Page 53 - Canine Lameness

2.3 ­inematic Analysis 25

Out-of-plane In-plane Out-of-plane
(head toward camera) (head away from camera)

Altered length measurements True length measurements Altered length measurements
Altered joint angels True joint angles Altered joint angels
Calibrated plane
Figure 2.7 A possible source of error in 2D kinematics: subject positioning relative to the calibrated plane
(rotation).

error, as is encountered with 2D systems. Unfortunately, even with technological advancement
and the declining cost of computerized hardware, the price of these systems remains high and
has limited their clinical application. Additionally, the complexity of the 3D models and operat-
ing systems makes every day clinical use challenging.

2.3.3 Kinematic Models
Clinically, kinematic analysis is most commonly performed by placing spherical markers on the
skin over specific areas of the body. The specific pattern in which these markers are placed is called
a kinematic model. The basics of these models and kinematic methods have changed very little for
over 180 years (Decamp 1997; Torres 2018).
Models used with 2D kinematic systems – These are simplistic and easy‐to‐use models focused
on one plane of motion, referred to as “planar” motion. Hence, these models are commonly
called planar models. Their pattern further defines them as linear, linked, or segment models
(Figure 2.8). In veterinary medicine, one of the most widely used 2D kinematic models for dogs
is a full‐body model (Figure 2.9).
Models used with 3D kinematic systems – In general, any model can be used with a 3D kine-
matic system, and historically, simple planar models described above have been used. However,
evaluation of true 3D joint motion requires more complex models, often referred to as rigid body
segment models (Figure 2.8). In the past few years, veterinary research has seen the use of these
models and systems increases. However, they are complex and require a larger number of mark-
ers as well as advanced 3D equipment and training to obtain clinically useful results. Currently,
use in a clinical setting is uncommon in veterinary medicine.