Ergonomics and Work-related Upper Extremity Disorders (WRUED)

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

2. 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)

3. Epidemiological Studies on CTD Bureau of Labour Statistics (U.S.): • >300,000 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

4. 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)

5. 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)

6. 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)

7. 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 >4 hours VDU work daily • Significant relationship between incidence of MSK discomfort andVDU work • http://www.oshc.org.hk/eng/research/research.htm

8. 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 Syndrome0 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)

10. 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

11. Specific Syndromes include: • Cervical spine problems • Rotator cuff tendonitis • Lateral epicondylitis • Carpal tunnel syndrome • de Quervain’s syndrome • tenosynovitis of forearm muscles • nerve entrapments • thoracic outlet syndrome • vibration white fingers

12. Ergonomics in Manufacturing (Karwowski & Salvendy, ed), Chapter 16: An overview of upper extremity disorders, S. Moore 5 conditions: • trigger finger/thumb • de Quervain’s syndrome • peritendinitis • lateral epicondylitis • carpal tunnel syndrome • Cervical and shoulder conditions are excluded • industrial - repetitive nature of work

13. 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

14. 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

15. 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?

16. 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

17. 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 - P&N, sensation, power or reflex changes

18. 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

19. 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)

20. 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

21. 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

22. 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 C7T1=3.6x higher in full flexion than upright posture

23. 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

27. Study on effects of static posture on performance of keyboard task

30. 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

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

32. 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

34. 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

35. Carpal Tunnel Syndrome (CTS) Objective Examination: • Tinel’s test - tapping the median nerve • Phalen’s test - full flexion of wrist • Palpation, observation • Neurological exam • Differentiation from Cx problems and local joint problems

36. Diagnostic tests: • EMG test: nerve conduction velocity • Vibrometry:measure vibration sense in range from 8 to 500 Hz • Neurometry: neurometer is use to assess sensory impairment

37. 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

38. Other medical conditions that may cause CTS • Pregnancy • Rheumatoid arthritis and other rheumatic diseases • Obesity • Diabetes • Hypothyroidism • trauma (fractures etc)

39. Tenosynovitis of forearm • Recognised occupational disease • repetitive actions of wrist / hand • related to compression of blood vessels with prolonged contractions of muscles • S&S: swelling, pain, ROM of wrist/hand, strength

40. 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

41. De Quervain’s 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++

43. Ganglions around tendons

44. 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”

45. 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

46. Machine operator with hand in awkward position Ganglions around extensor tendons

47. What do these motions have in common?

49. 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)

50. 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 Office Work vs Industrial Work