Ergonomics and Work-related Upper Extremity Disorders (WRUED)

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Ergonomics andWork-related Upper Extremity
Disorders (WRUED)
Grace Szeto Year 3 Ergonomics April 2002
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Work-related Upper Extremity Disorders (WRUED)

• Cumulative Trauma Disorders (CTD) Repetitive
  Strain Injury (RSI)
• Work-Related Musculoskeletal disorders (WMSD)
• Work-related Neck and Upper Limb Disorders
  (WRNULD)
• Occupational Cervicobrachial Disorders (OCD)
• Tension Neck Syndrome (TNS)
• Adverse Mechanical Tension (AMT)

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Epidemiological Studies on CTD

• Bureau of Labour Statistics (U.S.)
• gt300,000 cases reported in private industry
  (1993)
• 42,600 cases from motor vehicle and equipment
  manufacturing
• 38,300 from meat-packing
• CTS cases Days away from work 4.8 cases per
  10,000 workers (1994)
• CTS figures even greater than back pain

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NIOSH /ergo science/chapter1-6

• Detailed reviews of all studies on MSD/CTD
• Incidence rates/prevalence varies depending on
  definition of symptoms, or results of physical
  examination
• TNS among male industrial workers in US is 4.9
  by interviews, 1.4 by O/E
• Previous studies reported as high as 50-85
  (Silverstein et al, 1987, Hales et al, 1994,
  Bernard et al, 1993)

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US statistics of injuries due to repetitive motion

• 1994 Bureau of Labour Statistics
• All manufacturing - 49278 cases
• All private industries - 92576 cases
• Low back injuries of repetitive nature are
  included in this category (different in HK)

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Sommerich et al (1993)

• Summarised injury rates in shoulder region CTD
• Newspaper workers (VDU) 11 (Burt et al, 1990),
• Rotator Cuff Tendinitis in shipyard welders 18.3
  and 2 in office clerks (Herbert et al, 1984),
• 15 in grocery store checkers and 4 in
  non-checkers (Baron et al, 1990)

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Study in Hong Kong (Siu and Chan, 1998)

• 688 office workers surveyed
• 57 neck or shoulder complaints
• 48 back complaints
• pain, ache, soreness, numbness, cramping and
  tiring
• 67 reported gt4 hours VDU work daily
• Significant relationship between incidence of MSK
  discomfort and?VDU work
• http//www.oshc.org.hk/eng/research/research.htm

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Number of Confirmed Occupational Diseases in
1998-1999 Occupational Disease
1998 1999 Compressed Air Illness
3 3 Tenosynovitis
of Hand or Forearm 71 54
Carpal Tunnel Syndrome
0 1 Tuberculosis
39 57 Streptococcus suis
Infection 0 1
Occupational Dermatitis
34 21 Chemical Induced Upper Respiratory
Tract Inflammation 4 0
Silicosis
104 137 Asbestos-Related Disease
5 15 Occupational Deafness
631 388 Gas
Poisoning1 57
57 Total
948 734
(Figures from OSHC Hong Kong)
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Occupational Diseases vs Industrial Accidents

• Traumatic injuries resulting from accidents
• occupational disease - disease/condition caused
  by certain occupation
• Upper limb problems usually classified under
  occupational diseases
• Back injuries resulting from lifting - classified
  under industrial accidents

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Specific Syndromes include

• Cervical spine problems
• Rotator cuff tendonitis
• Lateral epicondylitis
• Carpal tunnel syndrome
• de Quervains syndrome
• tenosynovitis of forearm muscles
• nerve entrapments
• thoracic outlet syndrome
• vibration white fingers

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Ergonomics in Manufacturing (Karwowski
Salvendy, ed), Chapter 16 An overview of upper
extremity disorders, S. Moore

• 5 conditions
• trigger finger/thumb
• de Quervains syndrome
• peritendinitis
• lateral epicondylitis
• carpal tunnel syndrome
• Cervical and shoulder conditions are excluded
• industrial - repetitive nature of work

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Interpreting Epidemiological Studies

• Needs to know population studied, how condition
  is defined, how data is collected
• By interviews, questionaires (subjective)
• Days away from work
• Physical examination findings/ x-rays
• Physical diagnosis
• Discomfort? pain? Stiffness? Ache?
• Exact number is not important, rather the
  RELATIVE SIGNIFICANCE

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RSI and Office Workers

• Hours of continuous VDU work
• Improved computer technology
• Long hours of static posture
• Light-touch, highly responsive keyboards
• Use of numeric keypad - Data entry
• Use of mouse - graphic design, drafting
• Hi-tech transfer or storage of information,
  replace filing/photocopying

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Industrial Workers in Highly RepetitiveTasks

• Assembly line workers -e.g. electronic parts
• Packaging workers
• Factory workers - clothing, toy industries
• Use of hand tools- grip size, handle length
• Repetitive nature, speed and force of movements,
  joint angles-
• Affect length-tension relationship of muscles
• In Hong Kong- can you think of some local
  professions that may be prone to RSI?

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RSI/CTD in other activities

• Musicians - piano players and string instruments
• Sports players - depend on activity and equipment
• Housewives
• Teenagers playing computer games
• Gardeners - gardening tools
• Same risk factors - speed, force, repetition,
  frequency and experience

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Common Symptoms in RSI/CTD

• Pain - localised or referred
• Swelling - esp. in tenosynovitis - can resemble
  compartment syndrome
• Tenderness
• Weakness - can be generalised or specific
  muscles, loss of grip strength
• Headache, migraines
• Neurological symptoms - PN, sensation, power or
  reflex changes

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O/E Findings

• Decreased ROM
• Decreased muscle power
• Tenderness on palpation
• Postural changes - poking chin
• Muscle imbalance
• ve neural tension tests
• Are subjective complaints consistent with
  objective signs?
• ?Previous injuries or underlying conditions

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Sites and Nature of Pathology

• Neck tension neck syndrome (mechanical),
  cervical radiculopathy, degenerative changes etc
• Shoulder muscle tension (Cx related), tendinitis
• Elbow lateral or medial epicondylitis
• Wrist tendinitis, tenosynovitis, neuritis
  (carpal tunnel syndrome)

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Neck Problems

• Tension neck syndromes
• Cervical syndromes
• Cervicogenic headaches
• Cervical nerve root syndromes
• Brachial plexus sydromes
• Trapezius myalgia
• Pain in the neck radiating to head, shoulders,
  part of or whole upper limb

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Neck Probelms

• /- Existing degenerative changes in Cx
• Poor posture - poking chin
• Sustained forward flexion, or combined F/SF/R
• Most kinds of work involve looking down and
  head held in fixed positions
• Sudden movements, repetitive movements of head,
  or upper limbs - strain in stabilising muscles in
  neck-shoulder region

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Neck Problems - Research Evidence

• EMG studies - Trapezius
• Sustained abduction of the arms produced muscle
  fatigue in Trapezius - worse in patients with
  neck-shoulder pain (Hagberg, 1981)
• Muscle blood flow (muscle biopsy) and EMG
  activity are worse (decreased) in painful side vs
  non-painful sides (Larsson et al, 1994)
• Compressive loading at C7T13.6x higher in full
  flexion than upright posture

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Who get Neck Problems?

• Office workers - long hours of VDU work
• Problem with Monitor height, position, visual
  acuity
• Fine hand movements - stabilising muscles in neck
  and shoulders
• Workers who maintain their necks in flexion for
  long periods of time
• Lifting with both arms - prolonged, or lifting
  above shoulder height

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Study on effects of static posture on performance
of keyboard task
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Upper Limb Problems

• Tendinitis, Degenerative changes in tendons,
  impingement in rotator cuff muscles
• Scapular muscles - tightness in u. trap and
  levator scapulae, weakness in lower trap,
  rhomboids and serratus anterior
• Elbow - epicondylitis - medial and lateral
• Forearm muscles - tenosynovitis
• Thoracic outlet syndrome
• Rule out cervical and ULTT problems first

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Problem of Neural Tension

• Became widely recognised around the same time as
  RSI
• ULTT/Brachial Plexus tests - developed by
  clinicians in 70s-80s
• Australia - some clinicians treat RSI cases only
  with brachial plexus techniques

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Common Pathology

• Repetitive sliding of tendons in tendon sheaths
  -inflammation ? Tenosynovitis
• Awkward posture of joint (wrist) - cause
  compression of neural tissues / tendons ?CTS
• Forceful muscle actions - micro-tearing at
  tendon-bone interface ? tendinitis, tendonosis,
  traction spur
• Static isometric contractions - transient
  ischaemia in muscles, or compression on
  structures
• Adverse Mechanical Tension - muscles / joints
  working in awdward angles or adverse positions

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Carpal Tunnel Syndrome (CTS)

• Pathology irritation of median nerve at the
  wrist, usually due to compression by or
  inflammation of flexor retinaculum
• Symptoms
• numbness, tingling /-burning in the thumb, index
  and middle fingers
• Loss of sensation in fingers
• Loss of grip strength
• Feeling of swollen fingers

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Carpal Tunnel Syndrome (CTS)

• Objective Examination
• Tinels test - tapping the median nerve
• Phalens test - full flexion of wrist
• Palpation, observation
• Neurological exam
• Differentiation from Cx problems and local joint
  problems

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Diagnostic tests

• EMG test nerve conduction velocity
• Vibrometrymeasure vibration sense in range from
  8 to 500 Hz
• Neurometry neurometer is use to assess sensory
  impairment

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Who get CTS ?

• Office workers - keyboard work - resting wrists
  at edge of table, or holding wrist in excessive
  extension
• Industrial workers - highly repetitive movements,
  awkward hand postures
• Use of small hand tools - small grip size and
  awkward wrist positions - Dental technicians,
  electricians
• Carrying objects (e.g. large piece of glass,
  books)
• Vibrations, e.g. welders, power tools, drivers

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Other medical conditions that may cause CTS

• Pregnancy
• Rheumatoid arthritis and other rheumatic diseases
• Obesity
• Diabetes
• Hypothyroidism
• trauma (fractures etc)

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Tenosynovitis of forearm

• Recognised occupational disease
• repetitive actions of wrist / hand
• related to compression of blood vessels with
  prolonged contractions of muscles
• SS swelling, pain, ?ROM of wrist/hand, ?strength

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Common Pathology

• Repetitive sliding of tendons in tendon sheaths
  -inflammation - Tenosynovitis
• Awkward posture of joint (wrist) - cause
  compression of neural tissues / tendons
• Forceful muscle actions - micro-tearing at
  tendon-bone interface
• Static isometric contractions - transient
  ischaemia in muscles, or compression on
  structures
• Adverse Mechanical Tension - muscles / joints
  working in awdward angles or adverse positions

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De Quervains Syndrome

• Tendinitis of long abductor and short extensor
  tendons of the thumb, in the area of anatomical
  snuffbox
• Caused by repetitive frictions between thumb
  tendons and common tendon sheaths, running over
  bony areas
• Repetitive (forceful) pinching actions combined
  with flicking of wrist (e.g. scissors, pliers)
• Gardener - use of clippers
• Typists - excessive use of thumb, use of mouse

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Ganglions around tendons
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Vibration Syndrome

• Common problem in workers who use power tools
• Affected by duration of use and magnitude of
  vibration
• Symptoms include paraesthesia, loss of sensation,
  loss of fine co-ordination in fingers
• Can lead to carpal tunnel syndrome,
  tenosynovitis, nerve compression and damage,
  Vibration white fingers

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Occupational Risk Factors

• Posture - prolonged static posture, awkward
  posture
• External Load
• Speed
• Force
• Repetitiveness (action frequency)- combined wrist
  movts e.g.F, UD, pron/sup
• Personal characteristics
• Skills and experience of worker-work technique

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Machine operator with hand in awkward position
Ganglions around extensor tendons
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What do these motions have in common?
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3 Main Risk Factors for most work-related
musculoskeletal problems

• 1. Frequency, speed, repetitiveness
• (technical actions)
• 2. Force
• 3. Postures and movements
• (whole body and/or specific joints)

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Office Work vs Industrial Work

• Industrial Work
• More distinct repetitive actions
• Easier to separate into technical actions
• Higher force
• Movements may be large or small
• Posture - may be static or dynamic
• Easier to quantify movements

• Office Work
• Movements very fine, less distinct, more
  difficult to quantify
• Static sustained posture of upper body
• Fine movements of hands
• Low force
• Easier to measure posture but difficult to
  measure movements

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The RSI Epidemic

• Significant increase in compensation claims in
  large corporations such as Aust. Telecom in
  1970-1980s
• Heated debate in media, public and among medical
  professionals
• RSI - is it in the head or in the hand?
• Among physio., argument whether this is a
  cervical problem, ULTT, or muscle problem
• Criticism of the name RSI

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Psychological Impact

• Some researchers try to establish certain psy.
  profiles or personality types assoc. with RSI
• Small of cases can be Malingerers
• Dx like RSI or LBP can lead to stereotyping -
  workers who are genuine are also put in the same
  category as malingerers
• Pressure from employer to return to work
• Peer Pressure from other employees
• Pressure from within - fear of further injury to
  self

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Intervention Programs

• Workstation Modifications
• Worker Education - manual handling techniques
• Work Modifications- improve work habits and use
  of tools / aids
• Job Rotation
• Introduce Mini Work Breaks - Stretch Exercise
  breaks
• Remove stressful situations-improve job
  satisfaction

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Work Rehabilitation Programs

• Physiotherapy Assessment and Treatment
• (/-) OT Assessment and Treatment
• General conditioning and fitness training
• Work hardening
• Graduated Return-to-work Programs

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Summary

• WRMSD are problems characteristic of hi-tech
  culture - use of computers, industrial
  specialisation
• Terms highlight the work-relatedness of these
  conditions, include whole range of neck and upper
  limb conditions
• Important to examine patient and identify
  specific problems and pathology
• Identify risk factors
• Improvements in work situations is an important
  part in the rehabilitation program