A BARRISTER’S COMMENT ON THE ASSOCIATION BETWEEN TYPING AND CARPAL TUNNEL SYNDROME – Can Typing, as a Cause of CTS, be Excluded on the Basis of Epidemiology and Histological Study Alone?

In this feature article, guest writer, Michael Ditchfield, of Parklane Plowden Chambers, reviews medical literature on the link between computer keyboard use and carpal tunnel syndrome (CTS). In so doing, he assesses whether an occupational disease claimant, alleging that typing was an injurious exposure source, is without merit.

Michael was called to the Bar in 1993 and, in March of this year, was appointed as a Deputy District Judge on the North Eastern Circuit. Having been nominated as a ‘Leading Individual’ at the Legal 500 UK Awards 2019 and a ‘Leading Barrister’ at the Chambers Bar Awards 2019, he is an established advocate in industrial disease practice.

Aside from an interest in cases involving low-level asbestos exposure and extensive experience in noise-induced hearing loss litigation, Michael is constantly developing his understanding of complex work-related upper limb disorder (WRULD) epidemiology, which affects legal arguments on foreseeability of harm and causative breach. This article therefore serves as an example of his current focus.

BACKGROUND TO WRULD

WRULD is the modern and preferred umbrella term to describe the presence of symptoms in shoulders, arms, wrists, hands and fingers, where a work-related cause is alleged. These symptoms typically manifest as pain, tingling, affected sensation and weakness at affected sites.

The term covers conditions such as De Quervain’s tenosynovitis, lateral and medial epicondylitis and CTS. All have reasonably well-understood and demonstrable pathologies.

WRULD conditions may be caused by work. Alternatively, prior/coincidental existence may merely be aggravated or excited by working practices. The distinction is sometimes difficult to determine, but must be established.

Obviously and clearly, merely as symptoms arise in the context of work, it cannot be said that the underlying pathology has been caused by that work.

WHAT IS CTS?

Very simply summarised, CTS occurs when additional pressure is placed on the median nerve at the point[1] at which it passes from the forearm to the hand. The increased pressure[2] affects the blood supply in the nerve, resulting typically in tingling and numbness in the thumb, index, middle and ring finger.[3]

SHOULD CTS BE LINKED WITH WORK, LET ALONE TYPING?

The Court has no clear touchstone for deciding work-related causation in any given CTS case, unless it can be said that the basis of any causal relationship is supported by specific and credible studies, or otherwise.

It is sufficient to recognise, as a starting position, that ‘idiopathic CTS is the most common compression neuropathy presenting in the UK’. [4]

Studies have found a detected rate in females of at least 3.4%, with a probable minimal undetected rate of another 5.8%. It is thought these figures could be safely doubled if mild/barely reported cases are taken into account.[5]

There is, without doubt, a range of opinion on the risk factors predisposing or causing CTS, as well as to the relative strengths of those individual factors. Many, if not all of these, are common in the general population, both working and not.

The prospect that uncomfortable working positions can excite a latent or mild case of CTS, set against the background of an increasingly ‘computer based, sedentary workforce’, has the potential to fuel a view that typing has a close relationship with the condition.

THE INDUSTRIAL INJURIES ADVICE COUNCIL (IIAC) POSITION

Does commonly cited and readily available sources of Government-published data compliment the assertion that CTS is associated with keyboard activities?

IIAC Prescription

CTS is a prescribed disease under Schedule 1, Part 1, of the Social Security (Industrial Injuries) (Prescribed Diseases) Regulations 1985.[6]  Prescribed Disease (PD) A12 most clearly describes CTS in the context of vibration, but includes, as a potential cause, those cases where there is:

‘[repeated] palmar flexion and dorsiflexion of the wrist for at least 20 hours per week for a period ... amounting in aggregate to at least 12 months in the 24 months prior to onset’.

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Could this description encompass typing?

In any event, a disease will only be prescribed where both sub-sections (a) & (b) of section 76(2) of the Social Security Act 1975 are satisfied. Sub-section (b) provides:

‘[the disease] is such that, in the absence of special circumstances, the attribution of particular cases to the nature of the employment can be established or presumed with reasonable certainty’.

It is plain that typing is not identified as a cause of CTS in the same way as work with vibratory tools. Nevertheless, this inference alone would not prevent a Court, in an appropriate case, from finding that typing or keyboard work had in fact caused CTS. Nor does prescription denote that every case encountered by the Court is causative. The Regulations provide for the payment of benefits to entitled claimants and not for the determination of civil liability.

INSTRUCTING AN ERGONOMIST IN TYPING-INDUCED CTS CLAIM

The ergonomist’s role in a CTS case is typically to provide their opinion on the foreseeability of any risk of injury, stemming from the task(s) under consideration: not to perform a diagnosis and not to express their view on medical causation.

In the specific instance of alleged typing-induced injury, is the Court likely to consider that the ergonomist’s report is the silver bullet, capable in its own right of dismantling the claimant’s claim that keyboard work has led to CTS?

The Court may begin by asking whether there is a foreseeable risk of any injury (rather than the specific injury[7]) arising from the work at hand.

It is inevitable that an ergonomist’s view may also influence the strengths of submissions on causation when the medical stage of the investigation is reached.

RISK OF CTS INJURY FROM WORK?

Typing is an activity that shares common characteristics with other types of work involving repeated use of the upper limbs. Fine distinctions that exist between typing and other upper limb tasks, as well as the intent of any epidemiological or occupational study considering them, must be borne in mind when entering a discussion on foreseeability.

A useful starting point is to decide if there is a relationship between work, generally, and CTS.

There is a range of opinion both as to the risk factors predisposing to CTS as well as to the strength and significance of each of those factors.

Reporting in the Journal of Hand Surgery, Dias & Burke (2004) considered CTS incidence in ‘CTS and Work’.[8] Having observed 327 women, of whom 217 were in work and 55 worked in repetitive occupations, it was concluded that there was ‘no clear relationship between CTS and work’, though it could not be construed that work presents no risk of CTS development.

The common pleading with typing claims is that, by its intensive nature and potentially highly repetitive form, CTS may potentially emerge. On the contrary, population studies have shown that more women in non-repetitive occupations present with the condition than those in repetitive work. However, CTS-induced typing cases should not be dismissed on this basis.

Gallagher and Heberger (2013) were able to offer some insight in their study,[9] which sought to separate out the studied effects of force, repetition and combined factors in the causation of ULD in the workplace.

Although estimated peak hand force, forceful repetition rate, and percentage of time spent in forceful hand exertions were associated with an increased risk of CTS; similar associations were not observed between total hand repetition rate, percentage duration of all hand exertions, or wrist posture and CTS.

A causal link between work and CTS seems to be established, but only under a restricted and specific set of conditions where force of activity (in flexion and extension) was found to be a far more potent factor in causation than the effect of repetition alone.[10] Once again, that is not the same as saying that there is no risk where less potent force was at play: merely that that the incidence rate is likely to be lower.

This would seem to reflect the thinking behind the wording of PD A 12.

HOW DO CTS RISK FACTORS RELATE TO KEYBOARD WORK, SPECIFICALLY?

Writing in MacDonald’s Occupational Illness Litigation, Graham Coleman[11] noted the potential connection between risk factor types (force and repetition, force and posture and repetition and posture) and the development of CTS. Noting that some of these risk factors may be regarded (justified or not) as typifying the work of a typist, Mr. Coleman nonetheless remarked that:

‘... regarding keyboard injuries, the evidence for [typing causing] CTS is hazier’.

Posture

It is by no means clear from the IIAC position, considered above,[12] as to the degree of flexion and extension that constitutes a risk factor of CTS, or is capable of causing CTS. Various studies have concluded that, within the clinically normal range of movement (± 70°), around 15° extension and 20° flexion represents the comfortable or easy range. More specifically, in Biomechanical Risk Factors for CTS’,[13] a criterion of ± 30° was adopted.

In fact, teaching on correct posture in typing schools, before the advent of widespread keyboard use, advised typists to not rest their arms or wrists on tables or pads, the benefit of which is unsupported by research. Flexion and extension, provided non-‘excessive’, are each entirely appropriate movements, with there being no demand for the wrist to be held ‘in neutral’.[14]

Posture could be responsible for CTS, perhaps if an injury is sustained with force, but absent of a degree of motion which is notable and distinguishable from the normal and everyday, such injury will be difficult to associate with keyboard work. Joints are designed to move regularly, repeatedly and with force, in the context of ordinary everyday activity.

Intensity/Repetition

There is no clear Health and Safety Executive (HSE) Guidance on the nature, intensity and duration of keyboard use that may predispose injury; save to acknowledge that short, regular breaks are more likely to be beneficial in preventing discomfort.[15]

In their Risk Factors for Hand-wrist Disorders in Repetitive Work’[16] study, Mikkelsen et al (2007) found:

  • That force was more clearly associated with the prospect of injury than either repetition or position; and
  • That non-neutral positioning was not identified as a risk factor.

Elsewhere, Lassen, Vilstrup et al (2011) concluded, in a 1-year prospective study: Does Computer Use Affect the Incidence of Distal Arm Pain?’[17] (pain rather than identifiable injury as CTS being considered), that:

  • Keyboard time had no effect. Mouse and keyboard sustained activity, speed and micropauses were not risk factors for acute pain, nor did they modify the effects of mouse or keyboard time. Computer usage parameters were not associated with prolonged or chronic pain; and
  • Computer work was not related to the development of prolonged or chronic pain. Mouse time was associated with acute distal arm pain, but the impact was trivial.

A substantial study by Harris-Adamson et al (2014): ‘Biomechanical Risk factors for CTS’,[18] considered both separately and in conjunction, the effect of biomechanical factors on CTS causation. They concluded, in respect of 2,500 subjects, after a long-term follow up period, that:

  • Repetition (on its own) had no significant effect on the development of CTS;
  • The combination of force and repetition (including low repetition with high force) was significantly associated with CTS;
  • Fewer than 18 repetitions per minute did not increase the risk level until force was introduced at a high level;
  • For those performing jobs with higher hand repetition rates (>18 repetitions per minute), CTS risk increased by nearly 3-fold with only moderate peak hand force. At lower repetition rates, it was suggested that workers may tolerate greater levels of force than at higher repetition rates.

The Limitations of Self-Reporting

Factually-speaking, ULD risk is associated with ‘use’ of the upper limbs. Anecdotally, repetitive ‘use’ is considered to be the principal motivating factor that increases the risk of ULD.

In the same manner as with those who used vibratory tools, in research conducted by Thomssen & Mikkelsen et al (2007):[19] ‘Validity of Questionnaire Self-reports on Computer, Mouse and Keyboard Use’, showed that, out of 3,123 workers in industrial settings:

  • Self-reporting drastically over-estimated time spent on computers, with self-reported keyboard time being significantly at odds with objective measurement.

Accordingly, biased self-reporting[20] is thought to be one of the reasons why keyboard/computer use is associated (anecdotally) with distal arm pain and probably injury.

This makes sense, given that ‘use’, particularly of a computer, is likely to seek qualitative, rather than numerical data. The plain conclusion is that context must be examined to determine whether the test subject is speaking genuinely of ‘constant data entry’ or, more likely, of entry of codes and abbreviations, form filling and data recall.

Broadly, the ergonomic view seems to be that computer keyboard use does not involve repeated flexion and extension of the wrist, nor is it forceful by nature.[21]

It is important, then, to unpack the allegation. Performing a task more than once in the course of work would not necessarily satisfy an ergonomist’s definition of ‘repetitive’. It is more likely that the focus will be on frequency, posture and force, preferably in combination.

It is entirely typical for symptoms to be worse at work, without there being any impact on the underlying pathology – though test subjects rarely make this distinction, experts must.[22]

THE PSYCHOLOGY OF CAUSATION

At first blush, it would seem that typing and keyboard work, especially of high-intensity and long duration, satisfy most of the criteria set out by Mr. Coleman (in the section above). Undoubtedly, the belief in a linear connection has been increasingly accepted over time.

Appendix 2 (Health effects of DSE work and principles of successful prevention, treatment and rehabilitation) of HSE Guidance on the Health & Safety (DSE) Regulations 1992,[23] published in September 2003, asserts that:

  1. Use of a visual display unit (VDU) is associated with a range of symptoms related to posture.
  2. A range of conditions of the arm, including CTS, is linked to work activities.
  3. The contribution to onset of risk factors, such as keying rates, is not clear, but soft tissue disorders have often been associated with high workloads and tight deadlines.

Decades earlier, however, the HSE suggested that ‘the majority of the symptoms described by VDU operators are a reflection of bodily fatigue’. No clear association with specific injury was made, though guidance did highlight the propensity for VDU operator tasks to promote ‘distress’.[24] It is therefore apprehensible that tiredness could play a key role in satisfying a typist’s suspicion that there is an injurious relationship between their work and the onset of CTS.

Secretaries and temporary office workers are regularly listed as ‘at risk’ members of the workforce where ULD are in issue, but care has to be taken to consider CTS risk specifically.[25]

Nevertheless, HSE publications are of no use in establishing a causal link between CTS and keyboard use, either in general, or in any given case. The presence of a considered risk is not a matter relevant to the medical causation stage of any enquiry. The publications do, however, serve to fuel a pre-conception, if not a presumption, that the link between CTS and keyboard use is both established and simple to demonstrate, in the context of litigation.

This matter is further compounded by the standard methods of medico-legal enquiry and the psychology of the claimant, including ‘distress’. There is often an inclination to confuse and perceive that ‘hard work’ is responsible for, or prompts the onset of injury. In fact, ‘hard work’ may be responsible for no more than fatigue, distress and exciting already established symptoms.

It is well-studied, if not also well-understood, that the context in which an injury is suffered affects both outcome and attitude to recovery.[26] Could it not be the case, then, that cultural assumptions about the risks of repetitive typing, coupled with a sense that work is too demanding (perhaps especially if unrewarded or unappreciated), is a motivating factor for blame and attribution?

Grunert, Hargarten & Hamel et al (1992),[27] in a study of 200 participants, noted that persons injured at work reported some personal fault at a rate of 46% soon after the incident, but 6 months later, only 6% maintained their acceptance of personal fault. For persons injured in a non-work environment, apportionment of fault remained more consistent, with 71% accepting personal error at the outset, dropping to only 66% on the equivalent later review (6 months post-incident).

These factors are particularly ‘dangerous’ in the context of difficult-to-explain WRULD, arising in the course of work. There is a genuine risk that the injured party may be convinced that their injury was caused by work. This could explain why so many claimants fail to accurately demonstrate the details of their disabilities to subsequently instructed clinicians, compared to earlier recorded accounts.

The approach to causation of the medico-legal expert is a posteori, in effect. Whilst that approach cannot be overlooked as a useful methodology, psychological factors cannot be ignored and must be understood, both by the expert and by the Court. Patient account and history is so important and so often the only version of the ‘facts’ at this critical stage of the investigative process.

HIERARCHICAL APPROACHES TO CAUSATION IN TYPING–INDUCED CTS CLAIMS

Establishing a Relationship by Deduction, Rather than Observation (A Priori)?

The defendant litigant, when addressing a claim of this nature (or any other) on the basis of causation, ideally wishes to say, for example, that ‘typing can never cause CTS’.

An a priori approach to the question, in light of some of the published literature mentioned above, may provide adequate means to resolve such a question. However, a court is rarely, if ever, inclined to consider expert evidence in a factual vacuum or indulge in ‘trial by article’.

It may be difficult to contend that the argument surrounding causation of CTS by typing is settled by epidemiological study, no matter how wide. Studies of affected cohorts will potentially be subject to reporting bias. There are plain limitations to extrapolating from population studies onto the experience of specific cohorts and it is never really possible to extrapolate from any such study onto the risk factors facing a specific individual.

Although some exposure assessment methods, such as the threshold limit value (TLV) for vibration or chemical exposures, which estimates a single index for biomechanical hazard from multiple physical exposure domains, may implicitly consider interaction of causative factors, few studies have examined associations between CTS and exposures estimated with such multi-domain methods.

Super-imposing certain generic work activities onto the activities specific to keyboard operators, poses endless difficulties.

For example, Ettema’s (2004) study: ‘Histological and immunohistochemical study of connective tissue in idiopathic CTS’,[28] considered and noted the presence of synovial fibrosis in patients suffering from diagnosed CTS. By extrapolation, some experts argue that synovial fibrosis is the product of multiple minor traumas, which might be occasioned in repetitive work.

The paper, however, drew no such conclusions, indicating that the actual causes of synovial fibrosis were poorly understood. Further, the paper in no way concluded that work was responsible for the fibrosis in the small group studied. It seems just as plausible to contend that the CTS caused the fibrosis as much as the reverse.[29]

Of course, this does not mean that evidence from supportive literature must be abandoned. The state of learning is likely to influence the Court on the foreseeability of risk, the appropriateness of taking precautions (breach), as well as whether the general view on causation is more likely than not.

However, caution may be merited. Few sensible studies entirely deny the connection between typing and CTS and few make the connection.

Whilst it is tenable to argue that there is nothing immediately apparent in the literature to support a causal link between CTS and typing, this should not be seen as the equivalent of saying that the literature disputes a connection.

Most studies will consider ‘incidence’ in a studied cohort, rather than causation. ‘Risk’ is commonly used as a synonym for ‘incidence’ and should not be confused with causal relationship where risk eventuates.

The work of Atroshi et al (2007), in: ‘Carpal Tunnel & Keyboard Use at Work’,[30] is a key study that considered ‘incidence’ in a population of 2,495 test subjects. It should not, however, be read as suggesting that a causative connection does not exist between CTS and keyboard work.

The answer to the question posed: ‘is there a relationship between keyboard work and CTS?’ was ‘yes’. In fact, the authors found an inverse/protective relationship between groups that engaged in more typing than those who typed less frequently. Effectively, the more an individual typed, the less likely they were to develop CTS. This relationship, however, was of a statistical kind, i.e. how typing and CTS numerically relate. As is often the case, the authors were not interested in identifying/disproving a causal, coincidental or correlative relationship for the benefit of interested ergonomists and medico-legal practitioners. Rarely will literal interpretation of epidemiological theory verify a causal link between work and injury.

In other research that focused on ‘incidence’, as opposed to causality, Stevens et al (2001) conducted a survey of frequent computer users in: The frequency of carpal tunnel syndrome in computer users at a medical facility.[31] They found that:

Although 29.6% of the employees reported hand paraesthesias, only 27 employees (10.5%) met clinical criteria for carpal tunnel syndrome, and in 9 (3.5%) the syndrome was confirmed by nerve conduction studies. Affected and unaffected employees had similar occupations, years using a computer, and time using the computer during the day. The frequency of carpal tunnel syndrome in computer users is similar to that in the general population’.

The relationship between ‘work’ and CTS is difficult enough to establish on such methodology and by reference to published study. There would appear to be no absolute scientific consensus definitively linking keyboard tasks and CTS, but this will not prevent medico-legal experts from extrapolating. One cannot guarantee, in the factual vacuum, that the Court would be persuaded that a link exists on an a priori basis.

Establishing a Relationship on Known Facts, Without Assumption (A Posteori)?

Rather than asking ‘can typing ever cause CTS?’ the question should be:

‘... can typing cause CTS in these, or a given set of particular circumstances?

An ergonomist might invite consideration by the Court and the medical expert of:

  • Temporal ordering – this would exclude the presence of the injury before the work begins;
  • Temporal contiguity – ideally, this would identify a change in work/work rate/load, leading to acute onset;
  • Inverse relationship with work – this is not a universal principle for all disease, but a sign of work-related cause may be, e.g. improvement when not engaged in the activity;
  • Coincidence of mechanism and disease – the activity should be one which is likely to cause injury, such as sustained, forced wrist extension and tennis elbow;
  • Absence of other explanation – the Claimant must prove the injury and its relationship with work. The Court will wish to exclude other likely causes in each case; or
  • Cluster of claims – this may tend to suggest a relationship, but an absence does not disprove in the individual case.

A case-by-case approach is adopted in CTS claims. Where typing is concerned, it has not been immutably fixed that a ULD (not necessarily CTS) is not compensatable.[32]

Nonetheless, it will always be a matter of influence that typing work is performed by millions across the UK without incident. Some specific feature of the work, be it timing, posture, pressure or sheer volume, will often be required to satisfy the Court of the causative link.

It is the variability of these factors, the often subjective nature of reporting and the high incidence of idiopathic/non-work related ULD, which gives rise to the questionable nature of CTS causation.

COMPETING CAUSES

The Court must have regard to the burden of proof. Some people are certainly more vulnerable to develop ULD than others. It is for a claimant to show that the diagnosed condition is work-related, rather than for the defendant to show that it is not.

Whilst work can cause ULD, so can environmental, social and constitutional factors (see the Stevens study above as a practical example).

A claimant will then have the burden of establishing that the given condition is the product of the work and not one of these other factors.

Many factors may predispose an individual to development of CTS, including:

  • Diabetes (doubles the risk);
  • A high BMI;
  • Rheumatoid arthritis;
  • Trauma – particularly wrist fracture;
  • Hypothyroidism;
  • Pregnancy/use of the contraceptive pill; and
  • The menopause/HRT therapy.[33]

A cursory reading of scientific, epidemiological and histopathological studies shows that persons exhibiting the above factors are typically excluded from research cohorts, each having significant influence on the development of the condition in the general population.

Common observation shows that virtually all activities of daily living (at home, at work and at leisure) involve movement of the wrist (flexion and extension, as well as radial and ulnar deviation), yet people clearly engage in these activities without developing CTS. This brings us back to the criterion that, for work-related wrist flexion and extension to be ultimately responsible for CTS, the degree of movement and the degree of force must be notable and distinguishable from what might be considered normal or everyday.

CONLUSION

It is more common, in the medico-legal context and in litigation, that the a posteori approach is coupled with the a priori approach.

Without a clear touchstone for causation, one approach should not be permitted to the exclusion of all others; nor can it usefully be.

The defendant litigator will similarly wish to plough both furrows in tandem.

Given the emerging obesity epidemic, factors such as BMI and diabetes will become an increasingly significant risk factor for CTS. There is a predicted increase in CTS case numbers presenting in the younger demographics of the general population.

While lifestyle factors will make the extraction of work-related factors more confounding for the Court, when assessing causation, it is also probable that CTS and WRULD claims will soon be more common among employees in service-based, keyboard centric roles, as opposed to traditional manual labour roles. Understanding the link between typing and CTS is therefore ever important, in anticipation of an evolving labour market.

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Michael Ditchfield

Parklane Plowden Chambers

Email: This email address is being protected from spambots. You need JavaScript enabled to view it.

 

[1] The tunnel.

[2] Created by the tightening or narrowing of the passage formed by the carpal bones and its palmar sided, stabilising fibrous band.

[3] The distribution of the median nerve.

[4] Risk Factors In Carpal Tunnel Syndrome: J.M.Geoghegan et al: Journal of Hand Surgery (2004) 29B: 4: 315-320.

[5] Carpal Tunnel Syndrome and its Prevalence in the General Population: de Krom et al: British Journal of Rheumatology. 1998: 37: 630-5.

[6] PD A12.

[7] Hughes –v- Lord Advocate [1963] AC 837.

[8] (2004) 29B (4) 329-333.

[9] Examining the Interaction of Force and Repetition as Musculoskeletal disorder risk: A systematic literature review: [Human Factors 55(1) 108-124].

[10] Odds ratio of CTS from high force to high repetition = 15.5 but for low force & low repletion 1.0. High repetition to low force = 2.7 [see Silverstein, Lawrence, Fine et al (1987) “Occupational Factors & CTS”.

[11] Consulting Ergonomist: Graham Coleman Associates [7-241].

[12]IIAC ((2006) ‘Work Related Upper Limb Disorders’ CM6868).

[13] Occ & Environmental Medicine 0:1-9 (2014).

[14] See, e.g. Walmsley’s Commercial Typewriting (9th Ed. Pitman Pub), Universal Typewriting (3rd Ed Pitman Pub 1988) & HSE:G 2003 ‘H&S (DSE) R’.

[15] Para 62(c) 2003 Guidance to the Health and Safety (DSE) Regulations.

[16] Occupational Env. Med 64 527-533.

[17] Arch Occ Env. Health May 2011.

[18] Occ & Env. Med 2014.

[19] Occupational. Env. Med 64, 541-47.

[20] Especially from a retrospective analysis.

[21] Notably use of a mouse may be different. Andersen et al (2003 ‘Computer use and carpal tunnel syndrome: a one year follow up study’ JAMA 289, 2963 – 2969) reported a study of some 6000 employees (5658 at follow up) in Denmark. They concluded ‘In the cross sectional comparisons and in the follow up analyses, there was an association between use of a mouse device for more than 20 hours/week and risk of possible carpal tunnel syndrome, but no statistically significant association with keyboard use’.

[22] See Barton, Hooper et al Occupational Causes of Disorders in the Upper Limb. BMJ 1992 304.

[23] Pages 45-48.

[24] 1983 “HSE: Visual Display Units”.

[25] The most recent publication being the guidance booklet “Upper Limb Disorders in the Workplace”. HSG60 (rev) 2002.

[26] Paterson MC & Burke F.D (1995) Psychosocial consequences of upper limb injury. J. Hand Surgery 20B: 776-81.

[27] Grunert, Hargarten, Hamel and Matloub Sanger et al: Predictive Value of Psychological Screening in Acute hand Injuries (1992) J. Hand Surgery.

[28] 2004 Journal of Bone & Joint Surgery 86A No. 7 July 2004.

[29] See also e.g. Chell, Stevens & Davis “Work Practices and histopathological changes … in CTS in women”: Jour of Bone & Joint Surgery: 1999; 81-B:868.

[30] Arthritis & Rheumatology Vol 56 No11 [Nov 2007].

[31] Neurology. 2001 Jun 12;56(11):1568-70.

[32] See Pickford v ICI plc & Fifield v Denton Hall Legal Services, amongst others.

[33] See Geoghegan, Clark & Bainbridge et al “Risk Factors in CTS” Jour Hand Surgery {2004} 29B 315.