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User Manual


Orientation Diagram

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Participant Meta Data

This section displays the additional participant details manually inputted by the user at the collection stage.

Step Events Graph

The Step Events Graph is an event trace of detected steps from each leg. Legs are color coded and each detected step is marked as a shape on the timeline:

  • Light Blue is Front Left (FL)
  • Red is Front Right (FR)
  • Dark Blue is Hind Left (HL)
  • Orange is Hind Right (HR)

Step parameters are mapped as shown below:

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Regions of interest can be selected and statistics will be displayed in other parts of the interface. For periods where no steps are detected (holes), no data is displayed.

The Step Events Graph also displays Markers made during the recording process as well as links to Media taken during the recording.

Step Detection

The Step Events Graph is fed by information from the GaitKeeper algorithm. This algorithm is fed from IMU data gathered from MX sensors on the legs. For the algorithm to work properly, sensors should be attached securely and in the correct position.

  • Sensors should be mounted on the OUTSIDE of the limb
  • Front Leg sensors should be mounted BETWEEN the Wrist and Elbow
  • Hind Sensors should be mounted ABOVE the Tarsal/Hock joint
  • Sensors should be mounted with the LEDS pointing UPWARDS

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The algorithm works on a transformed version of the raw data and picks out the moment the foot leaves the floor (Final Contact; FC) and the moment the foot touches the floor (Initial Contact; IC). From this timing data the other gait metrics are derived.

The algorithms has been validated on a large cohort of dogs of various ages, sexes, breeds. For full details of the validation study and technical details on algorithm, see 1

Export

The Export button provides a direct download to all results from the GaitKeeper analysis. It is provided for doing further statistical analysis or research outside of the interface.

NOTE: Once the data has been exported, it is up to the user to keep backups of the data and to enforce any access control or security policy. Any files on a local disk or network drive are not under version control, access control or part of any backup routine provided by VetSens.

The format of the exported data is in comma separated values (CSV) file. Headings are provided for each column and some packages may specify to ignore or remove these.

In Excel, a screen-shot of the data looks like

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The columns are as follows

Heading Desc Units
Timestamp Time of the event as STRING timestamp
(yyyy/dd/mm HH:MM:SS.fff)
 
Leg Number INT
1=FL, 2=FR, 3=HL, 4=HR
 
Leg Name STRING
FL=front left
FR = front right
HL = hind left
HR = hind right
 
Swing Time UINT32 (seconds)  
Stance Time UINT32 (seconds)  
Step Time UINT32 (seconds)  
Velocity UINT32 (m/s)  
Length UINT32 (meters)  
Peak Jerk UINT32 (m/s/s/s)  
UNIX Timestamp number seconds since 1-1-1970 00:00:00 INT32

Share Option

The share button can be used to give a read only access to a particular set of results. This option is designed for users to give owners or interested parties access to the results. Upon clicking the share button, you will be required to enter the email address of the recipient.

Settings

Settings can be used to change various behaviors of the interface.

Media

During the collection phase, it is possible to collect videos and photos. These help give context to the recording or preserve environmental information that may influence how the results are interpreted. Media files are stored in their own tab window and linked in the Step Events Graph.

NOTE: Time synchronisation between the steps and media data may not be perfect as the camera has its own independent clock source to the sensors.

Radar

The Radar plot is used to view asymmetry between several parameters. Selecting regions of the plot highlights key metrics in the data for easy reading. Parameters available in the radar plot are:

Step Time

alt text Step time is defined as the time taken for IC to IC on the Same Foot. Step time for a lame leg will usually be higher for a lame leg than a healthy one, although if bi-laterally lame there may be no observable asymmetry. Step Time will also be different in different gaits for the same animal and so its important to make sure measurements are made in a consistent gait.

Step Phase

alt text Swing time is the time between a FC and IC event: the time the foot is in the air. Sometimes swing time is termed suspension phase.

alt text Stance time is the time between a IC and FC event within the same step: the time the foot is in on the ground.

As a rule of thumb, the normal ratio of Swing:Stance is 40:60 per leg respectively. This ratio allows for regular, full length strides. In lameness it is often the case bearing load is painful and in such cases there is often an reduced stance time in the lame leg.

Step Length

alt text Step Length is defined as the distance the foot moves inbetween a FC and **IC event. Only the distance in a forwards direction is taken into account (caudal-cranial axis).

Step length has relationships to pain, muscle control/tone. It is normal in healthy animals to observe a variety of step lengths within legs at a given gait.

Step Velocity

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Step Velocity is defined as:

It is important to note, this is NOT Swing Velocity (the velocity of the limb during Swing Phase).

NOTE: Gait is a very complex topic and difference models exist for each mode: walking, trotting, galloping etc. As such, analysis should normally be carried out on steps taken in a single gait. GaitKeeper does not include a gait detection component and so it is up to the user to select steps on consistent gait for measurement. This may be done with the assistance of the Media tool. For more information on definitions of gait cycle see 2.

Balance

The Balance plot is used to make it easy to spot asymmetries. Legs are displayed side by side and parameters can be selected for viewing. Parameters available in the balance plot are:

  • Step Time
  • Step Phase
  • Step Length
  • Step Velocity

NOTE: Gait is a very complex topic and difference models exist for each mode: walking, trotting, galloping etc. As such, analysis should normally be carried out on steps taken in a single gait. GaitKeeper does not include a gait detection component and so it is up to the user to select steps on consistent gait for measurement. This may be done with the assistance of the [Media][#media] tool. For more information on definitions of gait cycle see 2.

Table

Lameness, disease, pain and injury manifest in gait in different ways. Often measurements at different speeds can be used to exacerbate symptoms. The Table View makes several statistical features readily available for any selected set of steps in the [Step Events Graph][Step Events Graph].

Variability

Variability is calculated as defined in 3:

where $\sigma^2$ represents the variance calculated as the squared deviation of the variable from its mean.

Asymmetry

Asymmetry is calculated as defined in 3:

where $\overline{x}$ is the mean value of a set.

References

[1] Ladha C, O’Sullivan J, Belshaw Z, Asher L GaitKeeper: A system for measuring Canine Gait. Sensors (Basel). 2017 Feb 8;17(2). pii: E309. doi: 10.3390/s17020309.

[2] Timothy M. Griffin, Russell P. Main, Claire T. Farley Biomechanics of quadrupedal walking: how do four-legged animals achieve inverted pendulum-like movements?. Journal of Experimental Biology 2004 207: 3545-3558; doi: 10.1242/jeb.01177

[3] Ladha C, Del Din S, Nazarpour K, Hickey A, Morris R, Catt M, Rochester L, Godfrey A. Toward a low-cost gait analysis system for clinical and free-living assessment. Conf Proc IEEE Eng Med Biol Soc. 2016 Aug;2016:1874-1877. doi: 10.1109/EMBC.2016.7591086.