Full body modeling with Plug-in Gait
- Gisela Roberts
- Dev Ops
- Ben Stanley
If you require Plug-in Gait full body modeling, use both a lower and an upper body model to provide the data you require for your clinical analysis.
The following topics explain:
For a description of the labeling skeleton templates to be used with Plug-in Gait lower body, upper body, or full body models, see Plug-in Gait labeling skeleton templates (VSTs) in Vicon Nexus.
Outputs from Plug-in Gait full body model
Use a Plug-in Gait lower body and upper body model if you require the kinematic and kinetic calculation outputs listed in Outputs from Plug-in Gait lower body model and Outputs from Plugin Gait upper body model. The output variables are prefixed by the appropriate context (L for left or R for right).
Marker sets for Plug-in Gait full body modeling
There are two variations of the standard lower body model:
- A single sacral (SACR) marker
- Two posterior superior iliac spine (PSIS) markers for the pelvis.
These markers provide the same function; if you use two PSIS markers, Plug-in Gait calculates the midpoint between them and uses that to perform the calculations. If you use a single SACR marker, you identify that position to Plug-in Gait rather than having it calculated.
If you use a SACR marker, you must modify the supplied VST, which uses PSIS markers, or to obtain a ready-made SACR version of the Plug-in Gait VSTs, contact Vicon Support.
In addition to the standard lower body marker sets, an additional marker set enables you to use a knee alignment device (KAD). The KAD markers (left and right KAX, KD1, and KD2) are used instead of the THI and TIB markers in the standard model to calculate the orientation of the medio-lateral axes of knee and ankle respectively.
A variation of the KAD marker set defines the additional LMED and RMED markers for the medial malleoli. The MED markers enable Plug-in Gait to automatically calculate the tibial torsion measurement. For further information on the KAD and MED markers, see KAD marker sets for Plug-in Gait lower body model.
When you use KAD+MED markers, in order to verify the ankle axis, the Plug-in Gait Static pipeline displays the torsioned tibia instead of the untorsioned tibia. If joint angles are required, you must also run the Plug-in Gait Dynamic pipeline.
Marker placement for Plug-in Gait full body model
The following images show front, back, and side views to demonstrate where to attach the full body model markers to your patient. You do this when you are capturing a static trial as described in the Vicon Nexus User Guide.
Some markers are shown from two views to help you better determine their position on your patient.
The following image shows the front view. This view includes the knee alignment device (KAD) marker variations, which are shown inset, with dashed lines to indicate that they are optional. If you have chosen to use a Plug-in Gait marker set that includes KAD markers, attach the KAD pad to the patient instead of the THI and TIB markers. For details on the KAD, see KAD marker placement for Plug-in Gait lower body model.
As shown in the following images, some asymmetry is desirable as it helps the auto labeling routine distinguish right from left. For a full body set, you can place the THI, TIB, UPA and FRM markers asymmetrically. Similarly, avoid symmetrical placement of marker clusters or groups of markers and also ensure markers are asymmetrical within each cluster/group.
The left body markers are not labeled in this figure; attach markers on that side in a similar way (with some asymmetry) to those on the right.
To assist with labeling, place the UPA, FRM, THI, and TIB markers at slightly different heights on the left and right sides:
Upper 1/3: RUPA, RFRM, RTHI. RTIB
Lower 1/3: LUPA, LFRM, LTHI, LTIB
The following image shows the back view. This view includes the sacral (SACR) and knee alignment device (KAD) marker variations, which are shown inset, with dashed lines to indicate that they are optional. For details on the SACR marker, see Marker sets for Plug-in Gait lower body model. If you have chosen to use a Plug-in Gait marker set that includes KAD markers, attach the KAD pad to the patient instead of the THI and TIB markers. For details on the KAD, see KAD marker sets for Plugin Gait lower body model.
The right body markers are not labeled in this figure; attach markers on that side in a similar way to those on the left (with some asymmetry as described above). The RBAK marker has no equivalent marker on the left side; this asymmetry helps the autolabeling routine determine right from left on the subject.
The following image shows the right side view. This view includes the knee alignment device (KAD) marker variations, which are shown inset, with dashed lines to indicate that they are optional. If you have chosen to use a Plug-in Gait marker set that includes KAD markers, attach the KAD pad to the patient instead of the THI and TIB markers. For details on the KAD, see KAD marker sets for Plug-in Gait lower body model.
The left side view is not shown; attach markers on that side in a similar way to the right markers (with some asymmetry as described above).
For detailed guidance on placing markers on a patient for full body modeling, the following sections:
