Musculoskeletal Modeling

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14 Νοε 2013 (πριν από 4 χρόνια και 7 μήνες)

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Musculoskeletal Modeling

Colin Smith

A method for Studying Movemen
t

Things we can measure in movement:

Kinematics (using motion capture)

Output Forces (Using Force Plates)

Muscle Activation Timing (EMG)

What about in vivo? We need a model

Muscle Forces

Bone contact forces

Musculoskeletal Models

Approach the body like a Machine

Model Bones as Rigid Bodies

Model Muscles as actuators

Inverse Kinematics

Collect Motion Data

Scale Model to match subject

Use least squares method to match position of
markers to model segments

We now know

the kinematics

of each body

segment

Inverse Kinetics

Solving the Equations of motion for each
segment, we can find the forces and moments
between each segment

Muscle Forces

If we know the moments at a joint, we can
find the muscle forces needed to create that
moment

Distribution Problem

Multiple Muscles cross each joint

Bi
-
articular Muscles

Ligaments

Bone
-
Bone Contact

Set up optimization problem

Solve to get Muscle forces

Forward Dynamic Model

Give muscle excitations

Find kinematics, resultant forces

How do we model muscle forces?

Hill Muscle Model

F = Muscle Force

F
0

= Max Isometric Force

v = Contraction Velocity

a =
Coefficent

of Shortening Heat

b

= a* v
0
/F
0

v
0

= Max velocity (F=0)

What can we do with a
Musculoskeletal Model?

Simulate Surgeries

Diagnose causes of atypical gait

Study Neuromuscular Coordination

Analyze Athletic Movements

Compute Internal Forces

Wear on Knee Replacements

Software Demo

How do we know the model is correct?

Must Validate!

Use Inverse Model to compute muscle activations

Compare against EMG data

Measure something in vivo

Bone contact force

The
eTibia

A parameter study

What are the most important parameters to measure in a Subject Specific
Model

Muscle Properties

Length

Cross sectional area

Pennation

Angle

Origin and Insertion locations

Tendon Slack Length

Bone Properties

Dimensions

Joint kinematics

Segment Properties

Mass

Inertia

Joint constraints

Error in Marker Locations?

The Coolest Models

The End