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Hip Joint Landmarks
Estimates for the Right and Left Hip Joint Center are represented as Landmarks that are created automatically when the V3D_Composite pelvis segment is created. The location of the landmark is defined as:
RHJC=(0.36*ASIS_Distance,-0.19*ASIS_Distance+0.5*RPV_Depth- MODEL::METRIC::Target_Radius_ASIS,-0.30*ASIS_Distance)
LHJC=(0.36*ASIS_Distance,-0.19*ASIS_Distance+0.5*RPV_Depth- MODEL::METRIC::Target_Radius_ASIS,-0.30*ASIS_Distance)
These estimates are adapted from the articles
Bell AL, Pederson DR, and Brand RA (1989) Prediction of hip joint center location from external landmarks. Human Movement Science. 8:3-16:
Bell AL, Pedersen DR, Brand RA (1990) A Comparison of the Accuracy of Several hip Center Location Prediction Methods. J Biomech. 23, 617-621.
Note that if the ASIS markers have been placed medial or lateral to the palpated landmark because the subject is overweight or because the markers can not be placed at these locations, it is important to measure the inter-ASIS distance and enter this value into the Subject Properties TAB.
Specifying the ASIS distance
For some subjects the ASIS markers may be difficult to place precisely on the ASIS, so they get placed laterally.
This results in an ASIS distance that is too big, and this directly affects the location of the Hip Landmark.
The ASIS distance is a Model Metric value that can be modified.
Switch to the Model Metrics Tab:
Select the ASIS_Distance item and select the Modify button
Enter the measured value of the ASIS distance.
The hip landmark will be based on this ASIS distance.