KINESIOLOGY FOR ORTHOPEDICS

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JOINT LOADING
Richard E. Hughes, Ph.D. Orthopaedic Research
Laboratories University of Michigan
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OUTLINE

• Biomechanical principles
• Methods for measuring/estimating loads
• Examples
• Spine
• Knee
• Hip
• Shoulder
• Conclusions

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Force Components
F
direction magnitude point of action
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Force Components
direction magnitude point of action
y
F
x
5
Ax CCW moment By CW moment
x, y are moment arms
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LIFTING A LEVER
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MECHANICS OF LEVER
3F 30FHAND
30
F
FHAND
3
FHAND
F
10
FHAND
F
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MECHANICAL ANALYSIS
FHAND
F
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NEWTONS THIRD LAW
FHAND
FHAND
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MECHANICS OF SPINE
2FMUSCLE 12FHAND
12
FHAND
FMUSCLE
2
FMUSCLE
FHAND
6
FMUSCLE
FHAND
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SEGMENTAL ANALYSIS
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DYNAMIC LIFTING

• Extra force required to accelerate box in hands
• Extra force required to accelerate body segments
• Extra moment required to rotate body segments

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OUTLINE

• Biomechanical principles
• Methods for measuring/estimating loads
• Examples
• Spine
• Knee
• Hip
• Shoulder
• Conclusions

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MEASURING/ESTIMATING JOINT LOADING

• Mathematical model
• Electromyographic (EMG) based methods
• Direct measurement with instrumented prosthesis

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BIOMECHANICAL ANALYSIS
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MEASURING/ESTIMATING JOINT LOADING

• Mathematical model
• Electromyographic (EMG) based methods
• Direct measurement with instrumented prosthesis

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ELECTROMYOGRAPHY
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EMG ELECTRODES
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MEASURING/ESTIMATING JOINT LOADING

• Mathematical model
• Electromyographic (EMG) based methods
• Direct measurement with instrumented prosthesis

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INSTRUMENTED PROSTHESIS
Bergmann, G. et al. (2001) J. Biomech. 34859-871
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OUTLINE

• Biomechanical principles
• Methods for measuring/estimating loads
• Examples
• Spine
• Knee
• Hip
• Shoulder
• Conclusions

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INTER-DISCAL PRESSURE
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HEAVY LIFTING

• Lifting carbon pieces out of smelter
  electrochemical cell
• Pieces weigh 890 N (200 lbs)
• 3327 N (748 lbs) lumbar compression

Hughes, R.E. (1995) Ergonomics 382476-2484
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LIGHT DUTY JOB

• Workers compensation LBP claimants return to this
  job
• No lifting
• 100 repeat claim rate
• Why?

Hughes, R.E. (1995) Ergonomics 382476-2484
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BIOMECHANICAL ANALYSIS
LUMBAR SPINE COMPRESSION 1372 lbs
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MUSCLE ORIENTATION
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OUTLINE

• Biomechanical principles
• Methods for measuring/estimating loads
• Examples
• Spine
• Knee
• Hip
• Shoulder
• Conclusions

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DYNAMIC ANALYSIS
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JOINT LOADING

• Methods
• Moments measured from gait analysis
• Muscle forces estimated from moments
• Mathematical model
• Results
• 3 x BW peak compression force
• 1 x BW peak AP force
• Minimal medial-lateral force

Mikosz,R.P. et al. (1988) JOR 6205-214.
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OUTLINE

• Biomechanical principles
• Methods for measuring/estimating loads
• Examples
• Spine
• Knee
• Hip
• Shoulder
• Conclusions

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INSTRUMENTED PROSTHESIS
Bergmann, G. et al. (2001) J. Biomech. 34859-871
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HIP ABDUCTION/ADDUCTION MOMENT
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RESULTANT FORCES
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HIP LOADS
FORCE (xBW)
Bergmann, G. et al. (2001) J. Biomech. 34859-871
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RESULTANT FORCE DURING STANCE PHASE OF WALKING

• 2.6-2.8 x BW (Davy et al., 1988, JBJS)
• 2.8 x BW (Bergmann et al., 1993, JB)
• 2.4 x BW (Bergmann et al., 2001, JB)

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OUTLINE

• Biomechanical principles
• Methods for measuring/estimating loads
• Examples
• Spine
• Knee
• Hip
• Shoulder
• Conclusions

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GLENOHUMERAL LOADING

• Method
• Isometric arm abduction
• Muscle force proportional to EMG
• Results
• Max 0.89 x BW
• Max at 90o abduction

Poppen, N.K. and Walker, P.S. (1978) CORR
135165-170.
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OUTLINE

• Biomechanical principles
• Methods for measuring/estimating loads
• Examples
• Spine
• Knee
• Hip
• Shoulder
• Conclusions

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Which of the following is the most likely
contributory factor to joint reactive force?
1. Body and limb gravity 2. Joint deformity 3.
Joint contact area 4. Ligamentous tension about
the joint 5. Muscle contraction about the joint
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Which of the following is the most likely
contributory factor to joint reactive force?
1. Body and limb gravity 2. Joint deformity 3.
Joint contact area 4. Ligamentous tension about
the joint 5. Muscle contraction about the joint
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IMPLICATIONS

• Weight reduction reduces joint loading by
  multiples
• Interventions that reduce muscle moment arms may
  increase joint loading

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THANK YOU