Download Slide 1 - Baylor University

A Proposed New Obstacle-Set
Algorithm for Modeling Deltoid
Tiffany Xu
Mentor: Dr. Brian Garner
Presentation Outline
I,
Introduction to muscle modeling and why that is needed?
II,
Application areas of muscle modeling.
III, Introduction to four mostly used muscle modeling methods.
IV, Studies carried out using the obstacle-set model.
•Description of muscle modeling using obstacle-set model.
•Difficulties encountered in modeling deltoid.
V,
A new obstacle-set model.
•Algorithm/methods.
•Results/comparison with data from other studies.
•Advantage of the new obstacle-set model.
VI, Conclusion.
VII, Questions.
Introduction to Muscle Modeling
In order to understand how each muscle works to influence
our body behavior, all the following factors need to be studied:
• Point of force application
• Direction of force application
• Force magnitude
But, not all of those factors could be obtained directly, which
is why computer simulation of muscle activity emerges as a
popular method to approximate the muscle moment arm.
Through out the study of muscle mechanics, muscle moment arm is
an eternal topic. Proper representation of muscle paths in
musculoskeletal models is important for accurately modeling the
magnitude and line-of-action of muscle forces.
Applications of Muscle Modeling
•Biomechanics (North Carolina State University, ergonomics research)
•Computer graphics
[1] Patria A. Hume, Justin Keogh and Duncan Reid, The Role of Biomechanics in
Maximizing Distance and Accuracy of Golf Shots. Sports Med 2005，35（5）: 429-449.
[2] Arpad Illyes, Rita M. Kiss, Shoulder Muscle Activity During Pushing, Pulling, Elevation
and Overhead Throw. Journal of Electromyography and Kinesiology 15(2005) 282-289.
[3] Marcus G. Pandy, Computer Modeling and Simulation of Human Movement. Annual
Reviews of Biomedical Engineering, 2001. 3:245-73.
Straight-line model
3D model via finite
element algorithm
Four Mostly
Used Muscle
Wrapping
Methods
Centroid line model
Obstacle-set model
Difficulty of Simulating the Muscle Path: Tension between
desire to have model accuracy, and desire to have simplicity
and computational efficiency.
Obstacle-set Model
The muscle path in this method is formed by several segments
of straight lines and curved lines joined together by via points.
And the anatomical constrains are modeled by cylinder, sphere,
stub, or other combination of those geometries.
Obstacle-set Model Has A Limitation
in Modeling Broad Muscle
However, modeling some broad muscles crossing
joints with wide ranges of motion can be difficult
owing to:
•Broad muscles are modeled with multiple bands.
•Each band’s path is computed independently.
The independent bands of the deltoid have a
tendency to slip around to unrealistic positions
behind the sphere.
New Obstacle-set Algorithm
--improvement was made
The aim of this study was to develop a
new obstacle-set algorithm that accounts
for connectivity between muscle fibers,
that will keep the fibers staying on the
surface of the obstacle-set without any
slip.
New Obstacle-set Algorithm
for Modeling Deltoid
•Origin sites on a fixed clavicle/scapula bone,
and insertion sites on a moving humerus, were
defined.
•A sphere obstacle was defined to represent
anatomy underneath the deltoid.
•Reference planes were specified.
•Fixed angles between the path and reference
planes were chosen to reflect the breadth of the
deltoid muscle between bands.
•Minimum-distance path of each muscle band
around the sphere and within a “path plane” was
calculated.
New Obstacle-set Algorithm
for Modeling Deltoid
The muscle paths were then applied onto the bone structure
reconstructed from the Visible Human Project data.
Sphere as the obstacle
Anterior, medial, and
posterior muscle path
planes and their
orientation; reference
planes and their
orientations.
Process of Simulation
60o
0o
30o
1. Move/rotate the humerus
2. Orientation of the anterior muscle path plane determined
3. Orientation of the medial and posterior muscle path planes changed
4. Minimum length of each muscle path computed
5. Above steps repeated to find the orientation value of the anterior
muscle path plane which minimized the sum of the path lengths
Results of the New
Obstacle-set Model
•No slip.
•Computational time was less than a
millisecond.
•Wide range of shoulder joint motion.
•Realistic configurations of the hypothetical
deltoid.
Results of the New
Obstacle-set Model
Why Say It Is Realistic?
Abduction moment arm for anterior,
medial and posterior deltoid from this
new obstacle-set model, compared
with experimental data from other two
studies.
-- Obstacle-set
-- Liu
-- Otis
1/3, Moment arm of anterior
deltoid during abduction
Results of the New
Obstacle-set Model
-- Obstacle-set
-- Liu
-- Otis
2/3, Moment arm of medial
deltoid during abduction
-- Obstacle-set
-- Liu
-- Otis
3/3, Moment arm of posterior
deltoid during abduction
Advantage of the New
Obstacle-set Algorithm
Advantages of this algorithm include:
•simplicity
•realism
•computational efficiency
•connectivity between muscle fibers taken into account
•flexible algorithm, so that an arbitrarily large number of
muscle bands could be used to model broad muscles.
Conclusion
Compared to other modeling methods, the new obstacle-set
algorithm, is not only simple and fast, but also flexible and
realistic.
This improved obstacle-set model, handles the problem of
slip that happened in the original one. The derived
connectivity algorithm keeps the fibers of a broad muscle
staying on surface of the sphere-shaped obstacle, which
makes the new obstacle-set model robust.
Comparison to the experimental data reveals a good
approximation of the moment arm. But more experimental
data needs to be studied and compared with, so that the
realisticness of this new model could be improved.
Thank you!
Any Questions?
References:
[1] Garner B.A., Pandy M.G., The Obstacle-Set Method for Representing Muscle Paths in Musculoskeletal
Models. Computer Methods in Biomechanics and Biomedical Engineering, Vol. 3, pp. 1-30.
[2] Silva S. Blemker and Scott L. Delp, Three-Dimensional Representation of Complex Muscle Architectures
and Geometries. Annals of Biomedical Engineering, Vol. 33, No. 5, May 2005 pp.661-673.
[3] Garner, B. A. and Pandy, M.G., A kinematic model of the upper limb based on the visible Human Project
dataset. Computer Methods in Biomechanics and Biomedical Engineering.
[4] Brian A. Garner and Marcus G. Pandy, Musculoskeletal Model of the Upper Limb Based on the Visible
Human Male Dataset. Computer Methods in Biomechanics and Biomedical Engineering, Vol. 4, pp.93-126.
[5] JC Otis, CC Jiang, TL Wickiewicz, MG Peterson, RF Warren and TJ Santner,Changes in the moment arms
of the rotator cuff and deltoid muscles with abduction and rotation. Department of Biomechanics, Hospital for
Special Surgery, New York, N.Y. 10021.