matching shoulder job demands to functional capacity

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

Sorry the video links are not active through the academia.edu site.

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