Center of Pressure in the Paws of Clinically Sound Dogs in Comparison with Orthopedically Diseased Dogs

Abstract

The center of pressure (COP) is recognized as a valuable tool for the assessment of orthopedic and neurologic disorders in humans. Relatively few studies are available in veterinary medicine, particularly concerning the COP in the individual paw. This study assessed the dynamic paw COP parameters during the stance phase of dogs with cox- or cubarthrosis (20 dogs each), as well as of 20 sound dogs. Data were obtained by walking over a pressure platform and analyzed within the diseased groups in comparison to the control group. Both diseased groups showed significant differences between the affected and non-affected limbs, but also in comparison to the reference limbs of sound animals. For coxathrosis, the primary increase was in the medio-lateral COP displacement and the COP area in both hind limbs. For cubarthrosis, the most prominent changes were an increase in the medio-lateral COP displacement in the ipsilateral hind limb and in the cranio-caudal COP displacement in the lame limb. Additionally, the COP area increased in both hind limbs. This can reflect a compensatory redistribution of the body mass as well as compensatory changes of body balance.

Changes in Ground Reaction Forces and Center of Pressure Parameters of Paws When Wearing Dog Boots in Dogs

“…The center of pressure (COP) describes the point at which the current GRF vector acts. If it is observed during walking, a constant change in its position during contact with the ground creates a COP path ( 19 ). As shown in Figure 2 , the mediolateral and craniocaudal COP displacements represent the difference between the maximum positive and negative excursions along the craniocaudal and mediolateral axes.…”

“…Furthermore, the COP area (%) increased in both the hind limbs. The main change observed in the coxarthrosis group was an increase in the mediolateral COP excursion (%) and COP area (%) in both hind limbs ( 19 ).…”

Ground Reaction Forces and Center of Pressure within the Paws When Stepping over Obstacles in Dogs

“…To be included in the mentioned study, the animals had to present a normal orthopedic and neurological examination. Furthermore, a symmetry index (SI) less than 3% was required, as a symmetry index of up to 3% is considered normal for dogs and values higher than 3% are considered to indicate lameness [27,36,37]. At least four valid passes for each limb (during obstacle measurements) were required for a dog to be included in the study, where valid passes over the obstacles were those where the animals did not touch or drop the obstacles, turn their head, or pull on the lead.…”

“…For this purpose, they were allowed to move freely in the room. As soon as the dogs became accustomed to the environment, they were subjected to a standard analysis of the ground reaction forces, as described by Reicher et al [27], before walking over obstacles. The dogs were led on the left side of the handler, as in everyday life, and always from the same direction at their comfortable speed for walking.…”

“…COP is the location where the instantaneous vector of the ground reaction forces acts. During ground contact, the position of the COP changes continuously, thus creating the COP path [27]. Analysis of the COP provides a dynamic reflection of global locomotion and postural control [28], and it has been used to quantify various gait abnormalities [29].…”