Upper body modeling with Plug-in Gait
- Gisela Roberts
- Ben Stanley
This section describes Plug-in Gait upper body modeling, so you can determine if an upper body model will provide the data you require for your clinical analysis.
For details about the labeling skeleton templates to be used with Plug-in Gait upper body models, see Plug-in Gait labeling skeleton templates (VSTs) in Vicon Nexus.
Outputs from Plug-in Gait upper body model
Use a Plug-in Gait upper body model if you require the kinematic and kinetic calculation outputs listed in the following table. The output variables are prefixed by the appropriate context (L for left or R for right).
| Output | Description |
|---|---|
| Kinematics: Angles | |
| ElbowAngles | Relative. The angles between the upper arm and forearm. |
| HeadAngles | Absolute. The angles between the head and the laboratory coordinate system. |
| NeckAngles | The angles between head relative to thorax. |
| ShoulderAngles | Relative. The angles between the upper arm and thorax. |
| SpineAngles | The angles between the thorax relative to the pelvis. |
| ThoraxAngles | Absolute. The angles between the thorax and the laboratory coordinate system. |
| WristAngles |
Relative. The angles between the forearm and hand. |
|
Kinetics: Forces |
|
| ElbowForce | The force between the upper arm and forearm. |
| NeckForce | The force between the head relative to thorax. |
| ShoulderForce | The force between the upper arm and thorax. |
| WristForce | The force between the forearm and hand. |
| Kinetics: Moments | |
| ElbowMoment | The moment between the upper arm and forearm. |
| NeckMoment | The moment between the head relative to thorax. |
| ShoulderMoment | The moment between the upper arm and thorax. |
| WristMoment | The moment between the forearm and hand. |
| Kinetics: Powers | |
| ElbowPower | The power between the upper arm and forearm. |
| NeckPower | The power between the head relative to thorax. |
| ShoulderPower | The power between the upper arm and thorax. |
| WristPower | The power between the forearm and hand. |
Marker sets for Plug-in Gait upper body modeling
The marker set for Plug-in Gait upper body modeling includes markers for the head, torso, and upper limbs.
There are two variations of the standard marker set for the upper body model:
- Additional upper arm (UPA) and forearm (FRM) markers
- No UPA and FRM markers
The UPA and FRM markers are optional; however, using them improves marker tracking during dynamic trials.
Marker placement for Plug-in Gait upper body model
The following images show front, back, and side views to demonstrate where to attach the upper body markers to your patient. You do this before 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.
As shown in the following images, some asymmetry is desirable as it helps the auto labeling routine distinguish right from left. For upper body modeling, you can place the 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 following image shows the front view. The left upper body markers are not labeled; attach markers on that side in a similar way to those on the right (with some asymmetry as described above).
The following image shows the back view. The right upper body markers are not labeled; attach markers in a similar way to those on the left (with some asymmetry as described above).
The following image shows the right side view. The left side view is not shown; attach markers on that side in a similar way to those on the right (with some asymmetry as described above).
The following tables list the markers defined in Plug-in Gait templates for upper body modeling and describe where to place them on the patient.
Head markers
The following table describes the markers positioned on the patient's head. To save time, many users buy a headband and permanently attach markers to it.
| Marker label | Definition | Position on patient |
|---|---|---|
| LFHD | Left front head | Left temple |
| RFHD | Right front head | Right temple |
| LBHD | Left back head | Left back of head (defines the transverse plane of the head, together with the frontal markers) |
| RBHD | Right back head | Right back of head (defines the transverse plane of the head, together with the frontal markers) |
If the back markers cannot be placed level with the front markers, you must configure Plug-in Gait to compensate for this during the subject calibration process. To do this, in the Properties for the Process Static Plugin Gait Model pipeline operation, under Assume Horizontal, select Head.
Torso markers
The following table describes the markers positioned on the patient's torso. The torso markers (C7, T10, CLAV, STRN) define the thorax sagittal plane; therefore, their lateral positioning is most important.
| Marker label | Definition | Position on patient |
|---|---|---|
| C7 | 7th cervical vertebra | On the spinous process of the 7th cervical vertebra |
| T10 | 10th thoracic vertebra | On the spinous process of the 10th thoracic vertebra |
| CLAV | Clavicle | On the jugular notch where the clavicles meet the sternum |
| STRN | Sternum | On the xiphoid process of the sternum |
| RBAK | Right back | Anywhere over the right scapula (This marker has no equivalent marker on the left side. This asymmetry helps the autolabeling routine determine right from left on the subject. Placement is not critical as it is not included in the Plug-in Gait model calculations.) |
Upper limb markers
The following table describes the markers positioned on the patient's upper body.
Marker labels shown with an asterisk * are optional; however, using them improves marker tracking during dynamic trials.
| Marker label | Definition | Position on patient |
|---|---|---|
| Left upper limb markers | ||
| LSHO | Left shoulder | On the acromio-clavicular joint |
| *LUPA | Left upper arm | On the upper lateral 1/3 surface of the left arm (Place asymmetrically with RUPA) |
| LELB | Left elbow | On the lateral epicondyle |
| *LFRM | Left forearm | On the lower lateral 1/3 surface of the left forearm (Place asymmetrically with RFRM) |
| LWRA | Left wrist marker A | At the thumb side of a bar attached to a wristband on the posterior of the left wrist, as close to the wrist joint center as possible. Loose markers can be used but for better tracking of the axial rotations, a bar is recommended. |
| LWRB | Left wrist marker B | At the little finger side of a bar attached to a wristband on the posterior of the left wrist, as close to the wrist joint center as possible. Loose markers can be used but for better tracking of the axial rotations, a bar is recommended. |
| LFIN | Left finger | Just proximal to the middle knuckle on the left hand |
|
Right upper limb markers
|
||
| RSHO | Right shoulder | On the acromio-clavicular joint |
| *RUPA | Right upper arm | On the lower lateral 1/3 surface of the right arm (Place asymmetrically with LUPA) |
| RELB | Right elbow | On the lateral epicondyle approximating the elbow joint axis |
| *RFRM | Right forearm | On the lower lateral 1/3 surface of the right forearm (Place asymmetrically with LFRM) |
| RWRA | Right wrist marker A | At the thumb side of a bar attached symmetrically with a wristband on the posterior of the right wrist, as close to the wrist joint center as possible |
| RWRB | Right wrist marker B | At the little finger side of a bar attached symmetrically with a wristband on the posterior of the right wrist, as close to the wrist joint center as possible |
| RFIN | Right finger | Just below the middle knuckle on the right hand |
