Scaling and Personalizing your model#
Musculoskeletal models must be adaptable to sizes and anatomy of various individuals to be useful for product design and to be used for applications, where high geometric accuracy is required, e.g. surface articulations and patient-specific pre-operative planning. A general method for scaling musculoskeletal models has been implemented in the AMMR. It allows the usage of built-in, user-defined anthropometric scaling laws as well as individual segment morphing.
See also
For more information about the scaling laws, see the AMMR Scaling documentation.
Scaling schemes described in the AMMR documentation are based on anthropometric measurements and affine transform scaling. Such schemes are good assumptions when more accurate measurements are not feasible or not available. Therefore, these schemes are used quite often. Currently, there are six built-in scaling laws available in AnyBody, which can be seen in the table below. The first three lessons of this tutorial will explain what these scaling laws are and how to configure your model to use them.
Scaling law |
Description |
|---|---|
|
Scale to a standard size; i.e. use 50th percentile sizes for a European male |
|
Do not scale; i.e. use underlying cadaveric dataset as is |
|
Scale segments equally in all directions; input is joint to joint distances |
|
Scale taking mass into account; input is joint to joint distances and mass |
|
Scale taking mass and fat into account; input is joint to joint distances |
|
Scale taking mass and fat into account; scale segments along X, Y, Z axes; input is scale factors along X, Y, Z axes. |
If improved precision of the scaling is needed, a natural next step would be to utilize subject-specific geometry available from the medical images. Medical images contain more subject-specific information about the bone shapes and local deformities that cannot be handled by the anthropometric regression equations.
The last two lessons in this tutorial introduce an advanced procedure of model personalization by means of nonlinear morphing for both bone surface and relevant soft tissue attachment sites, to take a subject-specific shape. In this example, bone geometries segmented from medical images will be used to demonstrate how geometrically accurate subject-specific models can be constructed.
Tutorial content