Estimates for the Right and Left Hip Joint Center are represented as Landmarks relative to the CODA and V3D_Composite pelvis segment coordinate systems.

You should notice the following for all equations:

1. The left and right side landmarks are defined exactly the same, except the ML direction for one side is negated.
2. The only difference between the equations for the CODA and V3D_Composite pelvis segments is that there is an offset (0.5*RPV_Depth-Target_Radius_ASIS). This is because the origin of the V3D_Composite pelvis is 50% of pelvis depth compared to the CODA pelvis origin.

You will see the following model metrics used in the equations below. These model metrics are automatically created when you create the CODA or V3D_Composite pelvis.

NOTE: RPV_Depth is included in the subject metrics starting in Version 5 and the Target_Radius_ASIS is included in the subject metrics starting in Version 6. In previous versions, these metrics must be added manually

When you create the CODA or V3D_Composite pelvis, the hip joint landmarks are automatically created using the Bell and Brand regression equations.

• Since the pelvis depth is defined differently between the CODA and V3D_Composite pelvis, use the set of equations which corresponds to the pelvis type you are using.

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.

Note that in the 1990 article the ML distance is listed as 0.14 instead of 0.36 as used by Visual3D. The confusion lies in the location of the origin of the pelvis used in the article. Visual3D uses the mid-point of the ASIS, the article uses the Right ASIS location.

Harrington provided two regression equations for the hip joint landmark

• The second set of equations requires the user to manually measure leg length. If you do not plan to manually measure leg length, use the first set.
• Since the pelvis depth is defined differently between the CODA and V3D_Composite pelvis, use the set of equations which corresponds to the pelvis type you are using.

Harrington ME, Zavatsky AB, Lawson SE, Yuan Z, Theologis TN.(2007) Prediction of the hip joint centre in adults, children, and patients with cerebral palsy based on magnetic resonance imaging. J Biomech. 2007;40(3):595-602. Epub 2006 Apr 3.

If no clinical measurements are taken, the following values are calculated:

Estimates for the Right and Left Hip Joint Center are represented as Landmarks that are created automatically when the Helen Hayes pelvis segment is created. The location of the landmarks are defined in the Pelvis Segment Coordinate System as:

These equations are adapted from the article:

Davis RB, Ounpuu S, Tyburski D, Gage JR. (1991) “A Gait Analysis Data Collection and Reduction Technique.” Human Movement Science, 10: 575-587.