NECK AND UPPER EXTREMITY
ERGONOMICS 101UUCSF Occupational Medicine CME
March 11, 2017Carisa Harris Adamson, PhD, PT, CPE
I have no personal conflicts of interest to disclose.
The UC Ergonomics Research & Graduate Training Program is supported by:
GooglePentax
LogitechSantos Human
Why Ergonomics Today?U.S. Companies Pay $62 Billion Per Year for Workplace Injuries
$16 billion direct costs from WMSDs
Indirect costs are 2-5 times greater
The annual cost to U.S. business of lost-time workplace injuries is greater than the GDP of 91 countries
http://www.lco-cdo.org/vulnerable-workers-final-report.pdf
Incidence & Prevalence
356,910 WMSDs* in private industry in the United States *
incidence rate of 29.8 per 10,000 full-time workers
median of 12 days away from work
accounted for 32% of all injuries and illnesses reported to BLS
Definition of WMSDs:• A pinched nerve; herniated disc; meniscus tear; sprain, strain, or tear; hernia; pain,
swelling, and numbness; carpal tunnel syndrome and tarsal tunnel syndrome; Raynaud's syndrome and Raynaud’s phenomenon; musculoskeletal system and connective tissue diseases and disorders, AND
• overexertion …repetitive motion…. multiple exertions or vibration.
Bureau of Labor Statistics. Nonfatal Occupational Injuries and Illnesses Requiring Days Away From Work, 2015. Available at: http://www.bls.gov/news.release/osh2.nr0.htm.
By Occupation
OccupationNumber of Incident
CasesIncidence Rate per
10,000 Workers
Laborers and freight handlers21,990 111.0
Nursing aides and orderlies19,360 180.5
Janitors and cleaners15,810 102.6
Heavy and tractor-trailer truck drivers 15,320 95.6
Emergency medical ttechnicians/paramedics 3,980 187.4
Firefighters5,630 168.5
Telecommunication line iinstallers/repairers 2,190 224.6
Incidence of Work-Related Musculoskeletal Disorders in Private Industry, United, States, 2015
https://www.cdc.gov/niosh/docs/97-141/pdfs/97-141.pdf
By Body Region
Type
Incidence per
10,000 FTEs(b)
Median
Lost Workdays(c) Median Cost(d)
All 90.0 56 $11,183
Back 40.8 35 $6,032
Shoulder 14.8 129 $28,228
Rotator cuff syndrome(e) 6.2 192 $37,835
Elbow/forearm 5.3 116 $18,083
Epicondylitis(e) 1.6 129 $19,484
Hand/wrist 15.3 79 $14,166
Carpal tunnel syndrome(e) 6.4 100 $17,536
Tendonitis(e) 3.4 95 $15,721
Knee 10.1 56 $14,245
Work-Related Musculoskeletal Disorders (WMSDs) of the Neck, Back, and Upper Extremity, Washington State Workers’ Compensation Compensable(a) Claims, State Fund and self-insured, 2002–2010
EEvidence from Epidemiological StudiesStrong EEvidence (++)Evidence(+)IInsufficient (0)
Force Repetition Awkward Posture
Static Posture
Combo Vibration
Neck & Neck/Shoulder + + ++ . . 0Shoulder 0 + + . . 0Elbow + 0 0 . ++ .Hand/WristTendonitis + + + . ++ +Carpal Tunnel Syndrome + + 0 . ++Hand Arm Vibration . . . . . ++Back ++ . + 0 . ++
https://www.cdc.gov/niosh/docs/97-141/pdfs/97-141.pdf
WWhy injuries occur
2001 National Research Council Institute of Medicine report on MSDs and the workplace
DDemand vs. Capacity
40
30
20
10
0
0 2 4 6 8 10 12 14 16 18
Load(kg)
Frequency (Lifts / minute)REPETITION
Unacceptable(Demand > Capacity)
Acceptable(Capacity > Demand)
Acute Injury
Repetitive StrainInjury, Fatigue
© Jim Potvin (2016)
FORCE
DDemand
EXERTION(FORCE)
FREQUENCY OF EXERTIONS (REPETITION)
DURATION OFEXERTION
RECOVERY
© Jim Potvin (2016)
CCapacity
Force production influenced by:
Number of motor units activated
Muscle fiber type
Muscle architecture (PCSA)
Muscle Length
Velocity & Type of Contraction
Muscle Fatigue
CCapacityFatigue: decreased ability to generate force (%MVC)
Symptoms: discomfort, pain, tremor, endurance
© Jim Potvin (2016)https://image.slidesharecdn.com/10motorunitsr20022013-al-131106170713-phpapp01/95/10-motor-unit-sr2002-2013-al-11-638.jpg?cb=1383757997
C of G
Demand vs. Capacity
Torque = Force x moment arm
Torque external = Torque internal
DDemand vs. Capacity
NECK & SHOULDER MUSCULOSKELTAL
DISORDERSNECK
UUpper Neck Tension Syndrome
SHOULDERImpingement Syndrome
biceps tendonitis
EEvidence from Epidemiological StudiesStrong EEvidence (++)Evidence(+)IInsufficient (0)
Force Repetition Awkward Posture
Static Posture
Combo Vibration
Neck & Neck/Shhoulder + + ++ . . 0Shoulder 0 + + . . 0Elbow + 0 0 . ++ .Hand/WristTTendonitis + + + . ++ +Carpal Tunnel SSyndrome + + 0 . ++Hand Arm VVibration . . . . . ++Back ++ . + 0 . ++
https://www.cdc.gov/niosh/docs/97-141/pdfs/97-141.pdf
Neck Tension Syndrome
•Aching discomfort at the base of neck/upper back- can be unilateral•Headaches due to radiating pain •Intermittent neck muscle spasms •Tenderness to palpation
• IR = 31.5 per 10,000 FTEs
• Among a large Danish Cohort Study:
o 12 month prevalence 31%
o Point prevalence: 21%o Prevalence Chronic
Symptoms >3mos): 14%
Picavet HSJ, Schouten JSAG. Musculoskeletal pain in the Netherlands: prevalence, consequences and risk groups, the DMC study. Pain.2003;102:167-78.
[Chaffin 1973]
Time to Fatigue for Sustained Cervical Flexion
• Annual Incidence of pain >1week in office environment 34%
• Prolonged neck flexion and rotation
• Increase computer use
Palmer & Smedley, 2007
Systematic Review (N=136; n=21)
Studies included
– 15 Cross-Sectional– 4 prospective– 2 Case-Control
• Static Neck Loading
• Repetitive or forceful shoulder work
• High Job Strain
Palmer KT & Smedley J. Work relatedness of chronic neck pain with physical findings—a systematic review. Scand J Work Environ Health. 2007;33(3):165-191.
Shoulder DisordersSupraspinatus tendon gets impinged under coracoacromial arch
Microtrauma of bicipital tendon (long) as it passes through the bicipital groove of humeral head
Time to Fatigue for Unsupported Reach Activities
Van Rijn et al, 2010Systematic Review (N=1739; n=17)
– 14 Cross Sectional– 2 Prospective– 1 Case-Control
High Force (OR 2.8 - 4.2)– >10% MVC– Lifting>20kg >10x/day– High hand exertion >1hr/day
oHigh Repetition (OR 1.04 - 4.7)
– Shoulder movements– Hand exertions (>2hrs/day)– Hand arm vibration– Working with hand above shoulder height– Working °
High Psychosocial Demand (OR 1.5 - 3.19)vanRijn RM, Huissted BMA, Koes BW, Burdorf A. Associations between work-related factors and specific disorders of the shoulder- a systematic review of the literature. Scand J Work Environ Health 2010;36(3):189-201.
Examples
DISTAL UPPER EXTREMITY DISORDERS
EElbowlateral epicondylitismedial epicondylitis
Hand/Wristsix extensor compartments
intersection syndromethree flexor sites
stenosing tenosynovitis
Entrapment NeuropathiesCarpal tunnel syndrome
Cubital tunnel syndrome Guyon's canal compression
Hand-arm-vibration syndrome
Lateral & Medial Epicondylitis
EEvidence from Epidemiological StudiesStrong EEvidence (++)Evidence(+)IInsufficient (0)
Force Repetition Awkward Posture
Static Posture
Combo Vibration
Neck & Neck/Shhoulder + + ++ . . 0Shoulder 0 + + . . 0Elbow + 0 0 . ++ .Hand/WristTTendonitis + + + . ++ +Carpal Tunnel SSyndrome + + 0 . ++Hand Arm VVibration . . . . . ++Back ++ . + 0 . ++
https://www.cdc.gov/niosh/docs/97-141/pdfs/97-141.pdf
Biomechanical Exposure
Systematic Review (N=633; n=13) on elbow disorders and work related factors
LE associated with:
– Handling tools >1 kg (ORs of 2.1–3.0)– handling loads >20 kg at least 10 times/day (OR 2.6) – repetitive movements >2 h/day (ORs of 2.8–4.7)
ME associated with:
– Handling loads >5 kg (2 times/min at minimum of 2 h/day), – handling loads >20 kg at least 10 times/day, – high hand grip forces for >1 h/day, – repetitive movements for >2 h/day (ORs of 2.2–3.6) – working with vibrating tools >2 h/day (OR 2.2)
vanRijn RM, Huissted BMA, Koes BW, Burdorf A. Associations between work-related factors and specific disorders at the elbow: a systematic review of the literature. Rheumatology. 2009;48:528-536.
611 people followed for up to 3.5 years
12 manufacturing and service sectors in WA
Case Criteria: pain at LE with resisted wrist extension & symptoms
IR = 4.91 per 100 person-years
Posture and force associated with lateral epicondylitis (LE)• ° for 40% AND
o Power grip [HR=2.8; 95%CI: 1.35-5.77]o 95%CI: 1.19-5.24]o %time forceful exertion [HR=2.3; 95%CI: 1.09-4.66]
Older exposed workers (35-64 yo) were 4x more likely to get LE
Engaging in hobbies/sports with high hand force did not increase risk
Fan JZ, Silverstein BA, Bao S, Bonauto DK, Howard NL, and Smith CK. The association between combination of hand force and forearm posture and incidence of lateral epicondylitis in a working posture. Human Factors. 2014;56(1):151-165.
Biomechanical Exposure
Hand/Wrist Tendinopathy
Irritation of EPB & APL tendons or synovium under sheath
Precision vs. PowerPower Grip A &C
Spherical grip A
Cylindrical grip C
Hook grip J
Lumbrical Grip
Precision Grip D-F
Lateral Pinch G
Pad to Pad Pinch I
Tip to Tip Pinch H
Increasing Strength
Prospective Right Wrist Tendinosis
Summary
28 MONTH FOLLOW UP N=413
Right Side
Incid./ 100 PYs
Right Side
Incid./100PYs
Extensor Tendonitis 22 4.56
Flexor Tendonitis 11 2.24
Dorsal Compartment 1 13 2.68
Flexor Carpi Radialis 7 1.42
Dorsal Compartment 2 2 0.40
Flexor Carpi Ulnaris 0 0.00
Dorsal Compartment 3 6 1.23
Flexor Digit.Sup. 5 1.01
Dorsal Compartment 4 6 1.21
Trigger Finger 2 0.40
Dorsal Compartment 5 0 0.00Dorsal
Compartment 6 4 0.81Intersection
Syndrome 0 0.00
Incidence of Hand/Wrist Tendinopathy
Harris, C. Eisen, E., Goldberg, R., Krause, N., Rempel, D. “Workplace and individual factors of Wrist Tendinosis among blue-collar workers- the San Francisco Study.” Scan J Work Environ Health. 2011; 37 (2): 85-98.
FCR > FDS > FCU
DC1(EPB/APL) >> DC6 (ECU) > DC3(EPL) or DC4(ED)
EEvidence from Epidemiological StudiesStrong EEvidence (++)Evidence(+)IInsufficient (0)
Force Repetition Awkward Posture
Static Posture
Combo Vibration
Neck & Neck/Shhoulder + + ++ . . 0Shoulder 0 + + . . 0Elbow + 0 0 . ++ .Hand/WristTTendonitis + + + . ++ +Carpal Tunnel SSyndrome + + 0 . ++Hand Arm VVibration . . . . . ++Back ++ . + 0 . ++
https://www.cdc.gov/niosh/docs/97-141/pdfs/97-141.pdf
NIOSH UEMSD Consortium StudyDetermine exposure-response relationship between physical exposure & UEMSDs413 individuals in 4 sectors followed for up to 28 mos.Individual exposure assessment & physical examsForceful exertion:
Pinch )
XTWA = [( X1*p1) + (X2*p2) + …. (X4*p4)]
0
1
2
3
4
5
6
7
8
9
10
Haz
ard
Rat
io &
95%
CI
lowVASmed high low
Tool Weightmed high low
Normal. Peak Forcemed high low
% Time Heavy Pinchmed high
Force Measures: age-, gender-, and repetition(reps/min)-adjusted
Biomechanical Exposure
Harris, C. Eisen, E., Goldberg, R., Krause, N., Rempel, D. “Workplace and individual factors of Wrist Tendinosis among blue-collar workers-the San Francisco Study.” Scan J Work Environ Health. 2011; 37 (2): 85-98.
Harris, C. Eisen, E., Goldberg, R., Krause, N., Rempel, D. “Workplace and individual factors of Wrist Tendinosis among blue-collar workers-the San Francisco Study.” Scan J Work Environ Health. 2011; 37 (2): 85-98.
Biomechanical Exposure
Harris-Adamson C, Eisen EA, Goldberg R, You D, and Rempel D. The impact of posture on wrist tendinosis among blue-2014;56(1):143-150.
Biomechanical Exposure
Carpal Tunnel Syndrome2 million outpatient visits for CTS
Over 400,000 outpatient carpal tunnel release surgeries per year
50% 1 month lost time
11% lost or changed jobs
Most common peripheral nerve entrapment syndrome
pheral nerve entrapment
70 mm Hg0 mm Hg
Nerve Compression - 4 weeks
Mild perineural edema Epineurial fibrosisPerineurial thickeningLoss of myelinAxon dropout
Rempel DM, Diao E. Entrapment Neuropathies: pathophysiology and pathogenesis. Journal of Electromyography and Kinesiology. 2004:14; 71–75Keir PJ & Rempel DM. Pathomechanics of peripheral nerve loading: evidence in carpal Tunnel Syndrome. Journal of Hand Therapy. 2005:18(2);259-269.
EEvidence from Epidemiological StudiesStrong EEvidence (++)Evidence(+)IInsufficient (0)
Force Repetition Awkward Posture
Static Posture
Combo Vibration
Neck & Neck/Shhoulder + + ++ . . 0Shoulder 0 + + . . 0Elbow + 0 0 . ++ .Hand/WristTTendonitis + + + . ++ +Carpal Tunnel SSyndrome + + 0 . ++Hand Arm VVibration . . . . . ++Back ++ . + 0 . ++
https://www.cdc.gov/niosh/docs/97-141/pdfs/97-141.pdf
Covariate N=2474 (179 cases) HR [CI]*Female 1.30 [0.98-1.72]Age ( 40 years) 2.84 [1.85-4.37]
2) 1.67 [1.26-2.21]Co-morbidities (DM, RA, thyroid) 0.95 [0.62-1.44]Non-occupational hand activity 0.58 [0.41-0.82]
>3 hrs/wk
*adjusted for gender, age, & BMI.
Personal Factors
Harris-Adamson C, Eisen EA, Dale AM, Evanoff B, Hegmann KT, Thiese MS, Kapellusch J, Garg A, Burt S, Silverstein B, Bao S, Merlino L, Gerr F, Rempel D. Personal and workplace psychosocial risk factors for carpal tunnel syndrome: a pooled study cohort: author response. Occup Environ Med. 2014;71(4):303-4.
WWRIST POSTURE PEAK HAND FORCE
Biomechanical Exposure
Harris-Adamson C, Eisen EA, Kapellusch J, Garg A, Hegmann KT, Thiese MS, Dale AM, Evanoff B, Burt S, Bao S, Silverstein B, Merlino L, Gerr F, Rempel D. Biomechanical risk factors for carpal tunnel syndrome: a pooled study of 2474 workers. Occup Environ Med. 2015;72(1):33-41
Biomechanical Exposure
Harris-Adamson C, Eisen EA, Kapellusch J, Garg A, Hegmann KT, Thiese MS, Dale AM, Evanoff B, Burt S, Bao S, Silverstein B, Merlino L, Gerr F, Rempel D. Biomechanical risk factors for carpal tunnel syndrome: a pooled study of 2474 workers. Occup Environ Med. 2015;72(1):33-41
% TIME HAND EXERTION(any & forceful)
REPETITION(any & forceful)
Risk of CTS increases linearly with increasing age and increasing BMI
Biomechanical factors associated with CTS• Peak hand force • Forceful hand repetition rate (>3 exertions/min)• % time in forceful hand exertions (> 11%)
Biomechanical factors nnot associated with CTS• Total hand repetition rate• % time any hand exertions• Wrist posture
[Forceful = grip]
Biomechanical Exposure
Harris-Adamson C, Eisen EA, Kapellusch J, Garg A, Hegmann KT, Thiese MS, Dale AM, Evanoff B, Burt S, Bao S, Silverstein B, Merlino L, Gerr F, Rempel D. Biomechanical risk factors for carpal tunnel syndrome: a pooled study of 2474 workers. Occup Environ Med. 2015;72(1):33-41
ACGIH TLV for Hand Activity
high risk-needs analysis/ job design
intermediate risk; surveillance and general controls recommended
<AL (0.56): low risk
TLV for HAL Score = NPF / (10- HAL)
% M
VC
Exposure1 N=2751 (n=186) HR*TLV for HAL 1.73 [1.19-2.5]TLV for HAL 1.48 [1.02-2.13]
Exposure2 N=2299 (n=84) IRR*TLV for HAL 1.95 [1.21-3.16]TLV for HAL 2.70 [1.48-4.91]
Risk increased for those above the Action Limit –current cutoffs might not be sufficiently protective
ACGIH TLV for HAL
1 Kapellusch JM, Gerr FE, Malloy EJ, Garg A, Harris-Adamson C, Bao SS, Burt SE, Dale AM, Eisen E, Evanoff BA, Hegmann KT, Silverstein BA, Thiese MS, and Rempel D. Exposure-Response Relationships for the ACGIH TLV for Hand Activity Level: Results from a Pooled Data Study of Carpal Tunnel Syndrome. Scand J Work Environ Health. 2014;40(6):610-20.
2 Bonfiglioli R, Mattioli S, Armstrong TJ, Graziosi F, Marinelli F, Farioli A, Violante FS. Validation of the ACGIH TLV for hand activity level in the OCTOPUS cohort: a two-year longitudinal study of carpal tunnel syndrome. Scand J Work Environ Health 2013;39(2):155-163.
Work Psychosocial FactorsN Cases(n) HR 95% CI
Psychological Demand 1538 102Low 41 1.00 refHigh 61 1.38 0.94-2.05
N Cases(n) HR 95% CIDecision Latitude 1530 101
Low 43 1.00 refHigh 58 0.85 0.57-1.27
N Cases(n) HR 95% CIJob Strain 1527 101
Low(Low Demand & High Control)
28 1.00 refActive
(High Demand & High Control)30 1.29 0.76-2.18
Passive(Low Demand & Low Control)
13 1.06 0.55-2.05High
(High Demand & Low Control)30 1.51 0.91-2.52
*Adj for age gender, BMI, study site
Harris-Adamson C, Eisen EA, Neophytou A, Kapellusch J, Garg A, Hegmann KT, Thiese MS, Dale AM, Evanoff B, Bao S, Silverstein B, Gerr F, Burt S, Rempel D. Biomechanical and psychosocial exposures are independent risk factors for carpal tunnel syndrome: assessment of confounding using causal diagrams. Occup Environ Med. 2016 Nov;73(11):727-734.
Are Predictors of Work Disability Different?• Defined as (SF-12 & DASH):
– Pace/Quality Change due to hand symptoms,– Lost Time due to hand symptoms, or– Job Change due to hand symptoms
Covariate HR
Female 1.75 [1.23-2.5]
0.83 [0.59-1.15]
2) 1.23 [0.80-1.87]
Rheumatoid Arthritis 1.85 [1.04-3.26]
High Job Strain(High Demand, Low Control) 2.38 [1.03-5.51]*adjusted for gender, age, BMI & study site
Biomechanical ExposuresExposure N=340 (n=178) HR*
PPace ChangeHal Scale 1.87 [1.19-2.94]Hal Scale>6 1.69 [0.97-2.93]
% time in All Exertions % 0.81 [0.50-1.31]% time in All Exertions>76% 1.96 [1.20-3.20]
Lost TimeTotal Repetition Rate 2.33 [1.02-5.34]Total Repetition Rate>24 2.16 [0.97-4.79]
Forceful Repetition Rate 2.23 [1.01-4.95]Forceful Repetition Rate>8 1.83 [0.88-3.77]
*All models adjusted for gender, age, BMI, study site & non-overlapping exposures
Exposure N=365 (n=118) HR*
JJob ChangeHal Scale 3.45 [1.60-7.43]Hal Scale>6 3.25 [1.46-7.25]
Total Repetition Rate 2.24 [1.13-4.44]Total Repetition Rate>24 2.47 [1.21-5.06]
% time in All Exertions 1.27 [0.65-2.48]% time in All Exertions>76% 2.76 [1.35-5.66]
% time in Forceful Exertions 1.27 [0.65-2.48]% time in Forceful Exertions>28% 2.76 [1.02-4.05]
*All models adjusted for gender, age, BMI, study site & non-overlapping exposures
Biomechanical Exposures
SummaryBeing female or having RA increased risk
Increasing age and BMI did NOT increase risk of disability but did increase risk for CTSHigh job strain increased risk of CTS anddisability
Pain was protective for time lost
Physical factors had strongest associations with job change (vs. pace change or lost time)
MMeasures of both forceful hand activity and repetition were associated with work disability
51
Milk and Dairy Production Chair Manufacturing
Mushroom Growing Stone Manufacturing
Hand Arm Vibration Syndrome
Changes in sensory perception which can lead to permanent numbness of fingers, muscle weakness and, in some cases, bouts of white finger.
Hand Arm Vibration Syndrome
RRisk FactorsVibration (ISO Standards 2631-5349)
o Magnitude
o Frequency
o Direction
Worker
o Exposure Duration
o Posture
o Contact Location
o Applied Force
o Temperature
ControlsSource Control
o Reduce vibration level
Path Controlo Limit exposure time
Receiver Controlo Vibration damping apparel
o Reduce other risk factors
ConclusionInjury occurs when (work) demand > (worker) capacity
Even low physical demand for long periods of time can exceed a workers capacity (ie., result in fatigue)
Force is an important risk factor for MSDs and can be measured in various ways:
Peak Force% time spent in Forceful ExertionForceful Repetition Rate
The ACGIH TLV for HAL is not adequately protective of workers
Risk factors associated with the severity of an UEMSD (work disability) may differ than those associated with its incidence
Questions & Commentshttp://ergo.berkeley.edu
Question #1
According to the Bureau of Labor Statistics, work related musculoskeletal disorders:
a) Have an incidence rate of 3 per 10,000 full-time workers
b) Have a low severity and rarely require time away from work
c) accounted for approximately one third of all injuries and illnesses reported to BLS
d) None of the above
Question #2Total repetition rate alone is an important risk factor for the occurrence of distal upper extremity musculoskeletal disorders such as wrist tendinitis and carpal tunnel syndrome.
a) TRUE
b) FALSE
Question # 3
In a recent large cohort study in the United States, the following exposure(s) were found to be associated with an increased risk of Carpal Tunnel Syndrome:
a) Spending more than 11% time in forceful hand exertion (Pinch>1kg or grip>4kg)
b) Forceful repetition rate >3/minute
c) -10 Scale (0 to 10)
d) All of the above
e) None of the above