This test exists in 3 different versions:
- Static weight bearing test
- Dynamic weight bearing test
- Kinetic weight bearing test
Static weight bearing test
In the incapacitance test, the animal is located in a holder specially designed to maintain the animal comfortably positioned on two separated sensor plates. The Incapacitance device enables then to quantify the spontaneous postural changes reflecting spontaneous pain by independently measuring the weight that the animal applies each hind paw on two separate sensors. Because normal rats and mice distribute weight equally on both paws, change of this equilibrium can reflect the level of discomfort due to an injured paw.
The static weight bearing test, although showing well correlated results vs. paw pressure vocalization test, calibrated Von Frey filaments (etc.) are highly dependent on the animal's (rat or mouse) position inside a stressful restrainer. This can make the experimental procedure time-consuming and difficult to use, particularly when large number of rodents are considered.
Dynamic weight bearing test
In the dynamic weight bearing test, the evaluation is performed on a freely moving animal. The dynamic weight bearing test calculates the percentage of weight borne by each paw compared to the total body weight while the animal is able to move freely, offers results that are much closer to reality. The study performed with mice and rats on three models of pain (inflammatory, cancer, neuropathic) reveals that the forepaw compensation is an important indication in the load pattern redistribution.
Kinetic weight bearing test
The unique "sensor-mat" technology originally designed by Bioseb for the Dynamic Weight Bearing application has been refined and adapted to make kinetic analysis possible. This allows the weight borne by each individual paw to be tracked during a walking sequence in a corridor. The Kinetic Weight Bearing Instrument provides additional information on applied weight as well as the speed and acceleration of each paw as the animal moves toward an end point of the runway platform. This additional information provides data on coordination and gait comparison paw to paw and step to step.