Scapula Orientation in a Virtual Wheelchair Push

Alicia M. Koontz MS, ATP
Michael L. Boninger MD, Rory Cooper PhD,
Brian T. Fay MS, Jim Dietzer

Human Engineering Research Laboratories - VAMC
Center of Excellence in Wheelchairs & Related Technology University of Pittsburgh
University of Pittsburgh Medical Center

Slide 1
Scapula Orientation in a Virtual Wheelchair Push

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Alicia M. Koontz MS, ATP
Michael L. Boninger MD, Rory Cooper PhD,
Brian T. Fay MS, Jim Dietzer

Human Engineering Research Laboratories - VAMC
Center of Excellence in Wheelchairs & Related Technology University of Pittsburgh
University of Pittsburgh Medical Center

Slide 2
Introduction
Background

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Shoulder pain/injury is a common and persistent problem among manual wheelchair users.

Physical demands and overuse of the arms

Shoulder position during propulsion may predispose to impingement

Movement descriptions are hampered by the complexity of the shoulder

Slide 3
Introduction
Shoulder Joint Complex

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Slide 4
Introduction
Research Objective

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Inherent problems with measuring dynamic scapula movement in-vivo

  • Record the relative position of the scapula in various stages of push cycle
  • Calculate 3D orientation of the scapula relative to the torso

Slide 5
Methods
Subjects

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8 men / 2 women with T2 level or below SCI

Experienced wheelchair users: 16.9 + 8.6 yrs

Adults: Mean age: 40.7 + 9.2 yrs

Average Mass: 80.6 + 13.7 kg

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Slide 6
Method
Experimental Setup

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Slide 7
Methods
Digitizing Stylus

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Custom-fabricated using FeatureCAM and a CNC mill

Three IRED markers on either side

3D position of the tip

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Slide 8
Methods
Scapula Palpation

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AA: Angulus Acromialis
TS: Trigonum Spinae
AI: Angulus Inferior

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Slide 9
Methods
Protopcol

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Six randomized hand positions:
-30°, -15°, 0°, +15°, +30°, +60°

Recorded chest markers in each position (10 seconds)

Left side analysis

Slide 10
Data Analysis
Local Coordinate Systems (LCS)

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LCS at the scapula and chest

Rotation matrices defined orientations relative to GCS

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Slide 11
Data Analysis
Scapula Orientation

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alpha = Protraction/Retraction

beta = Upward/Downward Rotation

Y = Forward/Rearward Tipping

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Slide 12
Results

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Beginning of push:

  • Maximally tipped forward (21.9° + 6.0)
  • Minimally protracted (15.0° + 3.7)
  • Slight upward rotation (1.5 ° + 4.7)

As the push progressed,

  • Forward tip angle decreased
  • Protraction angle increased
  • Upward rotation angle increased

Slide 13
Discussion

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Maximum relative changes in scapula orientations < 7 °

  • Majority of scapula movement occurs at higher degrees of humeral abduction
  • Large variance

Forward tip angles similar to Veeger et al., 1993 Larger up/down and protraction angles

  • Four unimpaired males subjects
  • Differences may be attributed to anthropometry and shoulder muscle imbalances

Slide 14
Discussion

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Excessive internal rotation combined with scapular protraction are impingement positions

Scapula motion necessary input for musculoskeletal shoulder models

Future studies to investigate the relationship between scapular kinematics and shoulder impingement in wheelchair users is warranted

Slide 15
Acknowledgements

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National Institutes of Health

(Project P01-HD33989)

Eastern Paralyzed Veterans of America

Veterans Affairs Pre-Doctoral Fellowship in Rehabilitation Science

Slide 16
Thank You

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For more information please contact:

Alicia Koontz
VA Pittsburgh HealthCare System
7180 Highland Dr.
Pittsburgh, PA 15206

TEL: 412-365-4858

Email: amkst63@pitt.edu

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Updated: February 28 2002

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Please note: This information is provided a archival information from the Rehabilitation Engineering Research Center on Wheeled Mobility from 1993 to 2002.

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