Gait analysis

Question 1

What are the two main categories of gait analysis?

Answer 1

Kinetics: study of forces generated during movement.

Kinematic: study of motion irrespective of masses or forces.

Question 2

What are the symmetric and asymmetric gaits?

Answer 2

Symmetric: trot, walk and pace.

Assymetric: canter, transverse gallop, rotary gallop.

Question 3

What forces are typically evaluated during kinetic gait analysis?

Answer 3

1. Vertical (most commonly evaluated).
2. Craniocaudal.
3. Mediolateral (least common).

Question 4

What does the craniocaudal force define?

Answer 4

Braking and propulsion.

Question 5

What is the difference between peak vertical force and vertical impulse?

Answer 5

Peak vertical force is the highest vertical force measured.

Vertical impulse considers both the magnitude of force and the time (area under the curve).

Both can be affected during lameness.

Question 6

Why are peak craniocaudal force and impulse typically divided into two separate measurements?

Answer 6

One is used to define braking, the other to define propulsion.

Question 7

What is the loading rate?

Answer 7

The slope of the ground reaction force curve. Includes both loading rate (up slope of the curve), and offloading (downslope).

In animals with lameness the rising slope is reduced, consistent with a more cautious initial placement of weight on the limb (reduced loading rate). The falling slope is increased, consistent with a quicker removal of weight from the limb (increased offloading rate).

Question 8

What are the two types of system that can be used for kinetic gait analysis?

Answer 8

1. Force plate system.
2. Pressure walkway system.

Question 9

What are the main differences between pressure walkway and force plate systems for kinetic gait analysis?

Answer 9

Pressure walkway systems can only measure vertical force, whereas force plate systems can measure vertical, craniocaudal, and mediolateral force.

Force plate systems have difficult evaluation overlapping footfalls in small patients, which is not an issue for pressure walkways as they can record information for each individual footfall.

Question 10

Why is measurement of velocity and/or acceleration important when performing kinetic gait analysis?

Answer 10

Because gait data is altered by large variations in velocity and acceleration.

A minimum of two photocells are required to measure velocity, three are required to measure acceleration.

Question 11

What percentage of weight is carried in the thoracic and pelvic limbs of the dog?

Answer 11

Pelvic limbs: 40%
Thoracic limbs: 60%

Question 12

What gait is considered ideal for assessment of kinetic gait data?

Answer 12

Walking or trotting are typically used as both are symmetric gaits.

Trotting may be more sensitive for detection of lameness, however, and there is not overlap of footfalls during this gait making evaluation easier.

Question 13

What is symmetry index and what is a normal level of assymetry?

Answer 13

Symmetry index is use of the animal’s own limb(s) as an internal control for comparison during kinetic gait analysis.

Normal asymmetry levels have been reported at <3-6%.

Question 14

What are some sources of variability during collection of kinetic gait data?

Answer 14

Variance attributed to the dog, handler, trial repetition, habituation in the testing area, extreme changes in velocity, stance time, or acceleration/deceleration.

Question 15

What are the three planes of joint movement during kinematic analysis?

Answer 15

1) Transverse
2) Sagittal
3) Frontal

Translations and rotations occur within these planes and include:
1) Translations: craniocaudal, mediolateral, and proximodistal.
2) Rotations: proximal/distal, internal/external, abduction/adduction.

Question 16

What are the benefits of 3D over 2D kinematic analysis systems?

Answer 16

3D systems avoid issues associated with parallax and perspective errors.

Question 17

What are the two types of markers used in kinematic gait analysis?

Answer 17

1. Passive (generally non-reflective in 2D systems, reflective in 3D systems).
2. Active (light emitting diodes). These eliminate marker merging and allow for close approximation of markers, but they require cabling to a power source, which can affect gait in some patients.

Question 18

What is skin motion artifact during kinematic gait analysis?

Answer 18

Movement of the skin over the bony landmarks during ambulation. This has been shown to be greatest over the stifle and hip (areas with greater skin soft tissue coverage compared to the tarsus).

The use of virtual markers may help to reduce this artifact and may also address the issue of visibility of medially based makers.

Question 19

What is the benefit of placing kinematic markers over bone landmarks?

Answer 19

1) It provides for an easily identified and repeatable location for marker placement.

2) It provides marker locations with minimal underlying soft tissue that may reduce skin motion artifact

Question 20

What factors might create variability in kinematic data?

Answer 20

The testing environment, equipment, patient, and primary examiner.

Question 21

What techniques have been used for waveform analysis of kinematic data?

Answer 21

Fourier analysis, wavelet analysis, generalized indicator function analysis.

These methods are preferred over simple point analysis (such as maximal and minimal flexion values) as they examine the entire waveform.

However, no single ideal analysis technique exists.

Question 22

What are some alternative methods of kinematic gait analysis?

Answer 22

1) Fluoroscopic techniques.
2) CT/MRI
3) Body mounted inertial sensors (containing accelerometers and gyroscopes).

Question 23

What is inverse dynamics?

Answer 23

The use of external (rather than internal) forces to determine joint forces and moments.