Page 48 - Canine Lameness

20 2 Objective Gait Analysis

Portability and Storage – Many PSW systems can be “rolled‐up” or deconstructed for storage
and/or transportation. This may be an important consideration for clinicians where dedicated
space is limited.
Kinetic Measurements – PSWs measure foot pressure and while sensor types can vary between
systems, all measure pressure only in the vertical direction. Pressure is related to but not the
same as force, measured with FPs. Clinically, vertical pressure measurements are often evalu-
ated similarly to GRF.
Temporospatial Variables (TSV) – The rapid collection and reporting of TSVs is a major strength
of PSWs. These variables (discussed later in this section) are calculated from the paw strikes
recorded by the PSW.

2.2.5 Pressure-sensitive Walkway Systems: Clinically Reported Values
Kinetic Variables – Pressure (vertical direction only) is the primary kinetic variable recorded with
PSWs (Figure 2.2). Some PSWs (i.e. Tekscan Walkway™) allow clinicians to use pressure measure-
ments to indirectly calculate force (PVF and VI) through a calibration process. Because this method
differs from direct force measurements obtained by FPs, these calculated force values are similar but
not directly comparable to ones obtained from FPs (Lascelles et al. 2006). Clinically, this means that
when evaluating patients (e.g. improved or reduced weight‐bearing), all measurements for compari-
son should be recorded with the same system (FP system or PSW system). How pressure values are
reported varies between PSW systems. Pressure values can be reported as a maximum pressure value
(Tekscan Walkway™) or as a scaled pressure value called a total pressure index (GAIT4Dog®).
Body Weight Distribution (%BWD) – This is calculated from pressure and is automatically cal-
culated by most PSW systems (Table 2.1). For the PSW systems that allow calculation of force
values, those can be used to calculate %BWD. See the FP section for additional information.
Temporospatial Variables (TSV) – These are not kinetic variables because they do not represent
force or pressure. Instead, they describe events related to time (temporo‐) and distance (‐spatial).
For example, stance and swing time are temporal measurement and stride length is a spatial
measurement. Stride velocity and acceleration involve both time and distance. Commonly
reported TSVs are listed below:
Gait Cycle (Stride) Time – The combined value of the stance time + swing time represents the complete
gait cycle of one leg. This occurs between each consecutive footfall (toe‐on to toe‐off to toe‐on).
Stance Time – This is the total time a foot is on the ground during the gait cycle (toe‐on to toe‐off).
This is often displayed as a percentage of the total gait cycle.
Swing Time – This is the total time a foot is off the ground during the gait cycle (toe‐off to toe‐on).
This is often displayed as a percentage of the total gait cycle.
Stride Length – This is the distance between two consecutive footfalls of the same leg. This repre-
sents the distance a foot travels during one complete a gait cycle.
Stride Velocity – This is the velocity (i.e. speed) at which a leg completes a gait cycle.
Stride Acceleration – This is the change in velocity (i.e. speed) between two consecutive strides.

2.2.6 Static or Standing Kinetic Analysis

The previous discussion focused on the more common dynamic kinetic analysis performed
when moving at a walk or trot. However, recently static kinetic analysis or “standing