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This information is for Vicon Nexus 2.10. For up-to-date help, see the latest Nexus documentation.

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Plug-in Gait requires a set of subject measurements to enable it to directly calculate kinematics (angles) and kinetics (forces, moments, and powers) from the measured XYZ marker positions. Some of the measurements you must add to the subject node are required for the model to run, and some are optional:

  • Required subject measurements You must add the required measurements to the subject node for your patient. Required measurements are listed in the following topics and are highlighted in pink in the Properties pane for the selected subject in Vicon Nexus.
  • Optional measurements You can add any optional measurements or leave them for Plug-in Gait to calculate.

The following topics list the measurements needed for each type of model:

Tip
You may find it helpful to take these measurements before you begin the subject preparation process in Vicon Nexus. You can use the Measure column in the tables in these sections to record the measurements you take for your patient, so you will have them to hand when you are ready to add them to your chosen labeling skeleton template (.vst file). You may want to photocopy the blank form for each patient before recording your measurements.To avoid the markers getting in the way, take the measurements before attaching markers to your patient.

Subject measurements for Plug-in Gait lower body model

The following table identifies the subject measurements that are used as inputs for running a Plug-in Gait lower body model.

Optional measurements (and/or those calculated by the model) are marked with an asterisk in the Name column.

NameDescriptionLeftRight
Body MassPatient mass._____ kg
HeightPatient height._____ mm
*Inter ASIS distanceThe model calculates this distance based on the position of the LASI and RASI markers. If you are collecting data on an obese patient and cannot properly place the ASIS markers, place those markers laterally and preserve the vector direction and level of the ASIS. Palpate the LASI and RASI points and manually measure this distance, then input into the appropriate field._____ mm
Leg LengthFull leg length, measured between the ASIS marker and the medial malleolus, via the knee joint. Measure with patient standing, if possible. If the patient is in the crouch position, this measurement is NOT the shortest distance between the ASIS and medial malleoli, but rather the measure of the skeletal leg length, so if a patient cannot straighten his/her legs, take the measurement in two pieces: ASIS to knee and knee to medial malleolus._____ mm_____ mm
*ASIS-Trochanter DistanceASIS-greater trochanter distance is the vertical distance, in the sagittal plane, between the ASIS and greater trochanter when the patient is lying supine. Measure this distance with the femur rotated such that the greater trochanter is positioned as lateral as possible._____ mm_____ mm
Knee WidthThe medio-lateral width of the knee across the line of the knee axis. Measure with patient standing, if possible._____ mm_____ mm
Ankle WidthThe medio-lateral distance across the malleoli. Measure with patient standing, if possible._____ mm_____ mm
*Tibial Torsion1The angle between the knee flexion and the ankle dorsi-plantar axes. The ankle is usually externally rotated with respect to the knee flexion axis.
If you are using a KAD, and the medial malleoli markers are attached to the patient, Plug-in Gait calculates the tibial torsion automatically.
_____ deg_____ deg
*Sole Thickness Delta2The difference in the thickness of the sole at the toe and the heel. A positive sole delta indicates that the patient's heel is raised compared with the toe._____ mm_____ mm
*Thigh RotationWhen a KAD is used, this value is calculated to account for the position of the thigh marker. By using the KAD, placement of the thigh marker in the plane of the hip joint center and the knee joint center is not crucial. If you do not use a KAD, this value is zero as the model assumes that the thigh marker is placed exactly in the plane of the hip joint center and the knee joint center. This value is calculated for you._____ deg_____ deg
*Shank RotationSimilar to the Thigh Rotation. This value is calculated if a KAD is present and removes the importance of placing the shank marker in the exact plane of the knee joint center and ankle joint center. If you do not use a KAD, this value is zero. It is calculated for you._____ deg_____ deg
  1. The tibial torsion measurement is only needed if you are using a KAD.
  2. The Sole Thickness Delta subject measurement is used if the subject is wearing high-heeled footwear but can keep their foot flat within the shoe. For more information, see Sole Thickness Delta subject measurement.

After you have recorded the measurements for your patient, you can create a subject node for the patient and enter the measurements into Nexus as described in Create a new subject from a template.

Sole Thickness Delta subject measurement

The Sole Thickness Delta subject measurement is used when the patient is wearing shoes or orthoses so that although the patient achieves foot flat with respect to the footwear, the sole of the footwear introduces a vertical difference between the toe and the heel. When this is the case, you can either:

  • Compensate for the sole delta by carefully placing the heel marker with respect to the toe marker and in the Static Settings dialog box, ensure the check boxes for Left Foot and/or Right Foot are cleared.

or

  • Measure the difference in the thickness of the sole at the toe and the heel, in the Static Settings dialog box, select the check boxes for Left Foot and/or Right Foot and then in the Properties section at the bottom of the Subjects Resources pane, enter the delta value in the SoleDelta (mm) box. The height of the heel marker used in the calculations will then be adjusted accordingly.

Subject measurements for Plug-in Gait full body model

The following table lists the subject measurements that are used as inputs for running Plug-in Gait for full body modeling.

Optional measurements are marked with an asterisk in the Name column.

NameDescriptionLeftRight
Body MassPatient mass._____ kg
HeightPatient height._____ mm
*Inter-ASIS distanceASIS-ASIS distance is the distance between the left ASIS and right ASIS. This measurement is only needed when markers cannot be placed directly on the ASIS, for example, in obese patients._____ mm
*Head OffsetPatient head offset in degrees.Only required if head is not level (calculated after running the Plug-in Gait model)._____ deg
Leg LengthFull leg length, measured between the ASIS marker and the medial malleolus, via the knee joint. Measure with patient standing, if possible. If the patient is standing in the crouch position, this measurement is NOT the shortest distance between the ASIS and medial malleoli, but rather the measure of the skeletal leg length._____ mm_____ mm
*ASIS-Trochanter DistanceASIS-greater trochanter distance is the vertical distance, in the sagittal plane, between the ASIS and greater trochanter when the patient is lying supine. Measure this distance with the femur rotated such that the greater trochanter is positioned as laterally as possible. If this value is not entered, a regression formula is used to calculate the hip joint center. If this value is entered, it will be factored into an equation which represents the hip joint center._____ mm_____ mm
Knee WidthThe medio-lateral width of the knee across the flexion axis. Measure with patient standing, if possible._____ mm_____ mm
Ankle WidthThe medio-lateral distance across the malleoli. Measure with patient standing, if possible._____ mm_____ mm
*Tibial Torsion1The angle between the knee flexion and the ankle dorsi-plantar axes. The ankle is usually externally rotated with respect to the knee flexion axis. The sign convention is that if a negative value of tibial torsion is entered, the ankle flexion/extension axis will be adjusted from the KAD's defined position to a position dictated by the tibial torsion value.
If you are using a KAD, and the medial malleoli markers are attached to the patient, Plug-in Gait calculates the tibial torsion automatically.
_____ deg_____ deg
*Sole Thickness Delta2The difference in the thickness of the sole at the toe and the heel. A positive sole delta indicates that the patient's heel is raised compared with the toe._____ mm_____ mm
*Thigh RotationWhen a KAD is used, this value is calculated to account for the position of the thigh marker. By using the KAD, placement of the thigh marker in the plane of the hip joint center and the knee joint center is not crucial. If you do not use a KAD, this value is zero as the model assumes that the thigh marker is placed exactly in the plane of the hip joint center and the knee joint center. This value is calculated for you._____ deg_____ deg
*Shank RotationSimilar to the Thigh Rotation. This value is calculated if a KAD is present and removes the importance of placing the shank marker in the exact plane of the knee joint center and ankle joint center. If you do not use a KAD, this value is zero. It is calculated for you._____ deg_____ deg
Shoulder OffsetVertical distance from the center of the glenohumeral joint to the base of the marker on the acromion clavicular joint. Some researchers have used the (anterior/posterior girth)/2 to establish a guideline for the parameter._____ mm_____ mm
Elbow WidthWidth of elbow along flexion axis (roughly between the medial and lateral epicondyles of the humerus)._____ mm_____ mm
Wrist WidthAnterior (palm side)/Posterior (back) thickness of wrist at position where wrist marker bar is attached._____ mm_____ mm
Hand ThicknessAnterior/Posterior thickness between the dorsum and palmar surfaces of the hand, at the point where you attach the hand marker._____ mm_____ mm
  1. The tibial torsion measurement is only needed if you are using a KAD.
  2. The Sole Thickness Delta subject measurement is used if the subject is wearing high-heeled footwear but can keep their foot flat within the shoe. For more information, see Sole Thickness Delta subject measurement.

After you have recorded the measurements for your patient, you can create a subject node for the patient and enter the measurements into Vicon Nexus as described in Create a new subject from a template.