Chapter 15 Flashcards
What is the difference between a planar and multi planar analysis?
A planar analysis is done in 2D while a multi planar analysis is done using 3D data.
What are the limitations and benefits of 2D/planar analysis?
It can not provide information outside the recorded plane - aka foot width or toe turn-out in a squat viewed from the saggital plane.
Less costly and less digitization of landmarks
What are the benefits and limitations of multi-planar/3D analysis?
- requires more cameras $$
- requires tons more digitization
- complex mathematical procedures
- get much more data with 3D
Describe the x, y, and z Cartesian coordinate system.
The x axis is left-right
The y axis is in and out of the page
The z axis is up and down
doesnt matter which axis is up, but must use the right hand rule
Describe the cylindrical coordinate system
The coordinate r is the length of the vector formed by the x and y coordinates. The coordinate (Phi) is the angle between the primary axis (x) and the vector r.
this is all happening within the x,y plane
The 3rd coordinate in the cylindrical system is the z-axis - which determines how far the coordinate moves upwards.
What happens when Phi is equal to 90 or 270 degrees?
Then the vector r is equal to vector y. Thus rotations will occur around the x axis
As Phi changes from 90 degrees, the ________________ becomes less accurate.
The planar projection angle
What is the planar projection angle
A planar projection angle is the angle between two lines or vectors measured after they have been projected onto a flat (planar) surface.
There will be discrepancies between PPA and the actual 3D angle if there is parallax error.
Define the scapular plane.
30-35 degrees anterior - natural orientation of the scapula and technically frontal plane of the scapula.
What are the problems with abducting the arm in the frontal plane of the body?
This actually requires abduction and extension of the humerus relative to the scapula.
Can cause issues such as shoulder impingement or “frozen shoulder” (damage to supraspinatus muscle.
2D motion analysis gives no quantifyable indiction of depth. What kind of error is this called?
Perspective error
How is virtual 3D space created?
1 - Stereoscopic Imaging
Images are slightly offset, such that one eye views the image slightly offset from the other. 3D movies are an example of this. They use stereoscopic imaging (videoing the same thing at the same time, slightly offset). Because each eye observes slightly different images, the brain receives this information in 3D.
- Anaglyph method: projects one red and 1 cyan tinted image and 3D glasses are worn. The glasses only allow each eye to see different images.
- Polarization method: polarized lenses only allow light waves that travel a certain direction, through the lens. One eye allows vertical while the other allows horizontal.
What is the minimum increase in digitization with 3D versus 2D motion capture?
2 cameras = 2X the landmarks
3 cameras = 3X the landmarks
Ect
What are optoelectronic cameras? What are they used for?
3D motion capture
These cameras are tuned to only capture infrared or near infrared light. Though many things absorb IR light (saunas ect) reflective tape will reflect it, which makes it suitable for collecting landmark data, without other data effecting the view. This greatly simplifies the digitization process.
What is the difference between 2D and 3D motion capture as well as defining a rigid body in 2D versus 3D?
2D:
- 1 camera
- 2 digitization points (proximal and distal)
3D:
- requires 2 or more cameras
- more complicated math
- minimum 3 points required (proximal, distal and segment orientation).
Why do research in 3D space ?
Sometimes 2D analysis is good enough however when anaylizing movements like supination and pronation of the foot, 3D analysis is more useful.
Foot pronation involves both abduction and Eversion of the foot, while supination involves both adduction and inversion.
True of false: foot pronation is bad movement mechanics during a squat.
False - foot pronation had no effect on knee or hip movement mechanics during a squat. Instead, foot pronation is desirable! We are meant to walk on uneven terrain. It is not pronation or supination that are bad for the kinetic chain, it is a lack of control within the foot and ankle joint, that makes us vulnerable in these positions.
What digital technologies can be used to digitize and view segments in 3D space?
1 - Computer Aided Design: creates a model in 3D space using a digital design
2 - Computed numerical control: carved out 3D objects from digital objects
3 - 3D Photogrammetry: take a bunch of photos of an object from different perspectives
Why is 3D printing valuable?
- can design personalized prosthetics by only taking a few measurements
How could 3D printing be applied to learning anatomy?
- digitally reconstruct cadaver bones
- 3D print cadaver bones
- replace muscles with chords
- cords are pulled on to move bones and learn anatomical actions
