Chapter 9 – Joint Hypermobility and Work-related Musculoskeletal Disorders (WRMSD)

CHAPTER CONTENTS

Definition of work-related musculoskeletal disorders(WRMSD) 127

Risk factors associated with WRMSD 128Multifactorial 128

Models for the pathogenesis of WRMSD 130Repetitive movement 131

Definition 131Repetitive movement biological responses and

pathology 131Repetitive movement vulnerability of the hyperrnobile

Individual 131Force 132

Definition 132Force biological responses and pathology 132Force: vulnerability of the hypermobile

Individual 132Awkward posture 133

Definition 133Awkward postures biological responses

and pathology 133Awkward postures: vulnerability of

the hypermobile Individual 134Static postures 134

Definition 134Static postures biological responses

and pathology 134Static postures vulnerability of the hvperrnobue

Individual 135Whole body vibration (WBV) 135

Definition 135Whole body vibration biological responses and

pathology 135Whole body vibration vulnerability of the hvperrnobne

Individual 135Cool temperatures 135

Cool temperatures biological responses andpathology 135

Cool temperatures vulneraouuy of the hypermobileIndividual 136

Psychosocial Issues 136Psychosocial issues biological responses and

pathology 136Psychosocial issues vulnerability of the hvperrnobile

individual 136

Application of ergonomic principles to reducethe risk of WRMSD in the hypermobileindividual 136

Ergonomics: the balance 137Primary prevention 137

Surveillance identilymq vulnerable JOintsand tissue 137

Education and training awareness of risk factors andrecommended posture, work practices and manualhandling techniques 137

Ergonomic assessment and management 138Secondary prevention 138

Job restrictions and task modifications 138Education and training to prevent persistence or

recurrence of Injury 139Ergonomic assessment and management 139

Tertiary prevention 139Rehabilitation and gradual return to work/conditioning

139Ergonomic assessment and management 140

Conclusion 140

9

Joint hypermobility andwork-relatedmusculoskeletaldisorders (WRMSD)

Jean Mangharam

Aims1. To provide the reader with background

information about WRMSD, including thedefinition, associated risk factors, proposedpathogeneses, and the associated biologicalresponses and pathology

2. To explore the potential impact of havinghypermobile joints and lax tissue on thedevelopment of WRMSD

3. To discuss pertinent ergonomic principlesand propose suitable applications.

DEFINITION OF WORK-RELATEDMUSCULOSKELETAL DISORDERS(WRMSD)

The prevalence of musculoskeletal disorders(primarily of the neck, upper limb and back)among the workforce of European UnionMember States and the United States of Americais high and continues to be a major reason forillness and financial burden in the workplace(Violante et al. 2000, European Agency for Safetyand Health at Work (EASHW) 1999, Kumar 2001).There is growing worldwide concern about theprevalence of musculoskeletal disorders in theworkplace. International meetings and workshops such as the one carried out in April 1998 bythe World Health Organization in Sweden, andseveral large-scale projects to investigate the problem, have been commissioned by national and

127

128 HYPERMOBILITY SYNDROME

international bodies. Three such investigationsand reviews include:

• NIOSH (1997) The National Institutefor Occupational Safety and Health(USA) carried out an extensive criticalreview of epidemiological evidence forwork-related musculoskeletal disorders forthe neck, upper extremity and low back.The review identified a number of specificphysical exposures strongly associated withspecific WRMSD, especially when exposureswere intense, prolonged, and particularlywhen workers were exposed to severalrisk factors.

• European Agency for Safety andHealth at Work (EASHW) (1999) TheEuropean Agency for Safety and Health atWork requested the Robbens Institute,University of Surrey, to describe and assessfindings of relevant research related towork-related upper limb disorders (WRULD).The review was detailed and systematicin its presentation of the nature of theproblem, and proposed models ofpathogenesis, biological responses andstrategies for prevention.

• National Research Council (1999)The National Institutes of Health (NIH)in the USA requested that the NationalAcademy of Sciences and NationalResearch Council convene a panel of expertsto carefully examine questions raised byCongress concerning occupationalmusculoskeletal disorders. Comprehensiveinformation related to tissue mechanics,biological responses and proposed theoriesabout the interaction between workplaceextrinsic and individual intrinsic factorswere presented.

'Work-related musculoskeletal disorders' (WRMSD)is an umbrella term used to describe musculoskeletal disorders which have been associated withthe work of the affected person. The term 'workrelated upper limb disorders' (WRULD) refers

particularly to work-related musculoskeletal disorders of the neck and upper limb. Several termshave been used to describe WRULD, includingrepetitive strain injury (RSI in Australia andthe UK), occupational overuse syndrome (OOSin Australia), cumulative trauma disorders (CTDin USA), occupational cervicobrachial disorder(OCBD in Japan, Switzerland and Sweden),tension headache and occupational disorder (inFinland) and Occupational Complaint Number2101 (in the former Federal Republic of Germany)(Ireland 1995).

The term WRMSD does not suggest or implyaetiology, nor specify a risk factor or anatomicalregion affected. It suggests that the disorder ismusculoskeletal in nature and is related to theoccupation of those affected. The primary reasonfor the controversy surrounding the terminologyand classification of WRMSD is its complex multifactorial aetiology, progression and prognosis(NIOSH 1997, Mayer et al. 2000). The WorldHealth Organization clarified this by stating that'Work-related diseases may be partially caused byadverse working conditions. They may be aggravated, accelerated or exacerbated by workplaceexposures and they may impair working capacity.Personal characteristics and other environmentaland sociocultural factors usually play a role asrisk factors in work-related diseases; whichmay often be more common than occupationaldisease' (WHO 1985, Identification and Controlof Work Related Diseases. Technical Report No.174. General: World Health Organization, citedin National Research Council and Institute ofMedicine 2001).

RISK FACTORS ASSOCIATEDWITHWRMSD

Multifactorial

NIOSH (1997) found that the epidemiologicalstudies investigating the role of physical factors,work organizational and psychosocial factors in the

JOINT HYPERMOBILITY AND WORK·RELATED MUSCULOSKELETAL DISORDERS 129

development of WRMSD for the neck, shoulder,elbow, hand and back were not guided by anestablished and consistent definition of WRMSD.The presentation of WRMSD may have been basedon clinical pathology, the presence of symptoms,objective pathological processes and/or workdisability (e.g. days away from work). Of thestudies reviewed, the most common health outcome was the occurrence of pain.

NIOSH (1997)and European Agency for Safetyand Health at Work (1999) have both stated thatthe lack of standardized criteria for definingWRMSD makes investigation and comparisonbetween studies difficult. NIOSH (1997) pointsout that it would be useful to have a concisepathophysiological definition and correspondingobjective clinical test for each WRMSD, to translate the degree of tissue damage or dysfunctioninto an estimate of current or future disability andprognosis. However, clinically defined WRMSDoften have no clearly delineated pathophysiological mechanisms for pathological processes.

Reviews of studies have shown that the physical risk factors that have been associated withWRMSD include repetitive movement, forcefulmovements, heavy physical work, awkward postures, static postures, contact stress (local mechanical pressure or high-impact external forces),hand-tool vibration, whole body vibration andcool temperatures (NIOSH 1997,European Agencyfor Safety and Health at Work 1999, NationalResearch Council 1999).

NIOSH (1997) summarized the causal relationship between physical work factors and WRMSD(Table9.1). The studies reviewed displayed strongevidence of a causal relationship between postureas a risk factor on neck/shoulder disorders; acombination of risk factors (repetition, force andposture) on elbow disorders; a combination ofphysical risk factors (repetition, force, posture andvibration) on carpal tunnel syndrome; a combination of physical risk factors (repetition, force andposture) on hand/wrist tendonitis, vibration onhand-arm vibration syndrome; and lifting/ forceful movements and whole body vibration on

Table 9.1 Evidence for causal relationship betweenphysical work and WRMSD (NIOSH 1997)

Body part Strong Evidence Insufficient EvidenceRisk factor evidence evidence of no effect

NeckandnecWshou~er

Repetition V'Force V'Posture V'Vibration V'

ShoulderPosture V'Force V'Repetition V'Vibration V'

ElbowRepetition V'Force V'Posture V'Combination V'

Hand/wrist - carpal tunnel syndromeRepetition V'Force V'Posture V'Vibration V'Combination V'

Hand/wrist - tendonitisRepetition V'Force V'Posture V'Combination V'

Hand-arm vibration syndromeVibration V'

BackLifting/ V'

forcefulmovements

Awkward V'posture

Heavy V'physicalwork

Whole body V'vibration

Static work V'posture

back disorders. There was insufficient evidenceof a causal relationship between vibration andneck/shoulder disorders; force and vibration onshoulder disorders; repetition and posture onelbow disorders; posture on carpal tunnel syndrome; and static work postures on back disorders. It was pointed out that high-risk jobs wouldtypically be composed of tasks that expose theworker to one or more risk factors.


MODELS FOR THE PATHOGENESISOFWRMSD

Several conceptual models have been designedto explain how multiple factors may interact toincrease the propensity of an individual to developa work-related musculoskeletal disorder.

A dose-response model for neck and upperlimb disorders was developed by researchersfrom Denmark, Finland, Sweden, England andthe United States (Armstrong et al. 1993). Themodel described four domains: exposure, dose,capacity and response. These factors interactwithin a model which considers the intrinsic andextrinsic influencing factors. This model emphasizes the cumulative nature of work-related neckand upper limb disorders.

A model developed by the National ResearchCouncil (1999) shows how environmental workfactors and the individual's personal factorscan have an impact on the physiological pathways, progression and outcome of a WRMSD. Themodel shows how individual factors and external factors, including external loads, organizational factors and social context, can have an

influence on the biomechanicalloading (internalloading and physiological responses), internaltolerances (mechanical strain and subsequentfatigue) and outcomes (pain/discomfort and subsequent impairment/disability). Arrows betweenthe workplace factors and the person (Fig. 9.1)indicate the various research disciplines (epidemiology, biomechanics, physiology etc.) that haveattempted to explain the relationship.

The model incorporates the role of variousfactors associated with WRMSD, including workprocedures, equipment, environment, organizational factors, individual physical and psychological factors, non-work related activities andsocial factors. The central physiological pathwayshows the biomechanical relationship betweenload and the biological response of tissue. Loadsof various magnitudes can change the form oftissues throughout the day (e.g. changes secondary to fatigue and work pattern or style). Thebiomechanical loading can lead to symptomaticand asymptomatic responses. If the load exceedsa mechanical tolerance, tissue damage or reactions will occur. The feedback mechanisms (e.g.pain) can influence the biomechanical loading

Figure 9.1 Conceptual framework of physiological pathways and factors that potentially contribute to musculoskeletaldisorders from National Research Council 1999. with permission from the National Academy of Sciences

JOINT HYPERMOBILITY AND WORK-RELATED MUSCULOSKELETAL DISORDERS 131

and load-response relationship. Adaptation mayincrease the tolerance for greater biomechanicalloading, or allow tissues to sustain a greater loaduntil tissue tolerance is exceeded. The symptomand adaptation outcome may subsequently interact with each other. Functional impairment mayresult from the responses, symptoms and adaptations. Disability may ensue if the resultantimpairment is severe. Similarly, and sometimesconcurrently with physical loading, undesirableorganizational factors and the social context, ifsufficiently intense, can influence the way inwhich the individual will respond and progresswith problems. Individual physical and psychological factors and non-work related activitiesmay also have an influence on the physiologicalpathways.

Repetitive movement

Definition

Repetitive movement usually refers to the execution of cyclical patterns of movement withoutregular pauses or breaks between the cycles.These cyclical movement patterns are usuallyexecuted to complete subtasks within a task, anda job would usually be composed of a variety oftasks. The level of risk imposed by repetitivemovement will depend on the frequency of thecycle, the force required during the movement,the duration of the cyclical movement, thefrequency and duration of breaks within andbetween subtasks, and the total cumulative exposure period. Often, the upper limbs, especiallythe smaller joints (e.g. fingers and wrists), aredynamic during repetitive movement, as thesetasks usually require high manual dexterity (e.g.typing or playing a musical instrument). Duringthese tasks, central and core muscles contractto stabilize the skeletal system while peripheralmusculature carries out repetitive contractionand relaxation (e.g. keyboard interaction requiresrepetitive finger flexion/ extension/ abduction/adduction while the wrist, elbow, shoulder andshoulder girdle remain static).

Repetitive movement: biologicalresponses and pathology

It has been found that repeated loading of tendons,especially if the load is tensile and in a transversedirection (e.g. gripping, passing bony structuresor adjacent tissue, in awkward postures or end ofrange), increases the risk of an injury (Armstronget al. 1984, Goldstein et al. 1987). The collagenfibres may separate from one another followingrepetitive activity, resulting in swelling and pain(Chaffin and Andersen 1991). The swelling maychange the coefficient of friction between thetendon and the sheath, leading to irritation of thetissues as the tendon glides repetitively within itssheath. A tendonitis or tenosynovitis may result.Histological changes have been found followingtendon loading (Backman et al. 1990).

Repetitive movement: vulnerability of thehypermobile individual

Joint hypermobility syndrome (JHS) patientshave been thought to be susceptible to tendonitisof the upper and lower limbs. The explanationmay be that there is a variation in the propertiesof their tendon collagen. Both deficiencies incollagen production and deficiencies in collagen turnover have now been recognized in different variants of Ehlers-Danlos syndrome (EDS)(Beighton et al. 1998, Miller and Gay 1987).Garcia-Cruz et al. (1998) found defective connective tissue in familial articular hypermobilitysyndrome. Biochemical (collagen types) andmorphological variations were found (generaldisorganization of dermal components, showinga loose collagen network characterized by thickbundles).

Despite the above findings, Larsson et al. (1993)suggests that hypermobility may be an asset tomusicians, who require repetitive movement oftheir joints. Results showed that musculoskeletalsymptoms associated with practice and performance may be due to lack of hypermobility of somejoints involved in intensive repetitive movement.Subjects who played instruments requiring much


more repetitive motion had symptoms thataffected their joints less often if the joints involvedwere hypermobile than if they were not. Larssonet al. (1995) reinforced their findings in ind ustrialworkers, when they showed that the individualwith a hypermobile spine was less susceptibleto back pain, in jobs requiring changing bodypostures.

Force

Definition

Force may be a risk factor in situations whenthe force required to carry out a task (one-offor cumulative) exceeds that which can be created(active) or withstood (passive) by the individual'smusculoskeletal system. Excessive stress or straincan result from a single forceful mechanical event(e.g. lifting, catching), from an interaction withthe environment (e.g. a fall), or from accumulatedstrain associated with loading of a structure.Probably - and more commonly - excessive tissuestrain can be caused by a combination of a singlehigh-force event superimposed on weak structures secondary to a history of repetitive loading(Ashton-Miller 1999). Force can be defined asexternal or internal, imposed either externally asa load, or internally created by a motor responseor passive tensile stretch of connective tissue.

Force: biological responses and pathology

Muscle injury The sarcomeres of musclesmay be damaged morphologically at focal pointssecondary to mechanical disruption duringcontraction-induced injuries. The inflammatoryresponse may further damage the muscle units.Striated muscle appears to be at higher risk ofbeing damaged during activation and being forcibly stretched, rather than during the isometricphase of muscular contraction. The stretch maybe self-initiated or secondary to external loading (Ashton-Miller 1999). Edwards (1988) hypothesized that eccentric contractions have a highpotential for muscle damage.

Passive tensile structures Collagen provides the tensile strength in dense regular connective tissue. Collagen is an extremely activesubstance that is sensitive to loading history.Fluctuating loading usually promotes collagenturnover, whereas static loading may lead to collagen atrophy. The turnover in avascular structuressuch as intervertebral discs takes much longer,and the various types of collagen have differentturnover rates (Ashton-Miller 1999).

Joint surface Radwin and Lavender (1999)discussed the findings of bone response to internal tissue loading. Several authors have reportedthat osteoarthritis in the hip and knees is moreprevalent in individuals employed in occupations that experience greater loading of the lowerextremity.

Intervertebral disc Researchers have foundthat prolapsed discs occur more frequently inthe forward flexed position (Adams and Hutton1982). In flexion, the anterior portion undergoescompression and the posterior portion of theannulus fibrosis is under tensile stretch. The disc,especially the vertebral endplate, is particularlysusceptible to repetitive loading and large compressive forces in the forward flexed position(Radwin and Lavender 1999).

Force: vulnerability of thehypermobile individual

For the hypermobile individual, it appears thatseveral structures may be vulnerable whenhigh forces are imposed. Muscle strain has notparticularly been presented as an issue for thehypermobile individual. However, passive tensile structures, bone structures and joint surfaceshave been presented as being vulnerable forthe hypermobile individual when placed understress.

Magnusson et al. (2001) showed that the passive properties of the hamstring muscle tendonunit of JHS patients are similar to those of controls. However, their results suggest that JHS


patients have a greater subjective tolerance topassive stretch, displaying greater maximal stretchangle (stretch sensation without pain) and corresponding peak moment.

Nijs et al. (2000) found that spinal and femoralbone densities (volumetric total and corticalbone at the radius) were lower in hypermobileindividuals, after correction for body mass index.Comparisons were made between 25 female (Caucasian) hyperrnobile individuals aged between 19and 57 years, and a corresponding age-matchedreference population. In contrast, an earlier studyby Mishra et al. (1996) found that although 31% of58 patients with joint hypermobility syndromehad significant arthralgia, there was no significantreduction in bone mineral density.

Proprioception is critical for the maintenanceof joint stability. Studies have demonstrated thatproprioception is less accurate in patients withhypermobility syndrome (Hall et al. 1995). Pathways between proprioceptive inaccuracy, kneeosteoarthritis and related knee disorders havebeen suggested (Sharma 1999, Sharma and Pai1997).

The vertebral column is stabilized by intersegmental muscles (e.g. multifidus, rotares, interspinales and intertransversarii) (Oliver andMiddleditch, 2000). Whereas spinal stabilitytends to occur at the segmental level, the moresuperficial longitudinal muscles counterbalanceexternal loads and achieve movement more successfully. Proprioception at the segmental levelwould therefore be especially beneficial toreduce the risk of injury of the facet joints andintervertebral discs. Because of proprioceptionlimitations, the hypermobile individual has beenthought to be at greater risk of spinal injury.Howes and Isdale (1971) stated that the 'looseback' syndrome is accepted as being more common than originally thought.

Despite findings from the above studies,Larsson et al. (1995) showed that there were nosignificant effects of tasks involving heavy liftingon hyperrnobile versus non-hypermobile individuals. However, the number of industrial workers

whose primary tasks involved heavy lifting inthe study was limited (12 females and 24 males).

Beighton et al. (1999)pointed out that throughout the literature it is widely thought that premature osteoarthritis may be a direct consequence ofhypermobility. However, final proof may onlyfollow a large and perspective long-term study(Beighton et al. 1998).

Awkward posture

DefinitionAwkward posture, as a risk factor, usually refersto working in a joint range that is not in neutraland which is often not optimal for muscular forcegeneration. Awkward postures may result froman individual engaging in poor or suboptimalwork practices and postures, or working withpoor tool design, furniture design, equipmentdesign and/or physical man-machine interfaces.

Awkward postures: biological responsesandpathologyAwkward postures often require muscles to exerta force in a range which is not optimal for forcegeneration (either in shortened or lengthenedposition), potentially leading to strain. Awkwardpostures may also place adverse forces on jointsurfaces which are not coupled with congruence,or compressive and stretching forces on various components of the musculoskeletal system,including muscles, discs, tendons, joint capsules,ligaments, connective tissue and nerve tissue.Should the awkward postures be repeated or sustained during static work, impairments of variouscomponents of the musculoskeletal system andtheir interaction may be affected. Lengths and theextensibility of various components of the musculoskeletal system may be altered and movement impairment may result (Sahrmann 2002).Hypertrophy or shortening of certain musclesand atrophy and lengthening of others may inthe long term lead to a muscular imbalance,especially if the postural muscles that providestability close to the joints are not adequately


recruited regularly, for maintenance of neutralposturing.

It has been shown that awkward posture ofa single joint (shoulder flexion alone) can lead toincreased discomfort, muscular fatigue (detectedby EMG changes) and reduced performance(Straker et a1. 1997).

Awkward postures: vulnerability of thehypermobile individualIt is expected that the hypermobile individual willbe especially vulnerable to working in awkwardpostures for sustained periods. Such individualsmay be particularly vulnerable to muscularimbalances, as the deep core muscles fail to stabilize joints owing to poor proprioception duringprolonged awkward static postures. Repetitiveawkward postures may not pose as great a riskat the hypermobile joints, because of the greaterextensibility of these joints. Silverman et a1. (1975)demonstrated that a clinically hypermobile individual has greater extensibility of the fifth rightmetacarpophalangeal joint by displaying the jointangle response to increasing loads. The load versus joint angle curves showed that less load wasrequired to extend the joint to similar angles asin controls, and the hypermobile individualshowed greater extensibility of that joint. Theauthors also showed that the extensibility ofjoints is inversely correlated with age. However,should damage occur, the alterations in collagenturnover and defects in connective tissue, as seenin Ehlers-Danlos syndrome (Miller and Gay1987) may leave the individual at risk of experiencing greater musculoskeletal problems, especially with increased age.

Static postures

DefinitionDuring prolonged static postures low-level muscular contraction is required to maintain the stabilityof a body segment. It has been suggested that muscular fatigue, tissue compression and alteration

in tissue extensibility may result in and lead tomovement impairment and muscular imbalances.

Static postures: biological responsesandpathologySustained postural muscle activity may lead tomuscle fatigue. Research has shown that musclefatigue does affect proprioceptive acuity. Becauseproprioception is known to be important formotor control, it has been hypothesized thatalteration in inhibition can increase coactivation,inefficient muscle use and the workload of themuscle affected (Ashton-Miller 1999).

It has been suggested that at low-level contraction adjacent blood vessels and nerves are compressed for prolonged periods, limiting blood flowand nerve conduction to the periphery (Grandjean1982). Hagberg and Hagberg (1989) reported thatat 30° of shoulder abduction, the perfusion of thesupraspinatus muscle may decrease as the intramuscular pressure increases with static contractionof the muscle. Decreased blood flow in the supraspinatus may cause degeneration of the tendonand rotator cuff tendonitis.

Veiersted et a1. (1993) found that myalgia mayresult at low prolonged contraction levels. Jonsson(1982) hypothesized that myalgia was secondaryto ischaemia due to high static load, with resultant occlusion or impedance of circulation. Hagg(1998, cited in EASHW 1999) hypothesized thatmyalgia may be associated with a specific patternof muscle recruitment, where selected musclefibres and motor units become vulnerable. Thereis evidence of variance between the characteristics of the fibres in those exposed to high repetitive and static workloads compared to those whohave not been exposed to these factors. The irregularities observed appear to be related to the fibremitochondria. Hagg (1998) suggests that mitochondrial disturbances in type 1 (recruited for staticload exertion) muscle fibres in the upper trapeziusmuscle follow exposure to static and repetitiveworkload. Hagg suggests that these types of muscle abnormalities may be a necessary but notsufficient condition for pain perception.


The physiological mechanism underlyingmuscle fibre abnormalities in the upper trapeziusmuscle following static loads and complaints ofmyalgia are only partially understood (Hagg1998). This is due partly to methodological difficulties in taking muscle fibre from human subjects.

Static postures: vulnerability of thehypermobile individual

Larsson et al. (1993)found that the daily problemscaused by hypermobility in musicians were notrelated to the total number of hypermobile jointsin a subject but rather to the use of certain jointswhen playing particular instruments. The percentage of subjects with hypermobile kneeswho reported symptoms was significantly higher(P < 0.001) than the corresponding percentageamong the subjects without such hypermobility.The proportion of subjects with hypermobility ofthe spine who had symptoms involving the backwas significantly higher than the proportion ofthose who did not have hypermobility. Theauthors felt that hypermobility of the spine, andto some extent of the knees, can be a liability during long periods of practice and performance inthe erect posture, as an overuse syndrome (i.e.pain in muscles involved in support function)may be presenting. Larsson et al. (1995) foundsimilar results when he analysed the effects of tasktypes on industrial workers. The authors foundthat workers with hypermobility experiencedmore back pain with sitting or standing jobs thanworkers without hypermobility. The corresponding numbers with back pain for jobs withchanging postures were greater for those withouthypermobility. The authors once again concludedthat hypermobility is an asset if the workrequires changes of body posture, but a liabilityfor those requiring static joints.

Whole body vibration (WaV)

Definition

Whole body vibration refers to mechanical energyoscillations which are transferred to the body as

a whole. The motion is usually measured in the'x' (front to back), 'v' (side to side) and 'r' (up anddown) directions. Once the direction of vibrationis defined the frequency and amplitude must alsobe specified. The exposure to whole body vibration usually takes place through a supportingseat or platform, generally in transportationvehicles (e.g. bus drivers, truck drivers).

Whole body vibration: biologicalresponses and pathology

Bovenzi (2000)states that studies show that thereis an excess risk of sciatic pain and lumbar discdisorders, including herniated disc, in the WBVexposed occupational groups compared to control groups. Mechanical overload and excessivemuscular fatigue has been shown by biodynamicand physiological experiments.

Physical changes and disc herniations havebeen caused in motion segments by exposure tocyclic and vibration loading. A vehicle driver isthought to also be at further risk when unloading, owing to back muscles that have fatiguedfollowing exposure to vibration (Pope et al. 2000).

Whole body vibration: vulnerability ofthe hypermobile individual

There has been no study found which proposesthat the hypermobile individual is more susceptible to problems following exposure to wholebody vibration. However, because of the vulnerability of hypermobile individuals to collagendamage and intervertebral disc dysfunction,caution is recommended in exposure to WBV.

Cool temperatures

Cool temperatures: biological responsesand pathology

Studies suggest that the physiological demandson muscle and related tissue will be greater for agiven task in a cold environment (EASHW 1999).


Increased muscle activity may arise from directcooling of tissue or postural changes.

Cool temperatures: vulnerability of thehypermobile individual

The hypermobile individual may be more susceptible to cooler environments. Joint hypermobilityand bilateral occlusion of the ulnar arteries presenting as Raynaud's phenomenon have beenwritten about (Haberhauer et al. 2000). Beightonet al. (1999) pointed out that alterations in thetotal volume and weaving of collagen may resultfrom external forces, and that collagen fibres maysuffer contractions when the temperature of theirsurroundings is changed.

Psychosocial issues

Psychosocial issues: biologicalresponses and pathology

Poor job or work organization, particularly lack ofsufficient control of the work by the user, underutilization of skills, high-speed repetitive workingor social isolation have been linked with stressin the workplace today. Increased specializationmay result in jobs that require repetitive movement and/or static positioning. Such jobs are alsousually associated with low job control.

It has been shown that there is an inverse relationship between physical load and job control(MacDonald et al. 2001). MacDonald et al. 2001found that the correlation between physical andpsychosocial stressors was strongest in bluecollar production and low-status office workers,supporting their hypothesis that covariation ismore pronounced in groups with greater taskspecialization. The factors that were especiallystrongly correlated were low decision latitude andphysical loading. Mental demands were usuallynegative with physical loading. The relationshipswere weaker in white-collar workers.

It has been shown that psychological stresscan increase muscular tension (Waersted andWestgaard 1996, Melin and Lundberg 1997).

Psychosocial issues: vulnerability of thehypermobile individual

It has been pointed out that psychosocial problems may be experienced secondary to painassociated with joint hypermobility (Grahame2000). Although no specific studies relate worksatisfaction and hypermobile individuals, it mustbe borne in mind that the interaction betweenunsatisfactory work situations and stresses experienced secondary to pain may leave the hypermobile individual more susceptible and potentiatethe risk of problems related to psychosocial issues.

APPLICATION OF ERGONOMICPRINCIPLES TO REDUCE THE RISKOF WRMSD IN THE HVPERMOBILEINDIVIDUAL

The word 'ergonomics' is Greek in origin andmeans natural laws (nomo) of work (ergo). One ofthe guiding principles of the science is creating abalance between the demands of a task and thecapabilities of the individual performing thattask (Fig. 9.2).

When the demands of a task, whether physicalor mental, are greater than the capability of theindividual doing the work in a specific environment, stress (physical or psychological), and consequently strain and injury, may result.

Figure9.2 A primary ergonomics principle: creating abalance between job task demands and individual capabilitiesin the work environment


For individuals who have limited physicaland psychological capabilities, or for tasks thatare highly demanding, the application of ergonomics is especially important. What must beborne in mind is that the balance betweenindividual capability and the demand of the taskis also highly influenced by the environmentwhere this balance must take place. For thehypermobile individual physical capacity maybe limited relative to certain risk factors of atask, such as high force and static postures,but increased for other factors of a task, suchas repetitive movement or extreme joint rangerequirements.

Ergonomics: the balance

The identification of risks, especially in thecontext of the essential functions of the job, is thefirst step in minimizing the risks associated withWRMSD. Once high-risk tasks are identified,specific risk factors can be objectively quantifiedusing currently available tools.

Risk exposure may be reduced by:

• Redesigning a job so that high-risk tasks areeliminated and not required;

• Redesigning the way in which a task iscarried out, so that there is less risk;

• Providing or designing equipment, toolsand man-machine interfaces to make thetask easy to complete;

• Training people or providing them withguiding procedures.

For any organization or individual (includingthe hypermobile), ergonomic principles may beapplied at all three levels of prevention: primary(prevention of onset of injury is a priority),secondary (the goal is to prevent disability andrestore function quickly) and tertiary (whenphysical impairment may already be present, butprevention against further injury or impairmentis required to reduce the injury-disability cycle)(Khalil et al. 1999).

Primary prevention

Surveillance: identifying vulnerable jointsand tissue

The vulnerability of the hypermobile individualrelative to work-related risk factors will dependon what the task and total job requirements are inrelation to the individual's grade of hypermobility,past medical history and specificity, and/or thelocation of hypermobile joints. The ergonomist'sawareness of the individual's past medical andcurrent history of hypermobility will providegreater ability to compare and match the individual with the physical and psychological demandsof their job. Creating a match between the job andthe user is usually attempted by altering the jobrequirements initially. If the task or environmentcannot be modified, guidance regarding the avoidance of high-risk tasks is indicated. For example,a hypermobile individual with a history of lowerback pain may choose to work as a cashier. Aspractitioners, we may expect that individual tobe especially vulnerable to prolonged sitting orstanding postures. Should they continue workingas a cashier without the ability to break away fromthat position, it is recommended that they altertheir posture intermittently between sitting andstanding, at an appropriate frequency, to reduceprolonged static positioning.

Currently there is no scientific evidence thatvalidates the use of preassignrnent medical examinations, job simulation tests or other screeningtests as a valid predictor of which employees arelikely to develop WRMSD (Hales and Bertsche,1999). However, a case for the introduction ofsimple hypermobility screening for those destinedto participate in pursuits with a high risk of injuryhas been made (March and Silman 1993).

Education and training: awareness of riskfactors and recommended posture, workpractices and manual handling techniques

Understanding the potential problems of jointhypermobility and high tissue laxity relative topotential work-related risk factors is imperative


for all parties involved in determining optimalergonomic settings for the hypermobile individual, including the ergonomist, the individualthemselves, and personnel who have an influence on selecting and designating tasks for them.Issues and factors about which it would beimportant to have an understanding include:

• High-risk work-related factors, includingstatic postures, high loading (force orrepetition) on connective tissues, possiblywhole body vibration, possible coldenvironments and possible high-riskpsychosocial factors;

• Applying basic control methods to reduce thetotal exposure duration, frequency and doseof the risk factor should be part of thetraining for the hypermobile individual;

• Postural education for dynamic tasks(e.g. lifting, pushing, pulling) and static tasks(e.g. sitting, standing, holding tools,interacting with work equipment);

• The importance of early reporting ofsymptoms and intervention;

• Encouragement to attend specialist physicaltraining (under the guidance of theirclinician) to improve the recruitment ofcore stability muscles, joint proprioceptionand kinaesthesia (movement awareness)may be of benefit;

• Ensuring task cycle breaks to reduce posturalmuscle fatigue.

Should the individual find that their thresholdfor mental demand or stress is potentially affectedby chronic pain or disability, the psychologicaldemands of the task must be considered. Suchpsychosocial factors as total workload, time constraints, lack of autonomy, lack of performancefeedback and control over their job must be considered and evaluated by the ergonomist.

Ergonomic assessment and managementThe ergonomist is encouraged to work closelywith the individual and the employer to provide

a systematic subjective and objective assessmentof the individual's status and job requirements.Analysis of the findings and synthesis of potential problems should follow, so that realistic recommendations to reduce the risk factors may beput forward. Appendix 1 provides an example ofan ergonomic assessment form used for thosewho require individual consultation and specificrecommendations. The reader will note that photographs are sometimes used to present the scenariomuch more clearly. Those approving and implementing the recommendations usually find thepictures particularly helpful.

Follow-up after implementation of the control measures is essential. It is also recommendedthat all ergonomic interventions be trialled priorto being accepted as the final solution.

Should permission be provided by the individual, it may be highly beneficial for the ergonomistto liaise with their clinician (medical doctor orphysiotherapist) to obtain a greater understandingof the individual's condition and provide feedback about the workplace findings. Hales andBertsche (1999) state that open lines of communication between employer, employee and thehealthcare provider are essential. Attending combined clinics may be particularly valuable forall parties involved (e.g. combined upper limbclinic at the University College London Hospitals,Rheumatology Department, attended by patient,rheumatologist, therapist and ergonomist).

Secondary prevention

Job restrictions and taskmodificationsEmployees returning to the same job withoutmodification of the work environment are at riskof recurrence (Hales and Bertsche 1999).The principles guiding the return to work include the typeof WRMSD, the severity of the condition and therisk factor present on the job. Following injury orpresentation of problems, it is highly beneficialfor the ergonomist to work closely with the clinician, should permission be provided by the patient.Understanding the pathology, tissue mechanics


and working diagnosis allows the ergonomistto analyse the individual's task more specificallyand reduce those risk factors that may be relatedto the condition presented. For example, a hypermobile individual may present with right shoulderinstability and scapulothoracic pain, especiallyaggravated by computer use. Closer analysis oftheir task may reveal that intensive mouse usein a non-neutral shoulder position is evident. Initially, the individual may be encouraged to avoidmouse - and possibly keyboard - use by carryingout alternative dynamic tasks (e.g. writing andfiling). As the individual recovers from the acutecondition, recommendations such as the avoidance of intensive right upper limb mouse use (e.g.substitution by keystrokes, or left-hand mouseuse), postural training at the workplace, tryingan alternative keyboard design (which does nothave a number pad attached to the right, whichwould normally restrict mouse placement) andtrying an alternative mouse design (e.g. a touchpad mouse, which does not require static shoulder girdle contraction) may be suggested. Theworkplace findings and recommendations mayalso provide the clinician with further understanding about the pathogenesis of the individual'scondition, and ideas for therapy (e.g. utilizingEMG biofeedback to train the individual torecruit lower trapezius for improved shoulderstability and muscle balance, or using proprioceptive neuromuscular therapy to regain normalproprioception and kinaesthesia of the upperquadrant).

Education and training to preventpersistence or recurrence of injuryIt is imperative that the hypermobile individualunderstands what the potential work-relatedfactors that may have aggravated their musculoskeletal condition are, so that exposure to themmay be reduced or avoided altogether. The ergonomist who has a full understanding of the individual's condition may be the practitioner best placedto provide this advice, as they may be mostfamiliar with the particular risk factors.

Ergonomic assessment and managementErgonomic assessments following injury or thepresentation of symptoms (reactive ergonomics)may reduce the scope of the assessment butincrease its detail, as high-priority factors to becorrected are usually revealed more readily.General prophylactic ergonomic risk assessmentstend to require the ergonomist to think in a broadand proactive manner, considering all factorsthat may pose as risks. Appendix 9.1 presents anergonomic assessment form which may be usedat all levels of prevention.

Tertiary prevention

Rehabilitation and gradual return towork/conditioningScientists confirm that rehabilitation and ergonomics applied together considerably intensifyand advance both the progress of the rehabilitation process and the return to normal life (Nowak1999).

Returning injured or disabled workers to theworkforce through accommodations and redesignof the work environment and tasks is possibleonly with sufficient information about the physical and cognitive requirements of the task (Mayeret al. 2000). A detailed ergonomic assessmentwould usually reveal the requirements and physical capacity of the individual. The latter may notbe easily obvious in the work setting, as psychosocial factors and fear of reinjury may preventthe individual from working at their actual physical capability. Functional capacity examinations(e.g. Key and Blankenship methods) may provide the ergonomist with subjective and objectivemeasures of the individual's capacity. However,the application of the objective measures maybe limited, because for many the information hasbeen collected within a controlled, rather than anatural work environment.

Providing the injured worker with a job withmodified tasks during rehabilitation or followingphysical impairment will allow them to maintain


their function and often promote positive perceptions about their capabilities. It is importantthat the modified task be one that is required fornormal or improved function for the organization(rather than created for the individual, withoutparticular benefit to the organization), so that theindividual may feel valued and functional on theirreturn to work. Clinicians must advise which tasksshould be avoided, at various progressive stagesof tissue healing or rehabilitation. Gradual increaseof endurance is important not only for improvingtotal muscular strength and power, but also foradaptation to new and controlled patterns ofmovement (demands of proprioception andkinaesthesia). Regular attendance at a workplacewill often require social interaction, and mayreduce the risk of the individual falling into thetrap of perceiving themselves as having a permanent disability.

Ergonomic assessment and management

Striking a balance between physical limitationsand job requirements requires a detailed understanding and recognition of all elements oneither side of the balance. The ergonomic assessment must usually be carried out with high sensitivity, so that progression to return to work canbe accepted rather than rejected by the individual. Should the individual be unwilling to increasetheir function, because of either fear of physical

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CONCLUSION

The prevalence of musculoskeletal disorders inthe workplace is high. The causes are thought to bemultifactorial and include repetitive movement,the force involved, awkward and static postures,vibration, temperature and psychosocial issues.It is important to have an appreciation of the biological responses and possible pathologies thatcan result from these factors in order to managesymptoms successfully. This is particularly relevant in the hypermobile individual, who is possibly more at risk because of their more vulnerabletissues. The application of ergonomic principlesis essential to prevent the development of musculoskeletal problems and successfully manageproblems when they arise.

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APPENDIX 9.1 143

Appendix 9.1

INDIVIDUAL ERGONOMIC ASSESSMENT

Personal information

Date: Ergonomic assessor:

Client name

Gender

Date of birth

Employer/company

Job title

Business unit/department

Manager/contact person

Work location

Relevant past medical history(stated by client)

Subjective assessment (reported by client)

Work status: Full-time/Part-time/PermanentfTemporaryfTrainee

Restrictions: Full duty/restricted duty/awaiting to return to work

Length of working day:

Frequency and periods of breaks (scheduled and natural):

Scheduled breaks:

Natural breaks:

Job description and designated tasks

Task Description (% keyboard, mouse, screen, telephone, writingwhere applicable)

Current relevant presenting complaints:


Mobility of client: Wheelchair /walking with aids/walking independently

If client ambulates, is there a limitation?

Objective assessment (assessor's findings)

Primary workstation layout(PHOTOS OR SKETCH)

Primary tasks observed

Repetitive Static Awkward Extreme Contact Vibrationmovement postures postures forces stress (high/(high/ (high/ (high/ exerted (high/ medium/medium/ medium/ medium/ (high/ medium/ low)low) low) low) medium/ low)

low)

Equipment measures (mm) (e.g. in office setting)

Equipment type and model if obvious:

Desk:

Chair:

Mouse:

Keyboard:

VDU:

Other equipment:

Seat-pan height:

Seat pan width x depth:

Lumbar support height:

Back rest width x length:

Desk height:

Desk thickness:

Keyboard height:

Screen size (diagonal length):

Top of screen height:

Screen depth from eye:

Anthropometric measures (mm)

APPENDIX 9.1 145

Anthropometric measures

Height:

Weight:

R/L-handed:

Knee height (heel to popliteus/top):

Mid-thigh height:

Hip height (joint):

Lumbar lordosis height (seat pan to lordosis):

Hips width:

Thigh length in sitting (buttock to popliteus):

Elbow height (seat pan to elbow):

Torso length (buttock to shoulder height in sitting):

Sitting eye height (seat pan to eyes):

Funct. reach length:

Health and safety

Has a risk assessment been carried out at your workstation?Have you received training related to health and safety?

Environmental conditions

Yes No

Acceptable Not acceptable to client (briefly stateto client issue) - recommended to be assessed by

employer

Lighting conditions

Observed general hygiene level

Observed slips, trips, falls, hazards

Current noise level

Current air quality

Current temperature

Problems identified1.2.etc.

Recommendations


Equipment

Equipment recommendationRationaleDetails of installation and training requirementsSuppliers

Access

I Access recommendationRationale

Workstation layout

Workstation layout recommendationRationale

Recommended workstation layout(SKETCH)

Training - postural re-education and work practice

I Training recommendationRationale

Task redesign

Task redesign recommendationRationaleAgreed by client

Other comments

Assessor's signature: _

Printed name (qualifications): _

Date: _

(Developed by Jean Mangharam for ErgoSense Ltd, 2000)

Documents

Chapter 9 – Joint Hypermobility and Work-related Musculoskeletal Disorders (WRMSD)