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Inhaltsverzeichnis
Functional joint center/axes estimation methods
The calculation of a functional joint is based on the movement of one segment relative to another segment. This allows to estimate knee- and elbow joint axes, hip- and glenohumeral joint centers.
The calibrations movements should have sufficient range of motion that the computation statistics produce a reasonable stationary point, but the range of motion should not be too large because soft tissue artifact (e.g. movement of markers relative to the underlying skeleton) should be minimized.
Typically specific calibration trials have to be executed.
Several cycles of movement should be included, but there is no study which analyses how many cycles is best. We recommend more than 3 cycles, othere recomment a minimum of 5. The optimal number may depend on many issues, including the joint and the amount of soft tissue artfeacts. Each user should experiment with his own measurement procedure.
Centre of rotation estimation
References
Ehrig RM, Taylor WR, Duda GN, Heller MO
J Biomech39p2798-809(2006)
CoRGamage2002
Attributes
Attribute | Default | Description | Required |
---|---|---|---|
name | name of the element | Yes | |
coordinateSystem | Yes | ||
biasCompensation | No | ||
biasCompensationIterations | 3 | No | |
Condition | |||
phase |
Generated trajectories
Name | Type |
---|---|
<name>Origin | 3d vector |
Generated parameters
Name | Type | Description |
---|---|---|
<name>OriginLocal | 3d vector | CoR in local coordinates of the parent system |
<name>Radius | Double | radius of the estimated sphere |
<name>FramesCount | ||
<name>RadiusStd | Double | std of estimated radius of the sphere |
References
Gamage SS, Lasenby J
J Biomech35p87-93(2002 Jan)
Halvorsen K
J Biomech36p999-1008(2003 Jul)
Examples
<Phase name="RAbduk" startEvent="RHS" endEvent="RTO" process="post" calibrateIncludes="dynamic_calibrate_right_shoulder" includes="dummy"/> <CoRGamage2002 name="RGHJC" coordinateSystem="Right_Acromion" phase="RAbduk" biasCompensation="true" biasCompensationIterations="5" calibrateIncludes="dynamic_calibrate_right_shoulder" includes="dynamic,static">RHUMS</CoRGamage2002>
SCoRE - symmetrical centre of rotation estimation
Attributes
Attribute | Description | Required |
---|---|---|
name | name of the element | Yes |
parentCoordinateSystem | Yes | |
childCoordinateSystem | Yes | |
condition | If the attribute phase is not used and if it is set to a mathematical formula which is 1 or 0 it is used instead of defined events | No |
phase | phase name, used if the phases are calculated elsewhere | No |
Generated trajectories
Name | Type |
---|---|
<name>Origin | 3d vector |
Generated parameters
Name | Type | Description |
---|---|---|
<name>OriginLocal | 3d vector | CoR in local coordinates of the parent system |
<name>FramesCount | double | count of frames used for the estimation |
<name>Radius | double | radius of the sphere around the origin of the parent coordinate system on which the origin of the child coordinate system is assumed to move around. |
<name>RadiusStd | double | standard deviation of the radien |
References
Ehrig RM, Taylor WR, Duda GN, Heller MO
J Biomech39p2798-809(2006)
Examples
<CoRSCoRE name="RGJCSCoRE" condition="RAbdukAngle<30.0" parentCoordinateSystem="RClavicle" childCoordinateSystem="RHumerus"/>
Notes
A warining is given, if the count of frames selected by the defined phases is smaller than 30. Keep in mind that even 30 frames typically are too less to get a „good“ estimation of a center of rotation. In this case the frames of the complete trial are used, which also typically does not result in an good estimation.