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Work-Related Musculoskeletal

Disorders

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DEFINITION OF WMSDs• Many different names

• Defined differently in different studies. WMSDs are defined by the World Health

Organisation as multi factorial where a number of risk factors contribute significantly to their development. The risk factors are classified as physical, work organisational, psychosocial, individual, or social-cultural (HSE, 1999).

NIOSH defines WMSDs as “those diseases and injuries that affect the musculoskeletal, peripheral nervous, and neurovascular systems that are caused or aggravated by occupational exposure to ergonomic hazards” (NIOSH, 1997).

• Injuries from mechanical stress caused by doing a certain job repeatedly or over a long period, these injuries will lead to abnormal conditions.

ABBREVIATIONFULL NAMECOUNTRY

RSIRepetitive Strain InjuryGreat Britain, Canada, Australia, Holland

WRULDsWork-related Upper Limb DisordersGreat Britain

CTDCumulative Trauma DisorderUnited States

ULDUpper Limb DisorderGreat Britain

OCDOccupational Cervicobrachial DisorderJapan, Scandinavia

OOSOccupational Overuse SyndromeAustralia, New Zeeland

MSDMusculoSkeletal DisorderHolland

WMSDWork-Related MusculoSkeletal DisorderWorldwide

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Cost of WMSDs•The precise cost of WMSDs is not known.

• Estimates vary depending on the method used.

•The overall cost to the British economy of all work accidents (including avoidable non-injury accidental events) and work-related ill health is estimated to be between £6 billion and £12 billion annually. This is equivalent to between 1% and 2% of total Gross Domestic Product per year (Davies and Teasdale, 1994).

•A conservative estimate published by NIOSH is $13 billion in the United States annually (NIOSH, 1996). Another estimate is $20 billion annually (AFL-CIO, 1997). It was estimated that the mean compensation cost per case of WMSDs was $8070 in 1993 (Webster and Snook, 1994).

•In general and regardless of the estimate used, the problem is large both in health and economic term (NIOSH, 1997). However, estimates may be inaccurate and in terms of cost need to include the medical costs, the workplace costs, and the effect on the quality of life of the sufferer.

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WMSDs RISK FACTORS• The World Health Organization

characterizes “work-related” diseases as multi-factorial to indicate that a number of risk factors (e.g., physical, work organizational, psychosocial, individual, and socio-cultural) contribute to causing these diseases (WHO, 1985).

• One important reason for the controversy surrounding work-related WMSDs is their multi-factorial nature.

• The disagreement centres on the relative importance of multiple and individual factors in the development of disease.

• HSE, (2002), classified WMSDs risk factors as:

Task-related factors, Environment-related factors, Psychosocial factors and Worker-related factors.

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WMSDs Risk Factors List:• Posture• Force• Velocity/Acceleration• Repetition• Duration• Recovery time• Workload and pacing• Cognitive demands• Hand-Arm vibration• Cold stress• Lighting• Psychosocial factors

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Some Examples of WMSDs

Shoulder Tendonitis

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Lateral epicondylitis

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Carpal Tunnel Syndrome

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ERGONOMIC WORK ASSESSMENT PROCESS:

• Assessing the risk of WMSDs is a major stage in the frame work presented by HSE, (2002), aimed for the management of MSDs risks.

• This stage usually involves two major

steps:

1. The first step is identifying problem tasks.

2. The second step is risk assessment.

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Simple Conceptual Model of an Intervention (Buckle, 1997)

Characteristics:

1.Badness- not measured, but assumed

2.Much initial effort, rarely seen through to full

implementation

3.Goodness- not measured, but assumed

1 1 BadBad

2 Ergonomic2 ErgonomicInterventionIntervention 3 Good3 Good

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Advanced Conceptual Model of an Intervention (Buckle, 1997)

To Tint T1 T2

Base line Assessment Re-assessment of Re-assessment of

Of Exposure/Effects Exposure/Effects Exposure/Effects

And Confounders And Confounders And Confounders

InterventioIntervention Groupn Group

ErgonomicErgonomicInterventioInterventionn

Control Group

TToo : Time lag before any intervention is : Time lag before any intervention is conducted conducted

TTintint : Initial time (when intervention is : Initial time (when intervention is conducted)conducted)

TT11 : Time lag 1 : Time lag 1

TT22 : Time lag 2 : Time lag 2

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Exposure and Effect Curves- Hypothetical Intervention Group

(Buckle, 1997)

Effect

Magnitude

Exposure

T0 Intervention T1 T2 T3 T4

TToo: Time lag before any intervention is conducted : Time lag before any intervention is conducted

TTi i :Time lag at stage i after intervention:Time lag at stage i after intervention

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Exposure and Effect Curves- Hypothetical Intervention & Control Group

(Buckle, 1997)

Control Group

Magnitude of MSDs (B)

Intervention Group Effect

Magnitude Intervention Group Exposure

Control Group Magnitude of MSDs (A)

T 0 Intervention T1 T2 T3 T4

TToo: Time lag before any intervention is conducted : Time lag before any intervention is conducted

TTi i :Time lag at stage i after intervention:Time lag at stage i after intervention

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PHYSICAL EXPOSURE ASSESSMENT TECHNIQUES

• Various methods are available for assessing exposure to the risk associated with MSDs. Li and Buckle, (1999), classified these methods as follows:

• Observational methods

Pen-paper based observational methods

Videotaping and computer-aided observational methods

• Direct methods

Posture assessment

Postural strain or local muscle fatigue assessment

• Self-report on physical work load

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RULA & QEC AUTOMATION

Why do we need to computerise?

Manual calculations are time consuming and vulnerable to error.

Few programs are available for RULA, only one program is available for QEC, and no program is available for QEC2003.

Available programs are expensive and large in size.

Computing time is nearly the same for manual calculations.

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RULARapid Upper Limb

Assessment Developed by McAtamney and

Corlett in 1993. Used for the assessment of the

severity of postural loading. Uses numbered divided sections for

the movement of each upper body part (head, trunk, upper and lower arms, wrist).

A minimum value is given to the range of movement that has minimum risk factors.

static or repetitive muscle work and force exertion is also considered.

action list indicating the level of intervention needed is then calculated.

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QECQuick Exposure Check

Developed by Li and Buckle in 1998.

Takes into account the back posture, movement frequency, height of the task, wrist posture, neck twisting, weight handled, time, force, vibration, visual demand, difficulty keeping up work and the stressfulness of the work.

QEC analysis gives exposure scores to the back, shoulder/arm, wrist/hand and neck.

QEC is sensitive to the change in exposure before and after an ergonomic intervention, and is suitable for comparing exposure either between operators performing the same task, or between people performing different tasks.

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QEC2003

• In 2003, a new version of QEC was developed by David et al., (2003), to improve the scope, usability and validity of QEC.

• The main features of the new QEC

version are: A one-page assessment sheet with re-

worded questions for the observer and the worker.

Improvement to the format of the scoring sheet.

A new variable in the observation sheet to calculate the driving exposure.

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RULA Software Development

• Developed using QBASIC and then using VISUAL BASIC.

• The software consists of 8 screens for entries input and one screen to show the results.

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QEC & QEC2003 Software Development

• Both Versions were developed using QBASIC and then using VISUAL BASIC.

• Both Versions consist of 2 screens for entries input and one screen to show the results.

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Software Validation

• The three programs are very efficient, reliable, practical, and incredibly small in size according to Dr. Guangian Li (a co-author of the QEC method).

• Total agreement with two statements describing the three software as being easy to use and saving time over the three manual methods by 10 postgraduate students.

• The three programs were used in a laboratory based ergonomic intervention study involving more than 1150 manual assembly tasks and in an ergonomic study in an automotive plant involving more than 500 manual assembly tasks and were found to be very useful, fast, efficient, and reliable when compared to the manual procedures needed to obtain the scores.

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Conclusion

• The three programs provided a practical and more efficient alternative to the manual procedures needed for obtaining the scores for QEC and RULA.

• Valuable time and resources could be saved if these programs were opted for obtaining the scores.

• The programs are very small in size and could be easily embedded or linked to any database or statistical package to enable the storage and further analysis of the results.

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THAT’S IT