreinformation on the clinical examination ofworkers with low back complaints (interview,medical examination, diagnostic tests, andelectro-physiological evaluation) see forexample Johanning, 2000.

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• objective measurement of the internalworkload: physiological and behaviouralreactions of the exposed worker.

• subjective experience of workload: by the useof questionnaires and interview techniques thepractical knowledge of the worker can becollected. The use of scales on which theworker can indicate the perceived risk for eachtask or operation gives a fast risk assessment.The accuracy of self-assessment techniques hasbeen debated, both for in terms of under-estimation and over-estimation (Bernard et al.1997). The arguments in favour of subjectivemeasurement (Wilson and Corlett, 1995) lie inthe independence of the measures and theability to acquire data that cannot be obtainedeasily by other methods (e.g. due to size limits).

The combined use of objective and subjectivedata can better indicate the risks in the worksystem. This then provides a basis for identifyingeffective measures for prevention and forassessing the changes that have beenrecommended following the ergonomic study.

It is important to mention that a method whichto one researcher or practitioner is an invaluableaid to their work, may to another be vague orinsubstantial in concept, difficult to use andvariable in its outcomes. In addition, the validity,reliability and sensitivity of methods may well beapplication specific.

Some specific instruments or techniques havebeen developed to evaluate physical load on thelower back during work tasks. Regardingassessment of physical exposure, Li and Buckle(1999) published an overview of currenttechnique with emphasis on posture-basedmethods. To evaluate lumbar load with respect tothe risk of overexertion during manual materialhandling the U.S. National Institute ofOccupational Safety and Health (NIOSH)introduced the ‘NIOSH’ method. This uses a liftingformula or equation with six task variables. A firstversion was developed in 1981, a second versionin 1991 (Walters et al. 1993). The NIOSH methodevaluates lifting demands and calculates arecommended weight limit in specific manualmaterials handling tasks, based on three criteria

5.1M E T H O D S F O R U S E I N T H E

W O R K P L A C E

In part attributable to the growing interest inergonomics in industry in recent decades,considerable effort has been made to improvethe usability and effectiveness of assessmenttechniques in the field. An ergonomic approachto work-related low back disorder risks focuseson the identification and evaluation of riskfactors in the task, the equipment, the workenvironment and the work organisation. Afteran ergonomic intervention, managementexpects specific advice as to how to improve theworking conditions and how to prevent lowback disorders. Experts in ergonomics agreethat a holistic, participatory and integratedapproach to the problem is needed produceeffective results. In this methodology, objectiveand subjective data are linked (Op De Beeck,1994a). The following items have to be lookedat simultaneously:

• objective measurements of the externalworkload: task, organisation andenvironment (physical and biomechanicalaspects)



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(biomechanical, physiological and psycho-physiological). The ‘lifting index’ provides a basisfor the identification of hazardous lifting jobs. The1991 lifting equation is applicable to a widervariety of lifting jobs than the previous method,but there are still certain limits or criteria when themethod cannot be used.

A variety of other assessment tools have been usedin ergonomic research. 3-D dynamic tools havebeen developed to measure the postures duringlifting (e.g. The Lumbar Motion, The Dortmunder,BackTracker). Furthermore, biomechanical modelsare developed to estimate the internal loading ofthe spine. With linked segment models, thelumbar net moment is used as an indicator of backload (van Dieën, 1999). The analysis ofelectromyographic signals (EMG) is often used topredict the muscle force necessary to perform atask (Hermans et al., 1999a) or to investigate ifmuscle fatigue is present by investigating thechanges in electromyographic parameters overtime (Hermans et al., 1999b). To obtain moreinformation on the use of this technique see thepublications of the SENIAM project, a largeEuropean Concerted Action on surfaceelectromyography.

Studies often use a combination of differentmethods to address physical load in a specific task.This is necessary to have a completeunderstanding of the physical load (Hermans etal., 1999a), although sometimes little agreementamong the methods is found (Lavender et al.,1999).

Measurement methods for individual andpsychosocial factors are primarily based on self-reported measures that focus on the appraisalprocess and on the emotional experience ofstress. Measures relating to appraisal need toconsider the worker’s perceptions of thedemands on them, their ability to cope withthose demands, their needs and the extent towhich they are fulfilled by work, the control theyhave over work and the support they receive inrelation to work. It is necessary to go beyondsimply asking workers whether particulardemands, etc. are present (or absent) in theirwork environments and measure various

dimensions of demand such as frequency,duration and level. Furthermore, theinteractions between perceptions is interesting,such as demand with control or demand andcontrol with support. In this context, theKarasek model is often used. More informationon the research on work-related stress can befound in the recent publication on stress of theEuropean Agency (European Agency, 2000c).



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variability between individuals can be betterunderstood (Marras, 2000).

Wilson and Corlett (1995) presented anoverview of methods for the evaluation ofhuman work. They list the main methods forexamining psycho-physiological functions (e.g.heart rate variability, critical flicker frequencytest).

Furthermore, modern epidemiological researchprinciples have been proposed to improve lowback disorder research methods and clinicaltests (Johanning, 2000; Dempsey et al., 1997).

5.2A D D I T I O N A L L A B O R A T O R Y

M E T H O D S

The understanding of the biochemical andbiomechanical properties of the vertebra, discand ligaments has been broadened by morerefined research methods. Many disciplinesincluding bioengineering, basic scienceresearch, medicine and epidemiology are nowinvolved in the analysis of low back pain.Careful characterisation of clinical findings andneurological examination of sensory changesand muscular weakness can aid in thelocalisation of a possiblemorphological/anatomical lesion and assist inthe differential diagnosis and treatment. Recenttechniques include: near infrared spectroscopy(NIRS) to measure the low-back extensoroxygenation during prolonged contractions(MacGill et al., 2000); analysis of endplatefractures in vitro or quantification of the fluidredistribution in the spinal motion undercompression (van Dieën et al., 1999b); andlaser-Doppler flowmetry to analyse myalgia ofmuscle fibres (Larsson et al., 1999). Thesetechniques are important to understand whysome people are at greater risk of developinglow back disorders than others and how



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6.F U T U R E R E S E A R C H T O P I C S

The European Agency for Safety and Health at

Work has surveyed Member States on their

future occupational safety and health research

needs and priorities (2000d). Psychosocial issues

and ergonomics, together with chemical risk

factors, emerged overall as the top priority areas

for future research. Within the field of

psychosocial issues, emphasis was placed on

stress at work. In the area of ergonomics,

particular priority was given to manual handling

and work postures. As the previous chapters

illustrated, both these areas are of importance

when discussing work-related low backDisorders.

As part of a procedure to prioritise researchneeds, the UK Health and Safety Exectutive(2000) have made a forward planning table onmusculoskeletal disorders in general. TheNational Research Council (1999), Bongers et al.(2000) and Marras (2000) have also formulatedfuture research topics for low back disorders.Based on these documents and discussion at theexpert seminar, a summary table of futureresearch themes is given in table 8. Expertopinion is that the main focus of future researchshould be the investigation of effective riskassessment methods and intervention strategiesin the workplace.

In addition there is a need to promote thesharing of research findings, for example theresults of interventions and effectiveness ofergonomic “check l ists and assessmentmethods”.

The various back disorders related to loads andother work-related musculoskeletal disordersare a continuum and not discrete topics. Theneed for a general prevention approach hasbeen explained in the previous chapter“Methods in Risk Assessment”. Consequentlysimilar research areas have been mentionedregarding research into other musculoskeletaldisorders (for example see Work-related Neckand Upper Limb Musculoskeletal Disorders,European Agency, 1999.)

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T a b l e 8 : S u m m a r y o f p o s s i b l e r e s e a r c h t h e m e s i n r e l a t i o n t o w o r k - r e l a t e dl o w b a c k d i s o r d e r s ( L B D ) .

Research topic Research issue

Extent, frequency and costs • The need for consistency in reporting data across all EU Member States: of LBD have more standardisation and greater detail in injury reports

Origin • Further research on the pathomechanisms of LBD (e.g. longitudinalstudies of back disorders using techniques such as magnetic resonanceimaging)

• Develop further models and mechanisms to investigate how tissueresponds to repetitive loading, what triggers inflammatory responsesand how these are influenced.

• Further use of laboratory studies to understand low back disorders

Risk factors • Focus the approach on “overload”• Studies into the effect of combinations of factors• The need for more detailed quantitative information regarding

exposure-disorder relationships. It may be necessary to split up thedifferent types of LBD and possible different risk factors

• Analyse if the risks for LBD differ between subjects with differentloading capabilities

• Understand the influence of non-biomechanical factors upon thebiomechanical load-tolerance relation and the risk of injury

Assessment methods • Studies to determine effective interdisciplinary approaches to theidentification of workplace risk factors

• Studies to develop and evaluate practical assessment methods, includingwith the aim of developing standardised approach

• Studies to determine effective and reliable approaches to the use ofroutine health surveillance systems to detect problems

• Need for valid quantitative exposure measures within comprehensiveepidemiological studies

• Further development of practical measurement systems

Intervention strategies • Need to evaluate the effectiveness of workplace-based actions andinterventions using high quality methodological studies, particularly todetermine what strategies and types of interventions are most successfuland why.

• Evaluation of work organisational changes• Evaluation of return-to-work and rehabilitation programmes• Study of interventions to develop criteria of what makes an effective

intervention.



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7.C O N C L U S I O N S

From the data on prevalence and cost to society

it is clear that low back disorders are an

important issue in today’s working environment.

However knowledge of low back pain is

considerable and improving and clear

approaches can be recommended to tackle the

problem. Progress has been made in the

application of ergonomics in the workplace and

in practical and effective assessment

techniques. Whilst some discrepancies are still

present in the literature it is possible to put

forward some consensus on priorities.

T h e e x t e n t o f w o r k - r e l a t e d l o w b a c k

d i s o r d e r s w i t h i n E u r o p e a n M e m b e r

S t a t e s

Recent data from the second European survey

on working conditions reveals that 30% of

European workers complain of low back

disorders. This survey and several review studies

have demonstrated that back disorder rates,

although wide spread in many occupations, vary

substantially by industry, occupation, and by job

within given industries. High prevalence rates

are found for workers in the agriculture and

construction sectors as well as in the health care

sector. Also jobs involving manual handling or

driving report high prevalence rates.

Although precise figures do not exist and the

lack of standardised criteria makes comparison

of data between Member States difficult, it is

estimated that the economic cost of all work-

related ill health ranges from 2.6 to 3.8% of

Gross National Product. In 1991, the total cost

of back pain to society in The Netherlands was

estimated to be 1.7% of GNP.

C u r r e n t k n o w l e d g e o f t h e o r i g i n o f

l o w b a c k d i s o r d e r s

In addition to the age-related natural

degenerative process, epidemiological studies

have revealed that ergonomic factors in the

workplace can lead to increased degenerative

changes in the intervertebral discs and other

structures due to chronic loading.

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Besides the disc related problems, muscular andother soft-tissue injuries are suspected when noother structural or neural abnormalities can beidentified on the basis of x-rays or bone scansand 95% of Low Back Disorders are termed“non-specific”. Injuries usually occur as aresponse to excessive load or stretch or as aresult of prolonged activation of back muscles.It is therefore useful to look at low backdisorders and the work-related risks in terms ofoverload of workplace demands on the body. Asall musculoskeletal disorders can be viewed thisway, this facilitates a common approach beingtaken to all work-related musculoskeletaldisorders.

E p i d e m i o l o g i c a l e v i d e n c e r e g a r d i n gr i s k f a c t o r s

Many review articles have been publishedinvestigating the risk factors of low backdisorders, including a multitude of physical,psychosocial and/or individual risk factors. Thenumber of epidemiological studies addressingpsychosocial r isk factors during work isconsiderably smaller than the studies focusingon physical load. In addition, the strength of theassociation is generally higher forbiomechanical physical factors. However, theempirical evidence linking psychosocial factorswith low back disorders is growing, especiallywhere physical risk factors are present. Reportedrisk factors requiring consideration in the worksystem are in respect to physical aspects: heavymanual labour, manual materials handling,awkward postures (trunk bending and/ortwisting), vibration and driving; and in respectto psychosocial work-related factors: low socialsupport and low job satisfaction.

S t r a t e g i e s f o r p r e v e n t i o n o f w o r k -r e l a t e d l o w b a c k d i s o r d e r s a n dk n o w l e d g e a b o u t t h e i r e f f e c t i v e n e s s

Strategies to prevent low back disorders includeboth workplace- based and health –care-basedinterventions. Increasingly there is recognitionthat an integrated approach including bothtypes of intervention is needed to tackle the

problem effectively. Regarding workplaceinterventions there is growing support for theeffectiveness of ergonomics (see below).Ergonomic interventions are based on a“holistic” or systems approach that considersthe effect of the equipment, the workenvironment and the work organisation, as wellas the worker. The full participation of workersin the ergonomics approach is essential for itseffectiveness.

R i s k a s s e s s m e n t m e t h o d o l o g y f o rw o r k - r e l a t e d l o w b a c k d i s o r d e r s

As described above there is evidence of theeffectiveness of the ergonomic approach forlocating risk factors and devising preventionmeasures. This approach focuses on theidentification and evaluation of risk factors inthe task, the equipment, the work environmentand the work organisation. Exposuremeasurements used in work-related studiesrange from very crude measures to complexanalytical techniques. More refined researchmethods in laboratory conditions are being usedand further developed to increase knowledge.

Using this increasing scientific knowledge,guidelines and standards have been developedand continue to be improved and refined. In thecase of risks from manual handling of loadsemployers are already provided with importantinformation to protect workers: The ManualHandling Directive (Council Directive90/269/EEC) has been made with the particularaim of preventing risks of back injuries duringmanual handling of heavy loads. It providesminimum health and safety requirements andan approach for risk assessment and prevention.Further development of guidelines andstandardised criteria are necessary to increasethe awareness of all possible problemsassociated with work-related low backdisorders, to increase the use of a standardisedapproach regarding risk assessment and toincrease the application of primary prevention inthe workplace.



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F u t u r e r e s e a r c h t o p i c s

In a report on future occupational safety andhealth research needs (European Agency,2000d) Member States prioritised stress at workand manual handling and work postures asareas for future research. There is support in theliterature for the ergonomic approach,contained in the “Manual Handling Directive”,as the basis for employers to take action. Toassist its application it is suggested that themain focus of future research on low backdisorders should be on how the ergonomicapproach can be used most effectively inpractice. Such research could include:

• Satisfactorily evaluated studies of “holistic”intervention strategies (for example:application of ergonomics; ergonomicsintegrated with rehabilitation and healthsurveillance)

• Studies to develop and evaluate practical riskassessment methods for use in the workplace

• Studies of the effect of combinations offactors and their practical assessment

It is proposed that the main focus of futureresearch be on strategies to prevent injury in thework place. However a number of areasconcerning laboratory analysis of the problem issuggested (for example: exposure measurementtechniques; joint movement measurementmethods and studies to further understand thebiochemical and biomechanical properties ofthe vertebra, disc and ligaments).



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Dr. Mark Boocock Health and Safety Laboratory (HSL)Broad LaneUK - SHEFFIELD S3 7HQ – United Kingdom

Dr. Paulien BongersTNO Work and EmploymentPolarisavenue 151 – PO Box 718NL - 2130 AS HOOFDDORP – The Netherlands

Dr. Gustav Caffier and Dr. Falk LiebersFederal Institute of Occupational Safety and HealthNöldnerstrasse 40-42D-10317 BERLIN – Germany

Dr. Jeronimo MaquedaInstituto Nacional de Seguridad e Higiene en elTrabajo (INSHT)c/Torrelaguna 73E – 28027 MADRID – Spain

Dr. Minori NakataNational Institute for Working Life (NIWL)ArbetslivsinstitutetS – 907 13 UMEA, SWEDEN

Dr. Hilkka RiihimäkiFinnish Institute of Occupational Health (FIOH)TyoterveyslaitosTopeliuksenkatu 41aAFIN - 00250 HELSINKI – Finland

Dr. Bente SchibbyeNational Institute of Occupational Health (NIOH/AMI)ArbejdsmiljoinstituttetLerso Parkallé 105DK - 2100 COPENHAGEN – Denmark

L e a d O r g a n i s a t i o n o f t h e T o p i c C e n t r eo n R e s e a r c h - W o r k a n d H e a l t h

Dr. J-L. Marié and Dr. J-C. AndréInstitut National de Recherche et de Sécurité (INRS)30 rue Olivier NoyerF-75014 PARIS FRANCE

A d d i t i o n a l e x p e r t s i n c l u d e d :Ms. Sarah CopseyEuropean Agency for Safety and Health at Work Gran Via, 33E - 48009 BILBAO - Spain

Lic. Jean-Philippe DemaretPreventRue Gachard, 88 BTE 4B - 1050 BRUSSELS – Belgium

Prof. Philippe MairiauxUniversité de LiègeService de Psychologie du Travail et des OrganisationSart Tilman IPSE Bat.B - 32 4000 LIEGE - Belgium

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

A g e n c y ’ s P r o j e c t M a n a g e rDr. M. AaltonenEuropean Agency for Safety and Health at Work Gran Via, 33E - 48009 BILBAO - Spain

P r o j e c t m e m b e r s o f t h e T o p i c C e n t r eo n R e s e a r c h - W o r k a n d H e a l t h

T a s k L e a d e r : Lic. Rik Op De BeeckPreventRue Gachard, 88 BTE 4B - 1050 BRUSSELS – Belgium

A u t h o r s :Lic. Rik Op De BeeckPreventRue Gachard, 88 BTE 4B - 1050 BRUSSELS – Belgium

Dr. Veerle HermansPreventRue Gachard, 88 BTE 4B - 1050 BRUSSELS – Belgium

T a s k M e m b e r s :Dr. Michel AptelINRS - Centre de LorraineBP 27 - Avenue de BourgogneF - 54501 VANDOEUVRE Cedex - France



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Dr. Luc QuaeghebeurCBMT, Occupational Safety and Health ServiceAd. Lacomblélaan 52 box 7B- 1040 BRUSSELS - Belgium

Dr. Jaap van DieënVrije Universiteit Amsterdam - Amsterdam Spine UnitInstitute for Fundamental and Clinical HumanMovementVan der Boechorststraat 9NL – 1081 BT Amsterdam – The Netherlands

E X P E R T W O R K S H O P o n W O R K - R E L A T E DL O W B A C K D I S O R D E R S

2 1 J u n e 2 0 0 0 , P r e v e n t o f f i c e s ,B r u s s e l s

P a r t i c i p a n t sLic. Rik Op De Beeck

Dr. Veerle Hermans

Lic. Jean-Philippe Demaret

Ms. Katie Polet

PREVENT, Belgium

Dr. Falk Liebers, FIOSH, Germany

Dr. Paulien Bongers, TNO, The Netherlands

Dr. Minori Nakata, NIWL, Sweden

Dr. Hilkka Riihimäki, FIOH, Finland

Dr. Jean Pierre Meyer, INRS, France

Mrs T. Koukoulaki, TUTB, Belgium

Ms. Sarah Copsey, European Agency for Safety andHealth at Work, Spain

S u m m a r y o f d i s c u s s i o n a n dc o n c l u s i o n s f r o m e x p e r t m e e t i n gr e g a r d i n g w o r k - r e l a t e d l o w b a c kd i s o r d e r s

A summary of the main points covered by the expertmeeting regarding prevention is given below:

• Work-related upper limb disorders and backdisorders related to handling of loads etc are acontinuum and this suggests a common, integratedapproach should be taken to the prevention of allmusculoskeletal disorders (MSD).

• Risk factors should be viewed in terms ofoverload from workplace demands on the body(e.g. combination of force, sustained force, staticforce, work organisation, stress etc). This enables acontinuum approach to be taken with other MSD. Itis a reason why for example only focusing onweights when assessing risk can be misleading.

• Work organisation is an important risk factor.

• An Integrated approach is needed-to prevention,training, surveillance, rehabilitation etc. Theeffective working of multidisciplinary occupationalhealth services is important.

• A Holistic approach to health and safety isneeded, for example not only can trips and fallscause injury, but in a susceptible, already weakenedback a slight awkward movement such as a slip ismore likely to give rise to an injury.

• Health surveillance should be used to look attrends in the workplace, not just focus onindividuals.

• Training will have success only if integrated into theoverall prevention approach and should be broaderthan only lifting techniques.

• Pre-employment screening: evidence of its valueis sparse.

• Return to work/rehabilitation: It is very importantto “stay active”. However whilst good as a generalrule this is not the correct approach for all conditions.

• Cross Europe common disease classificationwould assist a common understanding of low backdisorders.

• The Focus of future research should be on theevaluation of the effectiveness of workplaceprevention strategies. There is currently a lack ofgood evaluations of high quality, standardisedinterventions. This research should cover efficacy ofrisk assessment methods and prevention strategies;developing good practices and feasibility at theworkplace; evaluation of work organisationalchanges; workforce participation strategies; use ofroutine health surveillance; effective return-to-workprogrammes. What strategies or types ofintervention are successful? What contributes tosuccess? Such research should include assessment ofgeneral trends of what is successful and how tomake an effective evaluation.

• Support to encourage and promote the sharingof research activities and results, ergonomic“check lists” etc is needed.

• A common, integrated public health approachto the prevention of low back disorders is neededconsisting of combined and complimentary actioninside and outside workplace.


A.2C O U N C I L D I R E C T I V E

9 0 / 2 6 9 / E E C : 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 ( A N N E X I A N D I I )


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Council Directive 90/269/EEC of 29 May 1990 on theminimum health and safety requirements for the man-ual handling of loads where there is a risk particularlyof back injury to workers (fourth individual Directivewithin the meaning of Article 16 (1) of Directive89/391/EEC)

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

ANNEX 1

(*) 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 dThe manual handling of a load may present a risk par-ticularly 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 ma-

nipulated at a distance from the trunk, or with abending or twisting of the trunk,

• likely, because of its contours and/or consistency, toresult in injury to workers, particularly in the event ofa collision.

2 . P h y s i c a l e f f o r t r e q u i r e dA physical effort may present a risk particularly of backinjury 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 posture.

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 environment may in-crease a risk particularly of back injury if:

• there is not enough room, in particular vertically, tocarry out the activity,

• the floor is uneven, thus presenting tripping haz-ards, or is slippery in relation to the worker’sfootwear,

• the place of work or the working environment pre-vents the handling of loads at a safe height or withgood posture by the worker,

• there are variations in the level of the floor or theworking surface, requiring the load to be manipu-lated on different levels,

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

able.

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 yThe activity may present a risk particularly of back in-jury if it entails one or more of the following require-ments:

• over-frequent or over-prolonged physical effort in-volving in particular the spine,

• an insufficient bodily rest or recovery period,• excessive lifting, lowering or carrying distances,• a rate of work imposed by a process which cannot

be altered by the worker.

(*) With a view to making a multi-factor analysis, ref-erence may be made simultaneously to the various fac-tors listed in Annexes I and II.

ANNEX II

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

• is physically unsuited to carry out the task in ques-tion,

• is wearing unsuitable clothing, footwear or otherpersonal effects,

• does not have adequate or appropriate knowledgeor training.

(*) With a view to multi-factor analysis, reference maybe made simultaneously to the various factors listed inAnnexes I and II.



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tions that intradiscal pressure is minimised in the supineposition. However, the importance of intradiscal pres-sure in patients without a herniated disc (which is the sit-uation in most cases) remains unclear (Koes and van denHoogen, 1994). The authors concluded from their re-view that short periods of bed rest (2 or 5 days) were aseffective as longer periods (4 or 8 days) and have lessside effects (absenteeism from work and return to nor-mal level of activities). Also Scheer et al. (1995) found inthe literature three studies that favoured a brief periodof bed rest, on average 3 days, for acute non-radicularlow back pain. Van der Weide et al. (1997) found limit-ed or moderate evidence for the efficacy of a short peri-od of bed rest for acute low back pain patients and eventhe avoidance of bed rest. Normal activity should be con-tinued as much as possible. Adverse effects of bed restare joint stiffness, muscle wasting, loss of bone mineraldensity, pressure sores and venous thrombo-embolism(van Tulder et al., 1999).

1 . 2 S p i n a l m a n i p u l a t i o nVan der Weide et al. (1997) found moderate evidencethat spinal manipulation is more effective in the shortrun than other conservative types of treatment, such asphysiotherapy, at least for patients without radiatingpain. Contrary, van Tulder et al. (1999) mention con-flicting evidence.

1 . 3 E x e r c i s e t h e r a p yFor a population with more severe low back pain, exer-cise therapy may expedite a sense of well being soonerthan a placebo, but there is insufficient data to substan-tiate the trend. The benefits of the exercise approach aremaximal when individualised (Scheer et al, 1995). Koeset al. (1994) concluded that the most promising type ofintervention was the more intensive back schools. Vander Weide et al. (1997) found no evidence that this ther-apy was more effective than usual medical care. Van Tul-der et al. (1999) found strong evidence that exercisetherapy was equally as effective as physiotherapy.

1 . 4 M e d i c a t i o nVan Tulder et al. (1999) reviewed the effectiveness ofconservative treatment of acute low back pain. Belowsome of the effects of medication are summarised.

Non-steroidal anti-inflammatory drugs (NSAIDs) areused for their analgesic potential and their anti-inflam-matory action. There is strong evidence that NSAIDsare effective for short-term symptomatic relief in pa-tients with uncomplicated low back disorders, but areless effective or even ineffective in patients with sciati-ca since they do not relieve radicular pain. There ismoderate evidence that analgesics are not more effec-tive than NSAIDS. There is considerable evidence thatanalgesics provide short-term pain relief. There is con-flicting evidence regarding antidepressants versusplacebos on pain relief, also regarding colchicine. On

It is important to distinguish the different phases in thehistory of low back disorders, since prevention will differaccording to the specific phase. Often an acute, sub-acute and a chronic phase is mentioned. Regarding theexact duration of the acute phase and the start of thesub-acute phase, often contradictory results are found.The start of the chronic phase (and often mentioned thenecessity for tertiary prevention) is mostly mentioned tobe 3 months after symptom onset (e.g. Scheer et al.,1997; van der Weide et al., 1997; Frank et al., 1996b).

In this review interventions for acute and chronic lowback pain are mentioned, based on several studies. Franket al. (1996b) compared two reviews on the effectivenessof health care interventions in the USA and in the UK. Inthe Netherlands, the Dutch standard for low back paingives several recommendations (Faas et al., 1996) and ex-tensive studies on effectiveness of prevention strategiesare performed by Van Tulder and colleagues (1999). AlsoAbenhaim et al. (2000) and Carter and Birrell (2000)mention guidelines and possible interventions.

1 . I n t e r v e n t i o n s f o r a c u t e L o w B a c kD i s o r d e r s

1 . 1 B e d r e s tA period of bed rest was traditionally recommended forpatients suffering from an attack of acute back pain. Therationale for this was that patients experience relief ofsymptoms in the supine position and there are indica-

A.3O V E R V I E W O F

S E C O N D A R Y / T E R T I A R Y

I N T E R V E N T I O N S .



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the other hand, there is strong evidence that muscle re-laxants reduce pain and that different types are equal-ly effective in cases of acute low back pain. There ismoderate evidence that epidural steroid injections arenot useful in the treatment of acute low back pain.

2 . I n t e r v e n t i o n s f o r c h r o n i c l o w b a c kd i s o r d e r s

2 . 1 B e d r e s tThere is strong evidence that advice to stay active is as-sociated with equivalent or faster symptomatic recov-ery, and leads to less chronic disability and less time offwork than bed rest or usual care (van Tulder et al.,1999). Furthermore, Abenhaim et al. (2000) state thatpatients should maintain or resume their work activi-ties as far as the pain allows. Implementation of thisrecommendation should not be problematical, as longas the various stakeholders are convinced of the ne-cessity of minimising the duration of work absence (thechances of a timely return to work decline as the dura-tion of work absence increases), and there are no dele-terious effects of early return to work. Of course thisdepends on the diagnosis and severity of the individualback pain status.

When, after several weeks of treatment, a patient con-tinues to experience problems adapting to occupation-al activities, physicians should alert the worker’soccupational medical staff, if not initiate occupationalretraining. This recommendation is yet another reflec-tion of the necessity of minimising the duration ofwork absence, to avoid compromising the probabilityof returning to work. These steps should be taken asearly as possible, in contrast to the current practice. Itis important for all stakeholders to understand theneed to address the occupational future of patientsearlier than is often the case currently. The probabilityof returning to work is only approximately 50% after 6months of work absence and is only approximately30% after an absence of 1 year. Improving treatmentand rehabilitation methods should help to improvethese figures.

Also Carter and Birrell (2000) suggest for the manage-ment of workers with back pain encouraging theworker to remain in his or her job or to return at an ear-ly stage, even if there is still some pain. The followingsteps can facilitate this:

• Initiate communication with their primary healthcare professional early in treatment and rehabilita-tion

• Advise the worker to continue as normally as possi-ble and provide support to achieve this

• Advise employers on the actions required, whichmay include maintaining sympathetic contact withthe absent worker.

• Consider temporary adaptations of the job or pat-tern of work

2 . 2 S p i n a l m a n i p u l a t i o nNo evidence for the efficacy of spinal manipulation forchronic patients was found, whether compared to aplacebo or to other treatments (van der Weide et al.1997). Also van Tulder et al. (1999) mention conflictingresults.

2 . 3 E x e r c i s e t h e r a p yVan der Weide et al. (1997) found no evidence thatback school/exercise therapy is more effective thanusual care. Van Tulder et al. (1999) found strong evi-dence that exercise therapy is equally effective as phys-iotherapy and more effective than usual care by thegeneral practitioner in chronic low back pain. Scheer etal. (1997) could not draw any conclusions for the val-ue of exercise due to a limited group of studies. How-ever, in one of the four investigated studies, reducedwork disability days were mentioned when an individ-ual approach was adopted.

2 . 4 O r t h o s e sThe use of braces or orthoses increases with the dura-tion of pain. The rationale for using orthoses variesfrom restriction in performing spinal movements, pos-tural corrections (making the patient sit and stand in asupposedly better position) or the increase of the ab-dominal pressure, allowing a substantial proportion ofbody-load to be transmitted through the abdomenrather than through the spine. Also that generatedwarmth (by enclosing the skin) decreases the pain sen-sation, is suggested (Koes and van den Hoogen, 1994).However, most of these hypotheses have recently beencriticised (cf. supra) and it is concluded that no evi-dence is found that lumbar supports are effective inacute and chronic low back pain.

2 . 5 M e d i c a t i o nLimited evidence was found for efficacy of antidepres-sants, but no evidence for non-steroidal anti-inflam-matory drugs (van der Weide et al., 1997). Also in aprevious review of van Tulder et al. (1996), no evidencewas found for the efficacy of analgesics or muscle re-laxants. Only one study was found on epidural injec-tions. Again comments on the quality of the studieswere given.

3 . C o g n i t i v e a n d b e h a v i o u r a ls t r a t e g i e sA diverse array of psychological approaches and out-come measures are present, e.g. coping strategies,conditioning, stress reduction or relaxation, biofeed-back and/or use of imagery (Scheer et al., 1997). Theauthors reported the results of five high quality studiesand concluded that the idea that cognitive and behav-ioural strategies were effective in affecting vocational-



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ly relevant outcomes could not be supported. Recently,van Tulder et al. (1999) concluded that there was evi-dence that behavioural therapy had a moderate effecton pain, and a mild effect on disability compared to notreatment in chronic low back pain at all.

Carter and Birell (2000) mention beliefs and behaviourson the part of the patient that may predict poor results:

• A belief that back pain is harmful or potentially se-verely disabling

• Fear-avoidance behaviour and reduced activity levels• Tendency to low mood and withdrawal from social

interaction• Expectation of passive treatment(s) rather than a be-

lief that active participation will help

The moderate effect of antidepressants for conserva-tive treatment of acute and chronic low back pain (VanTulder et al., 1999) may reveal that there are some pa-tients who show psychological signs (such as tendencyto low mood and withdrawal from social interaction).This may be related to the vicious circle where not onlymuscles but also the central nervous system are con-cerned with pain (Johansson and Soika, 1991).


European Agency for Safety and Health at Work

Research on work-related low back disorders

Luxembourg: Office for Official Publications of the European Communities

2000 — 71 pp. — 14.8 x 21 cm

ISBN 92-95007-02-6

Price (excluding VAT) in Luxembourg: EUR 7


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