matching shoulder job demands to functional capacity
DESCRIPTION
This lecture provides a review of shoulder anatomy, presents a number of shoulder related injuries that may occur in the workplace, then presents a method to reduce injury risks by matching shoulder functional capacity with the demands placed on the shoulder joint during workTRANSCRIPT
Shoulder Biomechanics:Using ergonomics & kinesiology to reduce
occupationally related shoulder injuries
The Big Picture
Match Demand & Capacity
JobDemand
FunctionalCapacity
Shoulder Function:Boney Anatomy Refresher
© Primal Pictures 2010
Acromion
Coracoid process
Suprasternalnotch
Inferior angle
Scapular spine
Medial border Lateral
border
Shoulder Function: Humeral and Scapular Motion
The perfect compromise between mobility and stability
High Stability
Low Mobility
Low Stability
Moderate Mobility
Moderate Stability
High Mobility
The perfect compromise between mobility and stability
High Stability
Low Mobility
Low Stability
Moderate Mobility
Moderate Stability
High Mobility
The Big Picture
Match Demand & Capacity
DemandOn the
Shoulder
ShoulderCapacity
Are we currently doing a good job matching demands and capacities?
30% of claims are upper limb related
$1850 - $10500 cost / claim
What if we don’t match demands and capacities?
• Tendon– RC tendonitis– Bicipital tendonitis– RC tear– Bursitis
• Nerve– Suprascapular – Thoracic outlet syndrome
• Muscle– Prolonged muscle pain
What if we don’t match demands and capacities?
• Tendon– RC tendonitis– Bicipital tendonitis– RC tear– Bursitis
• Nerve– Suprascapular – Thoracic outlet syndrome
• Muscle– Prolonged muscle pain
What if we don’t match demands and capacities?
• Tendon– RC tendonitis– Bicipital tendonitis– RC tear– Bursitis
• Nerve– Suprascapular – Thoracic outlet syndrome
• Muscle– Prolonged muscle pain
What if we don’t match demands and capacities?
• Tendon– RC tendonitis– Bicipital tendonitis– RC tear– Bursitis
• Nerve– Suprascapular – Thoracic outlet syndrome
• Muscle– Prolonged muscle pain
What if we don’t match demands and capacities?
• Tendon– RC tendonitis– Bicipital tendonitis– RC tear– Bursitis
• Nerve– Suprascapular – Thoracic outlet syndrome
• Muscle– Prolonged muscle pain
Linking injuries to biomechanical mechanisms – Kinetics
Impact
Impact
© Primal Pictures 2010
Humeral head migration
Scapular rotationAcromion
Humeral Head
Linking injuries to biomechanics to injury mechanisms – Kinematics
Impact
Impact
Differentiating injury mechanics
Kinetics:Bone on Bone
Compression & Shear
Kinematics:Scapular and humeral positions and motions
Role: To transfer large forces
Role: To provide mobility
Shoulder injuries at work are complex!
• Kinematics• Scapular• Humeral
• Kinetics• Muscle force• Cumulative muscle
force• Neuromuscular Control
• Muscular control
Awkward postures
Repetitive work
Force direction
The Big Picture
Match Demand & Capacity
DemandOn the
Shoulder
ShoulderCapacity
Force
Posture
Repetition
Duration
Ergonom
ics
Critical Job Demands
1. Time
2. Arm elevation
3. Reach distance
4. Work direction
5. Force
6. Precision
How can we reduce job demands for the shoulder?
Force
Posture
Repetition & Duration
Force & Duration
Posture & Force
Force & Posture
1. Time• Are the arms elevated for more than 10% of the work cycle or shift time?
Reduce demands by limiting:exposure time
2. Arm elevation• Are the arms elevated more than 60° or more than 90°
Reduce demands by limiting:awkward postures
3. Reach distance• How far away from the body is the work?
Reduce demands by limiting:reach distance
4. Work direction• Are forces applied vertically or horizontally?
Reduce demands by controlling:force application directions
5. Force• What is the force required?
Reduce demands by limiting:peak and prolonged forces
6. Precision• Are precise movements required?
Reduce demands by limiting:precision requirements
< 10% of shift working overhead
Arm elevation < 60° Work is close to the
bodyApplied force is
downLow forcesLow precision
requirements
> 10% of shift working overhead
Arm elevation > 60°Extended reachesApplied force is
along the horizontalHigh forcesHigh precision
requirements
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A quick qualitative checklist to determine relative injury risk
The Big Picture
Match Demand & Capacity
JobDemand
FunctionalCapacity
Force
Posture
Repetition
Duration
ROM
Function
Kinesiology
Proper Posture Prevents Potential Problems!
C/T spine flexion, Forward head,
slouching
Imbalanced muscles, shortened pec major Scapular protraction
Crowding in subacromial spaceImpingement
How can we increase work capacity of the shoulder?
Abnormal motion Pain Limitations
First, we evaluate the capacity
Quick field tests for shoulder ROM
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Quick field tests for shoulder function
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Functional Capacity
ROM
Function
Is the capacity adequate?
Are corrective approaches required?
Integrating the test results
The Big Picture
Match Demand & Capacity
JobDemand
FunctionalCapacity
Force
Posture
Repetition
Duration
ROM
Function
Applying your skillsScenario 1
• 8 years on the job• 55 second work cycle • 15 sec. above 60° –
10 sec. above 90°• Precision placement
required• Good functional
capacity
Evaluate the job demands
Evaluate the functional capacity
Precision
required
Extended
reaches
> 10% time
above 90°
Good function
Good ROMModify the
job demand
Scenario # 2
• 3 years on the job• No set work cycle• 20 minutes / shift
working above 60°• No precision required
while overhead• Poor functional capacity
Evaluate the job demands
Evaluate the functional capacity
Pain during tests
Poor function
Poor ROM
Low force, No precision
< 10% time above 90°
Modify the functional capacity
Scenario # 3
• 14 years on the job• 30 second work cycle • 2 sec. above 60°• Some precision
requirement• Good functional
capacity• PAIN on functional tests
Evaluate the job demands
Evaluate the functional capacity
Pain during tests
Good function
Good ROM
Low force, Some precision
Work is close to the body
< 10% time above 90°
Rotate away from
the job
Scenario # 4
• 22 years on the job• 15 min work cycle• Arm height varies from
40 - 90°• High cognitive workload• Good functional
capacity• PAIN on functional tests
Evaluate the job demands
Evaluate the functional capacity
Your solution
???
• Kinematics• Scapular• Humeral
• Kinetics• Muscle force• Cumulative muscle
force• Neuromuscular Control
• Muscular control
Function and dysfunction
Shoulder Biomechanics
Workplace demands
The Big Picture
JobDemand
FunctionalCapacity
Force
Posture
Repetition
Duration
ROM
Function
Optimize the biomechanics of the shoulder joint
Ergonom
icsKinesiology